Why does a cutter rig point higher & sail faster? [Archive]

249

11-17-2004, 10:08 PM

Yes, racing boats do tend to set trends in design. But frankly are you sure that they are undesirable? Some of them are, but not all IMHO.

Secondly, all that extra stuff you mentioned that goes with a cutter rig also costs money, and quite a bit of it. So OK it may be worth it in a big cruiser, but to imply that racing rules is the reason cutter rigs are not used in other boats seems a bit of a stretch.

Re "Weight is a critical factor in racing boats.... Performance and the rules favour light boats."

Not really, surely? One of the most succesfull boats in the UK was the Sparkman and Stephens "Finnisterre" type "Sunstone", an extremely heavy boat. She won Yacht of the Year, I think (the top national offshore prize) under IOR, IRC AND IMS. She then came out here and won her class in the Hobart. She was so succesful that the ISAF's ORC had her re-measured at their expense, to see why rule favoured such a heavy boat.

Look also at recent Sydney-Hobart results, with boats like the Currawong Zeus II, the Joubert 41 and the Beneteau 40.7 doing very well. By today's standards it's hard to see those as light boats. Look also at the national IRC Offshore championship won by the Swan 48.

Considering that most racing sailors prefer light boats as they feel they are more fun, it seems quite possible that heavy boats are over-represented at the front of the fleet; after all very, very few of the old boats have crews and campaigns that are as good as those on the modern yachts. How many heavy boats have crews with proven racing skills (ie many national titles or similar), good deck gear and a full load of good sails?

re "Any extra weight aloft cannot be tolerated on yachts designs that chase light displacement and have such a poor stability curve."

Poor stability curve? If you take the Sydney 38 as an example of a typical modern racer/cruiser, I think you'll find that the modern boats have a very good stability curve. The current rule (IRC) does not penalise stability per se at all; it doesn't even measure it! One of the strongest of all trends under IRC is to optimise boats for MORE stability as the rule does not rate it.

Re "Heavier safe stable comfortable seaworthy boats cannot be designed to the paradigm "if racing boats don't do it its a poor option" and the comparison is foolish."

I suppose it depends what you call "safe" and "comfortable". I find heavy cruisers to be uncomfortable in their motion; it's a personal thing but often people just assume the slow lope of a cruiser is universally preferred.

I'm also not so sure about the safety aspect - for example in the '98 Sydney-Hobart the heavyweight long-keeled Swanson 42 Mintanta sank, as did the heavyweight long-keeled Winston Churchill. The Cole 43 Solo Globe Challenger rolled and lost her rig. Considering the very small number of heavyweight long keelers, they did very badly.

I interviewed two of the most experienced Sydney-Hobart skippers of all a while ago. Both started in the days of heavy long-keel planked and steel designs in the '60s. Both moved to S & S designs, Frers masthead riggers, IOR lightweight fractionals, IMS racers, IRC racers. Both said that their current IRC/IMS fractional bulb keelers are basically as seaworthy as their long keelers. One said that his safest boat ever was a beamy IOR boat with a very tall rig with in-line spreaders and runners, and his current Sydney 38 had the best offshore rig he'd ever sailed with.

I was surprised by their answers, but they have international wins, Hobart wins and about 70 Hobarts between them so I accept they know more than I do on this subject.

dionysis

11-17-2004, 11:41 PM

Maybe the reason cutter rigs can point higher - all things being equal, is that the foresail makes better use of the upwash from the staysail and main.

The single foresail is more effcient as a foil overall and so developes more drive than the cutter configuration.

So although the cutter may point higher, the sloop rig has better VMG

RDKinard

11-18-2004, 08:14 AM

It's interesting that you should ask.

For maximum close reaching, I had the staysail sheet blocks 1/2 way between the mast and toe rail, with the Yankee sheet blocks at the toerail.

During the Bermuda Ocean Race this year, two expert sail trimmers from the Naval Academy and British Royal Navy experimented and found the staysail sheet block should be on the same toe rail track as the Yankee sheet, and at the same angle, to make them work together. Doing this made their leech parallel.

Their explanation for the amazing close reaching and low wind performance of the cutter rig was it's ability to create a very smooth airflow from the headsails, over the main, gaining maximum "lift" from the combination. Also, the 110% Yankee and 75% staysail combination outperformed our 180% asymetrical spinnaker from 0 to 15 knots.

The results are undeniable, since we won second place in our division, only 8 minutes behind the leader after 7+ days and 750 miles of sailing.

Captain Rich

MikeJohns

11-19-2004, 05:22 AM

to imply that racing rules is the reason cutter rigs are not used in other boats seems a bit of a stretch.

Unfortunately you seem to have missed my argument here.

One of the strongest of all trends under IRC is to optimise boats for MORE stability as the rule does not rate it.
Remember initial stability is only part of the picture but along with it you tend to get low vanishing and a high inverted stability.

Racing boats and racing skippers have relatively large experienced crews. A yacht that is "safe" with 8 experienced sailors can be a death trap for mum dad and the kids.

Look at the Fastnet investigation, read the Southampton report.
Look at the real numbers the ratios, the crews, (and the hull conditions) for the yachts that founderd only then can you make a proper engineering analysis.

Heavier comfortable boats are much easier on smaller crews. Exhaustion and seasickness are the real enemies for a small crew in heavy weather.
Easily handled sail setups like the cutter rig have good functionality on these sorts of boats. They are not so good on a racing boat, for a number of reasons. That doesn't mean they are a poor option on other vessels.

Since much of this is an off theme debate we can discuss this later in a new thread. Please join .

249

11-20-2004, 04:31 AM

Mike, just quicly;

"Look at the Fastnet investigation"- done it.

"read the Southampton report."- I've read the available info.

"Look at the real numbers the ratios, the crews, (and the hull conditions) for the yachts that founderd only then can you make a proper engineering analysis."

Done it; as in, I was there for many days of the Hobart inquest.

"Heavier comfortable boats are much easier on smaller crews. Exhaustion and seasickness are the real enemies for a small crew in heavy weather."

As one of the most experienced Sydney-Hobart skipper of all mentioned, light boats get their faster and are therefore often LESS wearing on crews.

I'm sorry, but I find it very hard to tell someone who started sailing with a long-keeled Robb design, competed (and was on the winning team) in the '79 Fastnet, did the '70, '77, '84, '91 and '98 Hobart, did many others and won several times, has sailed S&S, Lexcen, Peterson, Frers, Robb, Farr, Cole, etc designs that he is wrong, when he tells me that the modern boats are just as good.

I don't find heavy boats comfortable because the gear is correspondingly heavier. I agree that many modern boats have very tiring motion (modern IMS boats are horrific, much worse than IOR boats because of their higher stability and different bow shapes. I find light boats with medium width sterns and seakindly hulls and medium weight concentration to be so far ahead FOR MY PERSONAL PREFERENCE IN COMFORT that it's no contest (even compared to one of S & S's greatest heavy displacement designs).

I also find (like the most experienced of all Sydney-Hobart owner/skippers, who sails his own boat back short or singlehanded across the Strait) that the modern fractional rig is incredibly easy to handle. You can go from 0-20 knots+ wind without changing sails; just wind on the backstay and adjust the traveller, mainsheet and jib leads. As one of the few offshore owners who runs his own foredeck, I'd go for a fractional every time, and every time I do an overnighter singlehanded I bless my fractional rig and its adjustability.

MikeJohns

11-20-2004, 06:18 AM

Dear Guest 249

So have I. Our interpretations are very different.

I consider that vessel accelerations, roll inertia, stability, broaching tendancy and structural durability to be important and weighty consideratoins in 'seaworthy' design.

Interstingly There are a few engineers and others who were not happy with the outcomes after the Hobart inquiry. Some felt that the boat designs were the main issues, and that the screening for unseaworthy boats is inadequate.

I always find it easier and safer to single hand a heavy displacement boat simply because of the more stable deck particularly working at or fwd of the mast.

As for your personal pref. Consider that your threshold for malaise may be well above that of most others.

A cutter rig with a self tacking boomed staysail and a furling outer jib may suprise you with its ease versatility and performance on a heavy cruising boat if you ever try such a vessel.

I could sell you some plans for a 56foot medium heavy cutter rigged ketch that would delight your wife (presumption) and keep her aboard on long passages! It is designed to be very seakindly and safe. You wouldn't want to race it but!

You still haven't joined ?

Cheers

249

11-21-2004, 03:15 AM

Yep Mike, I think there is a tremendous amount of personal variation in likes and dislikes. I can certainly understand people who don't like the sort of boat that I like, and vice versa. I just get antsy when people seem to say that what THEY like is the ONLY way to go.

I've done a couple of Sydney-Noumea or Noumea-Sydney runs/races on heavy displacement long keelers, one a cutter and one a cutter-rigged ketch. I can understand that some people like them, but they're not for me.

My girlfriend did the Tornado cat worlds 18 months after she started sailing....she is more of a speed demon than I am, so when we go cruising it will either be a superannuated Farr, a heavily reworked old Spencer 45 or 40, or a multi. If I did get a new boat built, it would certainly have a self tacker and perhaps boom on the jib (my brother's 38' cat has one, it's brilliant and I've experimented with one on my own boat but I lack the deck space on a 28'er). One of my racing boats has a self tacker and it's a gem. I used to race a 30' JOGgie with a self tacker and it too was great. Allied with a bendy mast, you never changed sails but never got bored. I often sail my own boat under main alone or with the No 3 which requires about 12" of sheet trim when tacking. Soooo much better than a big genny.

The 38' cat is a lightweight cruiser with wishbone main. The rig design means that there is very little extra gear as a result of the cutter rig, and being intrinsically a very fast boat (he's a former multiple dinghy champ in some of the hottest classes) used for liveaboard family cruising, the boat spends much of its time "throttled back" under staysail. For that, it's a brilliant setup.

Looking back, I realise that I got distracted by the arguments about light displacement boats and rating rules. I apologise. The initial thread was also about speed and pointing; I still reckon a cutter is not as high and fast but it does make a brilliant cruising rig in some ways.

Haven't joined 'cause I've forgotten my password!

RKennedy

11-21-2004, 03:51 PM

Hello

I love cutter rigged sailboats. Just why they point so well I think has various reasons. Smaller sails give better sail shapes on big boats with far less stretch. I suspect that the two sails give a more linear flow in the slot. The outer jib can often be sheeted in pretty hard on the wind without backwinding the mainsail luff even when its overlapping a fair bit.
There are huge variations inthe cutter rig and there is not much mention here of all the different options.

On the seaworthy boat and racing rules issue this man Mr Johns is voicing some wisdom here.

Opinions from people (experienced or not) are always available and always free. I usually find that the opinions of a racing yacht man will be (and appear in these postings) flavoured with a strong predudice towards racing boats. Ratonalisation of strongly held viewpoints based on opinions and flawed or incomplete observations leads to misinformation. Mr Johns is right in that the science and the numbers give us the truth. Passing on other peoples opinions is not the path to knowledge.

Having voyaged extensively myself (I am now 71) on many different craft in many different weathers I would like to make some observations and yes before you say it, these are my opinions .

I would say that the cutter rig is very versatile indeed on any platform, that it points well.
The 3/4 rig is very similar to the cutter under staysail alone. I see the yankee on a 3/4 often gets replaced by a masthead asymetric spinnaker these days so they are not so very different.

At my age a heavier more comfortable boat is nice. My wife and I now own a big comfortable ketch of 36 Tons that we often sail on long coastal passages just like Arthur Beiser in Minots Light with just my 14 yr old grandson. (It's cutter rigged and most everything furls ) For the number men its displacement to length ratio is 350, I would not go back to a lighter boat now and I think many die hard racing boat men miss out on the true joy of long term relaxed sailing.

We have had various racing yachts of differing designs and sizes none of them were as comfortable or dare I say as easy to sail shorthanded as our current boat when the glass drops. I have strong high solid safety rails, I own and often don, but never need to clip on my harness because the motion is slow enough for me to safely keep my feet . As the man says we Squish much more gently through the waves. Our boat is beautifully designed for comfort and performance, this is possible. There are a few yacht designers who can achieve this balance for a truely good cruising boat, but they have to look beyond the cruiser-racer cross breed.

I have finished with racing boats they do not make good cruising boats. But we still manage to race a few freindly duels we just don't win.

I saw the argument in this discussion that fast yachts are less tiring on their crew because they get there faster. This is racing talk. For cruising its just plain old hogwash.

I would like to liken boats to vehicles, a comfortable touring vehicle can be driven for days in comfort. Try it in a motor bike and sidecar, sure its fast and highway worthy but would you want to sit on it for 3 months and carry all your gear for the trip?

So I reckon as you get older you will get more conservative in your boat performance. As I once read on a Gravestone in Dunedin New Zealand where we had once made landfall. "Prepare yourself to follow me".

God Bless
R Kennedy

249

11-21-2004, 10:58 PM

"I usually find that the opinions of a racing yacht man will be (and appear in these postings) flavoured with a strong predudice towards racing boats."

But surely one could just as validly say "I usually find that the opinions of a racing yacht man will be flavoured with a strong prejudice towards cruising boats"????

"Ratonalisation of strongly held viewpoints based on opinions and flawed or incomplete observations leads to misinformation.....'

Hmm, OK, so we cannot have opinions?? Do you seriously believe people can know anything about a subject and NOT have opinions?

And how can you say that those who disagree you have "flawed or incomplete observations"? For example, material to which I referred came to me directly from two of the world's most experienced offshore racers. So how can you say that it is "flawed or incomplete"? Are you saying that men who have done some of the world's toughest races, where 9 and 6 other sailors died, have only "incomplete observations"? One was a world champion, both have been sailing offshore almost continually since the 1960s - their 40 years experience, with some 70,000 miles (just counting their Sydney-Hobarts, not the numerous Fastnets and ACs (including victories) and 1080 nm Noumea races and 1500 mile Suva races etc) experience is not enough observation for you?

"Passing on other peoples opinions is not the path to knowledge."

But logically, we can't apply that - because it is merely your opinion. I can't logically apply your opinion that we can't apply other people's opinion....it's totally circular reasoning.

And surely, passing on other people's hard won knowledge IS a path to knowledge. As Newton said, he saw further by standing on the shoulders of giants.

If I was not to listen to the hard-won experience of people who have sailed around the world, I would surely be unspeakably arrogant, would I not?

So by your ideals, I could not heed Olin Stephens' remarks about yacht design; I could not live to the ideals of Socrates or JS Mills, or anyone else as they were basically merely opinions; I couldn't pass on what classical musicians tell me of their favourite symphonies; I could not ask a leading structural engineer about stresses; I could not ask (say) Tiger Woods about what he thinks to be the elements of the perfect golf swing; I couldn't ask an America's Cup leading light what he thinks about sail design. In fact I could learn nothing that I did not experience myself. That would be a poor sort of life, wouldn't it? A stunted, blinded existence bounded only by what we can see and touch.

"Mr Johns is right in that the science and the numbers give us the truth."

What science? What numbers? The science has many different aspects and theories in competition.

For example, the science has always said that inverted stability is affected by the volume of a coachroof. But test-tank trials by Martin Renilson of the AMC, conducted after the '98 Hobart, demonstrated that in fact it had no effect.

So whose science do we believe? Who has the right numbers? Southampton or AMC? How can we fnd out? In fact because you say we can't get opinions passed from other people, we can't even ask independent experts which view they favour.

And putting your faith in science will lead us directly AGAINST your view that cutters are better upwind. The most advanced science in sailing comes from America's Cup derived tank tests, wind tunnel tests and VPPs. These are incredibly powerful tools - and they do NOT lead designers to use cutter rigs in their designs for offshore racers (despite the fact that the extra sail area if free or almost free).

So the science and numbers are clear - cutters are not as effective upwind. You can't have it both ways can you?

249

11-21-2004, 10:59 PM

Sorry, first sentence should have read "but surely the opinions of a cruising yacht man will be flavoured with a strong prejudice towards cruising boats".

B. Hamm

11-22-2004, 04:17 AM

We can point higher (10+ degress) and sail faster in light winds (up to 80% of true wind speed!), after converting our O'Day 37 to the cutter rig version. I fly a 110% high clewed Yankee and 75% Staysail.

Can anyone explain this phenomenon or share their similar experiences?

Technically it's still not a cutter, it's a sloop with two headsails. Having two (or more) headsails does not make the rig a cutter alone. The mast would have to be moved aft to near the mid point of the boat to make it a true cutter.

Bill H.

B. Hamm

11-22-2004, 04:19 AM

When power was limited aircraft were bi planes or even tri planes.

A large amount of work (lift) is generated by the area just behind the leading edges.

With almost 2X as long a luff the cutter does better.

And the slot accelerations of the sails do better at feeding the main.

Illingworth & Primrose ,"Offshore" or "Furthur Offshore" is still the Bible for Cutter folks not involved with go slow "racing " rules.

FAST FRED

In early days when power was limited as you mentioned, aircraft were biplanes primarily for structural reasons. Not for any interplay between the airfoils.

Bill H.

mistral

11-22-2004, 04:33 AM

Have we got some real statistics and data telling us that cutter-rigged boats point higher or is this just a chat based on a single experience????
i've always thought that cutter's biggest advantage was a better distribution of sail in rough weather, so less pitching, less heeling and overall better control of the boat, never heard about best pointing abilities, that sounds new to me!!!
Please let me understand !!!!

fair wind
Mistral

lucas adriaanse

11-22-2004, 06:00 PM

May be you did not point too high to start with. Don't know if you used the yankee on the previous rig config. But a high clewed yankee doesn't sound too much of an upwind sail, if you're looking for pointing ability. Probably the extra canvass has given you the power 'in the front' to just sail and point the boat as it would do with good genoas as well. You have probably gained the most in light airs on a slightly agitated sea, where you need some power from your foresails.
I don't know the standard O'Day 37, but might it get just too little power from her genoa ? More so from just a yankee ?

Lucas

dreamer

11-23-2004, 03:03 AM

One of the problems with modern "cutters", e.g. Island Packets, is that they are set up with a staysail set up inside a masthead genoa. In that case the staysail really just adds drag. The (upper and outer) jib needs a high cut foot in order to allow the (inner and lower) staysail to do some work.

I've always wondered about this setup. I chartered a cutter rig set up this way with the jib completely covering the staysail. In this case, it didn't seam as though the staysail was doing anything. Up or down made no difference. It sure looked cool though. ;)

Our boat is cutter rigged with a proper jib and staysail. In fact, the jib clew is so high off the deck you can't reach it once the sail is hoisted. In tandem with the staysail, performance is sweet. Here's a good shot of our headsails: http://sail2live.com/boats/sonadora/pictures/sonadora_sailing1.jpg.

We sail with all sails up to about 20kts. After that, we reef the main and sail with staysail. We've tried it with all sails up in 20kts. Fairly boisterous sailing, but not any faster/closer than with main/staysail.

One thing for sure, unless it's really blowing we avoid sailing to windward with main alone. It's anyone's guess what will happen when trying to tack.

too sweet

12-07-2004, 04:10 PM

On my island packet the difference between just the jenny and having up the staysail too is amazing. The boat points far higher and sails faster. This is mostly due to the fact that there is no slot effect otherwise though. The sheeting angle for the jenny is horrible since it has to be sheeted outside the shrouds. The shrouds are on the outside of the boat as opposed to being right next to the cabin. The staysail basicly gives the main its extra shot of energy that isnt being delivered from the jenny since its so far out. However my recent discovery to the staysails effectivenss is in vain though since i'll have j109 in a week which despite its shorter length far out performs the ocean cruiser.

FAST FRED

12-08-2004, 04:43 AM

"which despite its shorter length far out performs the ocean cruiser."

Tell us how you like the "performance" when shortning down the head sail alone offshore some night at O'dark 30 ,

when going bald headed neither the autipilot or self steering can't hold the unbalanced boat.

Cruisers are called cruisers because the design compromises favor CRUISING , over mere Flatwater "performance".

FAST FRED

SeaDrive

12-08-2004, 08:40 AM

Too Sweet, I don't understand. If the sheeting angle for the jenny is horrible without the staysail, it's still horrible with the staysail set, no? I can see that the boat might sail faster, but I don't see how it can sail higher without luffing the jenny. What have I missed?

Dreamer, I had gotten the impression from somewhere that a boat rigged like yours was more likely to have good balance with full main and topsail (yankee) than with full main and staysail. Is there a good reason not to strike the staysail as a first step in reefing? (It would go up again with reefs in the main when the yankee was struck.) Second question: what sails do you fly off the wind?

CT 249

12-09-2004, 12:46 AM

Re "Tell us how you like the "performance" when shortning down the head sail alone offshore some night at O'dark 30 ,"

If the set-up is like many modern cruiser/racer fractionals, all that involves is winding the roller furler in.

If the fractional set-up is one like mine, all that involves (for a considerable change in wind strength) is just reaching for the topmast backstay and giving it a tweak; easing a bit of tweaker to twist off the headsail; maybe bouncing a bit of runner; and easing traveller and mainsheet. Total time; 15 seconds or something. Time out of the cockpit - 0 seconds.

"when going bald headed neither the autipilot or self steering can't hold the unbalanced boat."

Why not? Lots of boats sail with very good balance under mainsail alone. Hell, anything from a Laser to a 28 footer (at least) can sail upwind and reaching with tiller fixed, if you have the boat trimmed right; that's not even using self steering.

My 4,400 lb 28'er will sail herself for years under main alone with the helm secured, upwind or reaching.

I use a headfoil and for singlehanded changes offshore at night, I'm fairly happy with it. I can get the gear on and off quickly and not stuff around on the bow.

Of course, most good fractional riggers will sail as fast and handle at least as well as many cruisers under main alone, so if things get nasty you just drop the whole jib.

sharpii2

12-09-2004, 10:48 PM

Hi everyone.

This is one of the most divergent and fracticious threads I have seen. It seems to me that it started out as a question of whether or not a cutter rig could end up pointing higher than a sloop.

Then it turned into whether light, tall, and fast racing (IMS)derived boats are A) less seaworthy, B) more seaworthy,or C) (heresey of heresies) about the same as heavier, full keeled (presumably based on older racing rules) boats.

Before I join the fray (hey. I'm from Detroit :D ) let me caution all of you on my absolute lack of credentials. First, I have never set foot in a yacht club. Second, I have never sailed beyond sight of land. And third, I have never crewed on a racing boat. The only one thing I can say in my defense is that I have read a lot. That being the flimsiest of defences, let me join the rumble.

I say a good cutter will out point a bad sloop on any day. What I mean by this, is that a sloop that has only one large head sail (redundancy for clarity ;) ) and insufficient luff tension, will have terrible trouble pointing high. It will work, of course, (like my old week ender type did) but will have to fall off a little to do so. Now. My understanding is that the required luff tension on a jib is some exponent of the length of the luff multiplied by its sail area :eek: . If that is true, the simple act of shortening the luff wire (on the inner jib, of course) as well as its smaller area may allow it to set much better than the single larger jib. The outer jib will still have the same luff length but maybe 45% less area. Not only that, but it would almost certainly be struck as soon as the wind picks up. Add to that the fact that the inner jibs center of area is now much closer to the luff of the main making it a sort of leading edge flap. It may be empowering the main more than it is getting in the way of the outer jib, thereby allowing the boat to point higher than it used to.
If, in its previous set up, the luff had higher sustainable tension, The large jib would be providing most of the drive and the main would be acting more as a spanker or a mizzen.
If such were the case and both set ups were racing one another up wind, the sloop would be the undisputed champ. Perhaps this is why masthead sloops were so popular while I was growing up. They are better up wind than any other kind of rigid rig. And, if their sail area ratio is kept within reason (about 13 to 16) and the hull is rigid enough to carry it (easy enough to arrange with heavy-light to light-moderate displacement), It can be a very sturdy rig. I read of one boat that had such a rig and was rolled several times, but never lost its mast or suffered any other significant damage to its rig or hull.
The only fractional rig I have experience with is the rigid, 3/4 kind. All the trailerable sail boats I have sailed have had such rigs. None of these boats had a back stay, so the luff on each sagged noticeably. None of them (even my beloved week ender type) pointed very well. But they pointed well enough to do their job. When I wanted to sail really close to the wind, I usually furled the jib. Doing that was also a handy way of reefing as well (which was probably why these boats were so rigged in the first place). With the jib furled, they all had adequate ballance and even good ballance if you gave the center plate lift a few turns. With one reef in the main, the ballance got even better. I sometimes refer to this type of rig as a 'two sail cutter' for this reason.

Bob

FAST FRED

12-10-2004, 05:15 AM

"and insufficient luff tension, will have terrible trouble pointing high."

Not so, the sailmaker can cut a sail that points almost as high IF he knows there is no backstay adjustment.

A properly built sail for a boat that uses less luff tension is only a sail cut modification.

I.m still waiting (40 years now ) to find a sail that works as well half rolled up as a correct sized & built hanked on sail.

0.5K to 55k and functional is a lot from one Universal window shade!.

FAST FRED

Another Novice

12-10-2004, 07:32 PM

I will likewise claim my inexperience ahead of time. I have 200,000 sea miles in as small as 30 and large over 100. I am an avid racing addict and started racing in order to extend my cruising range on the weekends. I now race more than I cruise. I have made my living at sea and now work ashore. I am still a novice without a doubt but have seen and experienced most rigs.

Personally I will never own anything else but a fractional rig "fast" boat again. I have been able to get out of a storm more quickly and have been able to avoid two hurricanes by flat out outrunning the storm. I have roler furling on my boat for cruising and when the weather gets badd offshore a roll the jib. Depower the main and never leave the cockpit. In fact with my new remote for the autopilot I don't even have to leave the dodger area if the weather is foul.

You are very correct luff tension can be accounted for however headstay sag which was spoken of as being a problem without a backstay can not be recut. Too much sag will affect pointing. Many boats I have seen that struggled with pointing usually had a 1-2 foot sag in the head stay. These boats are just not able to get the boat moving close to the wind due to the entry, forgive my lack of technical explanation but it is a very common problem I have seen many times. In fact in my own boat we were pointing 10 degrees lower than another boat we have always outpointed. The runner was brought on along with a bit of halyard and bang we started climbing up. 6 inches of head stay sag makes a huge difference.

My observation during this thread is that it is likely that if a real pointing difference was found on the new cutter type set up, it is most probably due to the smaller headsails not inducing as much sag and maybe the luff could have been a bit tighter on the genoa resulting in a little fuller entry making it easier to drive higher.

sharpii2

12-10-2004, 10:04 PM

"...I.m still waiting (40 years now ) to find a sail that works as well half rolled up as a correct sized & built hanked on sail.

0.5K to 55k and functional is a lot from one Universal window shade!..."

FAST FRED

Hi Fred

Very interesting point. Maybe thats the main vertue of a twin headsail rig. You can reduce the headsail area by either 55 or 45% by just dropping one of the sails. This can easily be acomplished without even leaving the cockpit. All that is needed is a downhaul. The 3/4 fractional sloop that I now use has one (it cost about $5). By relieving the halyard and pulling on a string, the jib comes down. Always. It may get a little wet as a fold or two may end up in the drink, but the sail area is efectively reduced 35% within a minute or two with no help from the crew.

Now back to your point. I propose a race.

Take two identical masthead sloops.
Rig one with a 120 jib (for a trully fair comparison)
and a roller furling set up. (and I mean a good one that doesn't jamb)
Rig the other one with twin jibs with a down haul only on the outer jib.
Now make them race upwind on a day when the wind strength is constantly varying from force 4 to 6 and back again.

To keep this as fair as possible, numerous such races would be needed. I would say at least seven. And the results would have to be averaged.

Now handicap in accordance with the cost of their rigs. In so doing, assume that each boat was designed originally for the rig it is wearing. (the cost of retrofitting is not counted, but the cost of extra headstays, making two sails, as well as the cost of the down haul and the roller furling gear is counted)

The winner is. The boat that delivers the most bang for the buck (or euro).

For instance. If one boat beats the other by 10%, but its rig costs, say, 13% more, it can still be considered the loser.

I would predict a close race. And I wouldn't dare predict a winner.

How about it?

Bob

mattotoole

12-10-2004, 10:15 PM

Rich,

Getting back to your original question, I think the answer is a combination of new and improved sails, retuning, and added sail area, but also the nature of that sail area.

First, of course we know what new and improved sails can do to a boat, especially these days -- your sails are not just new, but more modern. Sailmaking may have advanced more than anything else WRT to sailboats in the last 20 years.

We still don't know how your boat was tuned before. You said the Navy guys twiddled with the jib and staysail leads, moving them out to the rail. But where was your genoa lead to begin with? How straight was the headstay? Being sorted by really good sailors is always a great help.

Next, was your old genoa really an upwind sail, or compromised for reaching and roller reefing -- and therefore unable to take advantage of a tight sheeting angle anyway? I've been on plenty of boats where you could do anything you wanted with the jib lead, but the sail itself wouldn't let the boat point any higher. In that case, if there's room for a staysail to draw cleanly without interfering, it can only help.

Now the added area. IIRC the O'Day was not overcanvassed to begin with. Plus it had a relatively low-aspect rig. You've added sail area, which improves the SA/D ratio. But you've also added luff length, which I guess you could say increases the effective aspect ratio. Plus a jib has a better lift/drag ratio upwind, with no mast interfering with airflow. So besides adding sail area, you've also improved the overall lift/drag ratio.

Your cutter rig looks like it might be a hot tip for this boat. A friend of mine had one back in the 70s, and raced it extensively (PHRF). He had a full compliment of sails, including a blooper. I'll mention this discussion to him the next time we get together, and see what he says.

SeaDrive

12-11-2004, 10:34 AM

The winner is. The boat that delivers the most bang for the buck (or euro).

For instance. If one boat beats the other by 10%, but its rig costs, say, 13% more, it can still be considered the loser.

Efficiency in a rig is about more than speed per dollar, just as it is also about more than speed per square foot of sail area.

SeaDrive

12-11-2004, 10:37 AM

Not so, the sailmaker can cut a sail that points almost as high IF he knows there is no backstay adjustment.

I would change that to read "IF he knows how much the headstay will sag." The problem is that the amount of sag in a (relatively) slack headstay varies a lot, so a sail that looks good in a moderate breeze is a bag when the wind is strong and a flat sail is preferred. The reason racers do better with a tight headstay is that the sag is more nearly the same so the sail sets better, on average.

brian eiland

12-16-2004, 09:43 PM

Why does a cutter rig point higher & sail faster?

We can point higher (10+ degress) and sail faster in light winds (up to 80% of true wind speed!), after converting our O'Day 37 to the cutter rig version. I fly a 110% high clewed Yankee and 75% Staysail.

Can anyone explain this phenomenon or share their similar experiences?

Interesting observation experienced by many sailors in actual practice, particularly when the staysail was not located so close to the headsail as to effectively cut off the slot.

The jib(s) are there to divert the air that passes thru the foretriangle, creating drive. The two rigs should divert just about the same amount of air about the same amount and get about the same amount of drive.

Only partially true statement…..you haven’t accounted for the efficiency of this flow diversion. The cutter rig may perform this driving function with less overturning moment and less leeway inducement….and maybe even requiring less overall sail area.

…. but wouldn't the extra surface area of the staysail result in more lift, since there are two airfoils vs one? Does a bi-plane have more lift than a mono-wing aircraft with the same airfoil shape?

The extra staysail area will result in more lift. The bi-plane does have more lift, but not necessarily as a result of airfoil shape, it just produces more lift in a lower aspect ratio form (not as long a wing required)

The cutter rig I have found is an excellent rig.

If your yacht was designed as a cutter its mainmast will be further aft. I have found that Cutters rigged with a single headsail don't point as well to windward in a good breeze.

There are many good sailing boat configurations that are simply penalized out of existence for racing.

“Cutters rigged with a single headsail” have created an inefficient slot…..the throat of the slot is SO large at its opening and so comparatively small at its exit. I feel this is also a significant inefficiency with the std sloop rigged vessel at the lower panels of the rig. If we are assuming just horizontal air flow over the rig we see a very large receptive slot at deck levels and in these lower panel regions (ie; large distance between forestay and mast), but then necking down into a very restrictive slot between the leech of the headsail and the mast/mainsail….more on this later.

And I agree Mike, many innovations have been ‘rated’ out of existence

…. And the slot accelerations of the sails do better at feeding the main.

Not true. Exactly the same old explanation that just won’t die. The air flow in the slot is slowed. (the slot effect (http://www.boatdesign.net/forums/showpost.php?p=5685&postcount=3))

Since that time, rating rules and offshore racing sailors have tried full battens, wing masts, ketches, schooners, cat ketches, fractional rigs, long overlaps, no overlaps, unstayed rigs....to think that they are conservative and to think that racing rules are too restrictive doesn't seem right.

In fact, as far back as Uffa Fox designers have noted that there is a REDUCTION in the number of headsails (after all, if you really think that more is better you'd have a triple-headsail rig like boats of the 1920s wouldn't you?)

When you see a cutter rig upwind in the Vendee Globe, or in the really fast boats like cats etc, then there's some evidence that they are more effective.

Lets distinguish between our discussion of the pointing capabilities and the performance capabilities. The cutter rig, like the bi-plane, does possess more aerodynamic drag than the higher aspect ratio foils.

….. In that case the staysail really just adds drag. The (upper and outer) jib needs a high cut foot in order to allow the (inner and lower) staysail to do some work.

…..Given that, it's hard to see how any sail set on the forestay could be more efficient than a good genoa.

…… A well thought out cutter rig gives some options for reducing sail.

I’d say a lot of this depends on the proper separation of the headsail and staysail, and the sheeting angles and base available.

Cutter rigs remain a very good option for the larger yacht as an effective sail configuration. I would not recommend them for smaller yachts.

I would tend to agree with you there.

Maybe the reason cutter rigs can point higher - all things being equal, is that the foresail makes better use of the upwash from the staysail and main.

The single foresail is more effcient as a foil overall and so developes more drive than the cutter configuration.

So although the cutter may point higher, the sloop rig has better VMG

In a very brief statement, I think you captured the essence of it!

Sheeting Angles ? For maximum close reaching, I had the staysail sheet blocks 1/2 way between the mast and toe rail, with the Yankee sheet blocks at the toerail.

During the Bermuda Ocean Race this year, two expert sail trimmers from the Naval Academy and British Royal Navy experimented and found the staysail sheet block should be on the same toe rail track as the Yankee sheet, and at the same angle, to make them work together. Doing this made their leech parallel.

I’ve always felt this parallel leach situation was a very desirable configuration….a uniformity to the slot, vertically speaking. I seek this uniformity of both the ‘slot’ exit and entrance with my ‘aft-mast cutter/ketch’ (http://www.runningtideyachts.com/sail/). And elsewhere on this forum, aftmast (http://www.boatdesign.net/forums/showthread.php?t=623&highlight=aftmast)

The sheeting points on a cutter rig with its staysail reasonably spaced away from the headsail would very likely not end up “on the same toerail”. This would of course depend upon the cut of the two headsails. Certainly it should appear a lot easier for the sailmaker to cut the two ‘parallel’ headsails to work in harmony than the ‘triangular slot’ of the headsail/mainsail of the Bermuda rig.

And finally in the broad reaching situation, the wide sheeting base available to the multihull craft permits a larger overlapping headsail to be sheeted properly, rather than pinched in, closing up the shot and backwinding the mainsail.

Their explanation for the amazing close reaching and low wind performance of the cutter rig was it's ability to create a very smooth airflow from the headsails, over the main, gaining maximum "lift" from the combination.

This ‘combination’ of the sails is the key word. I think your combination (I fly a 110% high clewed Yankee and 75% Staysail) is the correct one for a cutter rig that utilizes a conventional mainsail. On my unconventional main-less rig I include more overlap of the two headsails as my staysail becomes my mainsail.

I love cutter-rigged sailboats. Just why they point so well I think has various reasons. Having voyaged extensively myself (I am now 71) on many different craft in many different weathers I would like to make some observations and yes before you say it, these are my opinions .

I would say that the cutter rig is very versatile indeed on any platform, that it points well.

The 3/4 rig is very similar to the cutter under staysail alone. I see the yankee on a 3/4 often gets replaced by a masthead asymmetric spinnaker these days so they are not so very different.

Interesting observations from a long time sailor.

And surely, passing on other people's hard won knowledge IS a path to knowledge. As Newton said, he saw further by standing on the shoulders of giants.

If I was not to listen to the hard-won experience of people who have sailed around the world, I would surely be unspeakably arrogant, would I not?

And putting your faith in science will lead us directly AGAINST your view that cutters are better upwind. The most advanced science in sailing comes from America's Cup derived tank tests, wind tunnel tests and VPPs. These are incredibly powerful tools - and they do NOT lead designers to use cutter rigs in their designs for offshore racers (despite the fact that the extra sail area if free or almost free).

So the science and numbers are clear - cutters are not as effective upwind. You can't have it both ways can you?

We should always be open-minded enough to factor in first-hand practical experiences in conjunction with the scientific theory.

That’s a pretty broad statement that “cutters are not as effective upwind”. Guess we would have to get into defining “effective”. Effective for the racer could be slightly different than effective for the cruiser. In this forum we’ve seen a few experienced sailors come forward with very definite experiences of pointing higher with a cutter rig. And the bonus is they did this with a lower aspect rig (or it could have been), with smaller size sails, and more versatility in the deployment of sail area. I would call this effective.

Granted there might be a higher drag associated with the cutter rig (maybe not as fast upwind), but the greater stability, and or decreased draft, etc could all be advantages for the cruising sailor.

In early days when power was limited as you mentioned, aircraft were biplanes primarily for structural reasons. Not for any interplay between the airfoils.

I don’t believe this was the inference when the bi-plane subject was brought up…..rather more lift at a lower aspect ratio.

Have we got some real statistics and data telling us that cutter-rigged boats point higher or is this just a chat based on a single experience????
I’ve always thought that cutter's biggest advantage was a better distribution of sail in rough weather, so less pitching, less heeling and overall better control of the boat, never heard about best pointing abilities, that sounds new to me!!!

I don’t think this is “chat based on a single experience”, but rather a look back thru a lot of history of sailing will bring up a VERY considerable number of such references. Besides, those other positive attributes you bring up aren’t insignificant in there ‘effectiveness’.

I've always wondered about this setup (set up with a staysail set up inside a masthead genoa). I chartered a cutter rig (?Island Packet?) set up this way with the jib completely covering the staysail. In this case, it didn't seam as though the staysail was doing anything. Up or down made no difference. It sure looked cool though.
On my Island Packet the difference between just the jenny and having up the staysail too is amazing. The boat points far higher and sails faster. This is mostly due to the fact that there is no slot effect otherwise though. The sheeting angle for the jenny is horrible since it has to be sheeted outside the shrouds. The shrouds are on the outside of the boat as opposed to being right next to the cabin. The staysail basicly gives the main its extra shot of energy that isnt being delivered from the jenny since its so far out.

Boy, here’s two conflicting views. The narrow sheeting base of the monohull, and too-close forestays could account for Dreamer’s observation…..(not sure that he was on a similar Island Packet cutter).

I would interpret Too-Sweet’s observation thusly; I believe he is of a performance vein, and thus would be dissatisfied with the ability to sheet the genoa in closer than the outer shrouds to effect pointing capability. What he experienced by inserting the staysail was creating a more uniform upwash to the genoa that allowed higher pointing by the genoa (the slot effect (http://www.boatdesign.net/forums/showthread.php?t=457&highlight=sail+aerodynamics)). If he refrained from overtightening up on the genoa, hopefully he left the slot open enough to not degrade the flow over the trailing staysail and mainsail.

Too Sweet, I don't understand. If the sheeting angle for the jenny is horrible without the staysail, it's still horrible with the staysail set, no? I can see that the boat might sail faster, but I don't see how it can sail higher without luffing the jenny. What have I missed?

Not necessarily is the sheeting angle still horrible. There is a fine line between enough slot, and not enough slot. Anyone with a rotating mast (particularly on a small cat) has experienced this phenomenon…..rotate the mast too much (in a desire to flatten the main) and you severely ‘choke off’ the slot between the jib and the main….performance drops immediately.

Simultaneously keep in mind that the trailing sail is providing the beneficial upwash to the headsail that promotes the headsail being able to point higher and drive harder (and this is true whether the trailing sail is a staysail or a mainsail). The shape of the headsail, both airfoil and entry angle are critical in meeting this extra capability to point higher. And these two features need to be accounted for under some different operating conditions between the top of, and the bottom of the sail plan. I am continuously amazed at the art of sailmaking that allows these guys to shape the headsail (fractional or masthead) and the mainsail of a sloop, to work together, considering the wind gradient and the widely divergent slot that exist in the triangular Bermuda sail plan. No doubt the shape of the genoa for a single headsailed boat should be shaped differently than one for a twin headsailed vessel. And with these different shapes there likely would exist different sheeting arrangements.

An interesting aside topic as I continue to research my twin-headsailed, mast-aft rig proposal, is that I feel a need to provide a less than optimum leading edge foil (furler foil) to the two headsails in order to defeat their extreme sensitivity to entry angle wind variations caused by the inconsistent wind and/or the inconsistent helmsman.

Next, was your old genoa really an upwind sail, or compromised for reaching and roller reefing -- and therefore unable to take advantage of a tight sheeting angle anyway? I've been on plenty of boats where you could do anything you wanted with the jib lead, but the sail itself wouldn't let the boat point any higher. In that case, if there's room for a staysail to draw cleanly without interfering, it can only help.

Now, the added area. IIRC the O'Day was not overcanvassed to begin with. Plus it had a relatively low-aspect rig. You've added sail area, which improves the SA/D ratio. But you've also added luff length, which I guess you could say increases the effective aspect ratio. Plus a jib has a better lift/drag ratio upwind, with no mast interfering with airflow. So besides adding sail area, you've also improved the overall lift/drag ratio

Good analysis

CT 249

12-17-2004, 04:19 AM

Re Brian's note re cutters pointing higher; "Interesting observation experienced by many sailors in actual practice, particularly when the staysail was not located so close to the headsail as to effectively cut off the slot."

Ummm, dunno about the number of sailors who have found a cutter rig pointing high in actual practice in a reasonable test. For example, the Whitbread Round the World winning maxi ketch Stienlager used a cutter rig BUT ONLY WHEN CLOSE REACHING. Today, researching another topic, I found an article by America's Cup winner and Olympic medallist John Bertrand, about the Peterson Admiral's Cup racer Superstar of 1977. John referred to the cutter rig as being a CLOSE REACHING RIG. It certainly was, in that style of boat; we used to use them in masthead one and two tonners in the late '70s and early '80s.

So we were NOT biased against cutter rigs. But they were NOT better upwind. They were used only for REACHING. At one time, in the very early '70s, Australian boats sometimes used cutter rig upwind, but as soon as sails improved the sloop dominated upwind.

It's fairly simple. Staysails were not rated at all under IOR. It was totally free area. So if cutter rigs were higher upwind, people would have used them. They weren't, so people didn't.

Either all of the world's best sailors were wrong, or this one case (with no controls re two-boating against another O'day, the state of tune etc) is wrong.....I know which one I'd choose, it's fairly logical.

Re "I don’t think this is “chat based on a single experience”, but rather a look back thru a lot of history of sailing will bring up a VERY considerable number of such references."

Yes, and almost alll of those references have fallen by the wayside now that modern sails and rigs have arrived. Cutter or double-head rigs were used at some times by many of the world's best ocean racers. Those sailors now use sloop rigs. Are they stupid? No.

Re "And I agree Mike, many innovations have been ‘rated’ out of existence".

Dunno....how many innovations are rated out of existence under IRC? How many are rated out of existence in the Open 60s, Mini Transats, ORMA multis. etc????

If you look at many of the innovations that were rated out under IOR, you'll see that many of them actually only produced a marginal improvement in pace, if any at all. Look at Cascade, for example. For a 37'er, it was dog slow.....it just rated like a 30. That cat ketch wasn't "rated out of existence", it was just rated properly, and Cascade and Denali and L'effraie kept on winning. Terrorist's and Hawkeye's bilgeboards were only marginally faster, if at all.

rE "Anyone with a rotating mast (particularly on a small cat) has experienced this phenomenon…..rotate the mast too much (in a desire to flatten the main) and you severely ‘choke off’ the slot between the jib and the main….performance drops immediately".

Not so; some world-class guys in some high performance small cats classes over-rotate their mast dramatically to depower; others in the same class de-rotate to depower. They often end up side-by-side around the course. We're talking guys who are top 10 in the world's most popular cat classes, here. They are NOT stuffing up.

I remain puzzled by "I would interpret Too-Sweet’s observation thusly; I believe he is of a performance vein, and thus would be dissatisfied with the ability to sheet the genoa in closer than the outer shrouds to effect pointing capability."

How could anyone expect to sheet a genoa inside the outer shrouds, unless in an extremely unusual boat?

sharpii2

12-17-2004, 09:53 PM

Efficiency in a rig is about more than speed per dollar, just as it is also about more than speed per square foot of sail area.

I couldn't agree more. If we went only by speed for dollar, I could propose a bed sheet and a broom stick for a forty footer. If it moved the boat at all, I could claim it won.

Like wise, I could put an articulating wing (ala Little Americas Cup) on the same forty footer and, with the greater performance, claim it won.(never mind the fact that it probably cost many times more than the boat and couldn't be reefed)

The forgoing are obviously ridiculous examples. But they really illustrate how silly things can get if one takes worthwhile concept too far.

In the case of the race I proposed, I do not think the results would be lopsided enough to lead to any such outrageous out come. I imagine that the two rigs would be quite comparable in price.

One would need the expensive roller gear (I have no idea how much it costs, but my guess would be a certain amount for each square foot or something like that) and two powerful winches.

The other would need: two head stays, two back set shrouds (or running back stays) to keep the inner stay tight, two jibs, and probably four winches. I don't know if four small winches cost more, the same, or less than two large ones, but I do know the extra shrouds and the exra stay as well as the chainplates for each will definately cost more.

I have a feeling that the two rigs would be within 10% of each other in cost. Maybe 15% at the most. The performance of each in varying wind strengths should pretty much cancel each other out.

In light to moderate winds, I would expect the roller reefing sloop to do better. After all, it has the one large jib. In stronger winds, I would expect the two jib rig to do better. It could drop one of its jibs and, presumably, the other would still be setting good. (as well as giving the main some slot effect help.)

The single jib, on the other hand, would by then be rolled to a small fraction of its original size and have lost most of its three dimensional shape. Its main purpose by then would be to act as windage to keep the bow from rounding up. With The weekender type that I had, I sometimes used the spool furling jib for pretty much the same purpose. I used it mainly to backwind the bow over when changing tacks. My light beamy cenerboarder just didn't have enough momentum to come about reliably in strong winds and a chop.

That being said, wouldn't it be nice to know if one rig had a definate cost or performance advantage over the other. What if one were slightly better than the other, but significantly more costly :cool: ?

I, for one, have never known a boat owner that didn't have to watch his wallet. If most boat owning households are anything like mine, the boat is the first thing thought about and the last thing con$idered ;) .

Bob

IOR Fan

12-17-2004, 10:03 PM

A point of interest here in ratings, IOR did allow staysails and the mighty blooper as free area. Even today the blooper is free area in many rating systems but is not seen on the course as its benefits are not great enough to justify the hassle. Staysails are allowed also free but we have very few people who use them as we have found that the speed increase is only in a very narrow wind range and direction. Specifically beam reaching and forward of the beam reaching.

My boat is close winded (24 degrees apparent) the sheeting angle is 7 degrees. It will not point higher or go faster upwind as a cutter. It is highly refined and while it is a quite old design it still points with the modern boats showing up. It would not point higher or go faster with a cutter rig, but add a staysail when we crack off to 40 degrees apparent moving the leads outboard and the boat jumps up .5 knots in speed. No doubt the cutter rig is extremely effective on a reach and has some handling advantages especially with roller furling for weather.

I do think 249 is correct it is not as effective upwind, race or cruiser doesn't matter, it is not as fast upwind. Other benefits may make it preferrable for an individual but that does not make it more effective on a point of sail.

MikeJohns

12-18-2004, 04:47 AM

I wonder if there might not be a lot of complex issues here, size of the boat, hull design, course sailed, wind strength, crew numbers, size of the sails. There are so many factors that need considering.

Consider a large cruiser short tacking to windward up a channel with a small crew ( look at the prior post by the chap Kennedy ), the cutter ( with self tacking staysl ) on a meagerly crewed heavy sailboat will outperform a single headsail and will work her way efficiently to windward (providing her Cp is not too high).
So will a 3/4 rigged racing sloop flying the appropriate sail. The racing sloop will go faster but that doesn't mean that the twin headsail is not the better rig on the cruiser.

As for IOR we saw some very odd designs under IOR, all rule cheaters but poor performers under other rating systems.
For example so many of those hulls go faster if the rule cheating scallops are smoothed out at the stern. Just a case of something that actually creates drag being worth doing because the penalty is slightly less than the rating gain. Nor was IOR (as Marchaj spent so much time pointing out) a rule that encouraged seaworthy designs.

MikeJohns

12-18-2004, 05:05 AM

For interest

Here is Wallaces "Sail Power" paragraph on 2 headed rigs.

IOR Fan

12-18-2004, 11:37 AM

Having sailed pretty much all major IOR designs from 1/4 tonners to 50's I would tend to take exception to the seaworthy comments. I have been in some of the worst sea conditions and storms on these so-called unseaworthy designs and came home everytime. What I found was the biggest issue was the loads. Because of the deep hullforms the boats did not plane and did not surf easily so when the wind increased the loads increased as the square of the wind and the loads between 20 and 30 knots were phenomenal. My current boat surfs easily and the loads are 1/4 or the loads on the old IOR boats.

When you put the boats under great load with a huge amount of sail up you find yourself in a less than stable situation. I suspect that if you put the same type of sail area up on a cruiser in 30 knots winds you would find the same type of loads and stability issues. Pushing a boat beyond its hull speed results in some abnormal behaviour.

It would seem that Wallace agrees with my assessment. The outboard sheeting angle of a cutter is the limiting factor in pointing. If you put the lead farther outboard to accomodate a staysail you harm the pointing angle.

CT 249

12-18-2004, 05:07 PM

Yep, Mike, it does seem to be very complex if you take it out of the straight context of pointing in a race.

Re "Nor was IOR (as Marchaj spent so much time pointing out) a rule that encouraged seaworthy designs."

As mentioned in another thread, I interviewed two of the world's most experienced owner/skippers of offshore racing boats. Both have been at the very front of the Australian fleet (winning Hobarts, nationals, representing in the Admiral's Cup and Kenwood etc) almost since the days when they had their first RORC heavyweight long keelers in the '60s; one a steel Halvorsen Freya type, the other a carvel planked Arthur Robb Lion. At least one (and I think both) did the '79 Fastnet, both (IIRC) did almost all of the bad Hobarts for the past 30 years.

Both went through heavy S&S designs of the late '60s/early '70s; into the Peterson/Frers masthead IOR days; to lightweight exotic hull fractionals by Farr and Dubois; into the IMS period with Farr and MBD designs. Both say that there was no great loss of seaworthiness and (in some ways) seakindliness through this period.

Many of the veteran boats that turn up for just about every Hobart are old IOR battlewagons, they got through the '98 and other races with no problems. When I hear names like Syd Fisher and Lou Abrahams tell me that their IOR boats were just aboout as seaworthy as their old RORC racers and their IMS boats, I have to say I give that more credence than I give Marchaj and his calculator and test tank.

Perhaps the best summation came from Lou. He said that his 42' masthead S&S boat was turned from a nice boat into a bit of a pig in some situations, when she was modified. Later, his Dubois one tonner was turned into a really good boat with modifications. I think the same thing happened to his Sydney/BH 41. As he says, it's not the TYPE of boat; it's how good an example the boat is of its type, and (perhaps even more importantly) fairly minor alterations (boom length, rudder configuration, ballasting) can make enormous differences one way or the other.

Re bumps. Yep, they seem silly and I'm glad my RORC boat doesn't have them. But any rule brings in various problems. Many RORC boats had very pinched sterns, and some (Rainbow II IIRC) had steel decks nailed over wood to reduce the rating (and stability). CCA boats got bad press at times. IMS boats can be a joke. International Rule metre boats were heavy, skinny half-tide rocks in my estimations.

And if you take away the rules, you end up with something like the unrestricted 18s of the 1980s; incredibly complex, incredibly expensive, hugely over-rigged, scary to sail. The same applies in many ways to the loosely-restricted 12' skiffs, and some of them apply to sportsboats. Moths have become very hard to sail, compared to the earlier Moths. Nigel Irens says the same things that happened to the 18s apply to the loosely-restricted 60' tris.

So IOR had its faults, but were they much worse than any other rule suffers under such pressure? Dunno.....

MikeJohns

12-18-2004, 09:44 PM

IOR fan
& 249

I suppose I should say that Marchaj spent so much time pointing out that the rules didn't necessarily reward seaworthy designs and at times rewarded some quite unseaworthy boats.
I agree it doesn't mean that they were all so.
But we are getting off the theme again.

mattotoole

12-19-2004, 11:21 AM

It would seem that Wallace agrees with my assessment. The outboard sheeting angle of a cutter is the limiting factor in pointing. If you put the lead farther outboard to accomodate a staysail you harm the pointing angle.

This is true, but there are other factors limiting pointing ability.

First, as I pointed out before, is the sail type. It's not fair to compare a racing genoa designed to go upwind and not really anything else, to a cruising sail designed to do everything plus roller-reef.

Second is the rest of the rig -- the mainsail, mast, rigging, etc. As an extreme example, an in-mast furling main with no roach, no shape, and a stout mast section, will limit pointing ability too. I know because I sail on a boat so equipped. It's otherwise a fast boat, but won't point because of the kind of rig ahd sails it has. Without at least a new main and some retuning it wouldn't any higher, and even then it wouldn't be much. But a staysail would make it faster without affecting its pointing ability. Most cruising boats are probably similar, including the O'Day being discussed.

Finally, there's the hull. I doubt this limits the O'Day, but so many cruising sailboats have inefficient hull shapes and keels with poor lift. Glomming on more sail makes the most of what they *can* do, because more speed generates more lift.

brian eiland

12-19-2004, 01:44 PM

Terrorist's and Hawkeye's bilgeboards were only marginally faster, if at all.

Don't know about Hawkeye, but Terrorist was significantly faster and better VMG if I remember correctly.

Brian wrote "Anyone with a rotating mast (particularly on a small cat) has experienced this phenomenon…..rotate the mast too much (in a desire to flatten the main) and you severely ‘choke off’ the slot between the jib and the main….performance drops immediately".

Not so; some world-class guys in some high performance small cats classes over-rotate their mast dramatically to depower; others in the same class de-rotate to depower. They often end up side-by-side around the course. We're talking guys who are top 10 in the world's most popular cat classes, here. They are NOT stuffing up.

The problem with correctly discussing this subject is defining the different conditions that can be present.

In some cases the diamond stays on the rotating mast are left very loose, so upon rotation the mast bows out considerably in the middle thus dragging the mainsail flatter for either depowering in heavier conditions or maintaining connected flow in light conditions For moderate wind conditions the mast would be under-rotated to give a fuller main. Notice here we are using the mast rotation to effect mainsail shape more so than as a leading edge element.

On the other hand some folks operate with tight diamonds that effect the mainsail shaping in the opposite manner. Very likely if we know it is going to be all light air sailing (racing) that day, we would opt for tight diamonds, flat mainsail, with a better leading edge to the under-rotated mast.

Next consideration would be the rotation center for the mast...where the rotation 'ball' supports the mast. If this rotation center is too far forward (towards the leading edge of the mast), then as the mast is over-rotated the slot between the jib and main is sqeezed (choked) off by the trailing edge of the mast and the jib

I remain puzzled by "I would interpret Too-Sweet’s observation thusly; I believe he is of a performance vein, and thus would be dissatisfied with the ability to sheet the genoa in closer than the outer shrouds to effect pointing capability."

How could anyone expect to sheet a genoa inside the outer shrouds, unless in an extremely unusual boat?

My mast-aft configuration is one example of an unusual boat that allows wide (or very wide) spreaders with narrower sheeting.

brian eiland

12-19-2004, 11:31 PM

Brian wrote:
I found this discussion today on the web that I took the liberty to add to this forum discussion of cutter rigs.

Raked Cutter Rig by WindSpeedYachts.com (http://www.windspeedyachts.com.au/sailing_multihulls.htm)

History.
Ever since 1851 when the Schooner America with her 11.5 degree mast rake won the America's cup, mast rake has been used to improve the performance of sail power as a propulsion method. Every high speed craft including land yachts, ice boats, windsurfers and racing Multihulls use mast rake to improve performance.
Yachts that race to a handicap don't use mast rake because it is penalized by the handicap rules. In handicap racing the fastest yacht is not the winner, the yacht that sails closest to her handicap is the winner. Our yachts are not designed to any racing rules they are designed to be safe, efficient and comfortable.
The cutter rig has historically been the rig of choice for the monohull cruising sailor.

The Modern Raked cutter Rig.
In 1991 we proudly redeveloped and introduced the modern, efficient raked cutter rig into cruising Multihulls.

The Raked Cutter Rigs features:
+A 7.5 degree mast rake, the key to the whole modern cutter rig working so well:
+Parallel fore stays for the greatest cutter effect.
+The distance between the forestays is spaced for maximum sail efficiency.
+The Jib easily tacks between the stays.
+Low aspect ratio rig to increase stability, reduce rig loads and reduce pitching.
+Low centre of gravity, low wind resistance cruising rig.
+The stay sail is close to the deck which improves efficiency and pressurizes +the windward nets and lifts the leeward nets reducing on board spray and increases stability.
+With the roller furling Jib on the composite bowsprit, which is wide enough to walk on and the fully battened stay sail on the fore beam, the fore triangle is broken into two easily handled sails.
+The large fully battened mainsail is reduced in area by the mast rake.
+This long low sail plan increases stability, reduces the sail handling effort required by the crew and off the wind increases the power to propel the yacht.

Notes
This rig is the complete opposite approach to the trend for high aspect ratio fractional rigs being installed on cruising yachts.
We have observed the trend by designers and builders to increase the height of masts to "improve performance" however we are informed by boat owners that increased speeds are achieved by reefing the mainsail. This is not surprising, tall masts raise the centre of effort of the sailplan, this increases the heeling force which pushes the leeward hull further into the water increasing hull drag. If you look into the hull shapes, for example a 12 m catamaran with fat hulls 1.2 to 1.4 m wide on the water line and fixed keels, the drag on these hulls when the leeward hull is depressed increases considerably. This type of hullshape is happy with both hulls evenly floating while motoring or sailing down wind not being pressed hard to windward or reaching.
The high aspect ratio racing rig works exceptionally well on racing yachts however it does not make slow hull shapes fast hull shapes.
How does mast rake increase yacht speed?

The more horizontal the fore stay angle the greater the vertical lift generated by the jib. Effectively lifting the bows which reduces the yachts displacement which reduces wave drag and increases the yachts speed. Raking the mast aft has a similar effect to fore stay angle.

With a vertical mast the forces generated by the mainsail are forward and downwards but by raking the mast aft these forces are rotated to become forward and upward resulting in increased speed due to decreased displacement.

The effect of mast rake is apparent sailing to windward but far more obvious when reaching and running.

Because the bows are not driven down by sail pressure we can use finer bows which further reduce drag and pitching.

Another advantage of mast rake is reduced pitching caused by the lack of the pendulum effect.
With a vertical mast in a sea way the masts mass and momentum forces the bows and sterns up and down alternately greatly increasing the pitching.
With a raked mast in a sea the masts mass and momentum forces are rotated to force the bows forward and the sterns up and down alternately greatly reducing the pitching.

The combined effect of the lift generated from the raked cutter rig, the lift generated from the under wing, the extra buoyancy and dynamic lift generated by the inboard flair and the stabilizing effect of the rudder mounted foil combine to reduce heeling, under wing wave impacts, yacht motion and increases average speeds.

The Raked Cutter Rig of the WindSpeed 40 has proved to achieve higher average speeds than any other rig aboard a liveaboard cruising Multihull yacht yet encountered.

Test results
Test have been undertaken on many yachts over many years but the most convincing test was aboard a 2000 kg 10 metre racing Multihull with a 15 metre rotating mast. This yacht started life with a vertical mast, and over two years the mast was raked progressively aft with consistently improving performance. The lift generated by the raked mast allowed us to carry more sail area in stronger winds off the wind and when sailing to windward, the crew of four would sit forward of the mast to keep the bows down.

On a 1.5m long radio controlled test model trimaran the mast was raked so far aft that the model capsized bow over stern from the lift generated from mast rake!

Note: We were testing the feasibility of using surface effect wings for racing trimaran beams at the time and these foils may have contributed in the capsizes [tested in 1981]

Conclusion
Our theoretical calculations and practical testing indicate that the raked cutter rig on the WindSpeed 40 generates 240 kg of vertical lift in 18 knots of apparent wind and sailing to windward at 8 knots this reduction in displacement equates to approximately 0.1 knots extra yacht speed! The lift generated by the raked cutter rig increases as the sheets are eased which increases the improvements in downwind yacht speeds

(opinions of www.windspeedyachts.com.au)

Brian added a note: It doesn't appear from their posted drawings that the mast rakes back 7.5 degrees?

Skippy

12-20-2004, 12:57 PM

The more horizontal the fore stay angle the greater the vertical lift generated by the jib. ...
With a vertical mast the forces generated by the mainsail are forward and downwards but by raking the mast aft these forces are rotated to become forward and upward resulting in increased speed due to decreased displacement.
Which as CT has pointed out, introduces stability issues, which are especially important in cruising.

And since the mast and stays are heeled leeward, the aft rake decreases sail efficiency by increasing sweep, at least for the headsails.

The effect of mast rake is apparent sailing to windward but far more obvious when reaching and running.
Should that be "effect" or "benefit"? It sounds like the design is marketed to customers who respond to the idea of zipping back & forth on a reach, but may not appreciate the importance of being able to point. Plus the rake looks cool, i.e. more marketing.

Ever since 1851 when the Schooner America with her 11.5 degree mast rake won the America's cup, ...
The Raked Cutter Rig of the WindSpeed 40 has proved to achieve higher average speeds than any other rig aboard a liveaboard cruising Multihull yacht yet encountered.
So do racers, but they're designed for racing.

brian eiland

12-20-2004, 01:41 PM

Skippy,
I would like to just point out that those quotes you attributed to me should be directed to WindSpeedYachts from which came the discussion on their website

Skippy

12-20-2004, 01:58 PM

those quotes you attributed to me should be directed to WindSpeedYachts from which came the discussion on their website
ok, good point. btw, their cutter doesn't sound too bad from a marketing point of view (not that I'm in that field). There seems to be a trend these days toward "traditional values", and I can see that being associated with a traditional design like the cutter.

CT 249

12-21-2004, 06:49 PM

Re "The Raked Cutter Rig of the WindSpeed 40 has proved to achieve higher average speeds than any other rig aboard a liveaboard cruising Multihull yacht yet encountered."

Where's the proof?

Paul B

12-21-2004, 07:02 PM

You're asking for reality from the people who wrote that? Also from the text:

"Yachts that race to a handicap don't use mast rake because it is penalized by the handicap rules."

Wha?

The simple answer to the original question, "Why does a cutter rig point higher and sail faster?" is:

It doesn't (compared to a sloop rig).

FAST FRED

12-22-2004, 05:07 AM

On older boats the mast was raked so the weight of the tree would tighten the forestay.

With great backstay adjusters avilable , and metal rigging that stretches less than hemp , why bothjer EXCEPT for marketing?

FAST FRED

Are U serious?

12-23-2004, 10:51 PM

gybeset

02-01-2005, 04:44 PM

Quote: Originally Posted by FAST FRED
On older boats the mast was raked so the weight of the tree would tighten the forestay.

With great backstay adjusters avilable , and metal rigging that stretches less than hemp , why bothjer EXCEPT for marketing?

FAST FRED

Are U serious? says
Kidding right?

Maayyyteeee . we are serious, real question is Are U

No we are not kidding, Fast fred is on right track right, to keep headstay tight with timber mast , stretchy halyards , shrouds running stays , no powerful modern winches to tension jib halyards or runners ( Yo! 8" self Fabr. Highfield levers)
would be impossible on an Upright stick, looks at any old 18 footer, sandbagger type , bermuda dinghy or schooner of the day, rake is faster and still is in a few specific cases (Contender, Hobie 16,49er)

go do a real sail apprenticeship on overcanvassed antipodean skiffs ( that is including setting up and tuning) and find out , then U B serious

dionysis

02-01-2005, 06:09 PM

skinny boy

02-01-2005, 06:44 PM

Remember that aerodynamically, rake reduces forward thrust as the cosine of the angle. This leads to proportionately less sail drive in the most effective forward direction, which in turn reduces pointing.

This may be the major reason why racing boats tend to make their masts and forestays as vertical as possible.

Ah, most racing boats I know have rake and pre-bend making them anything but vertical. The fastest boats around these parts have more rake than the others like it. My rig carries a couple of degrees of rake and used to have more until I got my new sails. Pulling the mast back a bit increases my boat's pointing ability and every other boat I have been on. Standing the rig up even leaning it forward a bit helps off the wind to project more area.

brian eiland

02-01-2005, 09:13 PM

I think you will find that mast rake is used quite effectively in a great number of vessels. On small cats such as Hobie, Prindle, Tornado, etc, it allowed for higher pointing upwind, and reduced bow burying upon fast tacking downwind.

I've not had any ice boat experience but I would venture to guess they incorporate mast rake as well..... land-sailers as well.

A visit to WB-Sails (http://www.wb-sails.fi/) and click on "News" then "European Sail Trimguide" brings up some data on mast rake.

Then have a look at http://www.curtin.edu.au/curtin/centre/amecrc/papers/prc98/ ,"the aim of this research was to determine the interaction characteristics between the main sail and the jib, particularly the influence of raking the mast aft. The motivation for this investigation came after the World Titles in Kingston, Canada where the British fleet used rigs with masts raked aft by approximately 4. The Australian fleet, which up to that point had been dominating the international scene for a number of years, was significantly slower with upright masts, particularly in light airs."

Finally, have a look at this article by Paul Bogataj, "How Sails Work", (http://www.northsailsod.com/articles/article6-1.html) and note particularly this passage about the cord line of the mainsail, "Isolated Sails: A mainsail by itself (cat rig) is tapered, but if the mast is close to vertical it is actually swept forward. Recall that sweep is measured relative to the 25% chord line, which in the case of a tapered sail on an upright mast is angled forward. In this case, the forward sweep would have somewhat of a canceling effect on the increased upwash due to taper. The actual degree of upwash depends on the magnitudes of taper, sweep, and aspect ratio (height/width) of the sail. The sail still operates in the twisted flowfield caused by the boat moving through the earth's boundary layer, so an amount of twist would be appropriate. Raking the mast back increases sweep and will cause additional upwash on the top of the sail, necessitating more twist to the sail. Genoas and jibs are very tapered and swept. Those two features, combined with the already twisted apparent wind, cause significant upwash toward the head of the sail."

dreamer

02-02-2005, 01:01 PM

Dreamer, I had gotten the impression from somewhere that a boat rigged like yours was more likely to have good balance with full main and topsail (yankee) than with full main and staysail. Is there a good reason not to strike the staysail as a first step in reefing? (It would go up again with reefs in the main when the yankee was struck.) Second question: what sails do you fly off the wind?

SeaDrive - sorry for not replying sooner (like about a month ago) ;) .

The yankee (headsail not a topsail) has a high clew and when we've tried to fly yankee / main in high winds, we heal farther than we'd like to. I'm no expert, but I suspect with the high clew the CE is higher. The staysail is obviously lower and closer to the center of the boat which seems to keep us pretty well balanced. We will (hopefully) be getting a lower clewed headsail this season. Our full keel/attached rudder is fairly forgiving in terms of balance. That just means I'm a poor resource when talking about balance. :rolleyes:

Off the wind on a dead run in 15kts or up we just fly the main. If it's light, we won't try a dead run and will sail with all sails on a broad reach. This is where this setup really seems to make a difference. From about 2-3 kts up to about 15 kts on a broad reach I'm surprised at how well the sail combination works. I suppose it would be nice to have a 130 or possibly an asymmetrical for light air, but we're lazy and keeping a spinnaker full sounds like too much frustration in light air.

You can see our optimal sailing orientation in the link

http://www.sail2live.com/boats/sonadora/pictures/sonadora_sailing1.jpg

In this pic, we're heading due South. Wind's coming from slightly North of West if not straight form the West at around 15kts I believe and I'd say we're healing about 10 degrees. If I could choose the perfect way to sail around the world, this would be it! :)

Fair Winds,

Rick

SeaDrive

02-02-2005, 03:09 PM

... rake is faster and still is in a few specific cases (Contender, Hobie 16,49er)

I doubt the weight of the light masts is a factor in these boats. More important would be that the smaller angle between stay and mast increases the tension due to the pull of the leech and mainsheet.

dreamer: Thanks for the explanation and the picture. I suspect the fastest way to get your boat downwind would be with a convertional spinnaker, but it seems clear you don't want the trouble. Neither would I. Cruisers don't need to race. Beautiful boat.

MikeJohns

02-02-2005, 08:50 PM

Remember that aerodynamically, rake reduces forward thrust as the cosine of the angle.

The reduction factor will be a factor of (1- [cos(rake angle)]) which doesn't amount to much, for example at 7 degrees its about 0.0075 less.

gybeset

02-07-2005, 04:17 AM

We can point higher (10+ degress) and sail faster in light winds (up to 80% of true wind speed!), after converting our O'Day 37 to the cutter rig version. I fly a 110% high clewed Yankee and 75% Staysail.

Can anyone explain this phenomenon or share their similar experiences?
http://www.freecompromo.com/challenge/image/yachtdetails72.jpg

Phenomenon could be just the word for it , seriously tho the most CURRENT opinion we could seek here (particularly for a conventional leadbelly) would be from the skippers or designers of the Global Challenge 72ft Cutters that just departed NZ for Sydney

brian eiland

02-07-2005, 10:44 AM

Ah, most racing boats I know have rake and pre-bend making them anything but vertical. The fastest boats around these parts have more rake than the others like it. My rig carries a couple of degrees of rake and used to have more until I got my new sails. Pulling the mast back a bit increases my boat's pointing ability and every other boat I have been on. Standing the rig up even leaning it forward a bit helps off the wind to project more area.

How about this sampling from Ron Holland.

Alan Hugenot

02-08-2005, 12:54 PM

The answer to the original question of why will a cutter points higher than a sloop used to be common knowledge, normally acquired in the first year at sea by every working sailor.

Sometimes we all make the mistake of thinking that what we know is all there is to know. But, the truth is that racing sail has become so narrowly sloop oriented that the collective wisdom of the "powers that be" within the racing world have forgotten, or never even learned, much of what used to be common knowledge among ordinary working sailors.

Back in the days when cargo was moved by sail, no one set a Genoa nor a Spinnaker. Spinnakers are much less efficient than square sails, and Genoas are much less efficient than a schooner's "fisherman" sail. Indeed those two sloop sails are merely strange anomallies invented to help the inefficient sloop rig try to preform as well as a cutter, ketch or schooner. Actually, the only reason sloops dominate the racing circuit is because they are easier to understand, cheaper to build, and novice sailors can master their simplicity sooner, so there are today thousands of sloops and very few cutters, ketches, and schooners (I left Yawls out of the list because they are merely sloops with a mizzen tacked on).

Just 100 years ago the great ocean cargo ships, dependent on the wind, needed to point as high as possible and sail downwind as fast as possible, and they all used multiple headsails. And if they had needed genoas or spinnakers they would have invented them.

Unfortunately, the experience of most racing sail participants is limited entirely to sloops racing around windward and leeward marks. They simply have no intuitive gnosis outside the sloop's foretriangle (translate "can't think outside the box")

The slot effect is a well known principle of sail dynamics. It is a simple fact that the slot formed between a jib and the mainsail improves the apparent wind for the succeeding sail, a 150% genoa elongages the slot but the overlap does not have much effect on improving the apparent wind, any more than a 100% jib. However, it does improve boat speed on a spring reach. However, a succession of several slots as in the case with multiple head sails it improves the apparent wind for each following sail, with the result that a cutter can point much higher than a sloop. Just as a sloop can point higher than a cat rigged dinghy. A staysail schooner with two flying jibs forward of the staysail can likewise point higher than a cutter. This was common knowledge of all sailors for hundreds of years. But, today it is unfortunately not known by the rules committees, all of whom have never experienced this phenomena because sailing cutter headed rigs is simply outside their experience.

a quarter century ago, I used to win every race and take the championship trophy in all the PHRF handicapped races, because there the PHRF rules did not take into account my staysail. The rule writers were simply unable to conceive that just by setting the staysail inside the genoa I had doubled my leading edge, created a second slot and improved the apparent wind angle for the main. I checked the PHRM No FLying Sail rule, and it still allows me to fly a staysail inside the jib with no penalty, so long as my vessel is normally rigged with a permanent stay for the staysail. This also allows me to rig the staysail inside my downwind spinnaker on a spinnaker reach, instead of carrying an asymetrical tri-radial. This improves my boat speed by around 50% on that reach, and while my fellow competitors are penalized for carrying their tri-radials, I am not. They end up owing me time, when I have the clearly faster boat.

The fact that multiple head sails allow a boat to point higher was common knowledge among working sailors who sailed their ships every day with no engines and lived aboard year round. Today, most racing sailors are lucky to get four days of sailing in per month for 9 months of the year. Which only amounts to 36 days a year, so it takes them 12 years to acquire the experience in sail that any apprentice deck hand would pick up in one year sailing a ship at sea. Yet, today most of our sailing instructors become certified "experts" with less than three years of part time sailing behind them. Consequently, since the teachers don't know about multiple head sails, improved apparent wind, slot effects and increased leading edge, how can we expect the students to know about such things.

To me it is amazing that experienced folks from racing sail, will question these long proven physical principles, simply because it is outside their experience. And, yet they won't take the time to research the subject which their avocation depends upon, even though they can find time to watch the super bowl. Instead they accept the "received" wisdom on the docks, which is that the sloop is the finest possible rig for racing sail. Have they also forgotten that the original Yacht "America", which was designed for speed, and which took the America's cup home to the New York Yacht Club was a cutter headed schooner? They probably did not realize that the ownere had experimented with several other rigs on this hull before desciding that a cutter headed schooner rig was fastest?

Alan Hugenot
Naval Architect & Licensed Master in Sail
Retired Collegiate Racing Sail Coach
Certified Coastal Cruising Instructor A.S.A.

dreamer

02-08-2005, 01:13 PM

yeah! :D

wow, that was great and it really helps explain why our boat was not as much of a dog as I expected it to be. Even Bob Perry poo-pooed the cutter rig on our boat (his design). But I think he too, as the others you mentioned, may have simply forgotten what a great combination these sails are.

I suspect you hit the #1 reason why sloops dominate: ease of use. I've had seasoned sailors (well, at least 72 days of sailing ;) ) on our boat and they were confused by the whole thing. I would suspect that a racing crew would see the extra set of lines a nuisance.

http://www.sail2live.com/boats/sonadora/pictures/sonadora_sailing1-small.jpg

amolitor

02-08-2005, 01:16 PM

Then why do windsurfers (cat rigged, note) point higher than just about anything else?

Also, if someone could explain current thinking on 'slot effect' I'd appreciate it. It's my impression that the theories of 20 years ago on it have been pretty thoroughly debunked, and that there are now new theories about it. I didn't really understand either one, so I don't know which is which ;)

dreamer

02-08-2005, 03:29 PM

Windsurfer doesn't count...not a displacement hull. C,E, and M scows can also point higher. Again, not a displacement hull.

gggGuest

02-08-2005, 04:50 PM

> Just 100 years ago the great ocean cargo ships, dependent on the wind, needed to
> point as high as possible and sail downwind as fast as possible, and they all used
> multiple headsails. And if they had needed genoas or spinnakers they would have
> invented them

You don't think the limitations of the materials and equipment they had might just have been a very small factor in this?

amolitor

02-08-2005, 05:38 PM

Could you explain why non-displacement hulls don't count?

Cat rigs have the property that you can sheet them clean across the boat. Sloops and cutters can't bring the headsail(s) in even to the mast. On a cat rig, if you've got sail shape to keep the lift forward of the beam, and enough fin/keel in the water to keep you from crabbing too much, you can point like crazy.

The only relevance of non-displacement hulls that I can see if that they go fast, so your fin(s) can generate tons of lift without stalling.

Anyways, still not seeing any credible argument that cutter rigs inherently point higher than sloops, and I am nearly certain that cat rigs "inherently point higher" than either of the others, whatever that means. They're less efficient, so aren't as good at anything else.

Richard Petersen

02-08-2005, 05:39 PM

They ran out of time. Steam powered boats were begining to appear on the ocean. Hi-tech of the day did them in. What is the speed of the Tall Ships in the present day?

CT 249

02-08-2005, 06:11 PM

"the truth is that racing sail has become so narrowly sloop oriented that the collective wisdom of the "powers that be" within the racing world have forgotten, or never even learned, much of what used to be common knowledge among ordinary working sailors."

I beg to differ, because your facts are wrong. The twin-headsail rig was used commonly in the '70s FOR CLOSE REACHING. Sailors like Dennis Connor and John Bertrand used them BUT ONLY FOR CLOSE REACHING. They were perfectly aware of twin headsail rigs but they knew they were not as effective upwind.

In the late '60s/very early '70s twin head rigs were used upwind in heavy air in Australia, but as soon as sailcloth improved and larger single headsails could be built and retain their shape, the twin head rig was relegated to reaching.

Later, the Whitbread maxi ketch Stienlager set twin headsails, main, mizzen and mizzen staysail so they were completely aware of importance of the slots, as was Farr who designed it and remains the top designer in the world. Yes Stienlager used them only FOR CLOSE REACHING, not upwind.

Almost every good middle-aged offshore sailor has had experience with twin headsails, thanks very much. The skippers of many of Australia's top boats (Ragamuffin, Challenge) were leaders in the twin headsail area; they know about it very well.

Nigel Irens is very innovative and very aware of older craft, hence his designs for gaff and lugger styles (which he sails himself). His tris are not constrained by rules yet they are sloops. Why? 'Cause it's faster.

"those two sloop sails are merely strange anomallies invented to help the inefficient sloop rig try to preform as well as a cutter, ketch or schooner."

So why did old rules like the CCA have a rig allowance that rated a schooner rig as something like 90% of a sloop, and a ketch about 94% of a sloop?

Why do current rules give much lower ratings to ketches, yawls and schooners? The IOR Mk IIII rated the mizzen at only 1/3rd of its actual area (Shape f Speed p 267 and many, many other sources) and did not count mizzen staysails at all. Mk IIIA had even "cheaper" sail area in the mizzen.

So the IOR rated a ketch with about 1000 ft of upwind sail at about the same as a sloop with 866 ft2, YET THE SLOOPS WERE NORMALLY FASTER...lots of people in '88/'90 looked at doing ketches for short courses because of this favourable treatment - yet they only worked in the Whitbread when other factors (machine measurement, Mk IIIA and heavy boats etc) also had major effects.

Lots of people looked long and hard at ketches at that time but they realised that EVEN WITH FREE SAIL AREA they were slower around most courses.

"Actually, the only reason sloops dominate the racing circuit is because they are easier to understand, cheaper to build, and novice sailors can master their simplicity sooner"

What? Pros race winged and canting keel water ballasted carbon fibre boats with Code Os and runners and they are worried about simplicity? Yeah, right.....

So why don't cat rigs rule, by the way?

"Just 100 years ago the great ocean cargo ships, dependent on the wind, needed to point as high as possible and sail downwind as fast as possible, and they all used multiple headsails. And if they had needed genoas or spinnakers they would have invented them."

And just 100 years ago the great steam ships and railway engines needed to develop as much power and speed as possible when hauling trains and cargo, and they used steam reciprocating engines. And if they had needed turbines, diesels and electricity, they would have invented them.

No, Uffa Fox and other contemporary accounts record that as sailmaking technology advanced, the number of headsails was reduced because one big sail was faster. Look at the J class and you'll see the number of headsails was reduced from 3 to 1 as sailmaking improved. It's damn simple, it's there in the pics and the plans.

The reason for multiple headsails is well known - those sails are terribly heavy and hard to handle and there's no way the comparatively small crews could have set and worked a single massive headsail.

"Unfortunately, the experience of most racing sail participants is limited entirely to sloops racing around windward and leeward marks. They simply have no intuitive gnosis outside the sloop's foretriangle (translate "can't think outside the box")"

It depends where you come from. Some of us have raced gaff ketches, sailed schooners, etc. Many of the top skiff sailors regularly race the old gaff skiffs. Some of us race long distance. Most of the top Australian big-boat owners have experience in other rigs (at least one sails a gaffer, one formerly owned the 23 metre Cambria which started off life as a multiple headsail boat and was for a long time a ketch) yet they all sail sloops. Why? "Cause it's faster.

For a start, the most common boats sailed by top-level sailors are the Optimist (sprit cat) and the Laser (cat). This is demonstrated by records on the Oppie site and other places. So once again your facts are wrong.

"The slot effect is a well known principle of sail dynamics. It is a simple fact that the slot formed between a jib and the mainsail improves the apparent wind for the succeeding sail, '

Hmmm, ask Arvel Gentry about that one.

"Today, most racing sailors are lucky to get four days of sailing in per month for 9 months of the year. "

But what about those who sail 300+ days per year while in AC and Volvo and other campaigns? The ones who I know who do such sailing are well in touch with their heritage; the family spe******es in rebuilding classic boats when not sailing in things like the Olympics and AC. Yet they sail sloops, racing and cruising...

"Have they also forgotten that the original Yacht "America", which was designed for speed, and which took the America's cup home to the New York Yacht Club was a cutter headed schooner?"

Yes, and that was in the 19th century. Saying that we shoould still look to "America" for our designs is like saying that the current Mercedes Formula 1 team should look to Benz' 19th century car for design clues, or that modern aircraft should be a biplane because biplanes dominated early flying.

"They probably did not realize that the ownere had experimented with several other rigs on this hull before desciding that a cutter headed schooner rig was fastest?"

Well, that's fairly well hidden history AFAIK. Can you provide sources?

"America" did not actually beat one of the syndicate's previous boats as demanded before the full price was paid. In fact, IIRC, Steer WAS paid the full price - but I think the cutter "Magic" (oowned by Stephens, syndicate head) beat America in NY tests. In the actual AC itself, the little cutter Aurora (much smaller boat) came home fast and would have beaten America under any rating system - but it was merely first home for hte Cup.

Why not read Alf Loomis' 1940s book "Ocean Racing" and read how the Malabars and other schooners, despite their low rating, were defeated by the sloops and yawls as ocean racing developed?

Richard Petersen

02-08-2005, 06:37 PM

Multiple sails are -were a fact then, because getting the goods to port safely after being demasted in a storm, was most important. Lose sails, still have 2 or 3 to make port. Same for warships then. Racing has few restraints.--------------I remember also about the selection of America over a better boat.

brian eiland

02-08-2005, 07:00 PM

...Also, if someone could explain current thinking on 'slot effect' I'd appreciate it. It's my impression that the theories of 20 years ago on it have been pretty thoroughly debunked, and that there are now new theories about it. I didn't really understand either one, so I don't know which is which ;)

Have a look here using the 'search tool' for this forum (handy item!)
Sail Aerodynamics and the Slot Effect (http://www.boatdesign.net/forums/showthread.php?t=457&page=1&pp=15&highlight=slot+effect)

amolitor

02-08-2005, 07:06 PM

Yeah, I re-read THIS thread and found an earlier cite of THAT thread and read it. Alas, after I posted here ;)

Thanks!

CT 249

02-08-2005, 08:13 PM

Thanks for that Brian, I've only got Arvel's stuff on hard copy.

Mr Hugenot, the url Brian gave provides the perfect answer for the reason that, as you put it, rules committees no longer know about the slot effect and acceleration; it's because the accelerated flow doesn't exist. Criticising committees for not knowing about accelerated flow through the slot is like dissing them because they don't believe in the Easter Bunny.

The knowledge that you claim generations of sailors to have had is incorrect. The flow is SLOWED between the sails, as proven by modern aerodynamic testing.

brian eiland

02-08-2005, 08:50 PM

Thanks for that Brian, I've only got Arvel's stuff on hard copy.
The knowledge that you claim generations of sailors to have had is incorrect. The flow is SLOWED between the sails, as proven by modern aerodynamic testing.

Here's another reference to Arvel Gentry's work that I had put on my website, but its a little more difficult to understand http://www.runningtideyachts.com/articles/SailScience1.html

A better explaination of sail aerodynamics can be found here by Paul Bogataj http://www.northsailsod.com/articles/article6.html It is well worth the little inconvience of registering for the PDF file. In fact I would suggest one download it and make a copy to read.

I can't totally fault Alan Hugenot. While he mixed the 'succeeding sails' explaination up , I've actually made that mistake myself when I was writting a posting ...sort of reversed the order. The point is I do not think many modern sailors realize the correct explanation for the slot effect, nor its implications in making a very powerful sail out of the headsail(s)...considerable more than the mainsail. And I still believe that the sloop configuration with its uneven (triangular) slot between the headsail and the mainsail has some considerable improvements that might be made.

And cat rigged boats do not outpoint a headsailed boat. Ask Mr Hall at Hall spars. And I've seen what a mizzen staysail can do for a ketch rig on a Morgan OutIsland.

gybeset

02-08-2005, 09:06 PM

"They ran out of time. Steam powered boats were begining to appear on the ocean. Hi-tech of the day did them in. What is the speed of the Tall Ships in the present day?"

damn those modern 'canting keel" raceyachts that run diesels to tack etc, can we regulate them to STEAM, may help prove a point that there NOT sailing anymore !!!!!

amolitor

02-08-2005, 10:15 PM

> And cat rigged boats do not outpoint a headsailed boat. Ask Mr Hall at Hall spars.

I should have qualified that, I think. I certainly don't mean that if you simply rip the headsail off a sloop it points better!

It's possible that something like this is true: When all design stops are pulled out, and you're building a sail-powered devices for no purpose except to point as high as possible, you'll do better with 1 sail than with more than 1.

But before I get much further, let me confirm whether or not it's TRUE that windsurfers do in fact point higher than just about anything? I have certainly heard this to be true, but I'm no windsurfer, and I've not paid much attention to them.

Alan Hugenot

02-08-2005, 11:13 PM

Dreamer:

Cutters are great preformers. That multiple slot allows you to ghost along in very light airs. A schooner, which can rig numerous slots can actually move along at 50% faster than a sloop in light airs. For example, picture two vessels with a waterline of 45 feet, one is a sloop and one is a schooner. If the schooner skipper is experienced and well versed in apparent wind, sail dynamics and proper sail trim, he can get his schooner up to hull speed on a reach in a 10 knot breeze. That means that he will be bowling along at 8 to 9 knots, while a perfectly trimmed sloop in the same breeze will be unable to develop enough horsepower to keep above 6 knots on the same reach. That three knots is a 50% increase.

That schooner will simply be using the multiplying effect of the multiple head sails to achieve sufficient horsepower to push along at hull speed. Similarly, your cutter will experience about a 25 to 30% better efficiency than a sloop when reaching along in light airs.

Unfortunately, this advantage disappears as the wind reaches 20 knots when all the hulls can acheive maximum horsepower, even without the slot effect.

Again, the sloop sailors only like to race in strong breezes and tend to call the race if the wind does not reach eight knots. But, you will find that your cutter will kick along at 3 knots in a 4 knot air.

I operated a traditional gaff ketch with a 45 ft waterline for many years and waxed numerous sloops in the light morning breezes.

But be careful, science has not figured out how the slot effect works. The results are undeniable but former theories of why it works have been disproved in controlled experiments. Many sailors believe that this also disproves the results. Suffice it to say that the multiple slots have the effect of moving boats faster, but we still can not explain exactly why in terms of physics.

You might want to get the book entitled "Auxiliary Sail Vessel Operations" by G. Andy Chase c. 1997 Cornell Maritime Press, which treats this subject fairly clearly in chapter 3 and 4. However, he does not make any comparisons of cutters to sloops. His treatment of improving apparent wind will give you a good feel for the forces involved in the discussion.

Alan

Alan Hugenot

02-08-2005, 11:46 PM

You are correct that the speeding up of the air flow in the slot has been proven to be an incorrect explanation for why the slot effect improves boat speed. Because the air in fact has been found to not speed up.

However, your conclusion that this then disproves the theory that increased slots improve boat speed, is a trifle hasty.

Although, the application of Venturi and Bernouli to sails may have been disproven. The fact remains that we still have lift occurring with all sails and foils, and no way to explain it witout Venturi and Bernouli.

Just because we can no longer explain it adequately, does not mean that it went away.

But, It still happens.

The slot effect is an empircally observed phenomena that has been measured and proven to actually occur. The result is that multiple slots do improve boat speed. Unfortunately, at this juncture we just don't know why.

It is up to physics to figure out why it happens. And while it may feel smug to believe that it does not happen, merely because the latest attempt at explaining it has failed. Such a course ignores proven truth.

With regard to cat rigs, windsurfers etc. and who points the highest. Again let's not get to hasty. If you want to compare the results of different sail rigs, you must compare them on similar hulls. The underbody hydrodynamics control how the "hull" responds, and how high it can point. A windsurfer's board is a very different animal under water that a spade keeled sloop or a full keeled cutter.

Also A windsurfer may point higher with a single sail, but many of these are not cat rigged, but are instead lateen rigged. If the sail overhangs forward of the mast, there will be an entirely different aerodynamic at play. Arab Dhows use lateen sails with no headsails. Again you need to compare apples to oranges.

That ignorant fool in SF

skinny boy

02-08-2005, 11:47 PM

Efficiency on a reach has not been the issue for this thread. The reason a cutter is more efficient and can be faster on a reach is glaring and obvious and does not have anything to do with the mystical slot effect that defies physics explanation.

Tripp Gal

02-08-2005, 11:48 PM

I honestly don't know how to begin. So how about I use my boat as a real-life example of a sloop and how your claims don't seem to match real-life.

If the schooner skipper is experienced and well versed in apparent wind, sail dynamics and proper sail trim, he can get his schooner up to hull speed on a reach in a 10 knot breeze. That means that he will be bowling along at 8 to 9 knots, while a perfectly trimmed sloop in the same breeze will be unable to develop enough horsepower to keep above 6 knots on the same reach. That three knots is a 50% increase.

I have a 45' boat. It's a fractional rigged sloop, and a racer/cruiser at that. In 10 true I see a velocity of 8.7 when the true wind angle is 90.

So I say that to your claim that sloops can't reach their hull speed in 10 knots of breeze is a bit off.

Again, the sloop sailors only like to race in strong breezes and tend to call the race if the wind does not reach eight knots. But, you will find that your cutter will kick along at 3 knots in a 4 knot air.
A sloop's inability to move in light air? Tosh. For my boat we consistently see a velocity equivalent to the windspeed or faster in true winds under 8 knots. In 4 knots of breeze we do 5.5-6 knots. So by your math that would be a 75%-100% improvement in efficiency by reducing the number of sails.

Alan Hugenot

02-08-2005, 11:53 PM

Generations of sailors knew about the improved performance caused by multiple slots between multiple head sails.

Physicists, tried to use Venturi and Bernouli to explain what was happening. But the physicists explanation has been proven wrong.

Just because their theory of WHY was incorrect, did not get rid of the fact that the slots result in improved boat speed.

None of the sailors knew anything about increased speed of air flow in the slot. Nore did they care about it. They just ovserved emprically that the boat went faster with more head sails.

What they observed can still be observed.

Unfortunately, most racing rules committees are ignorant of this, and continue not to incorporate it in their planning.

I have only been stating facts, not theories.

Alan

skinny boy

02-09-2005, 12:08 AM

Your "facts" are clearly not facts as demonstrated by the previous post by Tripp Gal. Interesting that you now call upon generations past. Generations of observers of the heavens swore by everything they knew and truly believed that the Earth was the center of the universe. They and their empirical observations were wrong. Slots have nothing to do with horsepower for cutters. No one has observed the "slot effect" in action. It was a model used to explain something because people couldn't explain why two sails were better than one. Since those days we have advanced and we know quite a bit about how two sails and more interact. Several references has been given here already. There are volumes more. Physics and aerodynamics offers some very specific observed, calculated and tested systems that show the effects in play. Bernoulli has its place and the "slot effect" just like the Bohr model in chemistry has a place in building a simple model to explain to laypersons so that they can have a simple if not clinical understanding of what is happening. Please don't claim "facts" based on flawed information it puts you into the mighetto category. Although it may be fun to see which one of you would win the arguement about whether a cutter or the Mac26 is faster.

tspeer

02-09-2005, 01:27 AM

...
Also, if someone could explain current thinking on 'slot effect' I'd appreciate it. ...

Best thing I've ever seen is A.M.O Smith's 1975 Wright Brother's Lecture, "High Lift Aerodynamics" (Journal of Aircraft, Vol. 12, No. 6, June 1975, pp 501-530). Smith was Chief Aerodynamics Engineer for Research at Douglas Aircraft and a Fellow of the AIAA.

Smith lists 5 effects of properly designed aerodynamic slots:
"1) Slat efect - in the vicinity of the leading edge of a downstream element, the velocities due to circulation on a forward element, for example a slat, run counter to the velocities on the downstream element and so reduce pressure peaks on the downstream element.
"2) Circulation effect - in turn, the downstream element causes the trailing edge of the adacent upstream element to be in a region of high velocity that is inclined to the mean line at the rear of the forward element. Such flow inclination induces considerably greater circulation on the forward element.
"3) Dumping effect - because the trailng edge of a forward element is in a region of velocity appreciably higher than freestream, the boundary layer "dumps" at a high velocity. The higher discharge velocity relieves the pressure rise impressed on the boundary layer, thus alleviating separation problems or permitting increased lift.
"4) Off-the-surface pressure recovery - the boundary layer from forward elements is dumped at velocities appreciably higher than freestream. The final deceleration to freestream velocity is done in an efficient manner. The deceleration of the wake occurs out of contact with a wall. Such a method is more effective than the best possible deceleration in contact with a wall.
"5) Fresh-boundary-layer effect - each new element starts out with a fresh boundary layer at its leading edge. Thin boundary layers can withstand stronger adverse gradients than thick ones."

Note that #2 is actually the opposite of some of the statements earlier in this thread. A main operates in a header created by the jib, but the jib gets a lift from the main - the net effect is greater than either sail by itself.

#5 is the typical explation for the benefit of slots, but #1 is the opposite of conventional wisdom. The slot does not accelerate the air at the leading edge of the main, it decelerates it compared to what it would be without the jib. And the slot does not really act like a venturi, because there's not a fixed massflow through the slot. As you close down the slot, the air can flow around the leading edge of the jib instead of through the slot, so instead of consistently raising the speed through the slot as the slot is closed down, the speed can actually decrease because of reduced massflow through the slot.

CT 249

02-09-2005, 06:40 AM

Hang on Alan, your first post attempted to tell us that the slot effect works by acclerating flow over sails further aft....now you're trying to tell us no-one knows how it works. Why not stick to one story at a time?

"A windsurfer may point higher with a single sail, but many of these are not cat rigged, but are instead lateen rigged."

What? A lateen rigged windsurfer? Gee, in all these years, racing windsurfers to world championship level, I never saw a lateen rigged windsurfer. Please tell me more.

"If the sail overhangs forward of the mast, there will be an entirely different aerodynamic at play."

Why? References please.

"The slot effect is an empircally observed phenomena that has been measured and proven to actually occur. The result is that multiple slots do improve boat speed. Unfortunately, at this juncture we just don't know why."

So...multiple slots increase boatspeed upwind, yet no grand prix sailors use multiple jibs upwind. So you, Mr Hugenot...you know more about going fast in sailboats than Paul Elvstrom; you must therefore know more than North, Connor, Cayard, Coutts, Scheidt who don't use them.

Gee, I'm honoured to have met you (in hyperspace at least)...the man who knows more than the world's most succesful racers. Wow.

So...we KNOW that sailors like America's Cup winners Connor and Bertrand and Blake were very familiar with twin headsail rigs when reaching, because there are pics of their boats doing so and they have written about it. YET they did not use them upwind; even when there was no penalty at all under rules for doing so.

So what happened? Did Connor, Bertrand, Tabarly, Blake et al suffer a simultaneous brain tumour that robbed them of this knowledge?

It's one hell of a call you make, sir...to say that almost every top racer and designer is wrong....even those like Tabarly who learned to sail on traditional boats, and those (Sean Langman of Xena, Nigel Irens) who still sail traditional boats. Somehow they've all got the same mental block that stops them from using their knowledge.

Well, let's all thank god we have you to tell us all where everyone else has been going wrong.

"Although, the application of Venturi and Bernouli to sails may have been disproven. The fact remains that we still have lift occurring with all sails and foils, and no way to explain it witout Venturi and Bernouli."

Yes there is, try Newtonian physics.

"Again, the sloop sailors only like to race in strong breezes and tend to call the race if the wind does not reach eight knots."

What???? Sorry???? Gee, we're definitely racing in different places. Ah yes, I can remember now...there we were, three days and 450 miles into the Sydney-Hobart and the race committee came by to tell us the race was off because the wind had dropped. NOT!

"If the schooner skipper is experienced and well versed in apparent wind, sail dynamics and proper sail trim, he can get his schooner up to hull speed on a reach in a 10 knot breeze. That means that he will be bowling along at 8 to 9 knots, while a perfectly trimmed sloop in the same breeze will be unable to develop enough horsepower to keep above 6 knots on the same reach. That three knots is a 50% increase."

But schooners rate lower than sloops under IMS and IRC. They rated lower than sloops under RORC and CCA and IOR. So if schooners rated lower AND when 50% faster, they'd win almost every light air race.

Instead, some late schooners like Pen Duick were converted to ketches (and went better). Their skippers went to ketches and then sloops in later boats. Alan, why did Eric Tabarly (a man who learned sailing in a traditional Fife CUTTER and died on it) throw away the schooner rig on Pen Duick III and IV (IIRC) and go to a ketch for his Whitbread maxi? Why did he then move to a sloop rig for his foiler tri? Was Tabarly suffering from some strange brain disease that made him move to a slower rigt? In that case, why did his boats get faster?

Uffa Fox (a man whose first boat was a cat ketch and who sailed and liked multiple headsail rigs for cruising) wrote in 1935 about the way that the J Class were moving from triple headsails, to twin headsails, and towards "the single headsail rig of the future". This was in reference to the Herreshoff J "Whirlwind".

Watson and Nicholson moved to fewer jibs in their succesive re-rigging of the Watson designed Brittania, perhaps the most succesful boat of all time. See the accounts in "The Kings yacht Brittania" and Ian Dear's "Enterprise to Endeavour".

So going for the sloop as the superior upwind performer, we have basically all oft he world's best racing sailors, as well as Watson, Nicholson, Herreshoff, Tabarly and Fox.

On the other side, we have Alan....and probably Mighetto.

Gee, hard choice.

CT 249

02-09-2005, 06:52 AM

>
But before I get much further, let me confirm whether or not it's TRUE that windsurfers do in fact point higher than just about anything? I have certainly heard this to be true, but I'm no windsurfer, and I've not paid much attention to them.

It depends enormously on the board and even more on the fin, rig and conditions. I haven't sailed modern FW boards in open waters much although I have sailed against championship level racers on them, and from memory they were pointing slightly lower than good catamarans and definitely lower than dinghies. FW boards rely on their fins and they much reach off and get good planing speed before even thinking of pointing.

Slalom boards point low, waveboards barely point at all.

I regularly race on dinghies against longboards (Olympic Mistral, former Olympic Lechner and original Windsurfer) and vice versa. The Lechner is the only one that can point with a dinghy upwind and then it's competitive with or slightly lower than a Moth, International Canoe or Laser.

The modern windsurfer RIGS are effective upwind due to their extremely flat low drag shape. It's quite strange to be on a slalom or Formula type board and pointing 50-55 degrees or so just on a fin. But the boards are aimed more to point low and go fast.

Skippy

02-09-2005, 09:16 AM

Well, are we reaching a consensus that Dr. Hugo is either very misguided or a troll? No offence Dr. Hugo, but I think you're way off base. And that's the NICE way of saying it. ;)

Sail interaction is a very important topic for anything larger than a sailboard or a cat-rigged dinghy, and I would very much like to hear about it. One decision might be whether to continue a serious discussion on this thread, or perhaps pick up the old one again? I'd hate to see Tom's contributions wasted on a food fight.

woodboat

02-09-2005, 09:50 AM

I don't know enough to argue the slot :) My first thought though is could you imagine a tacking duel upwind with a cutter rig? Maybe they didn't use one in americas cup not because it isn't faster but is simply difficult with which to race. Just a thought

skinny boy

02-09-2005, 10:15 AM

woodboat interesting idea, I would offer in opposition that multiple headsails developed over time due to the need for sailors to be able to handle them effectively. It was actaully easier to handle a smaller "working" sail than a huge sail. It was also much lighter and you didn't need a suite of different size sails stowed below for wind changes you could just use different combinations and stow on the boom.

In the end, I think it was ease of handling that promoted the cutter rig more than the sloop.

woodboat

02-09-2005, 10:35 AM

So you think in an Americas cup race it would be easier managing multiple sails even though there is a rule limit to available sails while racing and also when tacking moving two jibs. I think that the sail limit alone would be enough to oust a cutter rig even if it were marginally faster. Again I don't know.

Alan Hugenot

02-09-2005, 10:48 AM

Thanks to all of you who respond professionally and intelligently including, Brian and Mike, and especially Tom Speer. I appreciate anyone who is intelligent enough to back up their contention with hard science and cutting edge articles.

However, I do not appreciate others who only wish to hear themselves spout off, and so attack my intelligence and integrity, while backing up their mere opinions with nothing more than hype and inuendo. This is especially unappreciated when their entire experience does not include anything but racing sloops.

When we signed up for this forum we agreed to certian levels of decorum. This is supposed to be an intelligent discussion not a shouting contest where the loudest person wins. That kind of shouting and loud-mouthing may have work certain individuals when presenting a protest to a race committee, but it is inapprorpiate here.

If you can back up your contentions with actual personal experience or a scientific study, then present your case and your thoughts will be welcomed, but please do it in a patient and caring fashion.

If, on the other hand, you just want to enjoy a good shouting match then why not go to a pub? At least at the pub the other guy can punch you in the nose when you get out of line.

The truth is that the only thing your shouting will do here is to drive away other more intelligent and patient folks. But, don't fall into the trap of believing that just because you are the only one left standing that it will prove you to be RIGHT. It will have only proved that you need to re-learn some social skills.

Alan

skinny boy

02-09-2005, 10:52 AM

At one point the sail number was not limited but it went towards the single headsail as materials advanced and as technology advanced. It took winches to allow bigger headsails to be handled effectively. With a single headsail the sheeting angle could be decreased and as underwater foil shapes advanced this started bringing the boats closer to the wind and allowed pointing angles to advance. Multi headsails provide an advantage on a reach but when pointing hard on the wind the improved sheeting angles and overall foil efficiency of the sloop rig has won out.

water addict

02-09-2005, 11:11 AM

Way back when (1972), my family had an Ericson 37 that was originally designed as a cutter. We raced on the Chesapeake, light air most of the time. We tried the cutter rig for about half a season, with poor upwind performance in the light going. When the wind was above about 10 knots, we could hold our own upwind in a VMG sense, sheets slightly cracked, pointing low. We changed to a large single headsail and performance upwind, both point and speed improved. A good guage was that we had a sistership racing against us that was always rigged as a sloop. When we sailed the cutter rig, they always beat us. When we sailed as a sloop we beat them about the same as they beat us. Pretty telling comparison, at least for this one data point.

Thought I'd throw some gas on the fire....

Paul B

02-09-2005, 11:36 AM

I appreciate anyone who is intelligent enough to back up their contention with hard science and cutting edge articles.

When will you provide this? Also, please provide the name of the school where you earned your NA. I'd also like to know what school you coached, and what years.

That kind of shouting and loud-mouthing may have work certain individuals when presenting a protest to a race committee, but it is inapprorpiate here.

Once again, the bias of the "experienced seaman" against "them young racers" rears her head. I have raced for many years at high levels and have rarely been in protests, but I can say that the protests I have been party to, and the protests I have heard as a member of the committee, have never been shouting matches. If you knew anything about the topic you would not make such silly comments.

The truth is that the only thing your shouting will do here is to drive away other more intelligent and patient folks. Alan

Actually, it is people like you, who are so mis-informed and spout such nonsense, who drive the better people away from boards. It is sad to see the craziness that is being posted in various threads of this board these days.

Skippy

02-09-2005, 12:16 PM

Thank you for responding AH. For the moment, I'll refrain from using my little nicknames and whatnot.

Thanks to all of you who respond professionally and intelligently including, Brian and Mike, and especially Tom Speer.

First of all, let me just second that gratitude.

I appreciate anyone who is intelligent enough to back up their contention with hard science and cutting edge articles.

I do too, AH. I would appreciate it if you would do so.

... others who only wish to hear themselves spout off, and so attack my intelligence and integrity, ... hype and inuendo.

On the topic of spouting off, AH, I would call your attention to the length of your own posts. As for hype and inuendo, I notice you have chosen to toss around impressive buzzwords such as "slot effect", "apparent wind", and "multiplying effect". And I would wonder what is the intent of a comment such as "it may feel smug to believe that it does not happen".
The slot effect has behind it a long, sordid history of exagerations and old fish tales, most of which have been disproven. So I would agree with you that anyone promoting unproven, hyped-up theories must prove their point convincingly, based on hard sciene.

When we signed up for this forum we agreed to certian levels of decorum. This is supposed to be an intelligent discussion not a shouting contest ...

Bravo! Let's agree then, AH, that when we make a claim, we won't simply make unsupported statements such as

"The slot effect is a well known principle of sail dynamics",
"the slot formed between a jib and the mainsail improves the apparent wind for the succeeding sail",
"sloop sailors only like to race in strong breezes", and
"The results are undeniable".

Not to mention comments such as "Cutters are great preformers", supported by claims about reaching, when the current topic is pointing.
And as for decorum, if it's not too much trouble for you AH, could we also agree that we will not use a fake patina of decorum, as a cover for promoting nonsensical Ballerina Science. That's just my own personal preference: science first, then decorum.

If, on the other hand, you just want to enjoy a good shouting match then why not go to a pub? At least at the pub the other guy can punch you in the nose when you get out of line.

If it's going to a pub you're interested in, I recently posted an excellent drinking song on another thread. :) And please don't punch anybody.

The truth is that the only thing your shouting will do here is to drive away other more intelligent and patient folks.

Absolutely. I would also like to point out that there are plenty of bright, capable individuals who will be turned away by unproven nonsense, regardless of how cordially it is presented.

Physicists, tried to use Venturi and Bernouli to explain what was happening. But the physicists explanation has been proven wrong.

And finally AH, NONE of the basic principles of physics as of the 20th century, have been proven wrong in the classical realm. Any suggestion to the contrary is Ballerina Science. So unless you're sailing at the speed of light, or your boat is the size of an atom, any claim you make must be grounded in today's knowledge of classical fluid dynamics. It's the "slot effect" hype artists who have had it wrong so far, and you will need to do better than disparaging the scientific community to prove your point.

woodboat

02-09-2005, 12:29 PM

My question. The starter of the thread changed an existing boat to a cutter rig. He claims he sails higher and faster. Is he mistaken? Or is there a valid reason his boat is now faster?

mistral

02-09-2005, 12:41 PM

gggGuest

02-09-2005, 02:26 PM

My question. The starter of the thread changed an existing boat to a cutter rig. He claims he sails higher and faster. Is he mistaken? Or is there a valid reason his boat is now faster?

There are loads of potential explanations, starting with the simple one of new sails are better full stop. But the most likely one is that a well designed and rigged cutter rig is superior to a less well designed and less well executed sloop rig.

I do suspect he's mistaken about 10 degrees plus though. That is a truly immense difference. It suggests that the boat was say only managing about 50 degrees before and is capable of 40 degrees now. The trouble is its difficult to quantitatively assess boat performance. The only real way of doing it would be to line up his O-Day 45 with its cutter rig against another O-Day 45 with a Sloop rig of same age and see what happens.

skinny boy

02-09-2005, 02:29 PM

woodboat, most here that have a lot of time of a variety of boats seem to agree that the original post most likely did see an improvement, otherwise he would be lying and that makes no sense at all.

So we assume the poster did see an improvement and the reason why is most likely due to having new sails with better shape than the previous genoa. Just a better shape can make a huge difference in the speed and height achieved.

So then the thread went to more general cases about does a cutter in general point higher and go faster and of course you can see there is some opinion but the overwhelming anecdotal and physical evidence provided so far indicates that going to weather the cutter does not point higher and go faster. This seems to be related to sheeting angle and rig efficiency upwind more than anything else but I am sure someone will be happy to correct me on that observation. Note I did say efficiency upwind not reaching or running.

woodboat

02-09-2005, 03:57 PM

Thanks. I have been following the thread. The opinions seemed opposite. So only one could be true :) I also imagine that the boat as a whole is a factor. Meaning that one boat may be faster as a sloop while another maybe as a cutter. Points on both sides seem interesting but not totally conclusive. When the americas cup came in to play it seemed as though the sloop side was grasping at straws. There are 100 other reasons as to why a cutter is a terrible choice for racing, none of which have to do with speed. Heck I have seen a staysail used on a run without any discernable difference, yet it was used every time. So sometimes when it comes to speed the difference is so minute that I doubt it would be perceivable without extensive test gear. So without some real hard numbers I am left wanting for the truth :)

CT 249

02-09-2005, 04:25 PM

Thanks for the lecture on social skills, Alan.

The reason that some of us get rather irate at times is that your claims include a very strong implied (no, make that explicit) insult on the intelligence, character, research honesty and knowledge of the vast majority of the sail racing community.

You insult the intelligence and research skills of most of the world's best sailors by saying that they are ignorant of the slot effect and such, when they include people who have Masters Degrees in MIT about the science of sailing and such.

You say modern racing sailors know nothing about multi-slot rigs, when boats like C Class cats go to enormous hassle to introduce slots on their wing masts.

You say modern sailors are ignorant of history and the use of multi-slot rigs, when many of them in fact know and use them.

What you are saying is that YOU are wrong, and just about every designer, sailmaker and pro racing sailor is wrong.

These people make their living from their knowledge and skill; so you are basically saying that they have been ripping people off for years.

That's massive charges you lay agaiinst a large body of people; dishonesty, lack of professionalism.

Re "I appreciate anyone who is intelligent enough to back up their contention with hard science and cutting edge articles."

Umm, so who is being rude now? Are you not the first person to start implying here that people are not intelligent?

"If you can back up your contentions with actual personal experience or a scientific study, then present your case and your thoughts will be welcomed, but please do it in a patient and caring fashion."

OK. Several years' experience with reaching double head rigs on boats including;

Peterson 47 "Superstar"; Kaufman 2 ton "Mercedes V"; Kaufman One Tons "Priority" and "White Pointer"; Cole 43 "Rager", 73' Spencer "Buccaneer"; etc etc etc. Ketch sailing on Vindicator (900 mile Noumea-Brisbane passage), short sails on a Malabar gaff schooner, etc. Sydney-Noumea race (1080 nm) on 42' cutter "Quest". 50' Robertson gaff cutter/ketch Ron of Argyll in old gaffers' race. Cruises/passages on 38' cutter rigged catamaran.

Last time I sailed a cutter? This Sunday. For a cruising cat, the cutter rig is superb in terms of convenience, especially with a wishbone on the main. Peerless. But for best performance upwind, the inner forestay stays bare.

Last time I raced anything but a sloop? Last night. Last time before that? Last Saturday (missed the Sunday sloop race 'cause I was cruising on the cutter).

Those 5000 miles or so on ketch, schooner, and cutter rigs and on boats that used double headsails when reaching (or tallboy staysails under kites) proved EXACTLY what John Bertrand, Dennis Connor, Uffa Fox, Nat Herreshoff, Peter Blake, Eric Tabarly and many others have demonstrated in their writing. The cutter rig is NOT as effective upwind.

You still haven't answered the question; why would those who know and use double head rigs (as listed earlier) move away from them if they were better?

PS; I gave you references down to page numbers, book titles etc for my input. Where are your references in return?

skinny boy

02-09-2005, 04:44 PM

wb, opinions often times will be opposite. I happen to know my opinion is always the right one however :D

As for the observation about dependence on the boat you are correct from my experience it has a lot to do with the boat but when it comes specifically to close-windedness I can't think of a cutter that will out point the same hull with a single headsail simply because of sheeting angles involved.

Your observation on staysails is very true, I have seen two of the same make boats running under spinnaker one had a staysail and there was no discernable speed difference, however the skipper of the one without a staysail that day swears that on a beam reach he can not stay with other boats in his class without a staysail. So sometimes the evidence is anecdotal and sometimes conflicting even from the same sources. We all have our preferences and the evidence when marginal tends to somehow always point to what we want to be true. Except of course for mine which is I remind you always the true one. :eek:

CT249 is always reasoned and provides usually very specific support for his thoughts whether they are right or not depends on if they agree with me or not. But so far he has not steered me wrong in any thread I have had the pleasure of reading. The same I can say for TomSpeer and there are a couple others here which are great to get history and facts from. I am always good for an opinion though...

Tripp Gal

02-09-2005, 10:45 PM

Alan,

I'm not sure where your hostility is coming from. It seems that people are responding with specifics, articles, and real life experience.

As to why the fellow noticed an improvement when he changed his boat up to a cutter and new sails. I too believe that his new sails had quite a bit to do with performance. It's always impressive when you have been sailing with old sails how big a difference new makes. I raced last season with a set of sails that had sail life left but no shape life left in them. I went to new sails this year and couldn't believe how much the performance and personality of the boat changed (for the better). It never ceases to astound me how big a delta new sails make. A friend observed that sails are like our vision. People go for years thinking they see just fine until they go to the eye doctor and get an update on their prescription. Suddenly a whole new world opens up.

brian eiland

02-10-2005, 10:41 AM

First let me correct a previous staement I wrote,
And cat rigged boats do not outpoint a headsailed boat. Ask Mr Hall at Hall spars I meant to say unirig rather than cat rig

There are still some number of people who continue to refer to the 'slot effect' as a myth, ie;
....with the mystical slot effect that defies physics explanation
...Slots have nothing to do with horsepower for cutters. No one has observed the "slot effect" in action. It was a model used to explain something because people couldn't explain why two sails were better than one.
I made a reference to Paul Bogataj's excellent paper earlier "How Sails Work" (http://www.northsailsod.com/articles/article6.html). Well here is an excerpt from that paper that speaks to this interaction of headsail and mainsail, and then relates it to an actual sailing phenomenon that we experience on the water as well (rather than just theory):
____________________________________________________
Sails in Combination. Each sail by itself is much simpler than the combination of a foresail and mainsail as in the sloop rig. The sails are operating so close to each other that they both have significant interaction with the other. The most interesting feature of this is that the two sails together produce more force to pull the boat than the sum of their forces if they were each alone. Earlier, upwash was identified as the increase in flow angle immediately upstream of a wing. There is also a corresponding change in angle, called downwash, just behind a wing, where the flow leaving the wing has been turned to an angle lower than the original flow.

This is the cause of the well known “bad-air” that a boat just to windward and behind another boat experiences. The mainsail of a sloop rig operates in the downwash of the forward sail, causing the flow angle approaching the mainsail to be significantly reduced from what it would be otherwise. This decreases the amount of force that the mainsail produces. The observed affect commonly referred to as “backwinding” is partially a result of downwash from the foresail, but is also due to the higher pressure on the windward side of the genoa being very close to the forward, leeward side of the mainsail, causing the flexible material of the mainsail to move away from that higher pressure.

The foresail of a sloop rig operates in the upwash of the mainsail. The wind as far upstream as the luff of a genoa is influenced by the upwash created by the mainsail. Hence, a jib or genoa in front of a mainsail has a higher flow angle than it otherwise would have by itself, causing an increase in the amount of force that the forward sail produces. So, while the mainsail is experiencing detrimental interference from the foresail, the foresail benefits from the interference of the mainsail. Notice that more air is directed around the curved leeward side of the foresail. This causes higher velocity (lower pressure) and more force. The net result is that the total force of the two-sail system is increased, with the foresail gaining more than the mainsail loses.

There is a converse affect to a windward boat receiving “bad air” (downwash) from a boat ahead and to leeward. A leeward boat gains additional upwash (“good-air”?) from a boat just to windward and slightly behind that acts like a lifting windshift until it moves ahead of the windward boat. This is the same phenomenon from which a foresail of a sloop rig benefits.

Another consequence of the difference in flow angles that the two sails experience in each others’ presence is that the mainsail must be trimmed to a much closer angle with the boat’s centerline than the foresail, which is able to be trimmed to a lead position well outboard. This angle represents the difference in upwash on the foresail and downwash on the mainsail due to each other."
__________________________________________________

Tom Speer has made a number of references to AMO Smith's paper. It has been awhile since I read this paper, and I must admit it is rather 'technical', but if I remember correctly, it does imply that multiple, multiple slots (multi-element airfoils) do work in a similar manner to the single slot in that each preceding foil gains in its ability to 'point'. The question here is how many foils (multi-element headsails) are really practical on our sailing craft.

I'm more concerned with their most efficient interaction than how many their are.

For fun I included a figure from Mr Smith's paper. I need to reread this paper again and get back to Tom for proper interpetations and questions. As suggested by ....One decision might be whether to continue a serious discussion on this thread, or perhaps pick up the old one again? I'd hate to see Tom's contributions wasted on a food fight. I think I will revert back to the old Sail Aerodynamics for these discussions.

frankofile

02-10-2005, 11:49 AM

Taking a break from laughing at Frank... Seems to me that this discussion of "slot effect" is diverging because people assume different definitions of what the slot effect is. For example, I would have agreed with Skinny Boy that the slot effect theory is bogus, yet what I read in Brian Eiland's post does not describe what I thought the slot effect theory was.

I'll go first - My understanding is that the "slot effect" theory holds that air accelerates in the slot between two sails and by that means increases the lift of the more aft sail.

brian eiland

02-10-2005, 12:20 PM

I'll go first - My understanding is that the "slot effect" theory holds that air accelerates in the slot between two sails and by that means increases the lift of the more aft sail.

.....some excerpts from previous discussions....
Subject: How Sails Work, the slot effect

I noted that this forum (another one) has had quite a bit of discussion recently of "lee side air speed". Well, I couldn’t resist bringing up the closely related, and also much maligned subject of ‘air flow thru the slot’ created by the mainsail and the headsail.

....Now look at the rig’s aerodynamic configuration. We’ve had many years of controversy over the flow of air in the slot between the jib and the mainsail, and many incorrect explanations. We now know irrefutably that the flow between these two sails is slowed rather than speeded up, and that results in a higher pressure on lee side of the main and on the windward side of the jib; ie, the jib’s drive is improved, and the main’s drive is degraded!! Put another way, the mainsail provides an upwash for the jib that makes the jib both more efficient and able to point higher (its operating in the safe leeward position). The jib meanwhile creates a downwash on the mainsail that decreases its efficiency.

There are any number of reference sites for the correct explaination now, but I'll just add one more (http://www.runningtideyachts.com/articles/SailScience4.html) that appeared in the archives of my website. Granted, it is not as easy to understand as it speaks to the 'circulation explanation', but it also has some questions by persons with pretty weird misconceptions about the old explanations of how sails work.

Colin wrote:
So what about the 'slot effect' everybody seems to assume in our club - i.e. that the jib accelerates air over the lee of the main, reducing pressure and increasing left. Is that happening as well further away from the sails?

Brian responded:
No, the air is not speeded up in the slot (on the lee side of the main). The air is speeded up outboard of the sail-plan (the lee side of the headsail). This speeded up air on the lee side of the headsail must eventually slow down to the free stream conditions as it leaves the sail-plan as a whole...but trhats another topic that Tom Speer can tell you much about.

I'll repeat an excerpt from my previous posting,"....that like a restricted water hose, the air is speeded up in the slot. This is another of those axioms that the textbooks have got wrong and have taught us wrong for so many years. But as Tom Speer noted, “there’s no way to finally put a stake through the heart of that old explanation—it just keeps coming back to life”.

frankofile

02-10-2005, 01:28 PM

My point wasn't that I don't understand "slot effect" theory, or that I think it's right or wrong. My point was that different people here seem to have different opinions of what the theory is.

Maybe we can agree that air does not accelerate through the slot; there is interaction between sails. Leave the term "slot effect" out and everyone's back on the same page.

That's all I want to say. Carry on.

gggGuest

02-10-2005, 02:24 PM

And una rig boats do not outpoint a sloop rig

Hmm. I would note that AIUI Cogito closes their slots and converts the rig to una upwind, where they require low drag and close windedness, and opens the slots downwind where they require high power and aren't worries about angle of attack or a drag penalty.

While anyone who attempts to compare empirically the performance of different styles of boats is being foolish, it is to say the least not obvious that in the highest performance regions sloop rigs are point higher. Another example would be the Formula 40 cats of a few years ago, who rapidly evolved from the planned sloop rig to a quasi una rig which had never had a jib larger than the minimum size storm jib required by the rule set.

Those are probably among the most close winded boats of all time. But there are loads of other factors that come into play, and for very many types of craft the slightly higher lift slightly higher drag two sail configuration is probably a better solution upwind.

There is a converse affect to a windward boat receiving “bad air” (downwash) from a boat ahead and to leeward. A leeward boat gains additional upwash (“good-air”?) from a boat just to windward and slightly behind that acts like a lifting windshift until it moves ahead of the windward boat. This is the same phenomenon from which a foresail of a sloop rig benefits.

While such a phenomenum undoubtedly exists I would question how often rigs would actually be close enough together for this to have a significant effect. Consider that the jib of the leading craft would need to be as close to the jib of the trailing craft as a jib normally is to a mainsail for it to affect the pointing angle. On the other hand the downwash, and more importantly the trailing votices from the rig persist for a considerably greater distance. The well known photo of Volvo 60s in light mist at Capetown in the last race demonstrates what an immense distance the trailing vortices can persist for in some conditions.

brian eiland

02-10-2005, 05:46 PM

Hmm. I would note that AIUI Cogito closes their slots and converts the rig to una upwind, where they require low drag and close windedness, and opens the slots downwind where they require high power and aren't worries about angle of attack or a drag penalty

I don't recall this exact rig. Do you have a photo? I think this is a solid wing-sail arrangement, right?
I suspect this is because the slot between these two elements is so small as to not benefit the overall situation. Her leading element is probably too small & narrow an area to benefit from the extra drive pressure it might gain from having extra flow go to the outside of the leading element

While such a phenomenum undoubtedly exists I would question how often rigs would actually be close enough together for this to have a significant effect. Consider that the jib of the leading craft would need to be as close to the jib of the trailing craft as a jib normally is to a mainsail for it to affect the pointing angle. On the other hand the downwash, and more importantly the trailing votices from the rig persist for a considerably greater distance. The well known photo of Volvo 60s in light mist at Capetown in the last race demonstrates what an immense distance the trailing vortices can persist for in some conditions.

I am familiar with that photo you speak of with the V60's, and it certainly displays the bad air downwind behind the leading vessel. But ask any top racer or the America's Cup guys about the 'safe leeward position', it is a very real phenomenum. In general the trailing vessel must have its bow up to the aft quarter or better of the leading vessel. Very importantly, remember the air begins to change direction well in advance of the forestay as a result of the rig's configuration. It does not just change direction as it hits the forestay.

gggGuest

02-11-2005, 03:03 AM

But ask any top racer or the America's Cup guys about the 'safe leeward position', it is a very real phenomenum. In general the trailing vessel must have its bow up to the aft quarter or better of the leading vessel.

Oh sure any and every half decent racer knows about that. But its not that the leading boat starts performing better. The point is that when you're in the trailing position you're sailing where the wind flow is being bent by the rig of the leading boat and so the wind getting to you is a degree or so different to the free flow condition and you're sailing in a header. If you look at all the wind tunnel outputs you'll see that the wind bend on the windward hip of the rig persists over a greater distance than the bend in front of the rig - its got to if you think about it, with those great trailing vortices disturbing all the wind flow aft of the rig.

brian eiland

02-11-2005, 06:52 AM

. The point is that when you're in the trailing position you're sailing where the wind flow is being bent by the rig of the leading boat and so the wind getting to you is a degree or so different to the free flow condition and you're sailing in a header.
No, if you (leeward boat) were then "sailing in a header" you would be at a disadvantage. Rather you are sailing in a slight lift as a result of the flow being bent around the outside of the leading boat's sails (in particular the headsail). A "header" would cause you to have to fall off slightly. Rather you can point up slightly.

Skippy

02-11-2005, 09:15 AM

gggGuest: ... when you're in the trailing position you're sailing where the wind flow is being bent by the rig of the leading boat and so ... you're sailing in a header.

brian eiland: No, ... you (leeward boat) ... are sailing in a slight lift as a result of the flow being bent around the outside of the leading boat's sails (in particular the headsail).

This is why in my aerodynamics post yesterday, I used the combination "leading/leeward" to describe the relative position of the jib, and "trailing/windward" for the main. Both of you are right, because you're talking about two different things. If you're in a trailing position, gggGuest is right. You're in the lead boat's backwash, which is air that has been turned into your bow. If you're slightly ahead of the other boat on the leeward side, then Brian is right. You benefit from the circulation effect #2: The air has not turned completely around the other boat's jib yet, so it's still moving somewhat more across your heading.

But to be fair to Brian, I think he does have one more point: If the trailing boat attempts to overtake the leading boat on the weather side, then the leading/leeward boat will benefit from the circulation effect, being propelled forward by the trailing/windward boat's upwash. While the trailing/windward boat will be sailing into the leading/leeward boat's backwash. So in that case, the leading/leeward boat has two effects helping it, not just one. That's the "safe leeward" position: It's leeward and leading.

brian eiland

01-15-2006, 05:03 PM

Something different...a gentleman wrote to me recently;

I have been interested in the idea of a forward raked mast with an
unusual sail layout for quite some time now, originally seeing the
idea at a student design show. The boat looked like the sailboat
equivalent to a future speculating auto show "Concept Car", with wild
ideas that gave little concession to practicality.
Kyle

Have a look at this futuristic design (http://boatdesign.net/forums/showthread.php?p=72778#post72778)

BOATMIK

01-17-2006, 08:00 AM

I'll go first - My understanding is that the "slot effect" theory holds that air accelerates in the slot between two sails and by that means increases the lift of the more aft sail.

That was the classical explanation of slots on wings and accelerated flow was suggested by an important aerodynamicist (Prandtl? from memory) almost a century ago.

The sad thing was that no-one actually did the science. They just took the aerodynamicist at his word because he was considered important.

Experiment shows the opposite.

The first time I was made aware of it were the articles by Arvel Gentry in the late '70s printed in "Sail" magazine.

With a reprint in a book "The Best of Sail Trim". Others may have been before him, but he mixed experimentation with reportage and explanation.

His articles are available at
http://www.arvelgentry.com/magaz.htm

Read them and you will know EXACTLY why Cutters and Sloops are slower than cat rigged boats upwind for equal sail areas.
Why sloops and cutters may be slightly faster on a reach or run in certain conditions than cat rigged boats for equal sail areas.

Read the articles, take the effort to understand them - and then you will be able to work out the answer to this thread!!!

Best Regards
Michael Storer
my boat pages (http://www.ozemail.com.au/~storerm)

brian eiland

01-17-2006, 08:46 PM

.... you will know EXACTLY why Cutters and Sloops are slower than cat rigged boats upwind for equal sail areas.
Why sloops and cutters may be slightly faster on a reach or run in certain conditions than cat rigged boats for equal sail areas.....
Pretty broad statement there. Why don't you try explaining that to Eric Hall of Hall Spars who I referenced an excerpt from under the subject thread Sail Aerodynamics (http://boatdesign.net/forums/showpost.php?p=5685&postcount=3);

"More recently I ran across a news article in the Sept issue of Seahorse magazine which discusses the very interesting full scale prototyping work being carried out on a J-90 class boat by Eric Hall of Hall Spars. Eric is now on his third-generation, free standing ,carbon wing rotating mast, with a una-rig mainsail. His “ thought process (and maybe not entirely logical) was: If biplanes became monoplanes and monoplane wings shed wires, why not an unstayed una-rig upwind” Boy, you would surely think this was the ideal upwind rig. In responding to an inquiry on upwind performance, Eric responds, “ first, of course, the boat would be improved upwind with a No.1 jib. Generally, we could not point as high as the others here (Block Island) and therefore had difficulty holding lanes.” He goes on to say, “this is a very interesting project that we especially want to succeed. I have been accused of a missionary zeal, which frankly keeps moving it along. It’s a real problem sometimes keeping focused on what we are trying to do in view of all that is ingrained in our minds about what makes sailboats work.

RHough

01-18-2006, 12:41 AM

Pretty broad statement there. Why don't you try explaining that to Eric Hall of Hall Spars who I referenced an excerpt from under the subject thread Sail Aerodynamics (http://boatdesign.net/forums/showpost.php?p=5685&postcount=3);

The split rig should be faster when maximum lift per unit area is needed. The single element rig should be faster when maximum L/D is needed.

Sailplanes need max L/D ... no canards that I know of.

Ice boats sail faster than the wind on all points of sail and use single element rigs.

A single element sailplan may well be a poor choice for a typical mono that sails in displacement mode most of the time. The AR of the sailplan is limited by the boat's RM (or lack of RM). For a given RM a multi element system can develop more power for the same area than a single element at the same AR.

MarioCoccon

01-18-2006, 07:05 AM

Hi Firends: I have to Sailboats one Columbia 39 and a Newport 27. It is worthy make the 27 cutter that can give me more performance and speed. Or a 27 is to small for that. The boat sail very fast but I read here that point more and go faster. What was a correct answer.

FAST FRED

01-21-2006, 05:52 AM

"The split rig should be faster when maximum lift per unit area is needed.
The single element rig should be faster when maximum L/D is needed."

You have been given the key to the answer.

For a really fast racer , in competiton the max LD will let you squeak out the highest pointing angle .

For a heavier cruiser that is slogging up a hill of big water , the angle will never be as high as much FORCE is need to drag the boat uphill.

That takes maximum lift , to create the force needed.

So if your in a Soling playing racer for an afternoon the sloop would be best choice.

If your attempting to drag a fat heavy Westsail to windward ,length of luff wire makes the power needed to climb hills.

The old byplanes were fantastic at low speed high angle of attack , only suffered when the speeds got too high for fat wings and them damn rig wires.

Not a problem for a 8K sailboat.

FAST FRED

markdrela

01-23-2006, 01:56 PM

What type of wing or sail is best for any type of vehicle depends a great deal on what dominates the drag of the vehicle. In general, to maximize glide ratio or pointing angle, one should maximize the overall vehicle L/D (a bit oversimplified for a sailboat, but close):

L/D = L / (D_wingsail + D_parasite)

On a sailplane, the D_wingsail (wing profile + induced drags) is nearly everything. D_parasite (fuselage + tail) is tiny by comparison. So

L/D ~ L / D_wingsail

which is maximized with a slender cantilever wing like you see on any sailplane.

But on a sailboat, D_parasite (hull hydro + aero drags) is huge by comparison. So to maximize L/D you want a large lift L to "dilute" this large D_parasite, even if D_wingsail is also made large as a result. Large lift naturally favors multi-element sails, for all the reasons listed by AMO Smith. This is especially the case if the sail area is constrained by rules or whatever.

An iceboat is probably closer to a sailplane than a sailboat in this regard, so it benefits from a rigid single-element sail more than a sailboat.

RHough

01-23-2006, 05:14 PM

But on a sailboat, D_parasite (hull hydro + aero drags) is huge by comparison. So to maximize L/D you want a large lift L to "dilute" this large D_parasite, even if D_wingsail is also made large as a result. Large lift naturally favors multi-element sails, for all the reasons listed by AMO Smith. This is especially the case if the sail area is constrained by rules or whatever.

An iceboat is probably closer to a sailplane than a sailboat in this regard, so it benefits from a rigid single-element sail more than a sailboat.

That makes no sense. All you need is a high value of L, not a high value of CL. To get L you can have more area at lower CL (and lower CDi) or you can have less area at higher CL (and higher CDi).

The value of D includes D(parasite) + Di.

For a given hull and speed, Dp remains the same so total L/D is governed by the L/Di of the sail plan. The sail plan that gives the L needed at the lowest Di will be the faster boat to weather.

For any value of L a single foil is superior to multiple foils.

It is only when other constraints are added that multiple foils become a good choice.

The only time a multi-element sail plan will point higher if is the vessel cannot carry a single foil of equal area and higher AR.

markdrela

01-23-2006, 06:08 PM

That makes no sense. All you need is a high value of L, not a high value of CL. To get L you can have more area at lower CL (and lower CDi) or you can have less area at higher CL (and higher CDi).
Not really. Di depends only on the span loading and the airspeed. Sail chord and CL don't really matter in this design situation. More specifically, as you increase chord with a given span, L, and airspeed, you find that CL decreases, CDi decreases, but Di ~ (area*CDi) does not change.

But this may be a somewhat overconstrained design situation. I'll still claim that when the drag is dominated by a hull whose drag is largely independent of what the sail does, then you want the sail to generate as much lift as possible, at least within righting-moment constraints. If the sail area is constrained, then a multi-element sail will easily beat a single-element sail in high-lift capability. This is true for soft sails and rigid sails. Note that Dennis Conner's AC Cat had a 2-element rigid wing.

RHough

01-24-2006, 12:01 AM

Not really. Di depends only on the span loading and the airspeed. Sail chord and CL don't really matter in this design situation. More specifically, as you increase chord with a given span, L, and airspeed, you find that CL decreases, CDi decreases, but Di ~ (area*CDi) does not change.

But this may be a somewhat overconstrained design situation. I'll still claim that when the drag is dominated by a hull whose drag is largely independent of what the sail does, then you want the sail to generate as much lift as possible, at least within righting-moment constraints. If the sail area is constrained, then a multi-element sail will easily beat a single-element sail in high-lift capability. This is true for soft sails and rigid sails. Note that Dennis Conner's AC Cat had a 2-element rigid wing.

If "Sail chord and CL don't really matter ..." then why does it matter that "a multi-element sail will easily beat a single-element sail in high-lift capability".

If CL and chord don't matter, area is not constrained. Then what does your statement about higher lift with constrained area have to do with anything?

I'm happy for DC that he had multiple elements in his wing sail, so? What are you trying to say?

There are only three ways to create more lift, more area, higher CL, or more speed.

Look at the trim angle needed to produce drive. The higher the L/D of the sail plan, the lower angle the trim angle needs to be to provide the same drive.

High CL planforms have rotten L/D ratios. Thus high CL (high lift per unit area) sailplans will not drive the boat at as small and angle off the wind.

If we want to sail close to the wind, and we know we need high L/D to do it, why even consider low L/D planforms?

BOATMIK

01-27-2006, 02:54 AM

Pretty broad statement there. Why don't you try explaining that to Eric Hall of Hall Spars who I referenced an excerpt from under the subject thread Sail Aerodynamics (http://boatdesign.net/forums/showpost.php?p=5685&postcount=3);

Mr Hall can access the articles of Mr Gentry that cover the point with care, logic and consistency - not to mention careful science.

Gentry covers the cutter rig specifically. Basically the inner headsail operates in such tight constraints from its proximity to the main and the jib that it is very difficult to get consistent lift from it.

In his general articles about "How Sails Really Work" he talks in more general terms about multi element airfoils.

For the record ...
http://www.arvelgentry.com/magaz.htm

Perhaps you could sneak a peek too.

:-)

Rhough is right on the money that Righting moment may be more of a determinant in choosing a multi element airfoil. It would have taken me a couple of days to come to the same conclusion!

Best Regards
Michael Storer

BOATMIK

01-27-2006, 08:21 PM

I probably am being mean to a deceased quadruped but I woke up wanting to post some pics of pretty boats.

All the boats below have no restrictions on the division of sail area with one exception. You can have any distribution between Main and Jib or Jibs that you like.

They also measure almost every square inch of actual sail - there is a strict maximum they cannot exceed.

Funny thing ... no cutters.

Another interesting thing is that some have a restriction on mast height. These tend to be sloops.

I suggest that if you want the cutter to be faster than a sloop you simply need to restrict the mast height further than in these examples - like maybe half :-) without reducing the allowable sail area.

However, even in this case the solution may be to go for two masts of the same max ht and a single jib on the forward one - but that is just intuition speaking - I have no hard facts to support my position at all!!

Note too the wide variation of hullforms and stability.

Anyway - enjoy the pics of all the lovely boats and remember why we all love this sailing thing!

Michael Storer

http://www.ns14.org/templates/JavaBean/images/sails.jpg
Australian NS14s - max hoist of main above deck 18ft/5.5m

http://www.redwingracing.co.uk/club_sailing/images/sailing.jpg
Bembridge Redwings classic long keel yacht designed a long, long time ago.

http://www.aclasscatamaran.co.uk/images/photos_06.jpg
A Class Cats

http://www.duboisyachts.com/Yachts/FullPelt/images/Full_Pelt_Info.jpg
Trimaran by Dubois to Formula 40 Rule. The F40 rule demands that there be a headsail - so it ends up being the size of the minimum storm jib allowable. If this restriction was not there the rig would look very much like the A-class.

SuperPiper

01-28-2006, 04:08 AM

Deeply Flawed Human Being:

So without design limitations, the jib would be small, as small as possible, or non-existent.

It makes sense to me and your anecdotal evidence seems logical. Is there a NA onboard that may comment to this? Is Eric Sponberg following this thread?

Skippy

01-28-2006, 09:58 PM

Look in the Aerodynamics thread. Tom Speer discusses how the jib reduces drag from flow around the mast.

brian eiland

09-15-2007, 09:20 AM

Frank MacLear of MacLear & Harris did some big, stout, cutter rigged designs; both with a boomed mainsail and boomless.

He also stepped the mast quite far aft to give the double headsails room to work. I was significantly influenced by these designs.

I just recently gathered some info together and posted it here:

Boomless Mainsails, Frank MacLear
http://boatdesign.net/forums/showpost.php?p=160630&postcount=63

Angantyr, cutter rig
http://boatdesign.net/forums/showpost.php?p=160631&postcount=64

Boomless Cutter
http://boatdesign.net/forums/showpost.php?p=160633&postcount=65

Falcon II
http://boatdesign.net/forums/showpost.php?p=160536&postcount=221

yacht371

09-25-2007, 10:03 PM

The Cutter rig is less effective than a sloop of equal sail area BUT can often set more sail area. Racing rules measure sail area, so racing boats need to get the maximum performance out of a fixed area. Cruisers on the other hand can set as much sail as they like, and a cutter rig is one way to get more sail area without raising the mast. From personal experience the cutter is very fast on a close reach where the double slot seems to work best. Upwind, I haven't seen one yet that gives as good a VMG as a proper sloop rig.

A single sail (cat rig) is even more efficient if the mast is streamlined and rotating. The disadvantages are such that you will only see this rig on racing catamarans that can remove the mast when not sailing.

brian eiland

09-26-2007, 08:41 AM

The Cutter rig is less effective than a sloop of equal sail area BUT can often set more sail area.

A single sail (cat rig) is even more efficient if the mast is streamlined and rotating. The disadvantages are such that you will only see this rig on racing catamarans that can remove the mast when not sailing.

I think it depends on how you define the terms "effective' and "efficient" you use above.

The "single sail is even more efficient"? I would refer you to posting #106 above, and could provide quite a bit more:
http://www.boatdesign.net/forums/showpost.php?p=40229&postcount=106

lewisboats

09-27-2007, 11:59 AM

Australian NS14s - max hoist of main above deck 18ft/5.5m

There's enough roach on those to make a Rastafarian Proud!

brian eiland

08-10-2008, 11:31 AM

Paul B

08-10-2008, 01:41 PM

I wonder why they would chose an overlapping headsail for upwind work!!...and a 'cutter' arrangement at that?? :rolleyes: :D

New olympic Tornado catamaran sail arrangement
http://www.sail-world.com/USA/index.cfm?SEID=2&Nid=47504&SRCID=0&ntid=77&tickeruid=0&tickerCID=0

I think I remember a lot of nay-sayers claiming that an overlapping headsail was not productive...no need for overlapping genoas, nor cutters :rolleyes:

There doesn't seem to be any more overlap than the Jib, both sails are sheeted near the front crossbeam.

I've also heard they've been furling the jib while going true upwind with the Code Zero.

The use of this sail basically changes the boat from a fractional sloop to a masthead sloop with a much larger "J" dimension.

This setup is only good for very light air, where the extra power is going to allow hull flying much sooner than the conventional setup.

I'm sure you would love to use this as a way to argue for the aft mast cutter configuration you are fixated on, but you are barking up the wrong tree.

brian eiland

08-10-2008, 11:21 PM

There doesn't seem to be any more overlap than the Jib, both sails are sheeted near the front crossbeam.
I'm having a real hard time telling exactly where this sail is sheeted, but I seriously doubt it is sheeted near the front beam...just wouldn't work with the clew that high

I'm sure you would love to use this as a way to argue for the aft mast cutter configuration you are fixated on, but you are barking up the wrong tree.
I'll have some more on this subject later....probably over here under Sail Aerodynamics (http://boatdesign.net/forums/showthread.php?t=457)

Have you read AMO Smith's paper recently posted there??
http://boatdesign.net/forums/showpost.php?p=215039&postcount=313
You might have a look at page #518, Multi-element Airfoils, and his references to the 'dumping effect' or 'dumping velocity' that Tom Speer has addressed on several occassions.

CT 249

08-11-2008, 04:48 AM

I wonder why they would chose an overlapping headsail for upwind work!!...and a 'cutter' arrangement at that?? :rolleyes: :D

New olympic Tornado catamaran sail arrangement
http://www.sail-world.com/USA/index.cfm?SEID=2&Nid=47504&SRCID=0&ntid=77&tickeruid=0&tickerCID=0

I think I remember a lot of nay-sayers claiming that an overlapping headsail was not productive...no need for overlapping genoas, nor cutters :rolleyes:

Perhaps the added performance may have just the tiniest amount to do with the fact that the gennaker adds an extra 25 square metre to the 24 sq me main and jib?

Oddly enough, more than doubling the sail area often increases speed.

Goran Marstrom and A Class designers are not complete idiots when they choose cat rigs for other boats, nor are the AC and conventional guys like Farr fools when they choose fractional sloops.

Paul B

08-11-2008, 01:13 PM

Perhaps the added performance may have just the tiniest amount to do with the fact that the gennaker adds an extra 25 square metre to the 24 sq me main and jib?

Oddly enough, more than doubling the sail area often increases speed.

Goran Marstrom and A Class designers are not complete idiots when they choose cat rigs for other boats, nor are the AC and conventional guys like Farr fools when they choose fractional sloops.

You and I and Farr and Melvin and the rest of the world simply don't understand the theoretical world.

We get too caught up in the real world issues like weight location and how it influences pitch, abnormally high loading due to reduced backstay angle (even requiring a backstay spreader arrangement), the alarming problems associated with lack of headstay tension (causing the sails to become fuller at just the time you want them to be flatter), headstay angle, aspect ratios, etc.

Let's face it, no one, well, almost no one, is pursuing the aft mast cutter configuration simply because we, the establishment, are all wed to the status quo. If we could open our minds we could see just how wrong we all are.

brian eiland

08-12-2008, 09:24 PM

Don't get too upset guys, I'm not going to use this Tornado double headsail configuration in support of my aftmast concept, but rather in support of the 'slot effect' that has come under attack again. ;)

Since it was a 'double headsail', I thought it might raise some ardor if I put it in the cutter subject thread. :D Granted, it is not being utilized in the conventional cutter scheme, and I'm sure they might wish to douse that jib when flying the flat code sail so they wouldn't have to play that delicate balance with that jib inserted so close between the other two sails. But then again, if they douse that jib, they just might not be able to fly the 'flat spinnaker' so close to upwind.

Perhaps the added performance may have just the tiniest amount to do with the fact that the gennaker adds an extra 25 square metre to the 24 sq me main and jib?

Oddly enough, more than doubling the sail area often increases speed.
Very true...even upwind somtimes :rolleyes::)

I've also heard they've been furling the jib while going true upwind with the Code Zero.
Might be too much a distraction to fool with this step. Besides that jib might just be allowing the code sail to point a little higher (slot effect)

The use of this sail basically changes the boat from a fractional sloop to a masthead sloop with a much larger "J" dimension.
But masthead rigs are not as good as fractional ones....:rolleyes:

This setup is only good for very light air, where the extra power is going to allow hull flying much sooner than the conventional setup. Hull flying could be attainable in light airs by crewing on the lee side. This code sail is providing more power to go to windward.

I'm sure you would love to use this as a way to argue for the aft mast cutter configuration you are fixated on, but you are barking up the wrong tree. I agree here. I'm not arguing here for my aft mast cutter, but rather the slot effect making that big headsail more productive.

Here is an interesting comparision....the Code 0 spinnaker John Lovell and Charlie Ogletree have developed and are considering using in the Olympic Regatta and the one they used in 2004 to win the silver medal.

Tornado Code 0: Imaginative Innovation or Unscrupulous Advantage

Yesterday Dutch Tornado sailor Mitch Booth (who won two Olympic medals for Australia in the 1990s, but that's another story) submitted for measurement for the 2008 Olympic Regatta a spinnaker that is significantly smaller and flatter than the ones traditionally used on the Olympic catamaran, which of course is most likely enjoying it's last Olympic regatta as it's been removed from the docket for 2012. The big advantage of this spinnaker is that in under 8 or 9 knots of breeze it can be used upwind as well as downwind. Winds for this time of year in Qingdao are predominantly under 10 knots and often very light. The American team of John Lovell and Charlie Ogletree worked with Booth and crew Pim Nieuwenhuis to develop the sail and may measure in one as well. The Australian team of Darren Bundock and Glenn Ashby have created one on their own at the last minute.

Because the class doesn't have any minimum measurements for the spinnaker, it should be declared legal for class competition. However, it could well mean the Tornado medals are awarded based on breeze strength. A light-air regatta and the boats sailing with this Code 0, for lack of a better term, will dominate. In more moderate conditions, the traditionally rigged boats will dominate.

Not surprisingly, class favorite Roman Hagara of Austria is steamed about the development and has said he is considering boycotting the event if the Code 0s are used.