Hull Shape for Down-Wind Sailing

Hopefully I will able to tell you all about the Sigmas appetite for fast sailing. I'm signed up for the CCC's North Channel race to Bangor this year - in a Sigma 33.

Cant wait..


Regards

Donald

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The perfect shape? its a Prout Snowgoose !!!! Twin hulls to stop rolling, double ended hulls. What more could you want? I am sure you are going to tell me.



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Re: Yes, a boat that can go to windward as well....

Yep your right! wont go to windward as well as a Rival. But does just as well as a Beneteau 361 in a very choppy F6

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I\'m with you but...

...having upset the mobos if I go for the AWBs as well I might not have the happiest of sailing years in 2004!

Unlike Claymore who clearly has more time on his hands, I'm off now. It's another private sector p**sup but then...

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Have a look at hulls based on the original Folkboat.
EG: Contessa 26, Invicta 26 and the like. They travel downwind as though on rails as long as the sails are balanced and reefed according to the conditions. Long keel with rudder fixed directly on the back = stable!

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Have been asked to sail on 'Siglet' this year. Still a fast boat despite being one of the older Sigmas.

See you in Bangor!

Regards

Donald

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I think you may be under a misapprehension - the hull shape you describe is probably at its worst directly downwind.

The fine entry and ample buttocks, allied with light weight gives, you outstanding off-wind performance and on a reach with an F6 sea running you can surf almost continuously.

For really successful downwind work you're looking at a square-rigger, with bluff bows - a typical 18/19th century man of war.

If you look at polar diagrams of all post Myth of Malham design boats you'll see a rapid fall-off between 0-30 degrees and 160-180 degrees apparent wind.
Your best polar is probably at 120 true which converts to about 90 apparent on a reasonably quick boat.

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I think there is a distinction to be made between the light, heavily canvassed, 'racy' and strongly-manned yacht which can surf downwind; and the typical small family cruiser, heavily-laden, and not too strongly manned under cautiously reduced sail. The latter is not likely to be surfing downwind, she will probably never exceed hull speed. The waves will overtake her from behind, lifting her stern and perhaps tending to slew her round making helming difficult.

I suspect Bob Tyler is right in his praise of boats similar to the Folkboat which "run downwind as if on rails" because they have long keels running right to the stern with the rudder hung on the back. I'm no naval architect but this rearward keel area must help them to run true, much like the feathers on the back of a dart or the fins on the back of a rocket (missile that is) ???

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Over or under canvassed

You 've probably hit the nail on the head - the wide-arsed cruiser, in lively conditions reefs down too far and has the boat being swung round by the quartering waves.

The long-keeler, comparatively undercanvassed, is likely to go offwind slowly and controllably.

If the cruiser fat-arse were to fly more sail and trim the boat properly he'd go offwind far more controllably and at twice the speed of the long-keeler.
This speed comes at a price, angular momentum is far higher, the amount of spray is greater and the margin for error is smaller.

It's a common fallacy to think that brute force and ignorance is the way to make a boat go faster - though it's my experience that racing crews frequently do substitute brawn for brain and speed for reduced margins of safety.

I nearly always sail single-handed and quite frequently manage to put between 9 - 11 nm into an hour on a 29'10" LWL boat.
The secret is to get the right balance of sail area between fore-triangle and main (hence the reason for having 4 reefs) and to constantly trim the boat. An electric autopilot is a valuable discipline, it won't cope with bad trim the way a good helmsman will.

Why have a sailboat at all if it isn't for the thrill of sailing, preferably as close to the limit as you wish to go - a powerboat is faster, less work and pulls the birds better.

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I am sure that you are right. Having owned a bilge keeler (Caprice), a Fin Keeler (Trident) and now a Long Keeler (Invicta 26) I have no doubt that the Invicta is the most sea kindly of the lot and, oddly enough, by far the fastest both on the wind and off it! Generally faster than a Folkboat or a Contessa equivalent.
A little more dificult to handle under power in confined area but no problem if you use anticipation.

On his second trip aboard, a 12 year old was able to control and steer under power to pick up the mooring through a bunch of very tight moorings.

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Re: Over or under canvassed

<<An electric autopilot is a valuable discipline, it won't cope with bad trim the way a good helmsman will.
>>
Absolutely - nothing induces early reefing more than the autopilot. If you don't want to freeze your backside off all across the Estuary (or wherever) steering, balance the sail plan and make it appropriate for the conditons.

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Aha.... I remember well racing close inside her in the closing stages of the Scottish Series overnighter a couple of years ago; the Sigmas had been parked in Brodick Bay I have to admit. The picture was: noon-ish, glorious sunshine, big wind, white caps and spinnies, broad reaching close inshore along the dramatic coastline up at Fallen Rocks with the Sigs, Class 6s and Class 5s all together after about 18 hours. "Hey, Siglet," calls one of my Arran boys, "see your mates a couple of minutes ahead?" One by one the Sigmas were running into a vicious cross-current of solid cold air blasting down one of the gullies, and wiping out in spectacular style. "If you hang a sharp right here, it'll mean that we can come too!!" Quick gybes all round.

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