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5052-H32
aluminum is the popular choice for fuel tanks so who was I to argue.
I drew the tank plan on the 0.032" thick sheet. The
dimensions are based on the stub wing area allowing room for the wing
skins above and below as well as some space between the tank sides and
the spars. As the front and rear spars begin their taper and
dihedral inside the fuselage sides and the fuselage itself is angled
between the spars, the tank sides are all different too. |
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The
plan is cut out using a jigsaw. I then bent the sides and
tabs by
clamping the aluminum to the table and applying pressure with a solid
straight edge to the over hanging portion. Once then bend was
started I used a hammer and rubber squeegee at the creases.
Once
done I use clamps to hold the shape. |
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These
are clecos and make holding it all together so easy.
The
rivets I'll be using are 1/8" solid aluminum. The drill bit
used
is made specifically for rivet holes as it is 0.004" larger than the
rivet. It is labeled #30. |
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Clamps are
no longer needed as the clecos do their job. |
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The spade
bit makes easy work of drilling the holes for the vent line and fuel
pickup. I later changed my plan on this setup and covered the
holes with a plate. |
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Prior
to riveting, all the holes are deburred using a large drill bit as I
don't have a deburring tool. Anywhere a rivet is going, the
protective plastic is removed. |
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PROSEAL!!
If I never use this stuff again it will be too soon.
It gets everywhere and sticks to everything no
matter how
careful you are. I apply it with an icy pole stick to both
surfaces to be riveted. |
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The
corners are pulled together and the top hole is riveted first.
There is no way I am going to place clecos in these holes as
they
would be ruined. Some Proseal is applied to each rivet prior
to
riveting....and the rivet gun gets Proseal all over it. |
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I
have drilled all the holes for the top of the fuel tank and have used
clecos to hold it in place. The holes are 1/2" in from the
edges
as the flaps underneath are 1" wide. I do not have enough so
just
space them evenly. |
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It
is hard to tell from the photo, thus the sailing boat, but the
tank has been filled with water and has remained full for 24
hours. Once the top is riveted on, the tank will then be
pressure
tested. The measured capacity is 39.5 liters which
is about
10.4 US gallons. |
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Work
has begun on the second tank and I have had to be really careful to not
make another left hand tank. One mistake I did make was
bending
the top lips before bending the sides up. In an ideal world
it
would all work out ok but bending by hand is not exact. I had
to
straighten out the two side lips and remark where the creases needed to
be. |
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A
good way to get a crisp crease line is to clamp the lip in the vice and
apply pressure with your hand. I bend it half way over right
the
way along and then go back and finish it off all the way. |
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For
the second tank I bought the AS&S version of Proseal which was
$17
plus shipping versus $100 for a slightly larger tube of Proseal from a
supplier here in Australia. The caulking gun makes
application a
breeze though it still manages to get everywhere when riveting. |
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I will be
using some scrap extrusions to build the supports needed to hold the
tanks between the spars. |
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Each
piece of extrusion has some hoop pine epoxied in place which will then
be sanded to the exact contour of the tank edges as the edges are more
rounded than a crisp seam.
I have decided to not go ahead with this plan but I will leave it on
the site. Maybe it will trigger an idea for someone else. |
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This
is a Rochester fuel sender I picked up from AS&S, PN 10-02045.
The hole in the tank has been rough cut with the jig saw and
finished off with a file. The float will rise and fall right
in
the corner as this is going to be the lowest point of the fuel tank
when in flight. |
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A tube
bender makes bending radius's a breeze. This is the beginning
of the tank vent line using 1/4" 5052-0. |
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I move the
handle through through 90o
and as easy as that, the tube has a perfect bend with no creasing. |
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After
another bend the vent tube is done and now has to have the end flared.
The flaring tool pictured is not a regular run of the mill
hardware item which flares at 45o but
one specifically used to make a 37o flare
which is the norm for aircraft fittings. |
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Clamp the
tube level and screw down the flaring "plunger" with the spanner.
Once that is done the end has a perfect 37o flare.
Then take tube, put it in a vice and hacksaw the newly flared
end clean off. |
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Do it again
but this time slide on the AN818-4D nut and AN819-4D sleeve before flaring the
end! |
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I
have shortened an AN833-4D bulkhead elbow and put it through the
outboard forward corner of the fuel tank lid. This
is where
the vent tube enters/exits. |
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Here
the vent tube is temporarily connected to the fitting. I plan
to
have it exit level with the leading edge of the wing. |
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Self
plugging
aluminum rivets are used to hold the fuel sender in place.
Can you spot the helicopter pilot? |
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Time
has come to permanently close the tank off. All of the
plastic
coating is removed from the aluminum sheet. I hand filed the
sharp edges off every rivet hole then Prosealed the 3/4" fuel outlet,
vent, the riveted AN867-1 welding flange into which the CAV-110 drain
valve will be screwed, the underside of the fuel sender and finally all
around the upper edges of the tank itself. |
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Once again
the self plugging
aluminum rivets are used for the lid of the tank. |
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Before
fitting the tank permanently in the stub wing, I am running a primitive
pressure test. I have capped off the exit fitting and screwed
in the CAV-110 drain valve. The balloon has been secured over
the vent elbow and tied off with one of those thick red postal elastic
bands. I inflate it by blowing air through the drain valve
while pressing it down. Time will tell. |
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.......and
it did. The balloon deflated after about 1/2 hour.
I
hadn't
yet added a dab of Proseal to the rivet heads on the lid as I was
waiting to do the other tank before opening the next tube.
It's a
pretty good demonstration of the effectiveness of Proseal but also the
self plugging rivets. These were the only two that leaked. |
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The
fuel cap sits snuggly inside a PVC reducer which will be the filler
neck that goes into the tank. I rested the upper skin on the
tank
and set the neck to go into the upper corner beside the vent.
The
PVC reducer has been pushed through the foam and then a hole is cut
through the carbon fiber. |
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I
had forgotten to make a hole for the fuel cap before riveting the lid
on so I marked it out and roughly cut the hole with a jig saw.
I
then rolled some gaffer tap onto itself and stuck it to the bottom of
the tank to act as one of those old fashioned sticky fly paper traps.
I shook all tank until all aluminum filings had gathered
around
the tape. I then used a 1/2 round file to finish the edges of
the
hole. |
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The tape
worked beautifully at catching all the filings. |
