micro bubbles in skincoat

[JV_Comp]

I am hand laying 9 oz S glass on a dry mold surface and top-wetting it with vinyl ester resin. By using a bristle roller and sgueegee I can remove almost all the micro-bubbles but not quite every one.

When I pull the cured glass off the mold there are some occasional tiny cavities on the skincoat surface (i.e. the side that lays against the mold). These are about the size of the tip of a ballpoint pen or smaller. I want a perfectly smooth skincoat surface.

Any suggestions on how to achieve a smooth skincoat surface with no cavities?

I have been making test panels using plate glass to simulate a mold. Once I perfect the technique, I want to use it for building a 15' long hull in a female FRP mold.

Try wetting the mold surface with resin and laying mat against the mold before your first layer of cloth. This will also reduce print through from the cloth.

[JV_Comp]

The problem I had with pre-wetting the mold was beading of the resin caused by the mold release agent. I tried Frekote and later Fibrelease (a water-based agent) and both caused the resin to bead up or fish-eye somewhat.

I would have liked to put on a smooth layer of resin and let it set up a little before laying the cloth but the resin doesn't want to lay down in an even film.

[JV_Comp]

I had a problem with micro bubbbles causing tiny cavities in the resin skincoat finish of a light skiff built in a female GRP mold. (Gelcoat was not used in order to save weight).

I solved the problem for both and hand layup and infusion in this way:

a) hand layup - lay 4.2 oz S glass (instead of 9 oz) on the dry mold (no gelcoat), flood the glass with resin by back-wetting and top-wetting, roll the glass repeatedly with a bristle roller.

b) infusion - lay continuous strand surfacing veil on dry mold, lay 4.2 0z S glass over the veil, lay the rest of the laminate over that and run the infusion.

Both techniques yielded a very smooth laminmate finish with no cavitites.

[Theo]

Brissel rollers tend to creat air bubbles. Try a groved roller or infusion.