Epoxy Mounting Hardware

[bristol27]

I'm wondering about the feasibility of using epoxy to secure deck hardware.

From speaking with a respected boat builder in my boat yard, he mentioned that the Gougon Brothers actually considered using epoxy to bed deck hardware as a viable option. That being said, I've never seen evidence of this method online so I wanted to see if others on this forum have heard of this, plus I was hoping you all might comment on the feasability of this option. To be clear, I've created a quick image that shows here's how I would install the fasteners in epoxy to secure deck hardware:

Using epoxy to mount hardware. The fasteners are shown in black, submerged in thickened epoxy.

To explain in more details, here's how I imagine the installation occurring:
1) Determine location of deck hardware
2) Thicken "block" into place where deck hardware will be installed (Note: my diagram shows the block installed below deck, however I could also install a block "in deck" so there wouldn't be any protrusion of the block below deck. This would be necessary for any blocks installed in the cabin top)
3) Fiberglass block in place so it's a structural piece of the hull.
4) Drill holes for deck hardware
5) Use empty caulking tube to fill holes w/ thickened epoxy.
6) Place deck hardware into position and push fasteners into epoxy.

With the basic idea understood, here are the advantages & disadvantages of this method:

Advantages:
* No leaky hardware. The fasteners are fully encased in epoxy and never actually protrude into the boat.
* Hardware may be mounted more firmly that the traditional "caulk + through bolt". The thinking here is that each thread will be encased in epoxy, effectively acting as multiple "nuts" to hold the fastener in place.

Disadvantages:
* More work to place hardware, also harder to move hardware around if necessary
* Epoxy may crack under hardware strain (?)
* For the cabin top mounting blocks, where the blocks will protrude above the deck to give the necessary depth for the fasteners, they will be a toe stubber (though...fasteners are a head bumper below deck)


Now for some more specific questions:

+ Has anyone has heard of this method used before?
+ Is it correct that epoxy bonded hardware will be more firmly in place than through bolted hardware?
+ If this method is feasible, could I use this for ALL hardware (e.g. chain plates)?
+ To me, it seems epoxy might crack if the hardware were to stress or flex - comments?

[LazyGuy]

I have never used this method exactly. What I have done is strengthened screw mounted hardware with the assistance of thickened epoxy. In the case of my traveler, I drilled the holes one size too big so the 4 to 4.5" screws did not have the amount of "Bite" that I wanted. So I coated the screws with lanolin, filled the holes with epoxy with cabosil and set the screws, through a piece of plastic and the track into the teak. The plastic isolated the track from the squished out epoxy. Two days later I came back, backed out the screws, bedded the track with boat-life and drove the screw back in. I have also employed this method for other screw mounted hardware but never for bolted hardware such as the bow pulpit, stern rail or stanchions. Those I only trust to backing plates and through bolts.

[Tallystick]

Just speaking to your epoxy mix, for this type of application I think adding chopped glass fibers in addition to the cabosil would be advisable to increase the tensile strength. My concern would be how well the strength would be maintained over time, with flexing, temperature cycling, and vibrations. Larger coarse threaded fasteners would give you the best holding power IMO.

[Carl-A259]

Well from your advantages list I don't see how it would be stronger, when the proper nut is used it doesn't back off. through deck bolts can be installed without leaking. I think that installing a knee much like internal chainplates have for chocks, cleats and stanchons would make for a stronger system. The weak link in deck hardware for the most part is the deck.

[bristol27]

FWIW department...personally I think there is a lot to be said for simplicity and the "KISS" theory. Over-boring the holes in the deck, epoxy filling, tapping out, sealant, installing bolts with a SS or aluminum backing plate and nylocks goes a long way.

I'm in agreement! After looking at this some more this past weekend, I'll stick with the traditional method of securing deck hardware.

Thanks for everyone's input, much appreciated.

[bigd14]

Fwiw I had good success tapping into an inch of g10 for a seacock backing plate. I did an unscientific pull test and it seemed very robust. But I think the traditional method is best.

When is launch date? :-)

[mitiempo]

That works well for a through hull as there is no load on it. The bolts more than anything stop it from turning as the mushroom is threaded into it as well.
But for a deck fitting that is expected to carry a load I would use a backing plate and nuts with lock washers. I often tap the deck for fasteners but always use washers and nuts.

[bristol27]

When is launch date? :-)

Dates! When I first started, dates were "real", but after learning that every project takes an undefinable amount of time until it's complete, I changed my tune.

Now I just say "when the boat is done, it's done". That being said....I hope to finish the exterior work by this spring. Wrap up interior instruction by mid summer, then paint next fall. With systems going in through the fall and maybe, just maybe, be in by end of 2012. Again though, dates are meaningless :)

[bigd14]

Yes, dates are meaningless in this business! Although our mutual acquaintance Miguel always says he's launching "On Friday!"

I'll stop in sometime and see how you're doing.

Doug