Eureka! Thanks so much Ward. Butyl tape and epoxy it is. Just not sure if I need West Systems thickener?
Mitch, the link you posted is exactly the right method to use, what we typically use is the term 'potting'. Check out the West System website how to articles... they are very good with better pictures, LOL!
You do not typically need a thickener for the epoxy. Most of the mounting bolts you will use through your deck will be 1/4" machine screws (bolts), some possibly 5/16". You wouldn't see anything mounted with 3/8" bolts until you get on really big bolts. No offense to Ward H, but you do not need to thicken the epoxy.
- Line up the piece of deck hardware you intend to mount and drill the holes in the exact position you need them, they will most commonly be 1/4" bolts.
- Remove the hardware and place 2 inch wide blue painters tape over the holes (this is important for controlling mess). Now over-drill the holes by one size. For 1/4" holes I over-drill to 5/16, but I will often go to 11/32... 3/8 maybe a little overkill but I have done that too. Essentially, drilling the original hole back to 1/4" in a 5/16" pot will give you a 1/32" 'wall thickness' of epoxy plus what is soaked into the plywood core. If you go as much as 3/8" for a 1/4" bolt, the epoxy wall thickness will be 1/16". It doesn't sound like much, but it more than needed. I find that going too big on the holes makes it harder to re-center the holes.
- Tape off the bottom of the holes with blue tape. Fill the hole with un-thickened epoxy... there is no need to thicken it and the extra step is wasted effort. Use a syringe, I can't stress this enough... it keeps things much less messy. Fill the holes to 99% full, no need to over-fill.
- Watch the holes as the epoxy settles... pop any air bubbles with a needle or safety pin and add drops of epoxy hen needed. The wood core will soak some epoxy up and the level will lower, keep them topped off to just barley below the top. This serves two purposes; The recess will help center the drill bit when you go to re-drill the 1/4" hole. If you over fill you will loose that helpful factor, have to sand the cured epoxy flush, and epoxy near the surface will be cut away in any case when you add a slight counter-bore to the hole. Remember, the top layer is already solid fiberglass.
- When the epoxy is cured, before you remove the blue tape, sand the holes only if needed. A detail sander like a hand-held oscillating tool and triangle sanding pad is perfect for this task. Remove the tape and place the hardware back over the mounting holes. Carefully align the everything so you are re-drilling dead center on the epoxy filled holes. sometimes I used a spring-loaded punch to mark the center of one hole first. Usually, when you use the method of only filling the hole 99%, the bit is pretty good at finding center on its own. I am guilty of overfilling holes when I work too fast. When you have one hole drilled dead-center you can drop the bolt into the hardware to help hold the remaining holes dead over their marks.
