FIberglass for plywood tank

[CJH]

No lack of confidence in the structure of the tank I'm planning, and at that glassing just the corners would help w/the structure. In any case, my concern is obviously in the sealer, and more importantly, it's impact resistance. I'm not dead set on fiberglass, BUT is 20mils of epoxy going to hold up to a falling rock w/o cracking???

Certainly epoxy has withstood impacts like this and not failed. But there are multiple factors at work, some involving the quality of the epoxy and some involving the quality of the application and conditions.

I have seen plywood exhibits being built at zoos and only sealed with a very thin layer of epoxy before the concrete rockwork was applied. Not only has the epoxy held up to hundreds of chuncks of concrete dropping on it but also hundreds of footsteps of workers grinding the small chunks of concrete into dust on the floor. Epoxy got scratched but did not fail, even when some of the exhibits were turned into flooded paludaria type enclosures later on.

At this point it's probably best to pick a product and call the company and see what they have to say.

As far as thinning, the Max ACR that Buckdog uses has thinning intructions on their website. I don't recall the recommendation. In my experience every company has different opnions on this as far as what solvents to use and what percentages, not to mention whether it's a good idea at all.

Personally, I think thinning the epoxy so it can penetrate the pores of the wood is a good idea for the first coat. This is often called a flood coat. But I don't do this for greater coverage as I believe that final build thickness is important, at least for my peace of mind.

So even if I do a 4 mil flood coat with thinned epoxy I will still go back and apply another 16 mil, for example, if a 20 mil build thickness is my goal.

 

[Buckdog]

Like CJH said it's best to check the their website on how far down to thin the epoxy. I thinned down some this evening for my same project but that had nothing to do with plywood. I was thinning on the fly, so to speak.

If you do a "bite" or "flood coat", you can either let it semicure and add a second regular (unthinned) coat directly or you can let your flood coat fully cure, sand it and add your second regular coat.