Super Slender Racing Yachts

[MikeJohns]

Super Slender Racing Yachts - An alternative to a modern trend

Here's an interesting web site from an engineer comparing hull forms with a different approach to model testing.

http://www.users.zetnet.co.uk/behemoth/mainframe.htm

click on "research"

Hi Mike

Very interesting approach, I have often thought that long and slim would be a better option to the Open 50,60,70 trend of wedge shape, it's the money side of things that tends to stop the experimental offerings, you know another surf board will match a surf board so thats what you design.

You are a long slim designer yourself aren't you?
Pun intended

Have you any plans to introduce anything in this line?

Incidentally did you have an email for the gentleman, I tried hid website contact but the email bounced.

Best regards
Peter

[MikeJohns]

Peter
No email I'm sorry, just a site I came across when browsing late one night. Presumably he'll get around to updating it one of these days.

Stability is a major issue with many of these wedge shaped boats, many of them really need canting keels to give them the righting moment when inverted, ie. they cant them to one side to get the boat back up (if they are still attached and working).

I have a nice relatively slim 56 foot steel cruiser design, I think I'll stick to that, you could race it if you wanted, wouldn't win though however it would look after you.

[deepkeeler]

I always thought it was a good idea for the racing boats to develop along these lines.
Would certainly make sense from the seaworthiness point of view.
Marchaj's scientific proof of seaworthy design seems to be largely ignored or rationalised away by the current racing community. By the sound of it they wouldn't be that much slower if they were long and slim.

[SailDesign]

Originally Posted by Peter Cottee

I have often thought that long and slim would be a better option to the Open 50,60,70 trend of wedge shape,

Yes, with the exception (and problem) that what drives the width is not actually speed, but speed combined with the 10-degree rule for movavle ballast. In order to make use of your movable ballast, you must have enoughh initial form stability to stay within 10 degrees of heel with it shifted. A long, skinny boat simply doesn't have that stability.
Steve

But you wouldn't need the movable ballast if you went slender, you can produce a powerfull hull from ballast ratio alone.

The movable ballast is also part of the self righting mechanism on these nightmares.

If slimmer the boats could be raced to windward too the opens are strictly downwind surfers

A move towards better seaworthiness would be sensible and the long slim approach would do that.

[SailDesign]

Paul,

You may be able to achieve a "powerful hull" from ballast ration alone, but the guy next to you at the start who _has_ movable ballast will have more power. You still want to race him?

Sadly, the canting keel is part of the self-righting package. Having one on a narrow boat would make it even better... However, things are waaaay better with canting keels than they were in the water ballast days, when it was impossible to load a tank after a turtling.

You say "If slimmer the boats could be raced to windward too the opens are strictly downwind surfers". You've never sailed on an Open Class boat, have you?

Moving towards better seaworthiness is always laudable, but is SuperSlender the right thing to do? With a skinny hull and a large ballast ratio, will the bow rise to the waves, or will you always got straight through them? Do you mind feet of green water flowing over your deck? How will they behave under short canvas in survival conditions? The old (or one of the old) definition of a boat as a hole in the water full of compromises still holds water, to mix a few metaphors. Form stability is a good thing, although taken to extremes it can bite you in the bum. So can most other ratios and numbers. Compromise, moderation, etc. will take you down the right path.

I'm not saying that today's surfboards are the answer to deep-ocean racing, but they are what we have now, and within the rules, they are the fastest thing out there. Should the rules be changed? Probably. How should they be changed? Well, the 10-degree thing should go, but how are you going to replace it's function? 20 degrees? 5 degrees?

Steve

Originally Posted by SailDesign

Paul,

You may be able to achieve a "powerful hull" from ballast ration alone, but the guy next to you at the start who _has_ movable ballast will have more power. You still want to race him?

Steve

Thats where rules come in I presume you have seen the intersting discussion at:
http://www.boatdesign.net/forums/sho...5575#post35575

Originally Posted by SailDesign

Paul,
You say "If slimmer the boats could be raced to windward too the opens are strictly downwind surfers". You've never sailed on an Open Class boat, have you?
Steve

Nope that's for the nutta's, I just read the article by one of the designers saying that the design critereon had a large component factored in to for downwind sailing on the Southern Ocean leg, and that the wetted surface was a bugbear in the light air regions.

As for the slim designs being wet. Well the wedges get very wet when they reamain upside down I do think they would be faster to windward, less energy loss in the pitching .

Cheers
Paul

[SailDesign]

Paul, when asked if you had ever sailed on one of the boats you were trying to trash, you replied "Nope that's for the nutta's". Apart from the appalling use of an apostrophe where there shouldn't be one you have just stated for the record that you don't know what you are talking about. The fact that an article by a designer stated that there is a large downwind component "factored in" does not even begin to imply that they are slouches uphill. Any more than a skinny designer saying he is going for upwind performance doesn'y mean that giany asymm is going ot keep the boat slow downwind.
With a 50/50 boat (DLR = 50, SA/D = 50) you have plenty of power for upwind work.
Steve

[SailDesign]

Now, if I could just hit the "T" instead of the "Y" more odtenI'd be all set....

[SailDesign]

Gaaaack! Time to sleep, obviously.
G'night!

Yes Ok I accept my caning. I tend to be a bit generous in my use of apostophe's

I suppose I also shouldn't have said "strictly" downwind surfers, but I do think that's a huge advantage of a surfboard hullform; being able to surf so easily on the face of the southern ocean swell where they spend so much of their Easting. I would hate to spend a month slamming to windward in heavy weather in one of the open 60's current forms, I would much prefer it in a slimmer hull.

I am sure that If the races were run counter to the Southern Ocean swell they would adopt a less extreme hullform and as a benefit would be less prone to stable inversion, that's the main reason I was "trashing" them. I am curently employed as the Master of a fisheries research vessel, I spend a bit of time in the southern ocean so I watch these boats and at times their expensive rescues with some interest. I think their survival is due to their speed and the hi-tech weather information. We have logged some of them and their transition across our large scale charts is astounding, considerably faster than the fishing vessels in transit (at times).

I have a 45 foot steel cutter that I have sailed around in the Southern Ocean a bit too so I have a little experience from a Bridge and a tiller!


Happy New Year
Paul

[JimCooper]

Originally Posted by deepkeeler

I always thought it was a good idea for the racing boats to develop along these lines.
Would certainly make sense from the seaworthiness point of view.
Marchaj's scientific proof of seaworthy design seems to be largely ignored or rationalised away by the current racing community. By the sound of it they wouldn't be that much slower if they were long and slim.

Hasn't it been done with boats like Van de stadts design for the fastnet that Chichester won in and also won the Sydney Hobart ? These were knocked off their perches by the flatter lighter beamier boats surely.