Interesting article about epoxy usage......
Posted: Wed Jun 02, 2010 12:55 pm
how much epoxy you should use on your boat. Its an eye opener:
More Epoxy Adds Weight Not Strength
Canoes gain weight when canoe builders guess at how much epoxy to use. Epoxy resin reinforced with fiberglass is a materials marraige like concrete and rebar. Adding un-reinforced concrete to a bridge deck makes the bridge heavier, not necessarily stronger. Simple calculations will help you nail the epoxy glass ratio, maximize strength and avoid deadweight on your canoe.
Start by confirming the surface area of the hull.
You do not need a nautical engineering degree, sophomore geometry will suffice. Use a flexible dressmakers tape to measure the working edge of each building form. Add the length of two adjacent forms, divide by two and multiply by the station spacing. You just calculated the area of a trapezoid. Now, divide by 1296 (square inches per square yard) and add the square yardage together to calculate the total surface area of your canoe.
Fiberglass absorbs one ounce of resin by weight; hence, it takes six-ounces of epoxy to wet out one square yard of six-ounce fiberglass. So for example: eight square yards of surface area will require 48 ounces of catalyzed epoxy to wet out the fiberglass. Naked cedar drinks up three-ounces of epoxy per square yard. That brings your estimate to 72-ounces. In addition, plan eight-ounces of thickened epoxy to fill minor voids (give or take -- depends on how tight your hull is and whether you build with or witout staples).
If you come up short, look at the floor. If the floor is clean, look for shinny areas, fiberglass floating on top of pooled up epoxy. Find and relocate the excess epoxy rather than catalyzing another batch and going for the heavyweight championship.
More Epoxy Adds Weight Not Strength
Canoes gain weight when canoe builders guess at how much epoxy to use. Epoxy resin reinforced with fiberglass is a materials marraige like concrete and rebar. Adding un-reinforced concrete to a bridge deck makes the bridge heavier, not necessarily stronger. Simple calculations will help you nail the epoxy glass ratio, maximize strength and avoid deadweight on your canoe.
Start by confirming the surface area of the hull.
You do not need a nautical engineering degree, sophomore geometry will suffice. Use a flexible dressmakers tape to measure the working edge of each building form. Add the length of two adjacent forms, divide by two and multiply by the station spacing. You just calculated the area of a trapezoid. Now, divide by 1296 (square inches per square yard) and add the square yardage together to calculate the total surface area of your canoe.
Fiberglass absorbs one ounce of resin by weight; hence, it takes six-ounces of epoxy to wet out one square yard of six-ounce fiberglass. So for example: eight square yards of surface area will require 48 ounces of catalyzed epoxy to wet out the fiberglass. Naked cedar drinks up three-ounces of epoxy per square yard. That brings your estimate to 72-ounces. In addition, plan eight-ounces of thickened epoxy to fill minor voids (give or take -- depends on how tight your hull is and whether you build with or witout staples).
If you come up short, look at the floor. If the floor is clean, look for shinny areas, fiberglass floating on top of pooled up epoxy. Find and relocate the excess epoxy rather than catalyzing another batch and going for the heavyweight championship.
