Mounting Aluminum Brackets to Fiberglass

[Newf]

I have to install a couple of aluminum brackets for additional support for my downriggers. My question is, should I bolt it directly to the fibreglass or should I add a smear of silicon or some other product between the two surfaces?
Thanks.

 

[bigbruce]

I have to install a couple of aluminum brackets for additional support for my downriggers. My question is, should I bolt it directly to the fibreglass or should I add a smear of silicon or some other product between the two surfaces?
Thanks.

I did the same thing and put 3M 5200 between the brackets and the fibreglass. No way the suckers are coming off!

 

[SpringFever552]

Sikaflex!!

 

[Newf]

Thanks guys. I will check these out.

 

[Howzer]

Don't use 5200... use 4200
and you should put a plastic 'washer' (make one out of some 1/8" flat stock) between the hull and the aluminum bar.

 

[Corey_lax]

Howzer is getting the post counts up!

I'll agree with him. I have 1/16" and 1/8" Teflon sheet at work that I use for gaskets all the time. I like a soft separator in between the gel coat and the aluminum. The sheets are pricey online but we buy from a gasket company in Vancouver and it's not too bad. We use it a lot at work so not sure what consumer price would be.

 

[bigbruce]

Howzer is getting the post counts up!

I'll agree with him. I have 1/16" and 1/8" Teflon sheet at work that I use for gaskets all the time. I like a soft separator in between the gel coat and the aluminum. The sheets are pricey online but we buy from a gasket company in Vancouver and it's not too bad. We use it a lot at work so not sure what consumer price would be.

If you never plan on removing the brackets, why would you do this?

 

[Howzer]

Leaning on the bracket could stress (crack) the f/glass more easily than with a gasket...

 

[Corey_lax]

If you never plan on removing the brackets, why would you do this?

I use it because it’s a slippery gasket and dense so it doesn’t compress much. I don’t want to remove something and find that the gel coat underneath is rubbed through.

Even if its bolted down tight, the aluminum is still going to move a little bit on the gel coat.

We use this stuff at work when we bolt aluminum to a steel structure. Both metals expand/contract at different temperatures and also have to move independently of each other for my line of work so this allows it to move around easier while separating the two metals. But with that said, if I didn’t have easy access to the Teflon sheets, I would probably just bolt the aluminum tight to the boat