Fuel Tanks - one way to do it!

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flysouth
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Fuel Tanks - one way to do it!

Unread post by flysouth » Tue Dec 15, 2009 10:45 am

If you are building here is one way to easily make tubular fuel tanks. As long as your design can handle tubes that is!

Or use these as aux tanks.

Aluminium tubes are available locally from Hulett Aluminium in Olifantsfontein. They know them as irrigation tubes and they sell them to farmers for those central pivot systems.

They are 101.6mm dia x 0.9mm (IIRC). I have them in my Grumman AA1 and they give an extra 10 galls per side. The very same tube material is STCd for Grummans in the US.

Note: the largest central tube is the standard Grumman spar/fuel tanks - the two outer tubes are the additional tanks carrying 5 galls each for 10 galls per side/20 galls total.

Here's a pic:
TWingtanks.jpg
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Re: Fuel Tanks - one way to do it!

Unread post by heisan » Tue Dec 15, 2009 11:19 am

Interesting. I was thinking about that, but got stuck on plumbing the vent lines. How do you vent the lines, when the dihedral places the tips (highest point of the tank) so far above the root?

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Justin
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Re: Fuel Tanks - one way to do it!

Unread post by RudiGreyling » Mon Dec 21, 2009 12:04 pm

heisan wrote:Interesting. I was thinking about that, but got stuck on plumbing the vent lines. How do you vent the lines, when the dihedral places the tips (highest point of the tank) so far above the root?

Thanks,
Justin
Justin, I guess the same way as in a RV...if it is a low wing!
See drawing, the vent lines run from the tank root rib, inside the tank along the top to the highest outboard point. It attaches to a fitting on the root rib.
Then one run another line inside the fuselage up one or 2 feet, then down again through the aircraft floor.

If it is a high wing, i guess you have a problem, but I have seen guys coil up AL tube 2 turns on the outboard ends, to limit spillage out the vents.
vent.GIF
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Re: Fuel Tanks - one way to do it!

Unread post by heisan » Mon Dec 21, 2009 12:20 pm

Doh... :oops:

That is what happens when you get stuck on an idea. I was thinking of aux tanks that get filled from a remote header tank. Once you have the filler cap at the highest point, things get a little easier.

I suppose with the Grumman set up, you can plumb the breather straight to the main tank breather without any problems?

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Re: Fuel Tanks - one way to do it!

Unread post by flysouth » Tue Dec 22, 2009 1:56 pm

The Grumman has a plastic (made mine of fibreglass) scupper which fits tightly around the fuel filler at the wingtip - this catches any spillage when filling and drops it via a 1/4 in pipe out the bottom of the wingtip.

The tank overflow vent is similar to the RV by the looks of things - it carries any overflowing fuel from the highest point (at the wingtip) and drops it out near the wing root.

At the wing root is also an air vent for the tank, just a piece of 1/4 in pipe bent and facing the airflow. Presumably helps pressurise the tank a bit to help the pumps along.

The nice thing about a tube is it's inherent strength and minimal welded joints - trouble free n my experience.

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