Friday, March 7, 2008

Gas Tank

Build hours: 436
In the last working post, we decided to order and wait for the canopies to arrive before continuing. While waiting, we decided to build the fuel tanks using leftover .016 6061 aluminum and pop riveted construction. Inspiration came from
Thanks Mr. Hoover!
Plywood/particle board forms for the tank front and back bulkheads were made from the plan layouts and the tank front and back were formed with 1/2" flanges. The tank bottom was cut out and bent per the plans. The tank parts weigh 1.25 lbs - which should be 1/2 the weight of the .032 5052 welded tank. Total cost was less than $95 dollars per tank.
Plan note:
Check the front and back bulkhead forms for proper clearance under the skin (approx 1/4" allows for padding under the tank on the rails and over the tank top under the skin) . The first rear tank bulkhead came out against the tank skin and the form had to be adjusted and the bulkhead remade.




After forming, the bulkheads were clecoed to the bottom. The front bulkhead flanges were turned in and the rear bulkhead flanges were turned out to accomodate the flange angles after forming an the tank slope. The tank top template was fitted and trimmed. The tank top was then cut, drilled and clecoed. One inch rivet spacing (117 total) was used and the rivet holes were dimpled to accept AAC rivets. The tanks will be completed by using red ScotchBrite and MEK or Alumiprep etching to clean the rivet lines and a generic ProSeal Epoxy from Van's Aircraft to seal the tank. No sloshing required!

An aluminum filler flange was found online from
and an AN867-3 was used for the outlet. The AN867-3 flange required turning on a lathe to remove the turned up edge and provide a wider flange.


4 comments:

  1. How did you bend the end pieces around the form? I tried but the flanges rippled too much. Did you use a shrinker? Thank you for taking the time to post your building experiences. Bob K (ul builder in VA)

    ReplyDelete
  2. Bob,
    We tried a shrinker but it really marked the edges. Our solution was to cut a 5-7 degree angle on the form the blank was to be bent over. The blank was clamped in the forms about every 4 inches and hammered over between the clamps causing a pucker under the clamp area. The clamps were tilted and the puckered area was hit creating a smaller pucker on each side - maybe a 1/2 inch pucker every inch. Here's the trick we learned - use a hardwood block with the same radius as the form that will cover 3 or 4 puckers. When you whack it, the pucker will be shrunk instead of jumping up at the ends of the block. You will notice the flange gets fatter - the material has to go somewhere. Moving the block toward the flange edge as you strike it will leave a fairly smooth flange. If your using 6061, beat it as little as possible since it work hardens quickly. Good luck!

    ReplyDelete
  3. nice blog on flange fittings can u write more on shims

    ReplyDelete
    Replies
    1. Sorry, I do not understand your reference to shims.

      Delete