need a few comments on keel board build

 I am trying to fine tune some dimensions. current project is a swallow tail keel. Dimensions are as follows  6'0 x 21 x 2.75 inches. Nose at 16. Tail at 16.5. Widepoint 3.5 inches foreward. Nose Rocker 3.75. Tail rocker 1.5. Swallow depth 5.25 inches. Tip to Tip 11.0 inches. Plan to use Futures boxes for rasta keels and some home mades. Box trailing edge one inch ahead of swallow. Im using a clark 6'2 supergreen blank. It will have a concave from 3 feet ( half way down the board ) through swallow. like a rich pavel i measured at Ocean Atlantic. Im about 165. im going to put slight cant on the boxes. I want to do a 6 oz bottom and double 4oz top. Using quik kick worried the thickness may be too much and the tip to tip length too narrow. my CAD design looks pretty smoothe with those dimensions but ive never made a keel swallow. Im putting in a probox trailing box in front of swallow. should i decrease the thickness? and if i want to do a MR style set up, would the placement of the fin boxes matter than much between switching out a twin style fin set up and a keel set up. i dont want to have it float too much. rails will be down, maybe a bevel in the front half. just need a few comments and opinions. maybe want to increase the glass to 6  and 6+4. i dont want the board to be too light. i like a little weight.

I love where you’re heading with this one, but I have to say that, IMO, there’s a big difference between an MR style “twinnie,” which is what I consider a true “twin fin” design, and a keel finned “fish” design. Different rails, different planshape, different rocker… aside from fins. So if you’re a purist, you can’t have one than the other just by switching out fins. You sound like you want to build a fish from the dims, but want to make a twin fin out of it by pulling the tips together a bit, not giving it such a deep fish tail, and switching out fins. And you can do that… but it won’t perform like an MR.

Pavel’s fish designs are exceptional, and you’re not making a mistake by following his lead… right down to the concave out the back. If you’re doing that, at 21 wide and a 16 1/2 inch tail, you could go up to 12 1/4 tip-to-tip, and up to nearly 6" deep buttcrack. But pulling the tips together will craeate more curve in the tail outline, and will make turning a bit easier. You’ll lose some speed, perhaps, however. A lot of the speed twin keeled fish boards have is from the really straight outline through the tail.

6/4 deck is not a mistake, either. That’s where I would go with a 6oz bottom.

If you don’t want too much float, go 2 5/8 or even 2 1//2 thick. I have 25lbs on you and ride a twin keeled fish that’s 2 3/4.

Go for it. You’re gonna love it when it’s done either way!