Fwiw, I read the Bernard Smith book "The Forty Knot Sailboat" many years ago and he seemed to think fat foils would work. But I'm not a rocket scientist, he was.

http://www.sailrocket.com/node/518

"Some things just didn't fit into the high speed sailing forensics puzzle and we refused to neglect them. We had been constantly told how thin foils were the only way to go... and yet our big, 'fat', Mk1 foil had repeatedly hit over 50 knots. When we applied the theories and associated numbers that sent us down the path to superthin foils to the old Mk1 foil it showed that we would be very optimistic to even achieve 40 knots. It was obvious that something was wrong..."

I suspect you'd have to break a lot of boards to make home-building them, according to your plan (aluminum molds, etc), affordable.

I can only imagine the cringe on any long-daggarboard owner's face when they become "bottom feelers"...

The Charlotte Sun Herald newspaper had you with 3rd place at the Charlote Harbor Regatta and you weren't even there to pick up your pickle dish.

This isn't your grand daddy's airplane prop...dagger board foil sections and loads are all completely different.



What about carbon over a cnc milled wooden core? This to me is actually very tempting. Does anyone have a rough idea on the laminate schedule for a board?? Foil section is the other big question, I doubt they are running NACA0012's? Last time I dug and dug for this data it was unubtanium and NACA sections came out ahead in my 2D analysis.

I wasn't there to race either so I guess it all works out.

Is this of any help?
http://www.hobieclass.com/site/hobi...01_Wildcat_daggerboards_for_comments.pdf

Still missing the foil section. Plan form dimensions are useful. In my case I would literally take my existing Infusion short boards and add length till I had the same area as the long boards. I'd do some tweaking to keep an elliptical plan form at the tip (lower induced drag). The reason for doing this versus say copying the Mk. 2 long boards directly would be so I can interchange boards at will.

Looks like an Eppler section on these A-Cat foil (note the ridiculous amount of carbon): http://lindahlcompositedesign.weebly.com/install-curved-boards.html

Here's a layup for some F18 shortish boards: http://www.youtube.com/watch?v=k6AzcUBHEzU

CNC cutting a wood core is possible, you would need to have some recesses in the max chord area to allow the required uni fibres to fit in, there would be a lot of finishing work to do, but its certainly feasible.

As a rough shot, I reckon around 8 layers each side of 300gsm uni IM or HM uni fiber is pretty much the bulk of the structural part done. then you need some RC200 biax or similar to hold it all together and you are good to go... remember that this is for around a 1.8m long foil with similar dimensions as a wildcat foil. Oh, and you need plenty of sand paper if you are going to do it this way!!!

Also, the wildcat foil is around 17mm thick, and you will get a lot more strength if you made yours at 21mm or so, its a bit more drag, but its easier to build a strong foil at this thickness.

Good Lord! No wonder they're so expensive.

The boards I have are the stock, short stubby boards. I'm guessing most anything would be an improvement so I see me laminating some cheap, throw-away plywood, shaping it with a rasp until it's time for a nap. Then, if that shows any improvement while actually sailing, I'll make a set out of better materials.

Bless all of you willing to go through the complexity of engineering. It definitely ain't me!

I just priced some UHM fabric per Macca's laminate schedule and it comes out to $700 to do 2x boards!! I would have to find some IM or HM at half that price to make it worthwhile.

I'll stick to wood. This looks like it might work and can surely be done with a belt sander on plywood.

how about a Sunfish centerboard?

That is an asymmetric foil, i.e it produces more lift at positive angles of attack than negative angles of attack. My understanding is current straight foils are symmetric. Otherwise you would have to tack the boards when you tacked the boat.

Thank you for the assistance, it is appreciated!

what's one more string to pull!?

Seriously, that may be the best idea to come out of the days discussion. Asym, tacking boards. Set up properly in shouldn't be too big a problem, particularly if there is a bigger gain to be had.

For the phantom boards we use some very special UHM uni's and I think the material cost is close to $700 per board.... But we do have the stiffest foils by a big margin.

Strength wise you will be achieving the same with standard modulus stuff, but it will just be more bendy.

Plywood is definately not adviceable for use as a high performance foil. On total I have four plywood foil breakages before going to strip-plank solid core. We even covered one set of foils with 600gsm triaxial S glass but the plywood core was unable to handle the loads
Strip plank solid spruce did the trick on the Tornado. For an F16 the rudder foils could be done the same way or even with a laminated hollow wooden core like Marström.

For the daggerboard wood is probably doable if you dont go to radical with the length and thickness. Old 18squares etc used wood based foils with success but they can be heavy and flex.
Covering a wood core with carbon is certainly doable, if you dont go too extreme. You can go extreme but it might break. That is what we have structural engineers for, and even they get it wrong now and then.

Wood is good. Carbon is lighter, stiffer and might also break


I just love being helpful...

I think the best approach is to build one board of wood based on the existing profile but longer, then do on the water trials. Question is how much longer?

Why dont you get onto Matt and get one of his F18 boards from the new boat?

Easy and he will be keen to see the difference too I reckon

Matt's busy, I'm not going to bother him with this.