My Cape Dory 28, being an early production fiberglass boat, came out of the factory with many effective but unusual features. You can see the tank mount jutting into the left of the frame in this photo (from when we painted the lockers).
New tanks, of course, are not cheap, especially when they must be custom-made to fit an unusual mount. With thee tanks cleaned out I called up a metal fab friend of mine and while she agreed to weld them we eventually decided this was a poor idea.
With this in mind I decided the only repair I was comfortable with was an epoxy and fiberglass coating which covered the tanks entirely, giving both the chemical bond of the epoxy resin to the fiberglass and the mechanical bond of epoxy to aluminum.
I started by ordering a quart of Gluv-It, a proprietary Marine-Tex epoxy meant for sealing and barrier coating, and by reading everything I could find on the subject, including this useful repair report from West System. On the (first) day of the repair I sanded each tank by hand and with a random orbit sander using 80-grit paper while my friend Libby cut out light fiberglass cloth to fit each of the tanks. When I returned I found that while the repair seemed effective the curing fiberglass had sprung up in places, creating air bubbles. When both tanks were fully cured I went over them carefully with a marker and utility knife, opening up any bubbles and marking spots where bare aluminum peeked through. I then mixed a batch of thickened West System epoxy and 406 filler and carefully gooped this into all of the spots I had marked. The end result is two aluminum tanks which are coated completely with epoxy and fiberglass, in effect creating a tank within a tank. I am in the same situation but with a 90 gal tank, 900.00 to renew, so I am looking in to repair options. After the area around the leaky rivets is cleaned and well scuffed, heat the area with a propane torch to drive off moisture and warm the metal. This amount includes seller specified US shipping charges as well as applicable international shipping, handling, and other fees. Estimated delivery dates - opens in a new window or tab include seller's handling time, origin ZIP Code, destination ZIP Code and time of acceptance and will depend on shipping service selected and receipt of cleared payment - opens in a new window or tab. This item will be shipped through the Global Shipping Program and includes international tracking. Will usually ship within 1 business day of receiving cleared payment - opens in a new window or tab.
The issue was the mounting brackets, or, more specifically, the material used to get a tight fit on the tanks.
Concerns were both the safety of welding around any residue left from the old fuel and worry that areas which were pitted but not actually leaking would continue to corrode. I did a lot of online research and found that this sort of repair is normally attacked from one of two angles. The most common technique here is to coat the damaged area with a liberal application of a specialty thickened epoxy. I gathered fiberglass cloth, sandpaper, and all my other standard epoxy tools (cups, chip brushes, etc).
This was done in three pieces, with circles for the top and bottom and a rectangle to wrap around the body of the tank. I had earlier called the West System Helpline and confirmed that there should be no bonding issues between competing brands of epoxies.

These were especially prominent at the edges between body and ends and on the end I had left resting on the floor. I skipped the 406 filler, which for some reason was very difficult to mix into the Gluv-It, and instead just waited to apply the epoxy until it was the consistency I felt would best paint on thickly without running. I took particular care around the edges of where the tank is tapped for fittings, trying to get a seal which will not allow any moisture to creep in between the fiberglass and the tank underneath.
With a bit of luck these should last the life of the boat, and the repair cost me well under $100, a fraction of the cost of new tanks.
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I was quite surprised to find that every aluminum boat owner I talked to said they had some sort of leak.
The heat initially thins the epoxy, allowing it to seep into the smallest crevice, and then speeds the gel time. Packaging should be the same as what is found in a retail store, unless the item is handmade or was packaged by the manufacturer in non-retail packaging, such as an unprinted box or plastic bag. Contact the seller- opens in a new window or tab and request a shipping method to your location. It is equipped with two cylindrical welded aluminum tanks of approximately 7-10 gallon capacity each (I haven’t bothered to measure them) which rest one to a side on custom fiberglass mounts in the cockpit lockers. Each tank is held to the mount with two steel straps using some sort of synthetic fabric between the painted steel bracket and the tank.
Despite the corrosion and pitting they were in surprisingly good shape for having spent all this time in a damp environment. Both tanks were gunked up with a couple pounds of solidified diesel which, fortunately, was not the rust I had initially taken it for.
The most common is to coat the tank from the inside by pouring in a specialty epoxy which is designed to coat interior surfaces as you roll the tank around.
For a superior mechanical bond I wet-sanded the neat epoxy into the aluminum using 120-grit paper. If these bubbles were to trap water rather than air they could be disastrous so I resolved myself to repairing them once the other tank was ready.
To reduce the possibility of destruction or distortion, I tilted the boat and only filled one end at a time since filling the boat up entirely might have done more damage to the seams.
Heat  the repair area with a propane torch (a heat gun will work) up to 180–220°F to dry out the repair area. If you reside in an EU member state besides UK, import VAT on this purchase is not recoverable.
In true Cape Dory style these mounts are quite beefy and have stood admirably to the test of time. This fabric has a feel similar to that stuff that goes under carpets and, not surprisingly, seems to have held some moisture.
This was easy enough to clean up as all I had to do was shake them and pour out piles of brown flakes. Despite the tenacity of modern epoxies I read multiple accounts where this mechanical bond had failed over time. I then mixed up half my can of Gluv-It and added some West System 406 Colloidal Silica Filler as a thickener and strengthener.

The only other difference from the first tank was that instead of leaving the tank on end to cure I rested it horizontally across a box and attended to it while it cured, pressing down bubbles as they appeared. As always, I’m open to criticism from anyone who wants to poke holes in my technique! It seems to have been not only an effective repair but one which I have not found a great deal of information on, either on the web or in print.
Over the past thirty-seven years this fabric created a path for moisture to contact the tank and the end result was that my pressure testing and a close inspection revealed a band of corrosion where each strap contacted the tank. The first was that this is a generally used to repair interior corrosion and I was uncomfortable with my seriously pitted tanks being repaired only by a thin layer off epoxy on the inside.
The fuel tanks, more so even than water tanks, are an area where I am not willing to take any risks. As it cures epoxy gets progressively less malleable and stickier, making it easier to hold the fiberglass down where it wants to spring up. I also found that this will remove bottom paint as well, just put it in a garden sprayer and keep the paint wet for about 30 min. For a those of you just curious about the boat it’s probably a bit long and dry but I hope the lack of brevity will be useful for anyone attempting a similar repair. Even with a sealed epoxy liner I didn’t like the chance of existing pitting trapping water and leading to further corrosion of the tank structure. While BP can get away relatively unscathed after releasing 4.9 million barrels of crude into the Gulf there have been incidences of sailors losing their boats (over cleanup costs) after entirely accidental releases of mere cups of fuel through leaking tanks and automatic bilge pumps.
I was also worried that the interior surfaces were still not sufficiently clean for a proper epoxy bond.
The thickened Gluv-It would not have be as effective for wetting out fabric which is really a job for neat resin. Complete heating and filling each rivet or seam section before moving on to the next to avoid too much heat loss. This cloth was applied over the still-wet Gluv-It and carefully smoothed down, removing all air bubbles. I then made my first mistake, which was to set the tank on end and leave it for the epoxy to set up. By this point I had the tanks in the backyard of the bicycle shop I work at and had started started rambling aimlessly around the shop looking for anything that might help.
Then I rolled and shook the tank all around the backyard until I thought I might pass out from the heat. Tip: if you ever try this, only us ferrous metals so you can pull it all back out with a magnet instead of shaking out the stainless ones one-by-one. With nice clean tanks I was very pleased to find almost no interior corrosion – it seemed the only serious damage was the exterior pitting.

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