Great Question! I might be building this winter and would like to save as much weight as possible and still have a tough boat. Looking forward to the replies.

although a relative newbie to the stitch & glue building I've done lots of glass work on other big boat projects. On the 2 Kaholo paddle boards I'm building I did the epoxy/cabosil filet with a 3/8'' radius then used 2'' bi-axial tape instead of the wood flour/epoxy fillets. I think the tape will be much stronger with a neglible weight increase.

 Ron

That's most interesting Ron, I'd like to keep up with your Koholo projects as I'm going to be ordering a full kit soon, and I know I'll have questions. Did you use knitted fabric, or cut tooling cloth on the bias? I've cut many a bias tape from 7781 style cloth.

I spent years in the glider repair business working mostly on German made sailplanes made of fiberglass, carbon and kevlar.  I built a few kits too. But the project that improved my wood working skills most was a broken wooden glider made in the 60's in Finland. The craftsmanship and technology used way back then was incredible! 

I run masking tape about a half inch down each side of the joint, dab in a wood flour mix (peanut butter consistency) and smooth it out with about a 1" radius tool. Leaves a small but strong fillet. Before it cures, but after it sets up a bit, pull the masking tape and lay on the 2" tape and wet it out. Never had a joint fail so it's strong enough, and my boats are pretty light. I have also added a bit of Cabosil to lighten the color a bit on some builds but normally don't worry about it. Adding it doesn't seem to effect strength and the few ounces of weight saved would be negligible.

George K 

There is another consideration before you use a pencil thin line of material for your fillet to save weight and that is what are you going to do with the outside of the joint (how strong do you need the joint to be?)

Some people don’t like the “very hard chine” (almost square outside corner) look so they round that corner as much as possible, even going through almost all 3 layers of plywood. If you are going for this “max rounding” of the outside of the joint you will need bigger fillets on the inside.

If you are going to leave the “very hard chine” look, you can get away with fairly small fillets as they really aren’t supporting much.

I have only built one boat but have learned a lot from it. What I found was the easiest and very effective was to use the stitch holes as a guide for my masking tape to make a nice clean fillet, and small size too. Then put down the 3in tape. Worked well, would do it again. The tape makes all the difference.

http://picasaweb.google.com/107267314409083170158/Chesapeake17Build?feat=directlink

Bump