Adhesive nuts for deck hardware, what glue for fiberglass?

[HeelBoy]

From Mcmaster Carr:

Have any of you worked with these lovely things?
Nuts and studs of various sizes, 316 stainless, they spread the load nicely and keep a low profile. An attractive alternative to needing a second person to hold nuts and washers inside the boat.

I'm wondering what adhesive would be best for sticking these to the inside fiberglass surface. Something thick to encapsulate them and not drip off the ceiling, but thin enough to get good adhesion.

 

[dlochner]

Yes, not those specific mounts. Weldmounts are popular with marine electricians for securing low weight devices and supporting cables. They work well. The main short coming is the price of the adhesive which has a fairly short shelf life.

Thickened epoxy would probably work. Not the 5 minute stuff, G Flex Thickened Epoxy might be a good choice.

G/flex 655 Thickened Epoxy Adhesive | WEST SYSTEM Epoxy

WEST SYSTEM's G/flex 655 Thickened Epoxy Adhesive bonds with Plastics, Metals, Glass, Masonry, and Fiberglass.

www.westsystem.com

Weld Mount - Adhesive Fastening System

A unique line of fasteners designed to be adhesively bonded to almost any surface, elimintating the need for drilling, tapping or welding.

www.weldmountsystem.com

 

[PaulK]

Used studs like that to mount the foot braces in my kayaks. They're designed to be installed with thickened epoxy.

 

[HeelBoy]

I was thinking more for structural hardware, in a sandwich with the deck (pictured). Effectively giving you a permanent threaded hardpoint in the deck.

 

[thinwater]

Thickend epoxy or Plexus. I've used both, zero failures. Not cleats, but holding down an AC unit and many hooks that see over 100# in shear.

Where did those come from?

Another proven option is to thread + epoxy the studs into 1/2" Garolite pads.

 

[PaulK]

For installing cleats and such the deck will need something solid in lieu of balsa or foam coring. Tightening the bolts would crush the core otherwise. Do you intend to remove or de-install these items? That might lead to them leaking. The expense and effort involved with installing the nuts or studs might be considerably more than simply using tape to hold standard nuts & washers in place when you install a fitting, too.

 

[HeelBoy]

Where did those come from?

Mcmaster Carr. Rather than re-purposed weld hardware, these are designed for adhesive.

 

[HeelBoy]

Do you intend to remove or de-install these items?

Going through a 40 year old boat... yup, I plan to remove and re-seal everything. The flanges on these are 1.5" across, should be suitable for shear loads. Backing plates will still be needed for things like halyard fairleads etc.

 

[dLj]

I've used those same connectors, or whatever they are called... Gflex 655 is my preferred adhesive for them as @dlochner has pointed out above.

dj

 

[Project_Mayhem]

If you're main concern is fastening them by yourself, I was able to tighten 95% of the bolts during my rebedding project using an impact driver. I'd be happy to share the tricks I that helped me the most.
For deck fittings that experienced high loads I used Unistrut washers as a backing plate. In other areas I used a couple of fender washers stacked together. Everything has held up for two seasons so far

 

[Tally Ho]

As I have replaced or rebed deck hardware, I try to use a hex-head bolt rather than a screw. I have 6 pairs of vice grips, and I can clamp them on several bolt heads, go below to put the backing plate and nuts on, and tighten them.

Repeat if necessary.

i like those fasteners, but question whether there is enough room under the deck for them (stanchions are pretty close to the outboard hull). And certainly it seems like a lot of effort for something I would hope to remove and rebed once (if done right). If the fitting is removed frequently, that is a different story I guess.

Greg

 

[jssailem]

For my winches, I chose 1/4 aluminum plate to back the hardware. Cut in a shape that fits the space under the cockpit combing as a backing. I drilled the hole pattern to match. 8/8 inch plate cost $19. One of the adhesive mount nuts described cost $17.59. I could not fit 6 nuts in the allotted space.

Nice idea but a bit pricey for the desired task.