Alternative to marvelous Buccaneer 24

Couple of revealing photographs. That Ketterman foil looks absolutely right to my eye and is of the correct small area - I'm convinced that many people get carried away with THE foil idea and their foils they put on multihulls have far too much span as well as area ... look at the four IT foils of long span on Off yer Rocker C Class, great gobs of drag - and apparently easily beaten by the purist C design. The Trifoiler's final shape, section and area, is the result of years of real world testing and sailing. They have to be small also because the Ketterman design has a reputation of being near hopeless in light conditions ... but what a magnificent rocket in a breeze.
There is a real People's Foiler for you Doug and if those brilliant ********, along with Hobie, couldn't make a production go of it .... who else would?

 

Gary, do you think it would be worth doing a Cp calculation by hand just to doublecheck the result you're getting with the program? It wouldn't take much time at all. If the actual Cp is .5 or below I wouldn't think you should disregard it because of a gut feeling?

 

I'll do that Doug - but first I compared a couple of my other fooling around designs: an Open 6.50 big dinghy (similar to the 5.5m I built) with 2.1 m WL beam (beam to length ratio of 1:2.5) with that of an Open 6 meter foiler main hull with a WL beam of 244mm (BL of 1:24 ratio) - one a wide hull light displacement with an extremely narrow LD hull - and the CP of the 6.50 big dinghy readout is 0.5257 while the foiler is 0.4951.... so something is wrong ... probably me. In reality the foiler should be way up ... and similarly so should Scissoring Sid.

 

Gary I had a problem with Macsurf when I ran numbers with the floats as an active surface it somehow blocked part of the main hull from the calculations in Hydromax. It only happened in the area where the floats touched the water If you have drawn the floats in I would suggest you try deleting them and see what happens.

 

Scissoring Sid started out as a "C Class" type foil tri with minimal 400mmm gunwhale beam, WL 100mmm less main hull - but now Sid has increased beam to 500mm at the normal gunwhale position (not the flared wing measurement) and still narrow 350mm WL beam ... the intention was a minimal boat to sail very fast in light airs and to lift off with the foils as wind increased, aiming for the best of both worlds.
So a sub 0.50 Cp is what I was aiming for .... and that is what I've got. Normally low Cp hulls sink deeper at speed .... but El Sid has foils which will lift hulls clear ... so the squatting is not an issue.
Sid IS very fine ended with small taper towards bow and stern .... therefore Freeship figures are correct.
Thanks Sam for the suggestion - but I drew Sid's main hull without floats. anyway.

 

Oh, another thing - easy to draw on paper, different to built with bending ply in reality. So the fine ends of Sid will end up in real life not quite so fine; therefore the Cp will increase a little. You'll get the figures later Doug.

 

Gary, you talk about lifting the hull clear with foils-how's that going to work when both the windward and leeward foils are set at the same angle of incidence? Without an altitude control system(wand),what will prevent the foils lifting until they breach the surface-and what happens then?

 

hey Doug, the windward foil will be clear of the water (because of dihedral and shallow floats, or even lifted) and the working leeward foil and IT rudder will be (I'm sounding more like you everyday, very bad influence) the correct sizes in that they will balance out between sail loads and foil lift: higher sail loads/more heeliing/but also more foil lift = correctly balanced platform. I don't want any wands in larger seas.

 

Thanks, Gary. You've had experience in using foils this way-what happens if the lee foil breaches?

 

On Groucho, my first inverted Y float foils were too large and downwind at speed the platform started rocking, first lifting the leeward foil almost out which immersed the windward foil ... which rocked us right back again etc. Not a good situation throwing the platform into a sort of heavy displacement keelboat running and rolling with kite situation; you know if this continues you're going to be up turd street. So the foils were cut back ... and the balance is now right, leeward foil lifts but doesn't rock, platform is in the correct equilibrium.

 

Thanks-hows the boat coming?

 

Roto-Tri

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what he said......

 

Down under here in the shaky isles it is winter, when the rains come - so El Sid has remained mostly undercover, just exposed to do some epoxy coating and to show to curious visitors ... but I get the plywood tomorrow and if the weather is okay I'll have Sid skinned in a couple of days. I have two other boats to look after (although I'll be giving Flash Harry away to a friend's son) - and Groucho, in some of the high winds here, crushed her old mast base bearing so I built a new male/female set, jacked up the mast on the boat, cut the damaged bearings off and replaced them ... so that is what I've been doing - that okay Doug. Do I have your permission?

 

Roto-Tri

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As usual, I'm impressed.....

 

I'm really liking the business of giving away the Flash to a young sailor, Gary. Get the kid out there messing around with his own hotrod and pretty soon he'll be bugging you for more info... or not. Sometimes it's hard to tell about kids and where they'll wander with their attention span. Our own son, who was in the hunt as the best soccer keeper in the state, got into fixed gear bicycles (fixies) and now he enters urban road races with the dang thing. No way to see that coming at all.