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post #7 of Old 07-28-2008
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Originally Posted by SEMIJim View Post
LOL! No, Hal, I was wondering how one actually secures those flange adapters to the hull, not how one goes about securing ownership of them.

Btw: I noticed Groco has 1/2" thru-hulls, ball valves and hose adapters, but no 1/2" seacocks or IBVF-series adapters. I've sent them an email asking them why that is.

A lot of boats are not able to screw the mushroom male portion of the thru-hull into the seacock or use a locking/compression nut on the thru-hull due to curvature of the hull. The curvature inside does not always match the curvature outside. What is commonly done is to place the thru-hull in a relatively flat spot on the hull exterior and then make up a wedge to back it within the boat. That way you get a good square fit to the thru-hull regardless if it attaches to the seacock or the compression nut.

What is commonly done, and it's not a bad idea even if the thru-hull passes through perfectly perpendicular to the hull, is to epoxy in a backing plate of marine plywood or even a piece of teak would work. You frame up a mold, for temporary use, and then your wood goes over the top of it. Mix the epoxy with an additive for strength and inject the epoxy into your mold (just dump it in and slap the wood on it) thereby bonding the wood to the epoxy and the hull. You can go overboard and even lay fiberglas over the new fairing thereby encapsulating the wood. Now you have the wood to secure your flanged adapter into with wood screws.

Edit: I just remembered an easier way to do the above. Take a can of baked beans and put the beans on to simmer with a dollop of brown sugar in them. Clean out the can and fill it an inch or so deep with thickened epoxy. Set it someplace where the fact that the can is going to get pretty warm does not matter and go eat your beans. About the time that the beans have passed through your system and are doing what beans do you can go outside, you're gonna have to anyway (!), and cut the bottom out of your can. You'll now have a very nice hockey puck that you can sand to fit the angle of the hull. Cut a piece of wood to fit the top of it and epoxy and clamp in place. Drill the correct size hole through it and install as below. by now the gaseous condition should have moderated and I'd say you're ready for ice cream!

You've also thickened the hull in the area of the thru-hull, never a bad idea, and you've created a deeper hole to fill with sealant when you install your thru-hull resulting in greater longevity to the seal with less potential for a leak.

If the hull where your thru-hull goes is pretty flat, inside and out, you can do all this much easier. Paint the plywood with epoxy after you've drilled a hole in it the size of the thru-hull. Then use thickened epoxy to secure the plywood to the inside of the hull. You can take your thru-hull and put it through the hull temporarily and use it with the compression nut to clamp the wood down until the epoxy sets. Then disassemble and mount and seal the thru-hull in the normal fashion. Again you now have a nice piece of wood to secure the flange upon.

“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.
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