epoxy instead of nails

What kind, options, etc.

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pete gibbs
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epoxy instead of nails

Post by pete gibbs »

Silly question probably but since epoxy will usually be stronger than the material its bonding together why not use only epoxy to bond certain pieces together without nails/screws or such?
I know in some applications screws are needed to draw and hold a piece but what about say a second layer of plywood for a transom or an area where you would rather not have screw heads or plugged holes?
I know two pieces of wood epoxied together will rip the wood apart before the epoxy gives up. Assuming you can hold the pieces together while the epoxy sets and the area being epoxied is large enough to make the epoxy joint strong enough naturally.

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Re: epoxy instead of nails

Post by jprice »

A lot probably depends on exactly how/where the piece will be used, and what kind of stresses it will be under. But I'm sure there's lots of places where it's perfectly fine to use just epoxy and no mechanical fasteners.

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Re: epoxy instead of nails

Post by sawford11 »

Pete - I agree with the above post...there are certain areas where the epoxy will hold sufficiently. For instance, I wanted a screwless top deck. I used weights and clamps to epoxy the mahogany coverboards to the underlayment. The coverboards had to be slightly bent to the shape of the deck, but with weights and clamps, I could hold the shape til the epoxy cured. In this case, if the epoxy failed, one of the coverboards could come loose. No big deal, boat won't sink!

However, for connecting ply to the frame members or other structural connections, I would use the mechanical fastener as well as epoxy. Here is something that I wrote a while back, which may apply to you question:

Epoxy is very strong, no doubt. But just using epoxy to hold a plywood panel to a frame member doesn't seem like the best idea to me. When I first got started, and as an epoxy test, I epoxied two plywood panels together with a simple overlap. Once the epoxy cures and you try to break the joint, the epoxy holds tight. However, if you continue to stress the panel joint, the plywood simply delaminates. The epoxy is simply holding the two outer layers of the panels to one another and as such, the joint is only as good as the weakest layer of plywood glue/lamination. I like having the screws driven through the plywood and into the solid wood members to ensure that the full section of plywood (i.e. all layers) are 'connected' to the longitudinal members. Just my opinion....

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Re: epoxy instead of nails

Post by Iggy »

For me it about bearing area... how much area of epoxy will be holding how much stress? For example: When I butt-jointed the sides for my 1/4" Meranti plywood sheets I didn't use any fasteners, just weight. The splice plate has a lot of area for the epoxy to hold and the spot where I put my joint has minimal stress.

However, for installing my chines I used fasteners, simply because there is not a lot of wood suface area to hold a highly stressed wood chine.. EXCEPT for frame 4 (last forward frame on Malahini) where I purposely did NOT put a fastener as it would likely split. However the chine blocking and frames 1, 2, 3, and transom held the chine in shape, plus the plywood over top will be epoxied so the chine wasn't going anywhere.

My finished deck is 1/4" strips of plywood epoxied to a 3/8" sub-deck, and while I used temporary screws between strips to hold it down till the epoxy cured, the final deck suface has no fasteners.

Again, area... epoxy wins when it has a lot of surface area to hold it down. Point fasteners win for smaller area's, or places you might want to make removable in the future (ie: my plywoof floor is screwed down only).
Ian (aka Iggy)
My Malahini Build

pete gibbs
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Re: epoxy instead of nails

Post by pete gibbs »

Yeah, all good thoughts and ideas.
I never thought of the weak link being the glue to the first ply of the plywood...
Well I'll certainly look at using only epoxy on the deck that takes only 1/8" plywood that I'd rather not screw down. I'll keep the screws on the hull though. Wouldn't want to strike something and the whole thing come unglued like a cartoon hahhahahha.

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Re: epoxy instead of nails

Post by bobinpowayca »

I'm building the Geronimo - the transom knee called for three laminations of 3/4" plywood, using glue and nails to nail the outer layers to the middle one. I didn't use the nails, just wetted the faces with epoxy, then a good layer of thickened epoxy in between, and a weight on top of the sandwich. I figured the epoxy I used would be just as good as the plywood's epoxy. Also I'll be putting four 5/16" carriage bolts thru it to attach to the transom and keel so this way I won't be drilling thru nails. Hope it works....
Built the Glen-L 17 (1988), Geronimo (2018)
PBR support (1968)

Old aussie
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Re: epoxy instead of nails

Post by Old aussie »

My therory on this subject is, if screws or epoxy can hold a boat together on there own, together you cant go wrong I screwed
every thing thru last layer of ply chines sheers keel. battons to frames . ..


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Bill Edmundson
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Re: epoxy instead of nails

Post by Bill Edmundson »

What are the consequences(sp) of you being wrong?

Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

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