Cy,

This tank is for a Hatz Classic biplane. The capacity approaches 22
gallons. The upper surface of the tank is screwed down to the top of the
forward and aft spars of the center section with a series of (11 on each
edge) 10-32 truss head screws. The tank measures 54" long and 28 5/8" wide.
The actual tank nests in between the forward and aft spars. The .090" is
specified in the plans.

Ebby


"Cy Galley" wrote in message
news:IMkUg.178242$FQ1.121119@attbi_s71...
How big is this tank that you are using 90 thou?


"Ernest Christley" wrote in message
...
Ebby wrote:
Dear All,

I am starting to build my center section fuel tank and need information
about how to swage holes in the bottom of the tank so that I can edge
weld the six fittings specified in the plans. Four of the fittings are
finger strainers and one is for the sight gauge. There is one more hole
on the top for the filler. As there are only six holes in three
different diameters, I was thinking about doing it using simple hand
techniques rather than expensive tooling.

Here is my idea. The tank is .090" 5052. I planned on drilling holes
(.180+flange dimension) undersize in the aluminum. Then centering the
holes over 3/8" steel plate with holes .180 oversize, then use a
polyethelene bossing hammer to swage the edge of the hole into the
female die hole. The holes in the female die would have the edges
relieved to accomodate a bend radius. It might be time consuming but
educational.

Any advice or previous experience to share


A piece of 1/2" plywood and a couple chunks of 2x4. Tack plywood to one
of the blocks and use a small hole saw with a 1/4" centering bit to cut
the inside diameter of the swage. The piece that you dig from the hole
saw goes on one side of the aluminum. Use a bigger hole saw, centering
on the same 1/4" hole, cut the outside diameter of the swage, then drill
the 1/4" hole all the way through the block. Drill a 1/4" hole through
the other block. Drill a 1/4" hole where the swage will go.

Thread a sufficiently long bolt through a fender washer, the block with
the plywood attached, the aluminum, the piece you dug out of the small
hole saw, the other 2x4 block, then another fender washer. Spin a nut
down to extrude the swage.

I don't know if this will work on .090, but I've used this technique on
thinner material.