M-4 fuel tank issues

Greenleaf · Post by **Greenleaf** » Tue Feb 11, 2020 5:34 pm

We recently bought a 1963 m4. When sumping, a lot of black crud was coming out. Last week I removed the tanks with the expectation of sending them out for welding and cleaning. Turned out the leak was from the sending unit gasket and the tanks are clean. The black crud is in the seam where the two halves of the tank were welded together. I tapped on the seam until no large pieces 1/16â€ dropped out. There are still fine pepper like pieces in the seam. Carb cleaner wonâ€™t touch it I wonder if itâ€™s some kind of oxidation or flux from welding.

Do you have any thoughts on what might clean it up? Steam clean, chemical or .....? I really donâ€™t want to send out in case of lose or damage. Maule said they donâ€™t have any way to get new tanks as the dies are gone.

The tanks are out of the plane.

Mog · Post by **Mog** » Tue Feb 11, 2020 7:24 pm

I assume you have the pillow tanks? My assumption is that you could gain a fair amount of fuel and range by having new tanks fabricated that fit the wing tighter. Might be worth looking into. I had my left tank overhauled in Moultrie and it has been doing great since. Wish I could help with the black stuff, but I have no idea. Maybe some extreme heat cycles could do it.

crbnunit · Post by **crbnunit** » Tue Feb 11, 2020 11:26 pm

I would LOVE to have bigger tanks...

Greenleaf · Post by **Greenleaf** » Wed Feb 12, 2020 7:20 am

Yes, I have the original tanks. Not sure how I could get larger custom tanks in as the originals were a pain to get out as it was. I donâ€™t want to spend money on new tanks at this time.

G-MAWL · Post by **G-MAWL** » Wed Feb 12, 2020 8:22 am

A "squarer" design of tank would gain about four gallons a side and fit easier !
It's plan size being 351/2 x 29 approx.
This would add about four gallons a side. I made up the formers for each end the front and back being flat faces. The base would step down at the inboard bottom stiffner.
The sump drain may need to be further aft requiring a new hole in the bottom skin.
Removal of either kind of tank would be easier if nut plates and screws held the front of the wing skin to the spar rather than rivets.
Don't think that would be a structural issue just more economic to rivet when manufactured.

Not sure what would be required paperwork wise.

Derek

Mog · Post by **Mog** » Wed Feb 12, 2020 2:55 pm

8 gallons would be huge!!

1:1 Scale · Post by **1:1 Scale** » Thu Feb 13, 2020 9:35 am

Mog wrote:8 gallons would be huge!!

Plus a couple more for the aux tanks? I have the top skins off my wings right now (among other things!), damn you people for putting ideas in my head!

Kirk · Post by **Kirk** » Thu Feb 13, 2020 3:10 pm

The 8 gallon gain is for changing all 4 tanks.
Itâ€™s about 2 more gallons per tank. Might be a little Less per tank for the aux?

Kirk

G-MAWL · Post by **G-MAWL** » Thu Feb 13, 2020 4:45 pm

I calculated 4 US gallons a side on the mains only. Although I never used anything other than the specs for the 36 gallons stock.
I have pillow tanks.
Derek

M-4 fuel tank issues

M-4 fuel tank issues

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