GRP/PU foam repair

[Guest]

Can the PU foam sold in ready-to-use canisters by builders' merchants/Diy shops ('No More Gaps' etc)' be used to repair puncture damage to the core of a double skin hull? It's a fairly small hole so I don't want to fork out for a 'pukka' kit, most of which risks going to waste. Or is that false economy?

Advice gratefully received.

 

[Guest]

About 2 years ago I did what you propose, BUT I opened up the sandwich from the top top to dry it out, then applied the foam covering it with "Gladwrap" and a board to let the foam set. Then new GRP was applied as a patch. So far I have had no problems. The area was about 1 square foot in size.

However, I have since been advised that the canister PU foam is NOT the same as the foam used in the original sandwich and is structurally weak.

For me it worked though, and I've had no problems since.

 

[vyv_cox]

If all you need to do is fill a hole, prior to laying upd GRP on top, then the single pack aerosol will do perfectly well. You need to be aware that it has nearly zero strength, but this may not be a problem. The next step up is the two-pack stuff sold by Strand, Glasplies, etc but this is not completely closed cell and will absorb water after a time. The stuff between your inner and outer hull mouldings is closely controlled at the factory and the DIY repairer has little hope of matching it.

For a small hole in wet conditions, try some epoxy (West or similar) plus microballoons. This has loads of strength and is completely impervious to water but has low density.

 

[oldsaltoz]

G’day jbjb.
If the damage you describe is the result of an impact, you may have cracks radiating out from the point of impact, further if it’s in a wet area you may be taking water between the laminate and foam core. If the hole is very small you may be able to run a drill down it then check the edge of the hole for cracks; they will have to be followed and ground out, a Dremal is a good tool for this. You can backfill the foam with Micro balloons (above water line) or micro spheres, (below water line) both will provide good strength and water resistance if mixed with Epoxy resin. They are very easy to sand off and new fibreglass can be applied to complete the repair.

Avaniceweekend Old Salt Oz……….