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Old 16-12-2015, 18:10   #1
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expoy options

I am in the process of adding a windlass to my boat, j-37. Bow has a slight camber. I will be adding a g-10 backing plate below deck. I am going to fill the void between the backing plate and the bottom deck with epoxy and wanted to get input on what to use. Dont want it get too hot and there will only be a couple of holes for it to off gas. My plan is to cut and drill the holes in the deck for the windlass slightly oversize. Attach plate to the bottom of the deck and seal the edges before pouring in the epoxy from above the deck filling the void and i will have oversized the holes to protect the core when i cut the actual holes all the way through the backing plate.

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jeff
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Old 16-12-2015, 18:46   #2
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Re: expoy options

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Originally Posted by Thank you dad View Post
I am in the process of adding a windlass to my boat, j-37. Bow has a slight camber. I will be adding a g-10 backing plate below deck. I am going to fill the void between the backing plate and the bottom deck with epoxy and wanted to get input on what to use. Dont want it get too hot and there will only be a couple of holes for it to off gas. My plan is to cut and drill the holes in the deck for the windlass slightly oversize. Attach plate to the bottom of the deck and seal the edges before pouring in the epoxy from above the deck filling the void and i will have oversized the holes to protect the core when i cut the actual holes all the way through the backing plate.
How thick will the gap be? That greatly affects how much heat could build up.

I would be tempted to first epoxy the deckholes innards to protect the core, then drill and test-fit the backing plate, then I would mix up epoxy with a filler like cabosil or cotton fibre to make a reasonably thickened paste, and trowel that onto the plate, then secure the plate to the underside.

Besides being potentially less messy and saving on epoxy (less runoff), the filler adds strength.
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Old 16-12-2015, 20:05   #3
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Re: expoy options

Save the precast FRP for flat locations.

Lay-up about 5 layers of 17-ounce biax and you will have a fitted backing plate that will better distribute the load to the structure than any backing plate, with no hard spots to damage the vulnerable inner skin. Cheaper, better, less work. Then just use plain washers (not fender washers--they are too thin).

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Old 16-12-2015, 20:27   #4
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Re: expoy options

I've done many fills, some over 1". I use West System. When I am worried about heat, I use a hardener for a hotter air temperature. Hot day hardener on a cool day slows the cure. Also on any fill like you're describing, I mix in West high density filler that has adhesive properties.
Another method (with epoxy not poly) is to pour in stages. As long as the previous pour isn't fully cured, the new pour will bond. Probably 30 minutes to half a day.
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Old 16-12-2015, 20:42   #5
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Re: expoy options

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Originally Posted by Lake-Effect View Post
How thick will the gap be? That greatly affects how much heat could build up.
My guess is about an inch at the thickest point and less for most.

Quote:
Originally Posted by Lake-Effect View Post
I would be tempted to first epoxy the deckholes innards to protect the core, then drill and test-fit the backing plate, then I would mix up epoxy with a filler like cabosil or cotton fibre to make a reasonably thickened paste, and trowel that onto the plate, then secure the plate to the underside.
I will drill my holes directly though the deck for the motor and chain hole and then put the solid g-10 plate under so that when i re-dill the holes all the way through the g-10 i will have as you put it, "epoxy the deck hole innards"
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Old 16-12-2015, 21:56   #6
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Re: expoy options

Just use a slow hardener. The slower reaction reduces heat build up. Using fast harder will increase the temprature.

You also need to use a structural filler, which will reduce the mass of epoxy, and thus the thermal gain.
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Old 16-12-2015, 21:57   #7
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Re: expoy options

If you are using WEST, you will want the Tropical hardener, not slow. It's what they recommend for casting pours.
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Old 18-12-2015, 13:29   #8
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Re: expoy options

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Originally Posted by Thank you dad View Post
My guess is about an inch at the thickest point and less for most.
1" - that seems huge. Is the underside that uneven? I would consider any gap more than 1/4" as a problem.

Maybe the better approach is to simply build up a few layers of epoxy+glass cloth under the windlass location, then use some oversize backing plates in G-10, 1/8" aluminum or similar under the bolts.
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Old 19-12-2015, 12:12   #9
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Re: expoy options

Something that would probably work very well is not well known by some but the mechanics in my shop used it all the time - a two part epoxy called Splash Zone. They called it Duck S**t because it turns a green color when mixed. They used it to create new prop shaft strut mounting bases and for any kind of structural work. It is moldable and you can apply it by hand as it is like a weak clay consistency, i.e. you can mold it by hand and it will retain its shape. You can use water to shape and smooth it.

Just an idea.

A-788 Splash Zone Compound - Z-Spar Paint | Fisheries Supply

Fisheries sells it but it is widely available.
Better description:
http://www.go2marine.com/product/79357F/splash-zone-compound-underwater-epoxy-putty-a-788.htm
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Old 19-12-2015, 17:13   #10
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Re: expoy options

Faced with a similar issue with my winch thanks to a curved deck, I made a template of the curve then used that to fabricate a spacer plate out of fibreglass and polyester resin to adapt the curved deck to the flat underside of the winch. Was cheap and easy to make, didn't need to be super accurate and meant I could attach it with polyurethane adhesive sealant instead of epoxy.

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