Aluminum or Stainless backing plates

[Ludicrous40]

Finally got some work done this past weekend (first reasonable weekend in New England this year…..ugh!)

This is my first full year with the boat, and I've learned enough about the previous owner that I'm actively checking his work on everything. Long story short, he didn't seal the core on anything added.

I removed the solar vent on the roof, confirmed that it wasn't sealed, and proceeded to check everything else on the roof. I had an idea of what I would find given the stains in the ceiling carpet in the cabin. On to the rocket launcher…clearly no core sealant, and there is a little depression in the roof from the center mounting point shown below ( I didn't realize the picture was blue from the still covered boat ).

I'm going to seal the core on everything, re-drill, and want to put backing plates on both sides of launcher mounting. So the question is Aluminum verses Stainless. Clearly aluminum is easier to work with, but I think I've read that there can be an interaction between the stainless hardware and the aluminum. Is that correct? Does it apply if I used Anodized aluminum?

Would you re-spray the fiberglass repair with Gelcoat before re-assembly?

 

[warthog5]

I've read that there can be an interaction between the stainless hardware and the aluminum. Is that correct? Does it apply if I used Anodized aluminum?

Yes....dissimilar metal's.....With anodized .....There is no anodized in the hole you drill.

If you use Stainless like some of us have done.....You need to find someone with a waterjet to cut it.....Cutting stainless any other way is a Mother Bear.

 

[Ludicrous40]

If I drilled out the plates, then had them anodized, would that work?

I need to check the $, but at work we regularly send out aluminum for anodizing.

 

[warthog5]

Yes, but use Tef-Gel on the bolts also.


Look up Tef-gel.

 

[DaleH]

You can use heat shrink on SS bolts and nylon washers to insulate between an aluminum backing plate and a SS washer that the SS nut will bear/turn against. I did that for years!

Make sure the HShrink covers the bolt head - works slick!

 

[TWOBOATER]

Use aluminum and lots of bedding compound. The bedding you use will coat the hardware and somewhat isolate the ss from the alum. Water-jet-cut ss backing plates? its a Parker for crying out loud, not a fighter jet!

 

[Megabyte]

I did my backing plates in stainless and had a local shop fabricate them to my specifications.
Any decent fab shop can drill, punch, or water jet. It's what they do.
Once fabled, they polished them and they looked fantastic.

Look for my spring project thread from 2011. The details are there.

Same issue as you. A previous owner mounted stuff and never protected the core.
The wet balsa in the roof was hogged out by chucking an allen wrench in a drill and having at it.

Next, I sealed one end with Gorilla tape, then poured epoxy into the void.
The epoxy soaked into the balsa and filled the hole which was later drilled for the rocket launcher mounting.

Came out quite well I think.

 

[DaleH]

TIP: Grind the end of the Allen wrench to form a cutting edge like a lawn mower blade, i.e., single edge. Now fly cutting is TOUGH, so go slow and hold on tight! Be safe ...