The problem with foam gunwales is that they must be built perfectly formed. Wood is naturally a linear material, so it easily curves in a uniform way. Foam is not. There really is not a perfect way, so far as I can tel, to clamp foam to a form perfectly while being able to see if you’re even clamping it in a uniform curve. I had taken this problem into consideration before my layup. I took the time to turn my mold over so I could get a really good look at my gunwale line to make sure that it was perfect. I had planned to just follow it for the gunwale placement. In theory, it’s not a bad idea. But in reality, it’s inconsistent. Once all those clamp are on there, you can’t see if you’re straight or not. So you’re just relying on feeling the sheer of the mold as your guid. At this point I really don’t know how my gunwales will look. I really wanted this boat to be very clean. After covering them in glass I may be able to sand them out perfectly. We Shall see.
On the good side, they are way lighter. Each outwhale is 8.5 oz. A piece of cedar the same size is 18 oz. My outwhales will need another layer of glass. But cedar ones would as well. So if you did four of these on a boat, that would be a savings of 40 oz. or 2 1/2 pounds. Another good point about this method is that it really is easy to do. And I think it will give me a nice structure to work with after it’s off the mold.
A couple ideas for next time...
It might be possible to use a 23 gauge nail gun to nail the gunwale to the mold for the preform portion of it. This would keep it from sliding up and down. And it would allow you to see the sheer line better. After it was in place, clamps would probably be needed to hold it better. After the gunwale was formed, it would be removed and the nails pulled out. Perhaps you could do this in the layup as well, but of course you would need to be able to pull the nails from the inside of the mold prior to release of the hull.
A second option would be to build a perfectly straight jig to form the gunwale in. This gunwale would need to be constructed of something flexible enough to be curved into place when affixing it to the hull. Perhaps a Kevlar sleeve would work. I don’t know.
One comment on the basalt Innegra. It drapes really well. I have some very fine stems and I was able to wrap the fabric around them after setting out.