Best cloth to glass under gas tank hatch?
 

What do you guys recommend ? I epoxied in 5" and 6" square pieces of 1/2" plywood (like original) ; now I need to cover the bottom surface with resin and cloth. Wondering what weight cloth to buy. Thanks!

Steve

I was just doing mine tonight out of the 20' sceptre and I use two layers of 1708. I used small wood squares like you did as well. I am no expert but that's what I did. I am using vinyl ester resin but if you use epoxy I would not use the matt in the 1708 and just use 3 layers of 17oz biaxal cloth.

I would suggest trying to lay in more layers of lighter cloth if you use epoxy. No mat, as the resin lacks the styrene to dissolve the binder in the mat. I would also suggest getting in at least one layer of +/-45 cloth in there. Which can be a diagonally cut piece of 0/90 or a piece of biax. I think if it is like mine, 3 or more layers of thinner cloth will be easier to fit in the corners than fewer thicker layers, like 17-24 oz cloth. Plus wet out will be easier. I would hit Merton's website/catalog.

Personally, I think the because people tend to drill into the hatch to mount leaning posts, the plywood initially helps, as it has some structure (versus foam or end grain balsa) but the grain orientation makes it vulnerable to water ingress, significantly more so than balsa. And heavier. But screws don't need backers as often. And compressive strength is good. But I hate how heavy my gas tank hatch is with a ply core. I will likely change it to divinycel this winter.

The deck on my seafari has a pretty thin inner layer of glass. Maybe 1/16" or a touch more under the balsa core. So if you do it right, you don't need lots.

I have a picture of a section cut of the balsa core deck with a dial caliper on it in my photo album, if that helps?

1708 stitchmat is fine to use with epoxy as its stitched, there is no binder in it, so no need to worry about having to dissolve it.

I used 1708 on all my hatches, but I ended up using polyester resin.Alot of my glass work was done in cold temps and I found the polyester resin an advantage when getting it to kick and cure pretty fast and properly.
I was able to apply it in the cold and then crank the heat up .I didn' t have the luxury to leave the heat on for long periods, which I would have had to do with epoxy, even using a fast hardener.

Thanks guys!

I used epoxy to laminate in the wood , but will use polyester for the cloth lamination layer. I'll probably go with 1708.

Steve

I have a bad tenancy to over build everything. Most of the glass I lay ends up being twice as thick and needed but other than the extra weight I don't mind having the beefier laminates. On the race boat I will be careful of this but on the other seacraft hulls I don't mind the weight. I think it some times it makes these tanks ride better. My gas tank hatch ended up very heavy but I think 50 years from now even if the wood rots out you still will be able to us it. The thicken resin between the small wood squares will keep together and it will be stronger than most other hatches even with out the wood in it if it rots. One layer of the 1708 might be sufficient but I went with two.