river boat bottom

I am rebuilding a river boat that I built about 25 years ago, the original bottom was 1/2" ply and a couple layers of six oz. cloth wetted with epoxy and the last 2 coats had graphite powder mixed in. That lasted about 8 yrs then I stripped and redid the glass and attached a sheet of 1/4" hdpe with stainless screws at 4"oc. with epoxy dribbled in each hole before the screw being set (pain in the***). That lasted a number of years but I think dissimiler expansion and contraction rates loosened up the sheet and I think it fell of(the boat wasn't mine through this time) leaving many holes in the glass and ply to soak up water and start to rot. So now it's my boat again and I hane a fresh piece of ply in place and I would like input as to what to put on it, same as I started with? or one layer of 10 oz. and kevlar or what?
thanks in advance
Bob

 

I assume you are going to apply a new layer of 1/2" plywood to the bottom. Totally encapsulate the ply both sides and all edges with 3 coats of epoxy. To waterproff it, 7 oz fiberglass 1 layer is sufficient. If your going to be beaching or scrapping the bottom use Dynel or better yet use Xynole cloth. Then the bottom is impact resistence and it is better then Kevlar. Raka epoxy handles both of these and lists prices. http://www.raka.com/