Fiberglass Tank Cover



I wanted to make a tank that looked like the angular tank on the 1919 Excelsior (google it- it is too cool).

I decided to make a cover to go over the original tank rather than figure out a way to make a tank that would hold gas, not leak and not fall apart.

Here is what I did. I got some old exhibit boards that I used in a recent trial. These boards are essentially rigid foam between plastic coated poster board. It will be fiberglassed over- the board is just to form the shape, though it will stay in permanently.

I measured the tank, decided the shape I wanted and cut the pieces out with a framing square and a utility knife. I then test fit it all together with masking tape. Once it all fit, I taped all the pieces together with clear fiberglass tape. I may use aluminum tape if I ever do this again- better tack.

As you can see, I measured and used a hole saw to cut out for the filler and the frame.


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Active Member
Dec 15, 2006
very cool idea
gives the look and less hassles
I may have to 'borrow' this idea :D


tank cover, step 2

After the tank was taped together, I covered it with fleece- so techinally, this is not "fiberglass" per se because I used fleece instead of glass fiber cloth. In fact, if I were to do this again, I would use either fiberglass cloth, or spandex. The reason is that the fleece soaks in tons of fiberglass resin, which is good, but it produces a rough texture that required more layers of filler and more sanding than it would other wise. The advantage is that only one layer of cloth was necessary where several (at least 3) would be necessary if a thinner material were used.

I stretched the fleece over the box I made (stretchiness is an advantage of fleece), and glued it on with 3M spray adhesive (let the adhesive thoroughly cure before putting the resin on, or it will cause the glue to begine to lose its hold...ask me how I know). After the glue is cured, mix the resin and hardener and saturate it. After the resin has cured, sand it as smooth as you can with 40 or 60 grit- you may sand through the top layer of resin, and that is OK, but do not sand through the cloth itself. After it is sanded as smooth as you can, apply another coat of resin, let it cure and sand again- it will be much smoother to start- be careful not to sand through to the cloth if you can avoid it.


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Step 3

After the resin layers are done, it's time for filler- be not afraid of Bondo- it works well, just apply in thinish layers and sand down. In the end, there will be less than 3/16 of an inch of filler in the deepest place (filling a slight bow), and a skim elsewhere. This part just takes sand and fill, sand and fill, guide coat, sand, fill sand- until you are satisfied.

After the major leveling is done, its time to break out the spot/glazing putty to fill pinholes and scratches. Then I used filling primer and got a very good finish. I still have one sanding, then a primer/sealer layer. At the spoy putty stage, i am using 220, then 320 grit. I forgot to say, but on the filler, I used 60 grit, followed by 100 and then 150.

At times, you will sand through the filling primer- big deal, just don't get down to the cloth.

Also at this stage, I used the same holesaw to cut out the filler hole and the frame.


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Before I mounted the cover on the tank, I coated the inside with a layer of resin to seal it against moisture...and whatever.

To mount it, I used polyurethane construction adhesive. It is chemical resistant (gas), waterproof and strong as all get out. I had the tank mounted to the bike when I glued the cover on. that way, I could make sure it was straight and ould line up right on the bike. I taped the cover downa and left it to cure.

Finally, after the adhesive cured, I used a polyurethane foam around the tank to fill the gaps, strengthen and provide more adhesion.

I have to trim the foam down, final sand, prime and paint.


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Beware- the tank cover above will crack on the edge when dropped on concrete from 5 feet onto a corner. ;)

I am using long hair fiber glass filler to repair- but other than that, it is done. My entire bike is still in rough finish and is being blown apart for painting...hopeflully done in a few weeks- i will post finalized pics as soon as I can....not soon enough!


Update pics

Here it is with one coat of paint at the mock up stage:


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