Oh well, Dave, I bet you had fun building the foil anyway. If the surface was not 100% after glassing.. thats what bog and elbow grease is for.

If I am to build another set of rudders, I want to try foam/glass. But I am not competent to calculate the glass layup. "Guesstimating" the layup will be costly in the long run, as some sets are bound to break..

It's tempting to do a female 'pirate mould' off some fabricated rudders I have, but that avenue is also full of problems (getting the mould flange correct, internal flange for joining, layup, legal/moral issues etc.). I guess most production foils have their foam CNC cut like Phil's foils does, or uses CNC'ed female forms.


Michael, you are correct in assuming that just one layer of glass is not enough. How much glass, weight of glass and orientation are issues you need to calculate before building. You also have to calculate how thick the glass will become after laminating, so you can get an exact fit. That is one of the reasons female moulds are so much easier to work with in a production environment.
You probably will get a better result with spruce strip planking and a thin layer of glass for abrasion resistance, wood is so much nicer to work with as compared to fiberglass and epoxy (probably cheaper also).

Using hot wire technique to make the foam core is pretty much standard today for homebuilders.

Perhaps some of the really experienced homebuilders (or pro's) here will share some experience on layups for foils.

I think what Carl says about buying what you can is good advice if you want to get on the water fast, with a good result. The seller of the core can probably spec out the glass layout and weight for you to achieve the 1/8" skin Carl mentions.

I would forget plywood without serious glass reinforcement. We have personally broken two centerboards of plywood without glass reinforcement.. Strip planking is much stronger than plywood, as half the wood fibers in plywood lies in the wrong direction and does not add to strength/stiffness.