some lokbox ply fins

benjjo86 · June 19, 2010, 4:55am

hi,

got inspired from alot of people on here, so thought i’d put up my progress so far…

my aim was two lokbox plywood keel fins. pretty much copied a Gephardt fin, figured at least for the first one i should know if it was me foiling or the shape. they could still use some work, and havent done justice to them, but i just couldnt sand anymore. I got some 3/8 3 ply from a carpenter’s scraps and went to work. i didnt have any of the right tools, so did most of this with a hacksaw blade, sanding block and wood rasps. its doable, but surprisingly long.

the 3/8 was just slightly larger than the box, but to get the right cant, i needed to really thin the wood tab.

was thinking from here i would wet out 2 x 6oz for either side and place the whole thing in a vacuum bag. to be honest, im really not sure about this step, so would appreciate any comments(i especially need the criticism). I was thinking of adding the roving around more because i thought it would make it more watertight in the end, but im not sure how those would fair in a vacuum bag.

once glassed, i thought i would cast the exact base and cant in just like its been shown here.

keep in mind this is my first attempt at bagging too!

thanks for everyone’s help already,

j

camplus · June 19, 2010, 5:58am

You may want to seal coat the wood before trying to lam in the bag. From my experience the vacuum tends to pull air from raw wood that gets trapped under the lam as the resin becomes more viscous. Foiled ply (more than solid wood) has a good amount of exposed end grain where air can and will escape from during rising temps. or under vacuum. 2x 6oz will only make it that much more noticable in the final product. Maybe it’s because I was using a very tight weave cloth when running those experiments - don’t know, but that’s the conclusion I came to.

Also, to get the cant you want you only have to taper the insides of the tab towards the bottom. Then rebuild or cast to get a snug fit. Make sure to seal all facets of the fin very well to avoid certain delamination.

Good luck. Hope that helps.

benjjo86 · June 19, 2010, 5:45pm

thanks! i was worried about the bubbles. im working with epoxy and had alot of fish eyes in my last project which were a pain, so ill for sure put a coat on first.