Guess I put my foot in my mouth again.
Well for those of you out there that don’t have to use Ethanol gasoline here’s how I have built over 30 fiberglass fuel tanks over 30 years ago that are still in perfect shape.
Most of my life has been spent in SW Florida,Bahamas, Caribbean and Atlantic waters using fuel from all kinds of out the way places. So,I myself have personally not been near Ethanol gas. All the tanks I have built were for Florida based clients and commercial working craft in the 3rd world.
2 years ago I talked at length with the Coast Guard building inspector about my past method of building and he said it all sounded fine to him.
The key to my method is to NEVER use any other type of fiberglass material other than 1-1/2 oz. chopped strand Matt. You MUST do a neat job through out the lay up.
Epoxy resins work just as well as good polyester resins like vynelester. I always used a brand of resin called Dion at the time. I have used just regular shop polyester resin too.
The deal is to wet the matt out well and hard roll out ALL air bubbles. Using chopped strand Matt the fiberglass strands are all less than 1-1/2” long so the chance of wicking fuel is almost impossible if being neat and rolling out properly all the corners.
Just contact your particular resin company and ask them about its ability with gasoline.
Here is my build sequence.
-Pour from a known bucket size the amount of gallons of gas you want to carry into the area where the tank is to go. Use water, say a five gallon bucket you have checked to make sure where the 5 gallon waterline is.
- once you have your amount in the boat...say 25 gals then take a sharpie pen and trace along the top edge of the waterline all around the hull sides and the bulkhead.
- bail out the water and then dry out the hull. Next use a car wax, mold wax etc and wipe on 3 layers from where all the fuel will be to the sharpie line. Do not buff out just get a good wax barrier coat on. This is your layer and separation of tank from the hull and interior parts. Coast Guard rules say you can’t have the tanks sides as part of the hull. Hence the wax barrier to separate the new tank from the old hull.
- after waxing lay in and glass in the 4 layers of Matt as shown with all over laps being nice and neatly
hard rolled out so ABSOLUTELY NO AIR IS SEEN. This is easy in polyester and a bit more effort is needed with epoxy resin as it’s not as viscous. It’s not a big area so not hard to do all at one go.
Make sure the matt layers extend at least 3-4” above the un waxed hull and bulkhead. This is your fuel tanks attachment flange- point.
- now you have a nicely glassed in tank shape that takes up no extra space. It should look nice and smooth and not too resin rich but not to dry looking.
- layup your tank top-lid in 4 layers on a flat panel of waxed Formica or what ever is smooth. When cured cut it to shape to fit on top as neatly as possible. A cardboard pattern is easiest to make and transfer to the fiberglass sheet.
- after the wax is ground off the lids sheet then drill out and install the fill and vent through hulls. Use bronze ones. The fuel pickup can be a store bought plastic one or what has lasted the best is copper tubing glassed into the lid. You can also lay up a section of the lid in thick Matt and then drill and tap into this. Using Teflon tape to seal the threads. Make sure all the fittings are at least 4” away from the lids side so you have room to glass the tanks lid in place.
- last thing is to glass the lid all the way around as shown.
If installing the fuel tank in the bow of any of my designs you could add a baffle to support the lid better or you could core the middle part of the lid. When opening your hatch it will now look like you have a nice floor in your skiff. You need to make the lid at least 1” higher than your fuel fill line to get the best at filling your tank.
You could slope the tanks lid a bit too if wanting water to drain aft.
When it’s all done you can pressure test the tank for leaks.
President Bush #1&2 and all family members have fished out of skiffs I built using the above method for the past 32 years. Skiff is still in the same family and still being used.
It’s easy, it works, but just stay away from ethanol gas.
