Bonding to hull - Light and Heavy items

[Chotu]

Originally Posted by coopec43

When I installed the sheaves blocks at the steering quadrant I sanded down the fiberglass each side of the quadrant (18 inch X 18 inch) and laid polyester/CSM. I then used polyester/CSM to fiberglass the SS angle to the hull.(I would have used 6 layers). (The mounts for the autohelm were done the same way)

The stresses on the sheaves at the quadrant could easily be 500kg but I'm confident they will hold.

I have a couple interesting stories of non epoxy adhesives working and surprisingly well. These were tests I didn’t want to make, but they happened none the less.

Polyester Resin to Marine Ply and Polyester to Epoxy

Due to my epoxy issues, I glassed in my cabin soles using polyester. The soles are high quality Okoume marine ply. The hull is epoxy.

I used an 8 inch, 200mm strip of biax at the join with a bondo (premix polyester/talc filler) fillet. Then laid the biax tape on the fillet, laminating it with polyester resin. The marine ply was also sealed in polyester.

From everything I’ve read online here and everywhere, this was not a good bond and I should have immediate failure and my boat would sink! Ha ha.

Well, I lost a window over the summer, then a rodent chewed through my solar wire, cutting off all power to my boat. I’m sure everyone can guess what happened with no electric power and a missing window while tropical storms went by.

I arrived back to the boat to find all of that which I just described underwater. It had been sitting underwater for months.

Surely I figured I’d have to tear it out and redo it all. Polyester??? Should have sunk my boat the moment I applied it according to the internet.

What I found after pumping out the water and letting it all dry was.... NOTHING.

No rot, no separation, no delamination, no moisture in the wood and the cabin soles are still bonded to the hull.

I have some mold to clean on the surface and that’s it.

Went against everything I’ve read online.

My take away is that your bond area plus the load is what matters with polyester. You want a lower PSI stress than with epoxy. So don’t try to bond your snubber line with something the size of a quarter using polyester as a secondary bond. Otherwise, it’s just fine.

Formica/3M Spray Adhesive

I made some very small test panels of Foamular insulation foam with Formica faces. I used 3M spray adhesive to bond it together. It was able to peel a little easier than I had hoped, but it was peeling the foam apart so the adhesive was working.

Well, one of the test coupons fell into the bilge and spent months floating in that flood water trapped under the flooded cabin sole.

Pulled it out after pumping out the water and it was like the day I made it.
What really confuses me is I thought Formica wasn’t waterproof

[coopec43]

Originally Posted by Chotu

I have a couple interesting stories of non epoxy adhesives working and surprisingly well. These were tests I didn’t want to make, but they happened none the less.

Polyester Resin to Marine Ply and Polyester to Epoxy

Due to my epoxy issues, I glassed in my cabin soles using polyester. The soles are high quality Okoume marine ply. The hull is epoxy.

I used an 8 inch, 200mm strip of biax at the join with a bondo (premix polyester/talc filler) fillet. Then laid the biax tape on the fillet, laminating it with polyester resin. The marine ply was also sealed in polyester.

From everything I’ve read online here and everywhere, this was not a good bond and I should have immediate failure and my boat would sink! Ha ha.

Well, I lost a window over the summer, then a rodent chewed through my solar wire, cutting off all power to my boat. I’m sure everyone can guess what happened with no electric power and a missing window while tropical storms went by.

I arrived back to the boat to find all of that which I just described underwater. It had been sitting underwater for months.

Surely I figured I’d have to tear it out and redo it all. Polyester??? Should have sunk my boat the moment I applied it according to the internet.

What I found after pumping out the water and letting it all dry was.... NOTHING.

No rot, no separation, no delamination, no moisture in the wood and the cabin soles are still bonded to the hull.

I have some mold to clean on the surface and that’s it.

Went against everything I’ve read online.

My take away is that your bond area plus the load is what matters with polyester. You want a lower PSI stress than with epoxy. So don’t try to bond your snubber line with something the size of a quarter using polyester as a secondary bond. Otherwise, it’s just fine.

Formica/3M Spray Adhesive

I made some very small test panels of Foamular insulation foam with Formica faces. I used 3M spray adhesive to bond it together. It was able to peel a little easier than I had hoped, but it was peeling the foam apart so the adhesive was working.

Well, one of the test coupons fell into the bilge and spent months floating in that flood water trapped under the flooded cabin sole.

Pulled it out after pumping out the water and it was like the day I made it.
What really confuses me is I thought Formica wasn’t waterproof

Chotu


You are not supposed to be able to polyester to epoxy but you can epoxy to polyester.

"While epoxy adheres tenaciously to cured polyester, the reverse is not true, so the bond between an epoxy repair and an overcoat of polyester gelcoat will not be strong. Use polyester for repairs that will be gelcoated. Cost can be the second consideration. Epoxy is three to five times more expensive than polyester." (Boats are Us)



I always thought Formica was waterproof but apparently not completly?

[Chotu]

Originally Posted by coopec43

Chotu


You are not supposed to be able to polyester to epoxy but you can epoxy to polyester.

"While epoxy adheres tenaciously to cured polyester, the reverse is not true, so the bond between an epoxy repair and an overcoat of polyester gelcoat will not be strong. Use polyester for repairs that will be gelcoated. Cost can be the second consideration. Epoxy is three to five times more expensive than polyester." (Boats are Us)



I always thought Formica was waterproof but apparently not completly?

That’s what they say, but “they” are wrong.

My cabin soles just spent months underwater.

I am walking all over them and they aren’t going anywhere. No delamination.

I think it has to do with a reduced bond strength as compared to an epoxy bond. If your bonding area is sufficient compared to the load, it works. If the piece is highly loaded with a small bond area it MAY fail.

I mean think about it. If you are doing a secondary bond polyester to polyester, you are relying on the roughed up surface to to hold the new polyester. It’s the geometry of all the little scratches and grooves holding things together, not a chemical reaction between old and new polyester.

If you make the same scratches grooves in epoxy, then bond to it using polyester, you’ll get the same secondary bonding quality as polyester to polyester.

This is a lower quality bond than a secondary bond formed by putting epoxy over a rough surface but it’s as good as a polyester/polyester secondary bond.

And that’s good enough with a 8” (200mm) wide piece of biaxial over a fillet to hold a cabin sole up.

[coopec43]

Originally Posted by Chotu

That’s what they say, but “they” are wrong.

My cabin soles just spent months underwater.

I am walking all over them and they aren’t going anywhere. No delamination.

I think it has to do with a reduced bond strength as compared to an epoxy bond. If your bonding area is sufficient compared to the load, it works. If the piece is highly loaded with a small bond area it MAY fail.

I mean think about it. If you are doing a secondary bond polyester to polyester, you are relying on the roughed up surface to to hold the new polyester. It’s the geometry of all the little scratches and grooves holding things together, not a chemical reaction between old and new polyester.

If you make the same scratches grooves in epoxy, then bond to it using polyester, you’ll get the same secondary bonding quality as polyester to polyester.

This is a lower quality bond than a secondary bond formed by putting epoxy over a rough surface but it’s as good as a polyester/polyester secondary bond.

And that’s good enough with a 8” (200mm) wide piece of biaxial over a fillet to hold a cabin sole up.

I won't argue with you regarding the area of the bond. That is why I f/g an 18 inch X 18 in piece of CSM to the hull before I fiberglassed the SS strips to the hull.

[clockwork orange]

Originally Posted by Manateeman

Plexus.
Only one issue. Removing anything stuck together with it. The company also gives great support to boatbuilders. Worth the money.
Makes 5200 look like kindergarten glue.
Happy trails to you
Mark and the manatee gang

I think you are overselling plexus a bit, as a guy who has been involved in re bonding an entire structural grid in a 36ft racing sailboat that was built by a highly regarded builder with the grid bonded to the carbon hull with Plexus that failed i am not as enthusiastic about it as you. I can not tell you why it failed but it did, extensively. For the OP's use i'm sure it would be fine.

[Chotu]

Originally Posted by coopec43

I won't argue with you regarding the area of the bond. That is why I f/g an 18 inch X 18 in piece of CSM to the hull before I fiberglassed the SS strips to the hull.

Exactly. It’s all about the PSI or the Mpa/Kpa.
(Hope I got the pressure units correct for you)

[Chotu]

Originally Posted by clockwork orange

I think you are overselling plexus a bit, as a guy who has been involved in re bonding an entire structural grid in a 36ft racing sailboat that was built by a highly regarded builder with the grid bonded to the carbon hull with Plexus that failed i am not as enthusiastic about it as you. I can not tell you why it failed but it did, extensively. For the OP's use i'm sure it would be fine.

What did you use to rebond that structural grid?

[jmschmidt]

I use rough up the to the hull fiberglass enough to get a grip and I use wood for a mounting pad soft enough to be penetrated by the 5/1 marine epoxy resin but hard enough to hold the screws tight.