Starting the Hull Fillets
I spent some time stringing lines and checking the alignment of the hulls. They didn’t line up perfectly, but with nudges and twists on the wires I could get things lined up. I checked my alignment before I started filleting each hull section and the hulls turned out straight.
My first fillet in the bow of the port hull was a total disaster. The Wharram plans call for a mixture of 90% glass bubbles / 10% colloidal silica for the filleting mixture. For me, this slumped horribly and I had to chase it back in place over several hours so I had a rough texture on the surface. As I went along, I added more and more colloidal silica to prevent slumping but still was not satisifed.
So I turned to the internet and my favorite boat building book by Sam Devlin for ideas. I couldn’t find other fillet mixture recipes that called for such a high proportion of glass bubbles. My tried and true mixture from previous builds was 1:1 colloidal silica and wood flour. Since I had stocked up on glass bubbles for this build (following the Wharram recipe) I wanted to use up some of these bubbles. So I added the glass bubbles to the mixture and found that a 1:1:1 mix worked very well.
Devlin’s book also reminded me that I liked to apply fiberglass tape while the fillets were still wet. I think it’s easier to work and the resulting fillet is nicer too. The Wharram plans call for fiberglass tape only along the keel but I decided to also tape all the bulkhead fillets. For structural purposes I think that fillets and tape work together like concrete and rebar - compression and tension.
Once happy with my filleting mix, I went back and put a smoother fillet over the port bow fillet and added biaxial fiberglass tape to the wet mix. And then brushed epoxy on until it was saturated. I decided to use biaxial tape for the keels for extra strength. Biaxial tape takes a lot more epoxy to fill in the weave and is harder to get a smooth surface so it was a trade-off. I only used biaxial on the keels - inside and out - and used regular cloth tape for the bulkheads and bunks and cabins.
