I'm getting ready to rig a ~54' sprits'l on my 16' White-style canoe. I need a shallow board--I often run in less than 3' of water. With twin boards I run each half-way down when called for in shoals.

At 10-15% of the sail size, I figure each board needs to be between 5.5' and 8' square. Wow. This would call for boards that seem too long for my conditions. I like leaf-style boards but am concerned with drag.

Input?

The 10-15% figure relates to the lateral resistance provided by the leeboard, the rudder and the hull.

To hijack your thread a bit...

Your leeboard article was interesting. Here in the UK single leeboards are vastly more popular than double boards, so it was interesting to be challenged to question why this is.

There seemed to be an assumption in the article that the boat will heel until the rail hits the water. I'm not a big fan of boats heeling, it reduces the apparent sail area, and in some hulls it increases the wetted surface area and causes steering problems. So maybe if the primary aim of having two lee boards is to reduce problems with healing, it would be better to just eliminate the healing with toe straps or outriggers.

None of this solves the shallow water issue, and I agree that two symetrical boards might well be the best answer in that situation (if you don't want to fit a dagger board).

One aspect of twin leeboards that does interest me is the idea of asymmetric foils. I've been put off trying the idea by the hassle of raising one board and lowering another. That said, I would be interested to try a boat with a long symmetrical foil that would be used for short tacking, and a second asymmetric foil that would be deployed when the boat was going to be sailing on the appropriate tack for a while.

Yeah, the whole boat taken into account, but I try to make it up in the boards. Anyway, I have an idea and won't sweat it too much.

Okay--just got back from a great sail today. Strong, constant winds, sailed with both boards partway down, boat ran perfect. Did drag the boards in shoals a bit. It's not hard to find a foot of water here and it's a joy to sail in over the flats; like sailing in an aquarium.

I have found many opportunities to sail rail-down, even when hiked out. I tend to really push the boat when I can, so it runs on its side often enough for me to need two boards. I realize many folks don't do that, but if one sails enough, and isn't stymied by the weather, then the need will arise.

The impetus for the article was to answer those who say "never" or "always" when talking about how a boat will act under certain conditions. I figured a pictogram of my argument would help.

I'm not one to hold forth on symmetrical/asymmetrical boards, but I'm sure others can.

Thanks for your input!

Leeboard Size

Ed I held back on writing anything on leeboard size until I'd had time to check some facts...

In his book Canoes Under Sail, John Bull suggets 3% of the sail area. The first leeboard I made was based on these dimensions, and I remember thinking that the board seemed small.

R. Mcarthy suggests in his book Canoeing (publ 1940) that you should have one square foot for every 25 sq. ft of sail (4%)

I have two Solway Dory leeboards which work very well. I mainly use the larger one, but I measured the smaller one as I know you are interested in boards for shallower water. When the boat is heeled to the rail the immersed area of the smaller boards is 5% of the total sail area.

What kind of wood is the average leeboard made from?
I was going to make mine from oak, unless there is a good reason not to. Oak is not cheap but I have easy access from Lowes/Home Depot. I am however open to suggestions.
Thanks
RED

Red, for years I have used red oak, simply because it is so available. The set I'm working on now are red oak.

Some say it's no good because it rots. Red oak is very porous, so you need to ensure you seal it very well. My current boards are sealed only with several coats of varnish and touched up as needed. The ones I'm building right now are epoxied and varnished. In any event, it works for me!