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Muaddib1116 · 13-05-2023, 13:03

I'm looking for a bedding compound that has a lot of compression strength and isn't permanent like thickened epoxy. Sealing ability is very secondary. Any ideas?

thinwater · 13-05-2023, 13:23

Quote:

Originally Posted by Muaddib1116

I'm looking for a bedding compound that has a lot of compression strength and isn't permanent like thickened epoxy. Sealing ability is very secondary. Any ideas?

Strength and poor bonding don't go hand in hand.

I don't know the application, but consider waxing (several coats) the surfaces, or adding a bond-break, like plastic wrap. Then use anything.

Emmalina · 13-05-2023, 13:33

Butyl rubber

Statistical · 13-05-2023, 14:27

The specific purpose might help.

Muaddib1116 · 13-05-2023, 15:26

I have a socket mount for a radar pole on my Transom. The pad of the mount is not perfectly flat, nor is my transom.Transom. I'd like to fit the pole and set it plumb with a bedding compound that sets hard enough to then Tighten the bolts down on.

fourlyons · 13-05-2023, 16:05

Quote:

Originally Posted by Muaddib1116

I have a socket mount for a radar pole on my Transom. The pad of the mount is not perfectly flat, nor is my transom.Transom. I'd like to fit the pole and set it plumb with a bedding compound that sets hard enough to then Tighten the bolts down on.

You could consider using 1/16" or 1/8" sheet rubber and cut your own gasket. Once you tighten it down it's surprisingly rigid. I find it at many hardware and marine supply stores in the US.

Muaddib1116 · 13-05-2023, 16:07

I'm not sure that would work well, since the two surfaces aren't flat to eachother.

wyb2 · 13-05-2023, 18:06

Thinwater’s suggestion above seems like the right move for that situation. By waxing both surfaces and hardware, you can basically pour yourself a custom shim that perfectly matches both profiles.

Use shims or leveling nuts to get the top piece where you want it and dam the edges with tape and popsicle sticks. Thicken the epoxy a little to help stop it from sneaking out any gaps in your dam and pour it in from the highest point. Depending on the size, you may consider working in stages to manage the heat of the cure. When it’s done you have a fully removable part that you can finish and reinstall however you want.

Obviously a little oversimplified, but that’s the general idea.

Muaddib1116 · 13-05-2023, 18:29

I do think that's looking like the best option right now. I'll give it some more thought.

marcjsmith · 14-05-2023, 05:17

Why nott something like 4200 slather it up. Put the fixture in place get it plumb. Let it sit until the 4200 sets up and then snug it down.

JBP · 14-05-2023, 05:52

Boat Life's Life Caulk polysulfide was once the standard for non-permant bedding before butyl became so popular.
3M 4000 UV is a setting, medium strength caulk that is resistant to UV and safe for plexiglass.
As suggested above, 3M 4200 is medium strength, but doesn't have as much UV resistance.
All of these will set so that you can later tighten down the bolts.
I'm sure Sika has comparable products.

Muaddib1116 · 14-05-2023, 06:08

I'm not sure 4200 or other common sealants get as hard as I'd like. Maybe 5200 with release wax on the major surfaces.

rslifkin · 14-05-2023, 06:21

Quote:

Originally Posted by marcjsmith

Why nott something like 4200 slather it up. Put the fixture in place get it plumb. Let it sit until the 4200 sets up and then snug it down.

That's what I was thinking. You can either use Thinwater's method to make a shim, or use something like 4000UV that's removable, but will take up gaps well. As Marc said, you apply the stuff, set the fixture on the deck and put the bolts in, but don't crank them down too much. Get it sitting where you want, let it cure, then tighten the bolts.

GreenWave · 14-05-2023, 06:47

Quote:

Originally Posted by fourlyons

You could consider using 1/16" or 1/8" sheet rubber and cut your own gasket. Once you tighten it down it's surprisingly rigid. I find it at many hardware and marine supply stores in the US.

I think this is the perfect soution for surfaces that are not perfectly flat and plumb. Go with the thicker one. I have also used butyle rubber (the tape form).