Slippery to windward?

I race on a course that relies very heavily on windward performance to win. Infact, I have observed that the best worker to windward has an unusually large probability of taking home the silver ware. The class is a Metre class but with restricted length overall, so long overhangs are not an advantage. Possibly even a disadvantage.
So what's the best shape to windward then? A narrow double ended, slab sided, deep hull shape that heels considerably until the deep bulb takes the strain OR a beamier, shallower, wide transom skiff type hull shape that provides more and more form stability with heel to generate more drive from the sails?
I have observed, however, that as the wind really freshens the narrower type excels with considerably less leeway than beamier boxes. Which tends me to favour the narrow boats but I'm not totally convinced.
Also, should the forward sections be v'd for better windward performance and is a beam to length ratio of 5:1 too wide for a slippery double ender please?
I appreciate all replies, R at N.

[PAR]

Windward ability is a function of appendage, sail plan and hull form design working in concert with one another. The beamy, firm bilge boats so common today, are trading off some windward performance for bigger gains in performance as the sheets are eased. The high aspect ratio sail plans and radical roach widths found on these designs help get back some of the losses as a result of the hull/appendage choices made in the design concept.

I've always favored narrow boats over the fat bellied types. Having a bilge is important for windward ability, it lowers the freeboard, drags the lateral plane fore and aft, helps keep the boat's bow up and they're easier to propel. They generally are more comfortable to live with on the water and have longer righting arms. A lot of narrow sail designs are near uncapsizable, but a large amount of the fat things seen on the water currently can be more stable turtle then on their feet.

That said, you'll lose the ability to plane off if you design too much bilge or draw out the hull form too thin for it's length. This can be death to a racer of planning and semi planning craft. You may get to wind a bit better then the others, but they'll blast past you on the down wind leg.

A racer is a real set of dilemmas for the design. Ultimately the goal is speed and handling, having a place to stow things, efficient engine selections, convenience items, comfort items, motion, etc. will all take a back seat to these things in the better racers and will not be issues in full out racers.

What designer's have done for quite some time, is to give the market as much of everything as they can. Some specific designs will lean toward speed/handling while others will want a softer ride in a confused sea and some stowage space so this design will pickup some displacement over a similarly sized racer. Most newer designs try hard to please as many folks, looking to buy a yacht in this size range, as possible. This leads to some ugly stuff being done with sail (the Macgregor 26 for example) and powerboats are not an exception of this rule either.

To answer your question, it depends on what you want . . .

[quicksail]

Look at the Int'l Canoe. These little buggers are suppost to be the cats ass upwind. Any design with huge righting moment and slim hull should do the trick. Keep an eye out for the new breed of canting keel boats. Also you should look at the AC design of late. These beasties really motor upwind. I hope this helps alittle.

Cheers,

[sorenfdk]

The forward sections should certainly not be v'd for good windward performance, but rather u'd.

A B/L-ratio of 5:1? That means the beam is five times bigger than the length! That is indeed wide - a L/B-ratio of 5:1, on the other hand, is certainly not ;-)

Way back in the twenties and thirties, they had a class of heavy double-enders in Norway called Skarpsno. Uffa Fox describes the class in one of his books. They had a L/B-ratio of about 4:1 and were considered very narrow. Apparently, they performed really well when the going got rough.

Thanks for the information. I really appreciate this feed back. Sorry, I meant length to beam ratio at 5:1
I have studied some of LFH's works ( possibly the greatest fan of slim double- enders and found that 5:1 is acceptable but from 6:1 and higher is considerably more favourable. No problem, I'll have a crack at shaping something at 5:1 because any narrower would not provide sufficient initial stability.
The yacht is an out and out racer. No considerations for storage or even comfort are needed. And as strange as it may seem, neither is downwind performance a consideration. We sail with long windward and reaching legs. Only one downwind leg is set. Even a wet bag will go on a reach and she's only got to hold her own downwind with a few tactics to maintain the lead.
Hence, I wish to shape a windward warrior. An out and out windward demon.
So, I'll go narrow and slab sided with U shaped forward sections. Why U shaped is my question? And should she be v'd amidships for a small portion at maximum permissble draft (of the canoe body) by way of the deep fin? Or better to go U here as well to provide a better end plate?
Also, is it beneficial to bring the C of G slightly forward as this is common practice with moveable ballast. Say from 3.5% aft to 2% aft?
Thanks for all your input. It is my desire to shape this thing ( I bought Maxsurf not long ago) and post my shape here for all to constructively criticise
Stay cool, R at N.

Thanks for your comments. Nice to find a slim boat fan out there. A 'skiffeater' if you may. I am particularly interested in your comment about bilges being important for windward ability. I presume you refer to the depth of the bilge rather than its shape. In yor opinion, should I go for a slack deep bildge then? Lemon Cranfield favoured these also. I don't go much on a hard turn to the bilge for a slim double ender. Thanks very much for your time, Red at Night.

Originally Posted by PAR

Windward ability is a function of appendage, sail plan and hull form design working in concert with one another. The beamy, firm bilge boats so common today, are trading off some windward performance for bigger gains in performance as the sheets are eased. The high aspect ratio sail plans and radical roach widths found on these designs help get back some of the losses as a result of the hull/appendage choices made in the design concept.

I've always favored narrow boats over the fat bellied types. Having a bilge is important for windward ability, it lowers the freeboard, drags the lateral plane fore and aft, helps keep the boat's bow up and they're easier to propel. They generally are more comfortable to live with on the water and have longer righting arms. A lot of narrow sail designs are near uncapsizable, but a large amount of the fat things seen on the water currently can be more stable turtle then on their feet.

That said, you'll lose the ability to plane off if you design too much bilge or draw out the hull form too thin for it's length. This can be death to a racer of planning and semi planning craft. You may get to wind a bit better then the others, but they'll blast past you on the down wind leg.

A racer is a real set of dilemmas for the design. Ultimately the goal is speed and handling, having a place to stow things, efficient engine selections, convenience items, comfort items, motion, etc. will all take a back seat to these things in the better racers and will not be issues in full out racers.

What designer's have done for quite some time, is to give the market as much of everything as they can. Some specific designs will lean toward speed/handling while others will want a softer ride in a confused sea and some stowage space so this design will pickup some displacement over a similarly sized racer. Most newer designs try hard to please as many folks, looking to buy a yacht in this size range, as possible. This leads to some ugly stuff being done with sail (the Macgregor 26 for example) and powerboats are not an exception of this rule either.

To answer your question, it depends on what you want . . .

So an international canoe on a force fed diet, so that she blows out to length/beam of 5:1 is the go!
Be great. Where can I study the plans of one of these things please? They are a Canadian pure breed race horse aren't they?
Thanks Red at Night.

Originally Posted by quicksail

Look at the Int'l Canoe. These little buggers are suppost to be the cats ass upwind. Any design with huge righting moment and slim hull should do the trick. Keep an eye out for the new breed of canting keel boats. Also you should look at the AC design of late. These beasties really motor upwind. I hope this helps alittle.

Cheers,

[sorenfdk]

U-shaped sections are better, because they don't pound so much going upwind. You can use v'd sections, but they should at least be rounded v-sections.

On a double-ender, the aft sections should be v-d, so amidships, they should be something in between the rounded v or u of the forward sections and the v of the sections aft.

I don't think there's much to be gained in moving the C of G forward.

If a beamy hull heels, (depending on its shape) you will notice that a line connecting the centroid of each immersed center moves off center and curves. This makes the hull act as a cambered, low aspect ratio airfoil, which may effect the performance to windward - it may even lift the wrong way. U sections, and brtoad hulls will have more of a tendency to develop hull camber, so it may be worth looking at the heeled hull shape (corrected for trim and draft) and see what is happening.

[tspeer]

I think the most important thing you can do is make the keel deeper. That reduces leeway, cuts drag, and improves stability. All good things for going to windward.