What Material, Aside From Epoxy, Can I Use to Close Out the Core?

[Tanqueray]

I had to rebed some mid-ship cleats that a PO had installed (not factory installed). When I tried to chamfer the holes to hold some butyl tape, I blew right through the top laminate and into a void space!

I drilled the holes a bit larger and used West Systems 6-10 Thickened Epoxy adhesive...it comes in a caulk tube with a static mixer nozzle, so you do not have to touch the stuff. The nozzle also made it easy to squirt into small holes (I plugged a few bolt holes from an old Bimini track I removed).

I pushed as much of the epoxy into the voids to try and fill them...

Once the epoxy hardened, I redrilled the holes for the cleats, and chamfered the holes for butyl tape. After tightening the through bolts, the cleats are very strong and water tight.

Just a thought....


Greg

[Chotu]

Originally Posted by rmhutch59

What's wrong with just using epoxy?

Some of you folks make my head hurt. Lol

[clv]

nothing, epoxy on polyester OK, polyester on epoxy not OK.

[Chotu]

Originally Posted by clv

nothing, epoxy on polyester OK, polyester on epoxy not OK.

Although it is ok. Just depends on the engineering and/or individual situation. Needs a bigger bond area if it's used as an adhesive. Needs nothing but tooth if used as a fairing compound.

[thinwater]

Originally Posted by Chotu

Some of you folks make my head hurt. Lol

Really.


I've been racking my brain and trying a few things on core scraps. Nothing good so far.


But there is a method that might help, allowing you to use polyester putties. Drill the core out from the inside (not the outside), putty up, and then bond a backing plate on the inside at the same time, and then re-drill.


It seems like more work, but it does a really slick job. Additionally, you can make the plug bigger, so polyester will work.

[Chotu]

Originally Posted by thinwater

Really.


I've been racking my brain and trying a few things on core scraps. Nothing good so far.


But there is a method that might help, allowing you to use polyester putties. Drill the core out from the inside (not the outside), putty up, and then bond a backing plate on the inside at the same time, and then re-drill.


It seems like more work, but it does a really slick job. Additionally, you can make the plug bigger, so polyester will work.

Hmmm!!!

This idea has some merit!

This might be it!

[thinwater]

Originally Posted by Chotu

Hmmm!!!

This idea has some merit!

This might be it!

I had an article in Good Old Boat a few years ago.


Just like the regular way, except you use a hole saw (small) from the inside, but use a depth gauge (tape) so that you do not drill the top skin. Pop the core out, and clean with a small chisel or screwdriver. Then putty the hole up, then butter a FRP backing plate and slap it in place. Very strong. It may even be faster if you have several to do, because there are fewer total steps. Easy when there is no liner installed yet.


Not my trick I learned it from an incredible DIY builder. He has an amazing blog. I almost bought the boat, because it was a DIY build to be proud of.
Scarab 22 construction

[kmacdonald]

The hull and deck putty can be made with fillers and vinyl ester instead of the polyester pre mixed hull and deck putty. Vinyl ester secondary bond is better than polyester. I like thinwaters advice but sometimes it hard to get to the underside and getting in there with a hole saw is even harder. Have you considered epoxy?

[BBill]

Think about this. Way back in the wood boat days far and few builders filled and drilled for hardware installation. Polysulfide alone worked fine and lasted many, many yrs without leaks. Then you rebedded for another term of yrs...and this is normal on glass/foam boat too. Wood and foam both absorb water and damage happens so I don't see the need in doing yours differently if epoxy isn't in the plan. Bed as usual, buy a moisture meter and do routine checks to stay on top of it.

As an afterthought. I use thin super glue for sealing wood holes. Might work for foam if it doesn't dissolve it.

[Uncle Bob]

Originally Posted by kmacdonald

The hull and deck putty can be made with fillers and vinyl ester instead of the polyester pre mixed hull and deck putty. Vinyl ester secondary bond is better than polyester. I like thinwaters advice but sometimes it hard to get to the underside and getting in there with a hole saw is even harder. Have you considered epoxy?

Have you read that he is unable to use epoxy, stated multiple times??

[thinwater]

Originally Posted by Chotu

I was thinking polyester would be fine. They always say it won’t bond to epoxy well (and it doesn’t if you peel it off) but it should keep the water out of the balsa, right?

The doubts the internet or Gougeon Bros marketing puts in your head sometimes can be quite loud.

Imagine this is for a deck cleat or a winch and there is a balsa core.

There will be a lot of cyclical loading. Will the polyester stay bonded to the skins, keeping all water out?

I don't think you mentioned if you are sensitive to vinyl ester resins. They contain epoxy sub units in the backbone, but I don't know if that is enough.


More generally, are people that have become sensitized to epoxy also sensitive to vinyl ester? Or is it different enough?

[lituya1617]

Given the flexing of FG and the fittings for cleats and other loaded fixtures, NOTHING known to man will assure water will not penetrate a hole drilled through the core! This is why balsa, an easily rotted soft material, is crazy as a deck core. Clamping deck fixtures with bolts crushes any core and creates leaks. The only way to transfer load from a cleat to a cored deck is to sleeve the bolt holes with high strength epoxy filler like MarineTex. You have to remove the core for about 1/2 inch around each bolt hole and fill the space around the bolt with epoxy filler. I use a grease gun with a needle to force the filler into the space through a small hole drilled in four places around the underside of the bolt penetration. I put the bolts in to create a "drilled space" (wrap bolts with Saran Wrap) while forcing the epoxy into the void. This epoxy sleeve gives the bolt something to clamp without deforming the deck top or bottom. When placing the cleat, I carefully bed it in 5200, then I bed the bolt heads in 5200 to prevent along-bolt leaks. Finally, I torque down the SS nylon locking nuts on stainless steel body washers under ordinary washers or I might use a backing plate on a larger cleat. Backing plates transfer bending motions to a large part of the underside of the deck but do nothing for the top side and so are problematic unless the cleat has a base plate too.. I prefer cleats with a built-in bottom plate because they effectively spread the bending stress to a larger area and prevent gel coat crazing. Firm pressure is essential to preventing leaks. But nothing is perfect. Cores are a cheap way to build a deck and they cause endless expensive problems in older boats.

[Chotu]

Originally Posted by lituya1617

Given the flexing of FG and the fittings for cleats and other loaded fixtures, NOTHING known to man will assure water will not penetrate a hole drilled through the core! This is why balsa, an easily rotted soft material, is crazy as a deck core. Clamping deck fixtures with bolts crushes any core and creates leaks. The only way to transfer load from a cleat to a cored deck is to sleeve the bolt holes with high strength epoxy filler like MarineTex. You have to remove the core for about 1/2 inch around each bolt hole and fill the space around the bolt with epoxy filler. I use a grease gun with a needle to force the filler into the space through a small hole drilled in four places around the underside of the bolt penetration. I put the bolts in to create a "drilled space" (wrap bolts with Saran Wrap) while forcing the epoxy into the void. This epoxy sleeve gives the bolt something to clamp without deforming the deck top or bottom. When placing the cleat, I carefully bed it in 5200, then I bed the bolt heads in 5200 to prevent along-bolt leaks. Finally, I torque down the SS nylon locking nuts on stainless steel body washers under ordinary washers or I might use a backing plate on a larger cleat. Backing plates transfer bending motions to a large part of the underside of the deck but do nothing for the top side and so are problematic unless the cleat has a base plate too.. I prefer cleats with a built-in bottom plate because they effectively spread the bending stress to a larger area and prevent gel coat crazing. Firm pressure is essential to preventing leaks. But nothing is perfect. Cores are a cheap way to build a deck and they cause endless expensive problems in older boats.

OK. I see you have done some of this work. But not enough of it to understand it completely.

First, balsa cannot be compressed anymore than marine plywood can. In fact it’s stiffer than that.

Second, this is a brand new boat, not an older boat.

Third, you should not be torquing your deck hardware at a level where you are crushing balsa or plywood. That’s over torqued.

Fourth, you should never use 5200 to bed deck hardware.

Fifth, The reason you are experiencing a flexing deck is because you didn’t use proper coring which would be balsa. Or a very hard and heavy weight foam. Stiffness comes from the core. From the composite panel. A piece of fiberglass is going to just bend. That’s why you have flexing. My boat has absolutely zero flexing anywhere. 1 inch thick core. Plus the skins. Doesn’t move at all.

Lastly, sleeving is what we are talking about. But we are not doing it for compression reasons. Balsa takes care of that. This is just to keep water out.

[Chotu]

Originally Posted by thinwater

I don't think you mentioned if you are sensitive to vinyl ester resins. They contain epoxy sub units in the backbone, but I don't know if that is enough.


More generally, are people that have become sensitized to epoxy also sensitive to vinyl ester? Or is it different enough?

It’s all about the Hardner. As long as it doesn’t use amine Hardner, ’m OK.

[Manateeman]

As I posted earlier, I’d take a try at Plexus. You could use two compression plates and aluminum thick wall pipe. I’ve done this in mast construction where you don’t want to squeeze the mast walls together. I use allthread rod with Tef-Gel if you ever want to replace the rod. I don’t know why you do not want to use 5200.
If you give Plexus something to grip, it’s amazing stuff. Toxic. Just follow the instructions.
You could CeraKote the plates and the pipe if you want to save weight over G10.
You could use G10 on one side and 5000 series aluminum coated on the opposite.
Plexus has a great engineering group and they know a reasonable amount about boatbuilding. A doctor could give you a skin allergy test but it mixes in a static tube.
Industrial Polymers might be another idea, but I can’t remember seeing anything better than Plexus.
Happy trails to you.
Mark and his offgassing manatees