Are we making any real design improvements??

[SuperPiper]

In the Vendee Globe, the new generation of Open 60s are beating the older generations of Open 60s. Although . . . the better skippers have the better boats and the better sponsored campaigns . . .

[DryWaves]

Speaking of ratios, do you know of any resource that would have the SA/DSPL and DSPL/L figures for the Olson 40 designed by George Olson? I've been running some comparisons with newer designs, but I don't have the numbers on the Olson 40.

Thanks

[edward]

Just on this issue, i have just posted a new thread about clinker hull design which is an older hull design. I have heard it said that the clinker design on certain hulls is faster that a smooth hull of the same shape. If this is so then we may be going backwards.

[edward]

Wardy

I have got interested in hull design because of another problem I am looking at - the design of curving canals across rough terrain that maximise the flow of water. I think boat hull design might provide a few ideas on how canal shapes might be modified to increase the flow rate for a given canal cross section area. Have you discovered any trends in boat speed from you data base, particularly in relation to clinker designed boats? I have a hunch that the ridges play a role in stopping transverse flows around the hull and that this might reduce overall drag.

[D'ARTOIS]

Check the America Cupper's designs - it has be executed by a long time already; specifically designs under Dennis Connors or whatever his name is - in the period that the Van Oossaanen keel was introduced.

There are no new idea's in marine design, only variables.......

[Tim B]

edward,

It depends under what circumstances they reduce drag. Let me give a similar example...

A powerboat with a stepped hull is incredibly efficient at high-speeds, but pitifully in-efficient at anything below planing speeds.

Similarly, there is a time and a place for clinker. The "transverse flow" does not actually exist at any great amount I'm afraid, the flow may be a few degrees from the centre-line but SIN (4 degrees) = 0.069 ie. 7% of the flow, which is incident to the hull along the forward section. I believe it straightens out after that (have yet to do the sums). What I suspect the clinker-style is doing is effectively giving a vertical lift vector, thus reducing the wetted surface area (and hence drag).

Anyway, that's my thoughts on that (I'll go and run the CFD at 4 degrees sideslip now)

Oh, and before I forget... D'Artois, which planet are you living on, man? of course there's new ideas in marine design. It's just that nobody's talking about them because they want to get there first!

Cheers all,

Tim B.

[usa2]

one would think that there are design improvements happening because people keep building new boats that are getting faster. Granted, they might be getting faster by 0.000000001 of a knot, as the Americas Cup has proved, but designs are still getting better.

[yipster]

"0.000000001 of a knot" isnt much i agree. AC boats hardly make 10 knots becouse they are limited by rules.
the new 50 meter high supercats and tri's do 20 / 30 knots without foils, now isnt that called progress?

[CT 249]

Not all of that improvement in speed is "progress" in the original sense of the thread, because waaaay back then Wardi was trying to isolate improvements due to reduced displacement, technology etc. The existence and performance of the 50m high supercats etc may well be largely due to improvements in technology that have fed back into design improvements.

It's not just the obvious things, like creating a strong, light structure, it's what else feeds into it.

If you look at a good '70s cat or tri (say a Crowther Kraken or Spindrift) and know what the designers were trying to achieve, you'll see that they were burdened by sails that became too full in strong winds, so the area had to be reduced and the boats had to be driven by less power than a modern boat. Therefore they had fine ended hulls, which then further limited top-end speed.

Now, with modern sails, a boat of the same dimensions will move much faster, so it can have fuller ends, increasing top-end speed in turn. But the progress is not due to some breakthrough in thought by designers, they just have different tools.

Another long-term trend has been to finer bows in dinghies and skiffs. It's easy to think we've progressed in that way, and in some ways we have - but there is evidence that the old guys woould have created narrower bows IF they didn't have the problem of having to support really heavy rigs swinging back and forth in the chop, and to cut down spray 'cause bailers weren't that good.

Sail one of the replica 1930s 18' skiffs and you'll quickly realise how important improvements even in mainsheet block and cleat design are, in that superior mainsheets make boats much easier to sail, so you can then move towards narrower waterlines, more "dangerous" shapes etc.

Even Moth design shows the trend; old gear like a heavy old alloy mast, big soft mainsheet on crude ratchet non-roller blocks, heavy wooden battens and dacron sail would make a modern narrow skiff unsailable.

Earlier in the thread there was some comment that restricted dinghy classes were the only place to look for "real" design improvements (ie those not influenced by "other" parameters). I'd have to say that the influence of superior technology is so vast that even those boats are influenced in design by the enormous improvements in sailcloth, spar material, hull material, gear and even clothing and health; modern physio and medicine allows for many guys to sail champion 18' skiffs into their 50s, whereas most of them used to retire much earlier. Now there's a bunch of people in each class with enormous experience in boathandling, and that (with coaching as well) seems to be feeding back into improved techniques that allow people to handle much faster but more "difficult" boats.

[yokebutt]

Yes, we've been making headway the last half-century and longer, may I for example mention monocoque construction (wood veneer or the many assorted fiber products available) instead of a giant bloody parallelogram like most plank-on-frame wooden boats are. Then, of course, there is the modern sail-cloth that doesn't need to be wetted down to hold air, and, of course, modern cordage, that doesn't stretch to the moon......


Please, give me a call if you wish me to slap you on the head some more.

All in good jest, Yokebutt.

[dionysis]

Yes, it seems to me that one of the major advances in modern times is the recognition that lighter displacement boats can be made to be faster and more seaworthy than the traditional kind.

[FAST FRED]

" modern cordage, that doesn't stretch to the moon......"

Could be an advantage for racing , But I had the priveledge of sailing with LINEN line at one time and it was fantastic.

So soft a 5/8 line would lay on both sides of a verticle hand, easy to handle and not at all harsh on the hands.

Have never experienced cordage as user friendly , EVER.

Is Linens loss an advantage?

FAST FRED

[saeble]

heh... I fell asleep at about page six, with all the large words and nitpicky numbers... my apologies if this has already come up...

If you're looking for a 'large leap' type change in sailing vessel design then you'll find its a pretty fundamental one and its only recently occured.

In order to make a sailboat go faster, you need to delete the sail.

"Huh?" you say... "What is he smoking ?" is the next thing to form in your mind...

I'd be willing to bet the biggest single improvement in sailing vessel... or, more accurately... and to give the game away partially...'wind powered vessel', will be when we remove the mast and install a driving rail or post for something like this :

http://skysails.info/index.php?id=13

The fully automated system proposed on that site is perhaps beyond your average sailor... but... if you accept the principile in its broadest sense then a whole world of new thoughts will populate your head.

The airfoil used in this system is too large and ungainly and no doubt expensive, but it does, as I say open the door to some possibilities.

My thoughts are that if you were to utilise a largish cat and put a simple hydraulically (or cable winch in an emergency)operated, 'canting mast', in place of your existing one, perhaps give it two axes of movement, seeing as you've already commited yourself to hydraulic rams/winches for mast control. Then you could attach your four control lines and attendant fast action electric or hydromotor winches and utilise a foil to yank you along at an obscenely fast rate of knots.

I wonder how much foil area you could get away with before your boat becomes an aircraft ?

I wonder how much this sort of vessel would turn the sailing world on its head ?

If you want a personal appreciation for air foils and kite type experiences you cant go past a two or four line stunt kite or foil, it will soon illustrate to anyone who flies one that there is most certainly another excellent way of harnessing the energy of the wind. Try this site for kites :

http://www.intothewind.com/

For more information on how foils work and are controlled, this is a good place to start :

http://www.flexifoil.com/

There are a bazillion other sites out there that deal with non-rigid, semi-rigid and even rigid foils. The adaption of these sorts of technologies to intermediate to large vessels is, to me, only a matter of time.

Incidentally, I am NOT in any way associated with any of the sites listed in this post. Seek your own reference material if you wish, its only a google search away...

[CT 249]

You're right in many ways, but originally the thread was about improving efficiency WITHOUT such major alterations.

Such thoughtsare far from "beyond the average sailor", but having (like many others) discussed these things in depth with those who sell them, it's clear that they also bring major problems of their own. To get upwind or maximum speed, the kites are laid low to the water - can you imagine Sydney Harbour on a Saturday, with 200 kites laid low and each of them trailing 100m of high-tension 4mm (IIRC) line out to the side? I sail cats at a beach popularly used by kitesurfers and there have been problems. They also work only when they have enough windspeed to develop lift (about 8 knots in the case of some IIRC), and again in a typical crowded, fluky port (Solent, Sydney, LIS) the idea of the average club/cruiser crew trying to handle one of these when they hit a lull and 100m2 of kite hits the water 100m astern is not nice.

Then again, I go sailing for fun and the popularity of boats like Lasers, J/24s Hobies and Beneteaus prove that (like me) most people don't need ultimate speed for fun; in fact some of the most efficient boats are quite boring to many sailors.

[GAZZABO]

Originally Posted by Chris 249

Iain Murray's challenge for the first AC using IACC class boats had a couple of Etchells, radically lightened and re-keeled and re-foiled, as trial horses. From watching them and talking to the guys who sailed them, I don't think they were consistently on a Melges' pace. The problem was that the reduction in waterline stuffed the shape. The same problem was found when IOr boats were converted to IMS.

Re fine bows. This is a trend that has been going on for many decades - but like so many, I think it's technology driven. Older spars and sails weighed so much more that the resulting pitching moment had to be fought with extra buoyancy up forward. Stick a few bricks at the hounds of a modern dinghy to compensate for the heavy old rigs, and you'll find the boat nosedives and pitches excessivley pretty quickly.

An example of how old the trend is can be seen by looking at Uffa Fox's 14s from the '30s - they show a fining of the bow and a broadening of the stern.

One area I can see as an advance is the shift to U shaped sections, from Vee shapes. The advantages are, of course, lower wetted surface and more dynamic lift. But why did it take so long for designers to go to "U"s and "planing flats" along the keel? In hard-chine skiffs, the use of sheet ply restricted the amount of U, but not in other classes. When many designers tried to increase volume (to reduce beam or float more weight), they simply increased the deadrise and stuffed up the planing qualities. It went on for years, until boats like March Hare came along. Even then Mike Jackson wrote how scared he was to go against conventional wisdom and go from Vee to U.

Yachts stayed Vee for even longer, until Carter etc started flattening hulls and then (IIRC) Peterson and Farr brought in very U-shaped bows - more effective, but ironically Farr at least did it to increase the rated displacement 'cause the "shoulders" of his U were on the fwd depth points. Ironic that IOr cops abuse yet it was the reason that Farr moved to a faster shape!

Some dinghy designers see more immersion of the stem as an advance. Maybe topsides flare should also be seen as an advance, although sometimes (IMS and IACC) it's restricted by peculiarities in the rules or boats.

IOR sterns leaned forward, btw, because the aft girth measurement was taken from the forward meeting of sheerline and transom. Moving the transom forward shortened the rated length, which was taken from one girth to another. However, moving trhe transom forward also put the measurement on a fatter part of the boat, increasing the rated width aft and therefore pushing the rating back up. So placing the corner of the transom was a game depending on the exact shape of the hull underneath IIRC.

Have you guys seen Francis Herreshoff's designs for canters and inclined solid wingsail cats from the 1940s (IIRC)? Scary. Jim Young (famous NZ designer, who emplpyed a kid called Bruce) built one of Herreshoff's canters. I wonder where it is?

Well well I am Gary Underwood and own Fiery Cross the Herreshoff/young Ultimate Sailing Machine featured in The Commonsense Of Yacht Design. Now 50 years old and in perfect condition. Jim Young kindly copied some photos of her building. Great little boat!