Hello all, I have applied my third layer of epoxy and 6 oz cloth to the bottom of my drift boat project. I am looking for information on the amount of graphite powder to add to my epoxy mix as I apply fill coats over the final glass layer. Also open to other tips or ideas for this stage of the project. Thanks!
Hey Jc, I ended up having to do something like 8 fill coats on my 20 oz triaxial bottom because I was putting it on way too thin. I can't remember the figure, but I put way more powder in the mix than was recommended simply because it wasn't covering like I'd seen on here. The argument is if you mix in too much graphite it makes the bottom softer than a more heavy epoxy mix. Anyway, I regularly launch at a kayak launch where you can't get a trailer closer than 150 yds on a gravel pathway. I drag the boat down that pathway and the boat just has tiny little scratches in the fill coats as compared to the few on river rock encounters. When installing my drain plugs I used a 36 grit belt sander to make the fitting flush with the bottom and that belt could not cut into the epoxy. So I say all this to say I think I put a few spoon fulls in the bottom total
Also consider that powdered graphite may make it more difficult to adhere a future patch or repair.
Be careful in how much you add to the epoxy, too much will make the epoxy brittle. I had this problem and had to remove a couple layers of epoxy with graphite and the went back and added several more.
Here's West Systems directions from their website. "Add to mixed resin/hardener at the rate of 10% by volume or 1.5 tablespoons per 8 fl oz. of epoxy".
I have now had my boat in service four years and the bottom has held up well.