You can buy kits of West Systems and other epoxies for the repair of fiberglass boats. They come with fillers ( glass beads of dust size) and cloth. I just used this to patch a fiberglass kayak I purchased at a garage sale for $40.00, which had multiple cuts it in from 45 years of shooting rapids. Now I am coating the entire hull and deck with colored gelcoat.
Always wear a top quality respirator mask and full eye coverage. Work with this cloth and dust indoors, where there is no moving air. After you get the stuff mixed up and make the patch, move the project outdoors or open the windows to air things out. Optimum temperature is 75 F.
West and Gudgeon epoxies are outstanding for making a strip boat. You can use lightweight wood like cedar or cypress, and thin the epoxy from its honey-like viscosity to more like thin paint, and it will be totally absorbed by the wood, using it for the fiber strength. Then put on a second coat inside and outside. Then the usual layer of glass mat and clear gelcoat inside ( which disappears for sight ). I used it to build a prototype butt stock for an HK-91.