Quick notes from here on as the exterior was considerably easier than the interior.
I bias cut the fibrglass for the exterior to get it to drape better. The epoxy application was much simpler than inside although I did find a few areas that ended up a bit on the dry side. Main reason for this was I ended up working into the evenings and the lighting was awful. This also resulted in a couple of unnecessary floating bubbles and drips – but all easily fixed. So much easier after having done the interior first.
One tip (I think) was to fibreglass across the sheer line; that is, when I fibreglassed the deck, I went to about an inch beyond the deck-hull join, and likewise when I fibreglassed the hull, so that the join between deck and hull was secured with interior tape and a doubling of the exterior glass.
I doubled the glass on the exterior hull from the sheer line to the keel so that under my body I ended up with 4 layers of 200g (6oz) fibreglass.
Having read about the difficulties of making a lightweight boat I spent a lot of time checking the weight as I progressed. One very useful thing here (especially to avoid wastage) was a cheap digital scale. I bought this from a supermarket for $16 and used it to successfully mix epoxy down to 1g hardener and 5g epoxy. I recorded the weight of each batch of epoxy and I weighed the boat after each major application so I could clearly see the increase from 12kg prior to exterior glassing to 19kg after the fill coats were complete.
I found the fill coats a little painful. I seemed to never quite get the right amount on. I’d put a coat on, sand some off, then try again; many times over. What was particularly irritating here was that to avoid excessive exposure to the epoxy while curing I would make myself wait a few days before any sanding. The time just seemed to drag!
If I was doing it again I’d make two changes.
Firstly, I’d use a slow hardener and warm epoxy/conditions. I found that on a few of my (autumn) evenings the temperature had dropped to maybe 15C and the epoxy had thickened and would spread easily. You want it to spread really easily so a really hot day with a slow hardener would be a better combination.
Secondly, I’d use a random orbital sander more extensively. I spent far too much time continuing on with hand sanding when I should have just used the ROS. The pads clog up quick but crikey it does a hell of a job!