No bond??

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Fuzz
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No bond??

Post by Fuzz »

So a good buddy has a 37 foot boat that was stretched 5 foot. The company that did the work has a good rep. The work was good enough you could not tell where they had cut the hull. They only use epoxy for this kind of work. My buddy is doing some major refit to the boat. In doing so we have found where the epoxy overlapped the old poly hull it did not bond! I am not sure how this thing did not break in half. You could take a nail bar and pry the epoxy layup off the poly with no sign of any sort of bond. Any of you guys ever seen such a thing???

fallguy1000
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Re: No bond??

Post by fallguy1000 »

Well, some predictability...

The substrate prep is key. If they left any gelcoat; that would be reason 1.

If they did not sand or grind with a wire brush or 60 grit max, reason 2.

If they laid it up even a little dry, reason 3. The old glass could have sucked the joint.

The poly bond is only 25% as good as the epoxy bond, so any weakness at the interface is acting on the poly. If they polished the poly with 225; the surface is too polished and the epoxy will not adhere well. Where it does grab, the poly bond breaks at 25% of the epoxy strength, etc.

You can probably determine which of these..but the entire job is a redo now..

My guess is sanded too fine; didn't use enough resin.
My boat build is here -------->

viewtopic.php?f=12&t=62495

Fuzz
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Re: No bond??

Post by Fuzz »

I am talking about areas three foot long with 18 inch or more of 3/8 thick overlap. There were a few places where a little of the old glass peeled up with the epoxy but most of the epoxy was almost mold smooth. Sanding much too fine seems like a good guess. Like I said the folks that did the work have a pretty good reputation but this is plain scary. The 5 foot stretch job cost over 100K and I kid you not I am surprised the boat did not break in half. I sure would not have liked stacking 20k pounds of fish on it and then have the weather lump up like it does in the Bering Sea.

Fuzz
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Re: No bond??

Post by Fuzz »

There was no sign of gelcoat being left on the hull. I did not see any sign of other contamination. The epoxy laminate looked good no clear fault I could see. I am thinking sanded way too smooth was the major problem. As of now the entire area that was stretched is going to be cut out and redone.
I well remember Cracker Larry talking about the things you find when you take a boat apart and this is just one more case of that.

fallguy1000
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Re: No bond??

Post by fallguy1000 »

My laminating table is sanded to 400 grit. Of course it is waxed, but I think glass would never come off it if the wax was not there. So a fine sanding job is only part of it.

Another possible cause is the presence of water. If the boat was not in a climate controlled building and had high moisture; that could cause all sorts of problems. Consider a boat that had dew on it when they laminated it. It might even cause blush. I don't know if there is enough co2 for blush to occur interlaminar. But other problems in Alaska coastal environment combined with crap epoxy and conditions for blush are exceptional.

1. Cold
2. Moisture
3. Cheap epoxy with IPD (ref. epoxy school website)
4. Gas fired forced air heaters provide more co2.

So, some blush event also possible. You might even feel it on the surfaces yet.

Of course all 4 events and the 5th high polish are possible, or the repair guys might have precoated the poly and missed the blush event?
My boat build is here -------->

viewtopic.php?f=12&t=62495

OneWayTraffic
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Re: No bond??

Post by OneWayTraffic »

Technically all that you know is that the bond is weaker than the internal strength of the epoxy and the poly. Even at 10% strength with a very large overlap and some mechanical friction grip there may have been a lot of strength remaining. Until it hits a wave wrong you might never know.

My guess would be some atmosphere contamination. I've heard of some gas space heaters doing that, but it's just a guess.

Fuzz
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Re: No bond??

Post by Fuzz »

I guess at this point it does not matter. The owner has lost all faith in the work and is replacing the whole back 10 foot of the boat rebuilt.
I was just confused as I had never seen a bond failure this bad :help:

OneWayTraffic
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Re: No bond??

Post by OneWayTraffic »

That’s the smart thing to do.

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