Cover it up with epoxy/woodflour putty if there's a hole and you'll be fine.

Next time put soap on the screw to keep it from snapping.

Laszlo

We used a lot of drywall screws as temporary clamps and they worked well.  A couple did get frozen with epoxy and had the heads snap off when we tried to remove them.  There have been no ill effects from puttying them over with epoxy and wood flour.  When the heads snap off, they do it at the beginning of the threaded portion of the shank so they're pretty well countersunk.

I am not so sure that I would like to get soap near curing epoxy.

Cheers!

In a Peeler Skiff, a broken-off drywall screw represents no danger whatever to the structure.  Entombed beneath layers of epoxy and fiberglass, water will never reach it to cause rust.  I'd forget about it.

   It is possible to use a tube screw extractor to remove the shank but you are left wit a hole as long or longer than the screw that will need to be filled.

One could also use parafin, wax, or screw lube for the screw threads. Since the lubricant will be inside the whole I do not think that would affect the structure too much. One could also just cover the head with epoxy and wood flour.

I like the paraffin suggestion better than soap.  I'll definitely use it on my next build.

Both soap and paraffin are hydrocarbons that will cause fisheyes and act as release agents if they are still there when epoxy is applied. Soap is water-soluble, paraffin is not. A surface that has soap on it can be completely cleaned with water and a rinse or two of denatured alcohol. Paraffin, wax and other non-water soluble hydrocarbons will stay there and screw up the epoxy.

Laszlo

   If you're not dealing with a bunch of screws, heating the heads with a soldering iron will do wonders for releasing epoxy.This is 20/20 hindsight, of course, but if you run into a reluctant fastener, it's worth a shot.