Super Reaper Composite Fuel Tank Mold Construction

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Mold Construction - Day 5

With the mold halves done, now it is time to make my first parts. I will be using 6 oz fiberglass cloth which will be hand laid into the molds. Here I have all my materials laid out and ready to cut the fiberglass cloth.

After about 30 to 45 minutes this is what I ended up with. I did not take any pictures of the actual lay up because it only involves cutting the fiberglass cloth into strips and laying them inside the mold and applying epoxy to wet them out. On the side I was going to put the fuel fitting connectors I laid up 5 layers of fiberglass cloth. The rest of the sides got 3 layers.

Here is a close up on the fiberglass lay up. The process went fairly easy and I did not have any problems getting the cloth to conform to the mold shape.

Both mold halves are done and I now have to wait until the epoxy cures.

Another close up of the lay up. This I believe this was the second mold half which yielded a little bit better result during the wetting of the cloth. It tended to be more on the drier side which meant I was using just the right amount of epoxy to wet out the cloth.

The next morning I came into my garage to check out the molds. Everything seems to be good and the epoxy has cured. The black dots you see printed on the cloth were my cut marks I made with a Sharpie when I was cutting out my strips.

I originally plan to join the parts by placing the two mold halves on top of each other. However, I decided to join the two halves outside the molds. Using some canopy scissors (ones with curved ends) I carefully trimmed away the excess cloth.

The canopy scissors as you can see do a great job of getting close to the mold edge and surface top.

This was the results after a little bit of prying and the help of my wife to hold down the molds while I pulled the parts out. The parts came out really good and I was impressed. The end sides are very strong and I was a little disappointed with the top and bottom sides where I only used 3 layers of cloth. I think next time I will go with 4 layers and increase the rigidity of the sides. But the tank will still work out.

After I little sanding of the edges I was able to get the two pieces to mate well. Again the little black dots were from cut marks while cutting strips of cloth to lay inside the molds.

Here is how I decided to plumb my tank. I was going to use the Dubro style tank stopper but decided to go with Festo type 6 mm fittings. I figured this would not be the only tank I would make so I might as well try them out.

The brass tubing is 3/16" which were silver soldered to the Festo type fittings. One bonus of the fittings being brass I was able to solder the brass tubing to them. The fuel line is standard Tygon tubing that we use with our turbine jets. I wrapped some copper wire around each connection to help make sure the tubing does not slip off. The Festo type fittings were mounted to the tank by drilling 3/8" hole which made for a nice tight fit. Although I did mix up some epoxy and cabosil to apply to the inside of the tank it seal the connection. I was pretty generous too and built up a good amount around the connector and up the brass tubing a bit. Remember once the two tank halves are joined, the tank will not be serviceable.

The two tank halves were joined together by clamps. With the clamps in place I was able to apply a bead of epoxy and cabosil along the seam. After the seam was filled, I applied some fiberglass tape normally used to join two wing halves together over the seam. I did one more application of epoxy and cabosil over the tape and seam to make sure it would seal the tank properly. Then I let it sit over night.

The next morning I removed the clamps and the tank was done.

Overall the tank came out pretty good. I will still go ahead and run some 3" fiberglass tape over the seam to make sure the tank is completely sealed. Then I will pressure test the tank.

The tank is test fitted into the Super Reaper fuselage and the fit is very good. I can't wait to get my Super Reaper back into the air and using my new tank I should get at least 8 minutes of flying time leaving plenty of fuel for landing and 1 or 2 go arounds if necessary.

This will probably complete my build documentation on my Super Reaper composite fuel tank. I hope you were able to get a better understanding of steps to take in making a composite part. Even though I made a fuel tank the same process can be followed to create anything your imagination desires. The process was quite fun and I learned a lot too. I will probably go on to make more fuel tanks and increase my skills at working with composites. One day I would like to try a fuselage as I have the desire to build a composite jet of my own design. So go out and try working with composites if you haven't already, it is not as hard as it appears. Good luck!

Super Reaper fuel tanks will be available for purchase soon. If interested please contact me at jr@houstonhobbies.com with "Super Reaper Fuel Tank" in the subject line.

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