The clay is oil-based and mineral spirits does clean it up nicely (as was the case cleaning my fingerprints off the plug – but I had to re-wax it because the mineral spirits also took off my Partall wax). I used an oil-based clay because I wanted something that wouldn’t dry up on me (and shrink) since the time between setting the parting board and laying the mold was probably going to be days.

I did use thickened resin to fill in the sharp corners just before placing the fiber reinforcements – using both milled glass fibers and micro balloons ( as written about HERE ). I’ve found that the milled glass fibers alone tend to make the mixture very dry but very very solid with terrific adhesion once cured. I added the microballoons to help get it to a more pasty consistency before the milled glass turned it dry. I simply didn’t have any colloidal silica to mix in but I have tubs of the other two. Finally, although I didn’t use veil, I did use a lightweight 3oz satin weave cloth for the first layer. At least on the horizontal surface where the parting board was, there doesn’t appear to be any print through – but we’ll certainly see when I pull the plug!

Regarding the clay left on the mold flange. If you used water-based clay you can clean it the same way you had to clean the PVA the first time. With a damp cloth it will all come off. If you used oil based clay you can try a bit of mineral oil on a rag to get it out. As an experiment try putting the clay on a smooth surface, use your thumb to press it hard, and clean it, to see how easily it works.

For the backing of the gel coat I use something to thicken resin and fillet any of the sharp inside corners. I start with a fairly thick coat of gel coat. When that get tacky you can spread on resin thickened with, I use colloidal silica. Make it a consistency that will not flatten out with gravity, short of peanut butter. You can put a layer of glass right on that while it is still in a mood to be formed. This way you will get a good bond to the paste with the backing of fiberglass. If you do not use one or two coats of a fine veil material (glass) right on the gelcoat you should consider using a chopped strand mat instead of weaved fiber, it is less likely to get print through.

I like the shape of the hull! Rounded top to shed water, that is a good idea.

Later,
Dan