Steve’s Boat Building An amateur’s attempt to build a strip plank dinghy

When the epoxy had hardened the next day, with some trepidation I pulled off the peel-ply. The result was not perfect, but for a first attempt I was very pleased. I made a couple of mistakes. I wish that I had primed the hull with a coat of epoxy and allowed it to harden, because, despite our vigorous efforts at applying pressure, small bubbles appeared under the fabric as the heat from the curing epoxy expanded the air entrained between the fibres of the timber. I had read of this problem, but because I was working in a centrally heated room, I did not think that the problem would occur. It did!

My other mistake was to not take enough care when aligning the tapers on the edges of the glass cloth. This needs to be done with great precision, because if, as happened with me, there is not quite enough overlap then when cured there is a small indentation along either side of the joint.

Because sanding through the fibres of the glass weakens the coating, after I had removed the peel ply, I brushed on a further coat of epoxy to allow me to sand the hull, and thus remove some of the more obvious lumps and dips. During this sanding process, I noticed a series of small, parallel ridges in the surface, and at first I was confused as to their origin. For those of you who are not familiar with peel-ply, it is a nylon-like cloth which has been treated with a release agent so that it does not stick to the epoxy. The idea is that it smoothes the epoxy over the weave of the glass fabric, and when removed takes with it any amine blush, leaving a pristine surface ready for further coats of epoxy, or of varnish or paint. The peel ply has a series of parallel red threads running through it at about 50mm spacing, and to my amazement I discovered that the ridges mentioned above exactly coincided with that spacing. Even West Systems, manufacturer of the peel-ply, are unable to explain why this has happened, as they have never seen it before.

(Note to the uninitiated: amine blush is a white waxy substance that forms on the surface of epoxy as it cures, especially if there is a high humidity. It can be easily washed off with detergent and water, otherwise subsequent coatings will not bond properly.)

Peel-ply ridges