# Securing fasteners in composites



## predacious (Sep 1, 2016)

There's a way to securely use fasteners in composite decks - it's a specific technique 


This is a boat I'm redoing - it's getting a grab bar. Boat has a nidacored deck- nida corevwill NEVER hold a fastener. The fastener would be held by the skins of fiberglass on the nidacore only - resulting in a failure. You can attempt to use 3m 5200 to bed the fastener - but I promise you it will fail !
Other composites are similar - divinycell voids/Penske board- these will not hold a fastener either. These are a brittle product - the vibration will cause the material to fracture and break surrounding the fastener - end result is a loose fastener. The inexperienced will use a larger fastener - only to make the hole bigger....


I removed the upper skin of fiberglass - due to the fact I'm refinishing the deck with awlgrip- there's another way to do it without removing the glass.

Locate the position the fastener will be in - drill a hole thru the upper skin only - allenwrench - sharpen the short end and chuck it up in a drill - work it in the hole you drilled and tear up the core. Use a shop vac and suck the remnants out

Epoxy - thickened epoxy - do not use polyester resin !

Fill the hole(s) let it kick and sand it flush if you need to. Use machine screws - example- I'm using 1/4-20 machine screws. Drill the hole to 7/32"
Dab a shot of 5200 on the hole and run the fastener in with an impact gun

The fastener will thread the epoxy. If you need to remove the fastener - use the impact gun and it will back out - run the screw back in and it's still tight 

Composites are designed to be thrubolted and sleeved - if the area is blind - use the method I described - it's the most secure method. Those toggle bolts tend to fail / I've repaired numerous boats that used them to hold leaning posts t/tops using that method - its a bad move


The mounting base of the grab bar in using is 3 1/2" I used a hole saw 4" and removed the upper skin and the coring- Filled the areas with the epoxy 

Again- I'm doing it this way because the deck will be refinished with awlgrip 

Epoxy and polyester gel coat do not play well together - a vinylester separation coat is needed 


Again - follow the method I've described to mount equipment to s composite cored area


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## Smackdaddy53 (Dec 31, 2012)

I used this method on my Maverick recenty to mount the poling platform. It worked great.


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## DuckNut (Apr 3, 2009)

If you embed the screw in the wet epoxy it will create threads before it kicks. Back screw out and attach item.

I wrote about this method about 5 years ago but I am glad to see it come back to life.


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## predacious (Sep 1, 2016)

DuckNut said:


> If you embed the screw in the wet epoxy it will create threads before it kicks. Back screw out and attach item.
> 
> I wrote about this method about 5 years ago but I am glad to see it come back to life.



seen a few other techniques used - repaired many of these attempts,at my shop....

that method of setting fasteners in wet epoxy doesn't sound very good - too much room for error.

the method I described,it was discussed/taught at an ABYC certification course I attended approx 10yrs ago


very common to see fasteners fail,fasteners securing consoles,leaning posts,ETC in composite cored decks,when done incorrectly.


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## DuckNut (Apr 3, 2009)

You are correct. I actually learned it a long time ago from the owners of West System.


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## Finn Maccumhail (Apr 9, 2010)

On my project I was wondering about this- specifically for attachmen


predacious said:


> There's a way to securely use fasteners in composite decks - it's a specific technique
> 
> 
> This is a boat I'm redoing - it's getting a grab bar. Boat has a nidacored deck- nida corevwill NEVER hold a fastener. The fastener would be held by the skins of fiberglass on the nidacore only - resulting in a failure. You can attempt to use 3m 5200 to bed the fastener - but I promise you it will fail !
> *Other composites are similar - divinycell voids/Penske board- these will not hold a fastener either. These are a brittle product - the vibration will cause the material to fracture and break surrounding the fastener - end result is a loose fastener. The inexperienced will use a larger fastener - only to make the hole bigger....*


I'm a first-timer doing a restoration and was planning on using Penske for the transom. Obviously the motor mounts will be sleeved and have the outboard backing plate but for the trim tabs would I need to have something besides Penske for the trim tab screws/fasteners to bite into? If so, what should I use?

I'm still a ways off from that point but want to do it right.

Thanks.


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## DuckNut (Apr 3, 2009)

Don't sleeve it. Drill the hole out a bit larger than the bolt, fill drill hole with thickened epoxy, then re-drill holes.

The trim tab screws are just that - screws. Drill holes and use 5200 on the screws and tighten them down. Keep your eye on them for signs of any possible issues over the years.


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## Crusty Fly (Oct 17, 2017)

predacious said:


> Epoxy and polyester gel coat do not play well together - a vinylester separation coat is needed



Can you expand on the vinylester separation coat?


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