A question for all of you on the sink drain

[ebb]

Hey Jerry,
It's just the apps that's different.....and maybe a little experience with new material.

I used some red 'electrical grade' polyester frp from McMCarr - both angle and sheet.

Be sure you remove manufacturing residue from the sheet, I did a small delam test when I did not clean with a solvent. Wasn't a good bond. I guess acetone is traditional solvent with polyester. Use 36 grit or similar to get tooth after cleaning.

The bulkhead nut , as I call it, that comes with the thru-hull fitting IS a discard when the thru-hull is used in a flanged seacock.

But when you are dry fitting, you can use the nut on the thru-hull to tighten up on your back blocking to see if you got the backing square to the inside glue up.
You have the thru-hull jammed tight in its hole form outside, with a batten off the ground.

If you are real paranoid about this stuff like I am, you can position the first layer of the inside backing, glass an/or ply, and get that square.
Wrap Seran Wrap on this first piece of the stack, which has a thru-hole sized hole in it where you want it. Tape it around the rim on top.
Cut an X in the middle for the thru hull to come inside without tearing it too much.
Have some thickened epoxy and put a dab under three corners (between the plastic wrapped piece and the prepared hull
then lightly, lightly, turn the big nut til things seem square. Maybe wood shims will help. They also can have their tips covered in Seran wrap
Let it go off. The wrap will pull off and the piece won't have epoxy on it.
Fill in this first gap between the little feet after final dry fit.
Or of course if you are happy with the fit you can glue this in now. It might give you a good fix on the sawsall hole you have to drill through the rest of the stack, Or the remaining block if it is a single piece.
Then stack layers dry until your thru-hull fits in the seacock the way you want it.
I did the thru-hull hole after the stack was glued in. I had the hole in the hull and it was relatively easy to judge how good my hole was by keeping the white bell of the blade even all round as it got buried. The sawsall hole left a little wiggle room for the thru-hull.

Naturally, do the thru-hull first, get the stack glued in. And dry fit the seacock.
There's no room in the bilge for a seacock, let alone three of them.
I spent time making sure the on/off lever was placed so it was intuitive to use.
If it's easy you'll exercise the valve like they say to.
By measure make sure the thru-hull does NOT bottom out in the seacock. (You'll have to cut it.)
Dry fit the thru-hull to position the seacock exactly, screw it in, get the assembly tight.
Then drill the flange bolt holes from inside. You'll have to remove the seacock so mark the holes to be drilled exactly.
You can judge right angle squareness from the flat and get the flange bolt holes coming through the hull with a pretty geometrical spread. Use a jig of some sort to aim the bit, small square right angle blocks. This does not require the ability to screw one large fitting with many tight threads into another. These bolts are going to be OK with a little fudge, just as long you DON"T aim them at the big hole.
Dry assemble the whole assembly. screw the valve onto the thru-hull first, make it happy in the hole
See if you did good with the bolts, hopefully you won't have to fiddle with them.
Tony G wants to lag the seacock on its hill of blocking. lots of meat, they should hold good.
But that means without through bolts the stack depends entirely on glue to hold everything together. The thru-hull screwed into the valve will be in the position of holding the valve assembly. Dunknow, I like the idea of clamping the whole lot right to the hull!