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Ballast tank bottom doubler?

Posted: Sun Nov 13, 2022 8:00 pm
by max
Hey all,

In looking through my kit contents I see that I have two pieces of plywood that are both labelled "ballast tank dbl". If I put these side by side they are roughly the right dimensions for the footwell, but the fact that they're labelled ballast has me wondering

Does the bottom of the water tank need to be doubled with a second layer of plywood?

The build manual doesn't mention this (indeed it only mentions adding a doubler for the area around the valve itself) but I thought I'd check in case there's updated thinking and the contents of the kit don't quite match the build manual anymore (a situation I've run into a couple of times already).


Re: Ballast tank bottom doubler?

Posted: Fri Nov 25, 2022 10:47 am
by max
Well after working on a few more jobs around the boat I've decided to just put in a small doubler around the seacock, as opposed to putting a doubler down on the entire bottom of the water tank. Don't know why I got the big pieces labelled like I did with the kit, but I can probably use them elsewhere in the build.

Re: Ballast tank bottom doubler?

Posted: Wed Nov 30, 2022 12:20 pm
by GregWads
Sorry I am not building from a kit, so not sure what is provided. I also wanted the tank to empty completely, which means the top of the drainplug flang needs to be at or below the level of the floor. I placed my drain plug nearly in line with the Centerboard Pin, roughly in the middle fore/aft of the tank. Plywood bends easily in one direction but not two. So cut a piece of 9mm ply the size of the water tank and located and drilled the hole for the drainplug flange. The 9mm was just a bit taller than the top of the drain plug flange, so I rerecessed the flange to make it flush with the top of the doubler. I sealed the doubler with epoxy and sanded. I also made a couple of thin strips, a couple mm tall and a couple of mm wide the ran the width of the tank athwartships, then glued them to fore and aft bottomg edge of the tank. I mixed up a big batch of thickend epoxy and covered the bottom of the water tank then inserted the doubler and screwed down along the center line so that it would form a shallow trough. When the epoxy was nearly dry, pulled out the screws. Next I put fillets in all the corners and filled the screw holes. To finishit up I gave the whole water tank a coat of epoxy mixed with graphite powder.

Re: Ballast tank bottom doubler?

Posted: Wed Dec 21, 2022 4:21 pm
by max
Greg I love that idea. In fact I love that idea so much I made a quick turn and adjusted my water tank bottom to follow your idea, almost exactly. I now should have much better drainage then my original plan (which came largely from the build manual). Thanks!