Several style main tanks
Over the time there have been several different style main tanks for the Ercoupe and Forneys and Alons. These are interchangeable to a certain extend, but some Ercoupes will need an exact replacement. Early prewar Ercoupes up to serial number 112 featured only one 7 gallon main tank on the right side. Ercoupes up to serial number 812 used two main tanks with openings to fit the main gear that was mounted on front of the main spar.
When changing the gear to mount to the rear of the spar, the tanks were changed, featuring now slightly more than 8 Gallons.
Through serial number 2622 Ercoupes originally had ternplate tanks, but were changed to stainless steel tanks of identical construction at the last of this series. Ternplate tanks were steel with a thin coat of lead; not what one wants in a light aircraft! Their advantage is that they could be soldered shut with assurance that they would not leek. Below an example.
Early Style 8 Gallon tank with cutout for main gear left side
|Early Style 8 Gallon tank with fuel sender unit right side||Early Style 8 Gallon tank left side|
These tanks came also as stainless steel tanks:"I did some additional research on the stainless steel material used in the tanks that replaced the ternplate tanks. The specification is AN-QQ-S-772-A.
It turns out that material is either 302 or 316 stainless steel. It is suitable for spot welding but NOT suitable for gas or arc welding.
The tanks are riveted together and sealed on the edges by what appears to be brazing - not welded.
If you have a leak on one of those tanks or otherwise need to repair it, do not try to weld it!"
With the fuel gauge moved to the left tank, the very common 9 Gallon tanks were introduced. These are made from aluminum.
Left a 9 Gallon tank versus the 8 Gallon tank, both right side
The 9-gallon installation requires cutting a specially shaped hole in the fuselage. Service bulletin 39 is describing the procedure for this upgrade.