Seaworthiness

Since it is my thread and I collected the data ...

If you look at boats that are limited to displacement speeds, you will find that passage speeds have not changed very much over the last 100 years. That is what you would expect, since the physics of oceans has not changed either. This years S-H was predominately upwind, and even the most modern canting keeled, rube goldberg designs were basically limited to displacement speed (as shown in the result that an old S&S design won the race on corrected time). IMO when boats that sail a course at lower S/L ratios beat boats that sail at higher S/L ratios, it is the fault of the rating rule. In the S-H I think that Ichi-Ban, Wild Oats, Love & War, and Skandia should have corrected out in that order.

The only reason that newer boats are "faster" than older boats of the same LWL is because they are able to exceed S/L = 1.34 a greater percentage of the time. The rating rule must try to account for this, but when conditions prevent the boats from sailing at angles that allow high S/L ratios, the "wrong" boat wins. Not on topic, but upwind speed for ocean racing boats has not changed very much over the last 100 years. S/L .9-1.3 is about where they sail. Ocean racing mono's just don't have the power to sail upwind much faster.

What they do have is enough power to sail in semi-displacement mode at S/L 1.5+ on some courses and truly plane on other courses. This shows in the higher average BDR and Downwind passage speeds that modern boats achieve.

If you look at the Trans-Pac (Southern California to Hawaii) it is a predominately downwind route as would be chosen by a cruiser. In 1936 Dorade was 1st to finish, 1st in class, and 1st overall on corrected time. Her S/L average was 1.14. In 1939 Dorade only managed a 0.90 S/L average for the Trans-Pac. The design did not change, conditions did.

If you look at best days run and downwind passages (the kind I would choose as a cruiser) you will see that mono hulls have been stuck under S/L 1.5 until the 1980's. The pre-WWII "wooden boats" averaged about 1.25 S/L for BDR, Plastic boats (post WWII) averaged 1.41 S/L. Dorade (50 ft LOA on LWL 38) managed a BDR at 1.44 in 1931.

As soon as you get into the ULDB era (post 1988 or so), the monohull average jumps to 2.44 from the 1.32 S/L that all the mono data points I looked at averaged.

The reason is quite obvious. Increased power to weight ratios. It only takes power equal to 3-4% of the boat's displacement to drive it at displacement speeds. It requires 10%+ power to weight for the boat to plane.

I most certainly agree that unless a boat has the power to plane in cruising wind speeds (Force 4-6?) there is no point in adopting planing hull forms. As you rightly state, they are fashion. If the boat will operate in displacement mode for 90% of it's sailing, it would be more seaworthy and seakindly to use a traditional hull form. If, however, the boat has enough power to exceed S/L 1.5 in moderate breeze it makes sense to me to adopt a planing hull shape.

One way to get high power/weight ratios is with high SA/D ratios. For a 10000 pound boat to plane you need 1000 pounds of drive force. If we design the boat to plane in 12 knots true wind we need about 1100 sq ft of sail area. (assumes Cl=1.9 for sail force = .912 pounds/sq ft). It is very hard to pack 1100 sq ft of sail on a 25 foot waterline.

When boats have high RM they can make 10% + drive force over a wider range of angles and spend more of the time at speeds above S/L 1.5. The Pogo does this at some angles in only 12 knots true (lower end of Force 4), In Force 5 she can sail faster than S/L 1.5 at all angles greater than 70 deg. At 130 deg off the bow the S/L ratio is 2.0+ in Force 5. when you get to Force 8 (35 knots) the Pogo can sail at S/L 1.5 + at all angles over 60 deg, and tops out at S/L over 3.0!

What does this mean to a cruiser?

Compare a typical cruise in a C30 and a Pogo40:
Victoria BC - San Francisco in October:___C30 7-8 days_____Pogo40 3-4 days
San Francisco - San Diego in October:____C30 4-5 days_____Pogo40 2-3 days
San Diego - Cabo San Lucas in November:_C30 8-9 days_____Pogo40 4-5 days
Cabo San Lucas - Maui in April:__________C30 23-25 days___Pogo40 12-13 days
Maui - Victoria in May:_________________C30 19-22 days___Pogo40 11-12 days

The obvious pattern is that the Pogo has more freedom to chose her weather. 3-5 day forecasts are much more reliable than 7-14 day forecasts. It is also obvious that the Pogo will need to carry a smaller load for each of the legs, so her performance and seaworthiness will not be compromised with extra "cruising stuff".

The greatest chance of gale conditions on the cruise is less than 3% on the Victoria - SF leg. The Pogo needs a 3-4 day window, the C30 needs 7-8 days. Expected conditions are 15.5 knots of breeze and 5-6 foot waves. I doubt that the Pogo would have a less seakindly motion under those conditions than the C30, they are not extreme.

As long as you cruise in boats with SA/D ratios less than 15:1 and D/L ratios of 200+ you might as well copy Dorade.

Just my opinions.

 

"If you look at boats that are limited to displacement speeds, you will find that passage speeds have not changed very much over the last 100 years."

I certainly don't agree with that. I don't think you can just pick a few few figures and use them to apply to the wider world. Sydney-Hobart S/Ls are definitely dropping. So is that of just about every race. If boats weren't getting faster why don't boats from the 1900s still hold the records? Why has the Transpac and Transat record dropped despite the boats being over 100' shorter these days?

The performance of boats limited to displacement speed, even boats that were quite heavy like an S&S IOR boat like Love and War, a Ganbare type Peterson or an early Farr type (which only surfed occasionally) was considerably higher than that of older boats. Take Caprice of Huon. In 1965 she was top-scoring boat in the Admiral's Cup and about as fast as any 45 footer. By 1973 she was 10% slower than the Lexcen and S&S heavyweights of similar length. She's been restored and is back racing, and she's about 10% slower than a modern 30 footer. A Beneteau 31.7 would be quicker. The old boats are not as fast in any conditions.

There is a reason that Dorade, Malabar, Caprice gave up ocean racing - they were outmoded in speed by later boats. Dorade just wasn't as fast as later yachts and she was beaten by them.

Look at great designs like the Reimers "Bachante" from the Great Lakes and the similar 62' Fidelis from Sydney (formerly NZ). In the mid '60s Fidelis took line honours in the Hobart. Last year she was 52nd across the line, behind old production 38 foot racer/cruisers. She was 2.5 knots slower than the top modern 60 footer. If a boat drops from 1st to 52nd over the line there is room to indicate that maybe, just maybe, boats are getting faster. When former champs average 2.5 to 1 knot slower than modern champs it is hard to see how they are not faster.

When Love and War won the '78 Hobart, she was 6th or 7th over the line. When she won the 2006 Hobart, she was 32nd over the line in a much smaller fleet.

Age allowance here in IOR days was about 0.5% per year, on top of other rating features like DLR and MkIIIA which gave older boats a big break. If boats were not advancing, even under that restricted rule, at more than 0.5% per year new boats would have been beaten. They weren't beaten, they normally won.

I have sailed an IMS nationals on arguably the most successful older boat in the ocean racing world today - 4 times UK Yacht of the Year; 4 times Fastnet class winner. Commodore's Cup victor. Sydney Hobart class winner.

This 1965 boat gets eaten alive by a Beneteau 40.7 in all conditions. It can't see which way a Farr 40 (IOR or OD) went. It gets hammered at about a minute a mile by a fast IMS 30 racer/cruiser.

Love and War was a knot slower even in her favoured conditions than a modern boat. That's a fact and it indicates the improvement in design since 1973.

In light winds, when no one is close to 1.34, the modern boats give the old boats a real caning generally. When you go a knot faster upwind in a breeze AND go much faster in light winds AND exceed hull speed and surf away downwind, that's good performance.

Personally, I can't see why a boat with a high S/D ratio should necessarily win. That will typeform design with all boats with very short length, massive rigs and RM for their length, and minimum displacement. Old boats may as well not turn up. Cruiser-racers may as well just not turn up. Boats with smaller rigs (more seaworthy, cheaper, arguably more efficient) may as well not turn up. And the boats that win (assuming enough turn up for a race) will still be slower than a multi.

Interestingly, there is a very strong correlation between having a system that means that development boats do NOT become totally obsolete quickly, and having a strong development class culture. The US gives very little care to outmoded development class boats, and it has a terribly weak development-class culture and most people sail ancient designs. The UK and Australia devote a lot of care to ensuring development boats stay worth something so owners can afford to sell them and then use that money to buy a new boat, and they have strong development class cultures.



That is what you would expect, since the physics of oceans has not changed either. This years S-H was predominately upwind, and even the most modern canting keeled, rube goldberg designs were basically limited to displacement speed (as shown in the result that an old S&S design won the race on corrected time). IMO when boats that sail a course at lower S/L ratios beat boats that sail at higher S/L ratios, it is the fault of the rating rule. In the S-H I think that Ichi-Ban, Wild Oats, Love & War, and Skandia should have corrected out in that order.

The only reason that newer boats are "faster" than older boats of the same LWL is because they are able to exceed S/L = 1.34 a greater percentage of the time. The rating rule must try to account for this, but when conditions prevent the boats from sailing at angles that allow high S/L ratios, the "wrong" boat wins. Not on topic, but upwind speed for ocean racing boats has not changed very much over the last 100 years. S/L .9-1.3 is about where they sail. Ocean racing mono's just don't have the power to sail upwind much faster.

 

Very nice posts, Chris and Randy.

Randy, I agree that for coastal cruisers intended for weekend sailings and occasional 2/4 days crossings, in an area where you have available good 3-5 days forecasts and where you need not to carry heavy loads because you have available 'land support' easily, it makes sense to go for light and fast boats. You may take advantage of their speed by covering a greater area in the same amount of time or the same one in an shorter time. The only draw back I see is that coastal waters may be or become very tricky, in spite of weather predictions, and you may get caught into trouble, suddenly struggling against strong head winds and confused seas, which can make life very interesting for an excesively light and beamy boat not able to quickly go through or run off. And to find those conditions in coastal waters is not so rare. In fact it may prove relatively common, at least in my experience. And let's put, over this, the possibility of a dicimated crew (seasickness, injuries or whatever other reason) leaving the helmsman alone to take the hardest of the punishment for several hours or even whole days.

For longer passages the risk of encountering this kind of limit situations is higher and you may be forced either to quickly run off, losing a lot of hard earned miles, run under drogues, lay at sea anchor or heave to. Running quickly off is better done with a lighter and shorted (chord) keeled boat, but for the other three options I think heavier boats with longer keels are better suited, generally speaking. And we have to take into account that when you go cruising for extended periods, specially in not so well 'land supported' areas, a light boat may have her running ability impaired because of heavy loading.

As I think a cruiser boat has to look after you in whatever the circumstances, even if the probability of being caught in life threatening situations is very low (For me a 0,01% is enough, if I sail other than alone), I would like my boat to be able to defend herself precisely at those moments. That's why advocate the use of boats relatively heavy (230-300 when loaded?), prudently beamed and freeboarded, with manegeable sail areas, a sheltered helming position, and a nice iron genny, for all around cruising use. Precisely because the sea is what it always has been.

Cheers.

 

I didn't say that boats aren't getting faster, I said displacement monohulls are not getting faster.

Look at the numbers:
Dorade: 52' LOA, 37.25' LWL, D/L 326
Cal 40: 40' LOA, 30' LWL, D/L 248
Farr 40: 40' LOA, 35.27' LWL, D/L 110
Mumm 30: 30' LOA, 27.56' LWL, D/L 97
Pogo40 (Cruise): 40' LOA, 40' LWL, D/L 82

In 1967 the Cal 40 was a lightweight skimming dish, fit only for surfing downwind ... at D/L 248!

It is not news that ULDB's like the Farr 40 and Mumm 30 can pull a horizon job on a boat that has D/L 300+

You cannot consider a boat with D/L under 125 to be sailing in displacement mode in breeze over Force 4. The reason that these boats rate so much faster than older boats of the same length is because they are not confined by displacement. The crew is also a larger percentage of total weight on the new racers, this increases their ability to carry sail.

I think I said that it was not until ULDB's that records started to fall.

If you compare cruising boats of like D/L, I think you will find that passage speeds have not changed very much in the last 50 years. Around the cans speeds have improved, due to better VMG up and down and the ratings reflect this more than any advancement in hull shape.

A 300 D/L boat in 20 knots @ 130deg might sail at S/L 1.60
A 110 D/L boat in 20 knots @ 130deg might sail at S/L 1.95
A 82 D/L boat in 20 knots @ 130deg might sail at S/L 2.05

The increase in race and passage speed is a result of boats with lower D/L being designed to cross oceans.

Higher rated speed is a function of both lower D/L and better windward VMG.
300 D/L best VMG .8 S/L
110 D/L best VMG .93 S/L
82 D/L best VMG 1.0 S/L

Since the rating rule tries to handicap 300 D/L boats and sub 90 D/L boats with one number, there will always be conditions that cause odd results. Love & War winning the S-H is one such result. If the race was a heavy air reach, there is no way she would have kept her time against boats that can sail at S/L ratios over 3.0

I think it is fair to say that new cruising designs of any D/L are not much faster than older boats of the same D/L. I think the newer boats are stronger and more seaworthy (for equal D/L) than the old ones were. Now that Cruising D/L's are under 200 in many cases, a semi-displacement hull with good power should be a joy to sail on a trade winds route. Since these boat also tend to have fin keels and more modern underbodies, they should also be better able to work off a lee shore and maintain control in conditions that would overwhelm the older heavier boats (forcing them to heave to).

 

But displacement boats, by their very definition, are boats that can not readily exceed S/L = 1.34, so of course, if you look at BDR, they don't appear to be getting faster. But modern boats can sail at S/L = 1.34 in lighter winds.
Also, as you state, modern boats can sail closer to the wind, so have a better upwind VMG.

 

Even before boats with DLRs under 125, design developments were leading to improved speeds. To take just one example, the Imp (Holland) / Dida (Peterson) shift to wider sterns in IOR boats, 78/79, created an increase in overall performance of about 0.75-1.5% in a single generation. Imp was sailing around in the 1977 AC and SORC with boats 2' longer.

Ganbare, at 35', was about 1.5-2% quicker than the 37-39' batch of S&S and Carter one tons of a year or two before.

These are displacement monos. They were getting faster, and significantly faster. PHRF, IRC, IMS, LYS and every rating or measurement system under the sun, as well as thousands of examples of boats out there sailing, proves that boats WERE improving in their speed well before they became semi-planing. It was in fact one of the great criticisms that designs were developing TOO fast, so that boats were outmoded too quickly.

A classic case would be the 1976-78 era. In half tonners, for example, the world crown went from a Holland 30 (narrow stern, masthead, heavy displacement, PHRF 144 approx) to a Davidson 31 (wide stern, fractional, light, centreboard) with the heavy-ish Holland custom SIlver Shamrock III almost winning the worlds in between.

This pattern continued. Farr's 1981 40 (The Roperunner) was uncompetitive by 1983 (apart from age allowance) and the 1983 vintage design 136 was outmoded by 1987 unless it was a heavy beat.

Records did start to fall before ULDBs. Kialoa (an S&S design) took the Hobart record in 1975; she was no ULDB. The heavy Frers Flyer took 10 days off the Round the World record in the second Whitbread; she was no ULDB. A Fastnet record was set in 1939 by the 85 ft Nordwind; broken in 1965 by the 90ft Gitana; smashed again (I think) by the 77 foot Condor (1) in 1979; then again by the 80ft Nirvana, a luxurious racer/cruiser. Nirvana, very much a displacement boat, also held the Bermuda record. The record cannot be denied; later displacement boats are very much faster than older displacement boats.

As I said, age allowance ran at abouyt 0.5% p.a. through the '70s and '80s. It had to, because boats were getting quicker at that pace. Try putting (say) Windward Passage II, Matador II or Sovereign up against Tempest, Kialoa III, Bolero or Baruna and you'll see how much speeds have improved. Even in the days of bad old IOR the old maxis like Kialoa II and Ondine III were well and truly out the back door against modern displacement maxis; they rated 10%+ lower and still finished well behind on corrected time.

This is looking mainly at passages, not round-the-cans.

 

I can't help with why but 'Hooligan V' (Ed Broadway, Royal Southampton Yacht Club) was a Max Fun 35.
http://www.simonis.com/gallery.php?did=9

Conditions: Wind F5, Sea 1 mtr.

She was corrected time winner of the 2 handed RB&I Race 2006:
http://www.simonis.com/news.php?pos=0&nid=32

And RORC Boat of the Year 2006, IRM Class 1.
http://www.maxfunboats.nl/news.php?pos=0&nid=47

And finally
http://www.hooligan-v.org.uk/

 

Yes Guillermo, it is a very nice boat (post 520), but even with a very small inverted stability and a 140ºAVS it is not necessarily more seaworthy than a beamy boat .
The Nordborg 40 has a STIX of 34.5, in MOC and LDC.

http://www.nordborg-baadbyg.dk/da/index.php?B%E5dtyper:Nordborg_40

By the way, I have got the Pogo 40(cruising version) STIX in MOC condition: 41.3.

 

I agree that in modern boats special care should be taken regarding the keel and the spade ruder. Some manufacturers have greatly improved safety in these areas. Cantieri del Prado, the manufacturer of Grand Soleil is one of them. Look at the Steel structure that holds the keel and the shrouds .

 

Nice, Vega.

 

You know I do not agree (And I'm not the only one around here) on how STIX works, because it can be very tricky. Beginning by the waterline length issue....

 

Quote:

Originally Posted by Vega
Yes Guillermo, it is a very nice boat (post 520), but even with a very small inverted stability and a 140ºAVS it is not necessarily more seaworthy than a beamy boat .
The Nordborg 40 has a STIX of 34.5, in MOC and LDC.

http://www.nordborg-baadbyg.dk/da/in...er:Nordborg_40

By the way, I have got the Pogo 40(cruising version) STIX in MOC condition: 41.3.

I believe that when you say, "I do not agree" you are talking about the STIX.
About it, you know that I have said that I believe there are better ways, for knowledgeable people, to analyze a boat’s seaworthiness. The STIX is designed as a general tool to give the max information on a boat’s stability with just one number. And looking at it this way, it is the best tool available.
Saying that, I would say that I agree with you about the waterline issue.

But the important issue is this one:

” even with a very small inverted stability and a 140ºAVS (a narrow boat) it is not necessarily more seaworthy than a beamy boat”.
About this I have said in previous posts:

Please look at the compared RM curves, in the slide taken from a presentation by Professor Miller about “Stability and Structure” for a 2003 Seminar on “Safety at Sea”.

Typically a beamier boat will have a bigger positive area under the RM curve and also a bigger area under the negative part of the RM curve, with a smaller AVS.

Comparing the Miller curves, the narrow boat is clearly more seaworthy, or at least its static stability curve is a lot better regarding Safety. Not only its Positive area is not much smaller than the one of the beamier boat, but also its RM moment at 90º of heel is more than 2 times bigger than the one of the beamier boat.
There is also a huge difference in the AVS of the Narrow boat (150) to the AVS of the beamy boat (105) and that corresponds to a huge difference between the inverted stability of both boats, as it is shown in the curve.

Now, if we compare the Pogo stability curve with the one from the Nordborg, we will see that, considering the Rightening arm, at 90º of heel, actually the Pogo’s arm is 2 times bigger than the one from the Nordborg and that the area behind the positive part of the GZ curve is more than 2 times bigger than the one on the narrow boat. And also that the difference in the AVSs (127 to 140) and in the negative part of the GZ curve is much smaller than the relative difference in the comparative areas of the positive part of both curves.

This will make the Pogo a more difficult boat to capsize and the Nordborg an easier boat to recover from a capsize. And I am referring to a totally inverted position, because the Pogo, with it’s bigger RM at 90º of heel, would recover from a capsize without rolling, faster than the Nordborg.

Of course I am not taking weight into consideration (to transform GZ in RM) nor am I trying to say that a narrow boat is less seaworthy than a beamy boat. I even consider that special care should be taken on the evaluation of the boat’s stability, with what you call a beamy boat, and that the stability curve should be carefully examined by every buyer.

I am only saying that a narrow boat is not necessarily more seaworthy than a “beamy” boat and that each case is a case. Every boat should be looked individually, avoiding generalization. If well designed, what you call “Beamy boats” can have advantages, different advantages than the ones you get on narrow boats.

What makes a good and seaworthy cruising boat it is not being narrow or “beamy” but the way those balances and advantages are put together, in a good or bad design. With an adequate balance between speed and seaworthiness, between the energy needed to capsize the boat and the energy to re-right it , and of course, a lot of other factors. In the end I believe that personal taste, regarding sea motion, interior space and aesthetics would be the factors that lead to a choice, providing the average sailor knows what he is buying.

 

I totally agree.
Doing a very quick and rough calculation the righting moment at 90º of the Nordbog (for 7700 kg) is around 4000 kgm and Pogos' (for 5300 kg) is around 4500 kgm, so not that big difference, and the Nordborg probably behaves in a more seakindly way, which is important for cruising mode, from my point of view.
My only concern with the Nordborg (from the point of view of stability) it that it seems to have a quite high Dellenbaugh's angle, so being quite tender. This may force to reef too soon....

By the way, do you have a profile or photo of Pogo cruising version's underwater hull and keel?

Cheers.

 

The photos appear to show an undamaged hull exterior. So mechanical failure of either the bolts or the backing plate? I'd be interested in hearing from the professionals about this.

 

Or the keel itself.