good source for ss backing plates?

[Rumrace]

Crushing is why I suggested a nylon CF or PC you’d be more likely to dent aluminum.

[cyrano138]

What source? I only saw the ebay link. Is 1/4 inch good enough for all backing plates? I was also thinking of using it for a transom backing plate for a small outboard. The transom is not that beefy I think because the boat originally had a well in the cockpit for a motor (it's a Cal 20).

[team karst]

Like this?

[s/v Jedi]

Originally Posted by cyrano138

What source? I only saw the ebay link. Is 1/4 inch good enough for all backing plates? I was also thinking of using it for a transom backing plate for a small outboard. The transom is not that beefy I think because the boat originally had a well in the cockpit for a motor (it's a Cal 20).

Not sure what you mean. I think $23 per square foot is a great price for 1/4” thick G10.

https://www.ebay.com/itm/28379370070...IAAOSwiI1eXdjH

Edit: Jamestown has it as well: https://www.jamestowndistributors.co...ct-detail/8758

[coopec43]

Would there be anything wrong with using a High Density Poly Ethylene (HDPE) plastic? (Plenty in re-cycle bins)





Advanced Poly | High Density Polyethylene (HDPE) Pipe and Plastic Fabrication

[Sailmonkey]

Originally Posted by coopec43

Would there be anything wrong with using a High Density Poly Ethylene (HDPE) plastic? (Plenty in re-cycle bins)





Advanced Poly | High Density Polyethylene (HDPE) Pipe and Plastic Fabrication

Hdpe plastic tends to cold flow with a continuous high load applied to it. Wouldn’t be my first choice to spread a load.

[s/v Jedi]

You may want to check out this place: https://www.oshcut.com/?src=fb-p-pri...Fpk4aE54b6uj8c

[Bowdrie]

"Cold Flow" generally needn't be a problem.
The amount of gelcoat crazing/cracking around hardware, compression damage in Teak cap rails, distorted windlass mounting flanges, distorted stanchion bases, warped aluminum hatch frames, etc., the list could be almost endless of the results of overtightened hardware that I've observed over the years.
Too many DIYs and some pros too, seem to approach hardware mounting as if they're torquing the head bolts on a Caterpillar Diesel.
It doesn't help the "gasket" qualities of whatever "goop" you use for sealing and makes any future removal that much harder.
Tighter is not always better, that goes for hose clamps too.

[cyrano138]

I ordered some g10 (1/4" for backing plates, 1/2" for kicker backing). Any advice on cutting, drilling, bedding, and securing it? I assume since it's epoxyi can treat out like any other fiberglass I want to bond.



Thanks for the advice!

[s/v Jedi]

Originally Posted by cyrano138

I ordered some g10 (1/4" for backing plates, 1/2" for kicker backing). Any advice on cutting, drilling, bedding, and securing it? I assume since it's epoxyi can treat out like any other fiberglass I want to bond.

Thanks for the advice!

I sand it, wipe with solvent then glue with thickened epoxy. For drilling, use regular metal hss drill bits. I also tap thread in it, using smallest diameter drill bit listed in tables.

For cutting, I use special jigsaw blades with carbide teeth: https://www.amazon.com/Bosch-T141HM1...s%2C107&sr=8-8

[coopec43]

Originally Posted by Bowdrie

"Cold Flow" generally needn't be a problem.
The amount of gelcoat crazing/cracking around hardware, compression damage in Teak cap rails, distorted windlass mounting flanges, distorted stanchion bases, warped aluminum hatch frames, etc., the list could be almost endless of the results of overtightened hardware that I've observed over the years.
Too many DIYs and some pros too, seem to approach hardware mounting as if they're torquing the head bolts on a Caterpillar Diesel.
It doesn't help the "gasket" qualities of whatever "goop" you use for sealing and makes any future removal that much harder.
Tighter is not always better, that goes for hose clamps too.

I couldn't agree more. If the backing plate is just slightly flexible it will help in avoiding hard spots.

"There is a special case for using thinner plywood, but I'll get to that later. The edges of the plywood should be tapered to prevent forming a hard spot in the fiberglass around the edges of the plate. The plywood should be coated with several coats of epoxy to seal out any moisture."

https://www.boatus.com/expert-advice...backing-plates

[cyrano138]

Originally Posted by s/v Jedi

I sand it, wipe with solvent then glue with thickened epoxy. For drilling, use regular metal hss drill bits. I also tap thread in it, using smallest diameter drill bit listed in tables.

For cutting, I use special jigsaw blades with carbide teeth: https://www.amazon.com/Bosch-T141HM1...s%2C107&sr=8-8

Thanks! I ordered a couple of those blades as well. Do you also use a bedding compound for the hardware (5200 or 4200 or something like that)?

[seandepagnier]

Originally Posted by Chotu

I hate to be someone that doesn’t answer the question, but truly, stainless steel backing plates are not a good idea.

they are way too difficult to work with, drilling those holes is ridiculous. It would be far better off substituting aluminum or G10 or even better.. the polyester equivalent.

Do it once with the composite material and never do it again.

Hoping to just talk you out of stainless. Too much work and it can still corrode.

Aluminum will over time (decades) corrode and cause aluminum oxide to build up pressure into wood etc and other issues. Drilling stainless is not actually very hard at all but it took me a while to figure out because if you do it wrong you kill the bit.

I ended up using all titanium for my chainplates, inside outside bolts etc.. There is no stainless anywhere (stainless cannot be fully trusted). The cost for me was lower than stainless because I got repurposed scraps of titanium. It is much harder to work with than stainless. cobolt drill bits and carbide tooth saw helped a lot, but its possible to use regular bits (re sharpening for every hole drilled etc)

[s/v Jedi]

Originally Posted by cyrano138

Thanks! I ordered a couple of those blades as well. Do you also use a bedding compound for the hardware (5200 or 4200 or something like that)?

Yes, for bedding compound use the butyl tape from Rod Collins from MarineHowTo (I wouldn’t use other types unless recommended by longtime user) or use a polysulfide caulk like Boatlife Life-Calk.

[s/v Jedi]

Originally Posted by cyrano138

Thanks! I ordered a couple of those blades as well. Do you also use a bedding compound for the hardware (5200 or 4200 or something like that)?

Here are some pictures. This is fiberglass material I made myself. This is 3/4” thick and 1/4” thick. It shows how neatly the blade cuts.