tank building question

[Ron Hess Sr]

need some infor on building a tank for a PA75, the question is if the pickup tube needs to be in line with the nva do I build that distance into the tank? which I measured at .810 to the center of the nva sitting on the maple mounts, without the 1/16" alum pads that the motor will sit on, then just sim the tank a 1/16"?could you help me out? Thanks for your time. Ron 

[Tim Wescott]

In line up and down.  Usually it needs to be a bit higher.  Side to side you want the pickup to be on the outside edge (outside of the circle) so it'll pick up fuel that's been flung there by centrifugal force.

[bill bischoff]

It is the height of the uniflow tube that matters, not the height of the pickup tube. If the front end of the airplane doesn't have room to raise/lower the tank to fine tune upright vs inverted, you can achieve the same result by moving the inside-the-tank end of the uniflow tube up or down. The pickup tube doesn't need to be aligned with the spray bar, and it doesn't need to be vertically centered in the tank.

Hopefully somebody will chime in with a starting measurement for the vent relative to the spray bar.

[Garf]

That's if you use uniflo. Not everyone does.

[M Spencer]

If say half your tank hight is 3/16 less than your .8 in. , Youve got leeway to raise the tank that amount, which
would lean it inverted / richen it upright , if the heads between the wheels .3/16 packer over for neutral position .

If your tanks symetrical , youd pack it down about level , C/L to NVA .

Give it a test run , if the rpms are near equal and angleing the nose up, with the plane both upright & inverted
gets you the same rpm increase , Ea. way up ,  hopefully its near correct tank hight / position .