I used to buy poly resin for $5 per gallon ( gas was only $0.19 gal. too ) , back in the 60's making surfboards and glassing tired old wooden Sunfish sailboards and skiffs . I even repaired my 1947 Chevy with the stuff .

The original Dynel was by Union Carbide , they quit making it years ago . The new stuff is even better . Mind you there are several versions out there , get the one with these specs;

54" wide roll
30x30, 660 denier 2-ply twisted yarn, 5 oz plain weave

The other stuff is much harder to work with and uses lots more resin per sq. yd.