I believe
> that I will attach onto the aft stem, a small trim tab that stays with the
> lines of the boat (i.e, not projecting down like a rudder). The trim tab
> itself will be constructed from glassed plywood. I would like to attach it
> to the stem using a square or two of sheet metal. These will function as
> malleable fixed hinges such that I can adjust them with some force into
> the correct angle to make boat steer straight and then it will stay that
> way.

If you want to be able to make occasionl changes, mount a conventional rudder.

Otherwise, forget the metal completelt and just use epoxy to glue on your trim tabs. A slab of 1/4 inch plywood should hold very nicely with a bead of epoxy on the 1/4 inch side. After it is on, one or two layers of glass cloth extending beyond the trim tabs will cover it, and increase the hold on the hull when you cover then with epoxy If they are not perfectly aligned, cut them off and sand the mount area smooth before gluing on another one.

Sight down the centerline of your hull. Usee a flashlight if necessary, and see if the boat curves. If not, aligning ht trim arab should be pretty easy. Ignore the fact that you steer in one direction, just put the trim tab so that it goes straight in line with the direction you want to go.

If you insist on using mechanical fasteners, I'd suggest you glue (epoxy) a strip of wood to the outside of the hull and use ordinary brass screws to hold on whatever skeg, trim tab or other device you desire. They won't last forever, but ther are easy to find and cheap and simple to replace.

If the boat is not twisted or misshaped, you should be able to correct this by changing balance or ballast in the boat, as George suggested earlier, and not need additional trim tabs and skegs. A rudder, on the other hand, by virtue of being adjustable, can correct for changes in wind, current, loading, or whatever, and might be a better solution --in the long run -- for your problem. Something to think about.

Paul Jacobson