I may not be up on things but I have never run across NACA foil shapes being applied to any boat part except daggers and rudders. Quality sailmakers can probably get the foil shapes they want but I think it is done by manipulation of the cloth and the stitchery and not using a wooden model.
The reason I mentioned the lead problem is your boat was equiped with a daggerboard trunk which would require spotting the sail accurately. If you go to leeboards you can, of course, move them all over the place to iron out handling problems.
I question your desire to use a tall sail. You went thru' a lot of effort to keep your boat from heeling and now you want to mount a very tall sail which can apply a lot of heeling moment to your hull. Since what you are doing is all rather experimental you could derive a lot of security and survive a lot of mistakes if you keep your sail's CE low and not too large in square feet. Because your boat is rather short it is not going to go fast. Once you get it near hull speed it is going to try to heel unless you dump air and slow down. Most of the kayaks that are adapted for sail have longish waterlines so they can use the high aspect sail effectively.
Maybe "stretch" is the wrong word. Sail fabrics are mostly woven so they have "give" in one axis or another. Sailmakers use this give to get the shapes they want. Of course, once the sail is filled with wind they don't want the shape to change. There is no give in blue tarp material. I wonder if you can even get some sort of foil without having the material develop a wrinkle somewhere.

: My understanding is a high aspect ratio sail is one which is tall and skinny
: rather than short and broad. The Balogh batwing sail looks like a high
: aspect sail to me so I assumed it was.

: My rig is a monohull with outriggers. All of the boats using Balogh's mast,
: sail and AKA's and AMA's assembly and other similar setups all seem to
: sail well whether the unit (sail, mast, leeboard) are positioned in the
: front, middle or rear of the monohull. So using a clone setup like them,
: it's hard to see how the sail, leeboard position could go wrong.

: My understanding is that no stretch in a sail is what we are looking for so
: it will hold its shape. So Dacron sails are better then Nylon sails
: because Dacron has less stretch.

: To build a sail similar to Balogh's batwings, you could use his sizes, which
: are on his site and then use the NACA foil shapes to get the shape and
: depth (chord) of the sail. Then white poly (don't know why this is any
: better then blue poly) could be used to make a cheap first sail. But
: better yet you could use Tyvek made by Dupont, which is a non-stretchable
: paper that is almost impossible to tear. It can be taped or sewed. You see
: this material as a wrap around new houses that are being built. Go to the
: post office and get a free large Priority Mail envelope. This is Tyvek.
: Try to tear it. Good Luck. If you should make a sail, post your results
: and pictures.
: Cheers,
: John