design for light airs

Well, I have written to Mr. Alan Buchanan and with any luck we will have the answer to question design displacement and ballast soon enough. I'll post when I receive a response.

Let me come at this question from a different angle, if I may.

Can I induce any of you with the computer know-how to compare the J-32 to the Crealock 34. The former represents a modern "small cruiser" and the latter an older version of the same.

The PHRF rating of the J-32 is significantly faster than the Crealock 34. The Crealock has the more narrow hull form that seems to have caught my fancy these days.

But here's the catch. Can we compare the two boats fully loaded with cruising stores for two? I suspect in a fully loaded condition that the superior speed of the J-32, particularly in light airs, disappears. Can anybody confirm or refute? Any what about motion in a seaway?

This is no idle question, for me. I aim to purchase a small cruiser at some point in the next five years when a good opportunity presents itself. Maybe even tomorrow should the right boat show up, as this Buchanan exercise has shown me. My first choice would be metal, but it has been clear from the beginning and certainly reinforced lately that no metal boat in my size is going to sail well in light airs. So . . . if I turn my affections to plastic boats, I have to choose between the modern approach, represented well by the J-32, or an older but not ancient design, represented by the Crealock 34.

Any analysis, comments, and observations would be greatly appreciated.

And perhaps I should state my intented use and prejudices here. I aim to use this vessel in retirement between Seattle and Alaska, up and down the inside passage. Maybe outside of Vancouver Island. Maybe to Mexico.

Personally, sailing is all about going to the windward in light and medium airs. All other points of sail are sub-dominate. That's because windward is where I always seem to be going, and in any case if you can go to the windward it sure opens up lots of cruising areas.

TIA.

 

Guillermo:

My mistake. I mistook tons/metric for English pounds. Thank you for the clarification.

I have friends who sailed the Pacific for 2.5 years in a early 1980s Beneteau 42 First. They started in Alaska, and turned around in New Zealand. The boat served them well and they loved it.

They had an epic return to Alaska. They ran out of money, so they left New Zealand and had only one stop before landing home in Alaska. They reported something like a month of sailing to the windward, every day, day in and day out, before pulling along side the Aleutian Peninsula, where they could turn downwind to home. The boat was up to it.

Other acquitances sailed in the Carribean seas in a different year Beneteau 42. It pounded so badly that when they landed in Mexico they swore off sailing, sold the boat, and got sued by the purchaser because the bulkheads were separating from the deck and hull.

I'm not sure what all this means, but it's fun to know. I'm pretty sure the two boats had different designers. I know the first boat was a Frers design (did I spell that right?). I'm not sure about other Beneteau.

 

I think this is a risky statement, being said like that. I'm not sure what you mean. Initial stability depends mainly on forms, and ultimate stability depends mainly on weight and its CG position. Modern racing machines are beamier (so higher initial stability, this is, higher GMo) and concentrate a big amount of weight in a very low position (bulbs) to get bigger righting arms at the higher angles (even canting it). If we diminish weight but keep its CG position the same, the increasing in beam increases the initial stability.....

 

I think if you were to build a scaled up whitehall pulling boat hull, put a deck on it, and give it a big carbon fiber rig and a canting keel you'd have a great light air boat. Something like http://www.chuckpaine.com/pdf/17NORSEBOAT17.pdf but with a larger sailplan, a canting keel, and enclosed side decks so it'd come up dry from a capsize.

A Ray Hunt 110 or 210 with a canting keel and a bigger rig would also work.

A boat I know to be devastatingly fast in light winds, and very easy to build, is the 11 foot Mistral Moth. Scott Sandell races his in the Modern Moth division, so his sailplan (see photo) is larger than those racing as Classic Moths. The boat is easy to build from sheet materials, and patterns can be had for $10. Though it's wide on deck, it's nearly V shaped midsection makes it very narrow on the waterline. The hull is deep in the water midships, with lots of rocker so that the knuckle at the bow, and the transom, are at or just above the waterline even with a 180 pound sailor aboard.

Scale a Mistral hull up by a factor of 3, build it out of Alucobond <http://www.alucobond.com/>, give it a lifting bulb keel (from a Hobie 33 maybe?), a carbon rig, and your new light winds 33 is off to the races!

I think keel (or daggarboard) and rudder areas should be generous, and sections forgiving (0012?) for light conditions. Getting the foils out of a stall as soon as possible becomes imperative. The ratio of lateral area to overall wetted surface might be an indicator of ability to do this. Trying to save on wetted surface by making the foils small would probably be a mistake, in my opinion.

 

Got an email from Mr. Dick Durham. He sold his Buchanan Yeoman Junior three years ago.

FWIW, I will be out of town for a week.

 

Well I was hopping that you were mistaken in that weight...and I was diplomatically waiting for you to correct...but no, it seems that you are really talking about an old 50ft, 10 T cruising sail boat.

It can only mean two things: Or you honestly don’t know of what kind of boat you are talking about or you know and then you are not being honest in this comparison.

About the Beneteau:

Anyway you are not being honest when you say that the Beneteau 50 "is a...good performer in their time”. Or perhaps you really don’t know that the Beneteau Oceanis 50 is the floating condo from Beneteau, a slow boat in the Benetau range. And even so your numbers are not right, the boat weighs only 13T ( this is the light weight boat, but I believe the 10T of the other boat is also a light weight) and has some more sail than the one you have considered ( instead of 105, it has 115.8).

http://www.beneteau.com/ressource/documents/4165/B_oceanis50_230606.pdf

The only 50 ft Beneteau that can be considered a “... good performers in their time” is the new First 50. This one will displace 12.8T for 138.7 m2 of sail.

http://www.naucat.com/katalog/repDetalj.asp?id=1293

Of course, has this it a new boat, you can consider the older boat, the one this one replaces, the First 47.7, that has a displacement of 11.5T and 120 m2 of sail Area.
http://www.beneteauusa.com/sail/previous/first/477_intro.php



The Luders 50ft/10T:

Alfred Luders was a good naval Architect who has made racing boats and cruising boats. HIs most famous boat is American Eagle, a racing 12 mR that was the Americans cup challenger in 1964. The boat was modified for ocean racing by Ted Brewer and has won a lot of races, including the 1972 Sydney-Hobart.

http://www.americascupcharters.com/us21.htm

His most known cruising yachts were the Sea Sprite series.
http://www.seasprites.com/BoatsFrame.htm

A 50ft Luders with 10T can only be a racing boat. I have doubts that you can call that a cruiser-racer, (the boat you have posted is racing), and I seriously doubt that that boat has only 10T.

Typically, racing extreme boats of that time (60’s) with around 15m were the 8mR class boats, a kind of scaled down America cup boat (the 12mR class).

A typical boat of that class, probably from the same time of that 50ft Luders is the Olin Sthephens designed 8m Racing sailboat Iroquois, a 1967 boat with 14M, displacing 9.5T with a beam of 2.4 a draft of 2.0. They don’t say the sail area, but typically in the 8mR class, it is between 75 and 80 m2. This boat is a very competitive one and has won the 1984 8mR cup in Norway and the 1985 Sweden cup.

If a truly fast, 46ft top of the range, racing boat of that time displaced 9.5T, how do you think it is possible a 50ft cruising boat to displace only 10T?

These boats were so beautiful and gave so much fun that the class still exists, with new boats competing against old boats.

Even today, using modern building techniques (cold molded mahogany and epoxy vacuum techniques) it is only possible to make a 8m Racing class boat with 8.2T, like the Spazzo, (2000 world cup winner with a LOA of 13,4 m carrying 82m2 of sail) .

http://www.spazzo.de/specs.html

It is just not possible to have a wooden 50ft cruising boat in the sixties with 10T.

Of course that boat you have posted looks like a racing boat (and it is racing in the photo) and even so, comparing its appearance with the one of a 8mR class boat, I would say that it must have more than 10T.


Only you, Guillermo, would try to compare a racing design from the sixties with a relatively slow fat condo from nowadays to see how they compare in their light wind performances saying :

“Just to compare old and new boats:
Fisrt, let's compare boats with similar overall length and recognized as reasonably good performers in their time.”

How about to compare 50ft modern fast cruising boats with old fast cruising boats and 50ft modern race boats with old fast race boats?

Here you have my contribution: This is a good fast old 50ft cruiser (Luders designed) sailboat with 13 T. They don’t say the sail area but in that time a cruiser had relatively small sails, by modern standards.

http://www.yachtshare.com/boats-for-sale/Luders_Yawl_2007_50_4604.pdf

Guillermo, I like boats and I like to discuss boats, but I don’t like pointless arguments nor I discuss to win or lose an argument, just to learn and to share what I know.

Obviously it is not your case. It is not the first time you utilize fallacious arguments to prove your point even if they make no sense at all (comparing an old racing boat with a modern slow cruising boat, regarding light winds performance).

I don’t know if you need to be always right or if you really don’t know much about sailingboats. For one that can go so low on devious arguments, you assume many times a patronizing tone, like in the post 63, while you say things that have no sense at all, like this:

It depends on the type of hulls Guillermo ...

Then in a 8mRacing 47ft boat (like the one posted) with a beam of only 2.5m and very little form stability, do we assume that it must have a very limited sail carrying capacity (initial stability)?

How the hell do you think it gets the initial stability to carry 93 m2 of sail? Certainly not in its form stability, but in its low center of gravity.

Please, Guillermo, try to be a little more modest and don’t assume other people don’t know what they are talking about. It is not agreeable and obviously it is not always true.

 

Here you are:

J-32
Lh = 9,88 m
Lwl = 8,84 m
Bmax = 3,35 m
Draught = 1,83 m
Disp = 4536 kg
Ballast = 1746 kg
Sail area = 48,12 m2
Power = 27 HP

Displacement /Length Ratio D/L = 183,15
Sail Area /Disp. Ratio SA/D = 17,84
Power / Disp. Ratio 6*HP/D = 16,19
Hull speed HSPD = 7,22 Kn
Potential Maximum Speed PMS = 8,11 Kn
Velocity Ratio VR = 1,12
Comfort Safety Factor CSF = 2,04
Motion Comfort Ratio MCR = 20,98
Screening Stability Value SSV = 72,2
Angle of Vanishing Stability AVS = 116,43 º

Roll Period T = 2,13 Sec
Roll Acceleration Acc = 0,19 G's
Stability Index SI = 0,64


CREALOCK 34

Lh = 10,38 m
Lwl = 8 m
Bmax = 3,05 m
Draught = 1,5 m
Disp = 5439 kg
Ballast = 2130 kg
Sail area = 60,5 m2
Power = 34 HP


Displacement /Length Ratio D/L = 296,3
Sail Area /Disp. Ratio SA/D = 19,88
Power / Disp. Ratio 6*HP/D = 17
Hull speed HSPD = 6,87 Kn
Potential Maximum Speed PMS = 7,96 Kn
Velocity Ratio VR = 1,16
Comfort Safety Factor CSF = 1,75
Motion Comfort Ratio MCR = 29,95
Screening Stability Value SSV = 45,52
Angle of Vanishing Stability AVS = 121,26 º

Roll Period T = 3,02 Sec
Roll Acceleration Acc = 0,08 G's
Stability Index SI = 0,99



A review of J-32: http://www.sailingbreezes.com/Sailing_Breezes_Current/Boat_Reviews/j32_review.htm

 

Paulo, you're getting insultant...Not good.

 

Can you explain that? I am not rude, least of all insultant...honestely.

 

Hiracer, has I have said I don't believe it, but here you have the Graph for those numbers.

 

Don't forget to take into acount substantial weight of the steel plates of the keel. (Keel plates are practically always much thicker then rest of the hull). That weight is oftenly forgoten in the calculations and only lead ballast is calculated.

I like the concept. Why Alucobond?

Milan

 

Well, you can go into something in between those two boats.
Some modern boats are strong probably faster than the Crealock 34 and still can carry a significant load
But they tend to be rare and expensive (not main big production market).

 

Two kinds of light wind conditions

It seems to me that there are two different kinds of light wind conditions.
1.) light wind and flat sea and
2.) light wind and glassy swell.

In the flat sea condition, a very light and preferably unballasted boat does the best. A light beamy keel boat does 2nd best. And a heavy keel boat takes up the rear. Even though the beamy boat might have a lower ultimate speed, that hardly matters in these conditons. A very light beamy boat such as the one I used to own with a large drifter is all but untouchable in these conditions for anywhere near the same investment.

In the glassy swell condition, things are reversed. The heavy keel boat now has the advantage because it can conserve its momentum. It is not stopped by every third swell it comes accross like the light, beamy, boat is and tends to keep on moving even when boats even with higher S/D ratios are stopped dead in their tracks. The light keel boat, once again, ends up in the middle.

Much is said about length/ displacement numbers, but I am more interested in Beam/Displacement. This number, I call the 'heft ratio'. Some very light boats, such as sea kayaks and even multihulls can have high heft ratios because of the extreem slimness of thier hulls. They, given the ability to carry sufficient sail area, should make excellent light wind boats. But they must present a good, sharp, 'V' to the swell. This can be done two ways:
1.) have a deep 'V' bow, and
2.) heel a flatish bottom over deliberately to present a 'V' to the swell. I once knew a heavy, full keel, but flat bottomed cutter which was respectable in light winds for this reason. Its large press of sail easily heeled it over to a certain point even in the lightest of winds. I used to call it the 4kt wonder. It always seemed to go 4kts, no matter what the wind strength.

I spent more time sitting on the lee side than I did on the weather side of my beamy centerboarder for the same reason

My heft ratio works like this: 20 disp. vol./Length * Beam^2. 'Beam' is taken as the (Waterline Beam + the beam 1/8th the waterline Beam up)/2. I consider a HR of 1.0 a good compromise. I like higher numbers such as 1.5 to 2.0, but thats just my personal taste. For multis, I add the Beams of the two most leeward hulls together to figure thier HR.

Bob

 

Interesting, Bob. There's an older moth design with a rounder midsection (BWL is wider, BMAX is narrower) and a fuller bow that will keep up with the Mistral Moth in light air and flat water. But the V section Mistral moves out in waves, as your analysis suggests.

Do you think the greater lateral area / total wetted surface ratio of a narrower boat may be helping the foils to get out of a stall faster (in addition to the momentum issue)?

When I have time I'll be interested to explore whether your heft ratio equation scales the same way as what I've posted for powerboats at http://www.boatdesign.net/forums/showthread.php?t=12440

My hunch is that a 5/3 scale Etchells, "turboed" with a big fractional carbon rig that flies masthead chutes, and a deep bulb keel, would leave both the Luders 50 and the Beneteau 50 in its wake, waves or no waves. And a lower Cp hull shape more like a whitehall pulling boat might do better still in the light stuff.

Anyone want to run these comparisons?

 

Bob, what kind of boats are you talking about? We were talking of 50ft boats. I think you are talking of dinghies when you mentioned unballasted sailboats, what the French call " small deriveurs", or am I not understanding something?

What do you mean by “glassy swell condition” (sorry about my English), do you mean small ripples in the water? What kind of swell do you normally have in light winds?

A 50ft boat has a big momentum and it will not be stopped by very small waves.

The experience that I have from club races tells me that in light winds, 3 to 7 knots, the ones that have an advantage are very light boats with a huge SA/D.
A heavy long keel boat simply can not, in light winds, physically carry enough sail to compensate its bigger height and its superior wetted surface area.
If we are racing in a lake, then those 10 or 12 m racing boats with 8 or 10 guys in a trapeze and very small ballast would win hands down.

Of course, I am not talking about light winds on a cruiser perspective, but on a regatta perspective, and that is not what was in discussion on this thread. In these very light conditions, I agree that the LWL is not what counts. In very light winds I have already beaten bigger boats that would be faster in more “normal” conditions, and I have also been beaten by smaller boats than mine, lighter and with a big SA/D.

In light winds, the quality of the sails (racing carbon sails) also makes a big difference.