Originally Posted by delmarrey
I'm not too worried about the crush. I use thick SS backing plates
. My main obvective is to seal the core
The risk of crushing is on the top-layer of glass, not the bottom so the backing plate doesn't help for that. The reason is that the injected epoxy
will travel down by gravity and the possible air inclusion (voids) are at the top, under the upper layer of glass. For clutches, cleats
and winches, you load the fasteners in shear which leads to increased risk of crushing. It's also very important to tighten the bolts to the recommend torque for shear loading. This info can be found in tables and it's a percentage of the breaking strength.
I'm not sure I like the holesaw idea with the flexing of the hull, especially under clutches, organizers and winches, I feel it may crack around the edges unless one were to put some layers of glass over it.
But that's the point: with the holesaw method, you don't have just a bond between plug
and upper layer around the edges: you have a much bigger contact area at the underside of the upper layer of the deck
. That bond is stronger than the deck
itself so it will never crack there. Even if it would, there would still not be any water
intrusion because the plug
extends 1/4" under the upper layer all around the hole. Finally, the fastener is only in contact with the plug, not with the deck. This distributes the stress forces over a much larger area. All good.