T&T: Backing material

[Mike Maurice]

> When installing additional deck cleats on our boat we had a machine shop
> make us big (unpolished) stainless steel backing plates.  We put 3M 5200
> on them before installing them under the fiberglass deck and snugging
> them up with the nuts on the bolts holding down the cleats.

I am not sure I would 5200. Unless of course you don't want to ever take 
this apart. The entire process of bedding components to the deck is 
fraught with potential problems.

Use an adhesive  and you can't get the parts apart. Ok for the deck to 
hull seam, but what about a deck fitting that may leak and then can't be 
removed.

Any sealant exposed to UV needs to be UV resistant.  4000 Sealant has a 
UV rating and might be a better choice. Any sealant exposed to UV will 
deteriorate. It's hard to identify UV resistant sealants, the key words 
seem to be resistant to weathering.

Like 101 Marine Sealant, possibly WM Marine Silicone Sealant.

See page 318 of the 2007 West Marine Annual Catalog.

Don't use 5200 for deck fittings that may ever have to removed.
There is sealing and there is adhesion. Choose the right material for 
the task.

If sealing, wait for the material to harden up somewhat before 
tightening down the bolts.

Mike
+++++++++++++++
Capt. Mike Maurice
Beaverton Oregon(near Portland).