Fuel dip stick calibration 1967 M20F

[funvee]

This is going to sound silly but I'm trying to make a dipstick for the tanks but the measurements aren't showing up as being linear. Does that make sense?

I thought it would be something like 4 gallons per inch but it doesn't seem to be that consistent. Are the tanks not regular shaped? For instance, is the bottom wider than the top so that 2" of fuel at the bottom is = 15 gal but 2" of fuel at the top of the tank is only 5 gal?

I should mention that I have the O&O bladders and the 32 gal tanks (64 gal total).

I did the search first but none of the threads seemed to have measurements that work for mine for some reason.

If anyone has an example of what the measurements should be, I would greatly appreciate the help.

Thanks

Shawn

[DrBill]

My "E" model with new 54 gal bladders is definitely not linear. I made a stick but I think I did not wait long enough for the fuel to flow completely. I'm going to make another one after my next flight when I drain one of the tanks.

My results were posted on another topic and were similar to non-bladder tanks which should be close.

BILL

[andrew]

The calibration is definitely not quite linear. They are integrated with the wing structure, and therefore angled with the dihedral. I haven't seen the bladders out of the plane, but I suspect they are also not entirely a uniform shape through their vertical extent. I have 54G bladders in my '68G and the calibration I came up with is attached.

[funvee]

At least that would explain why mine appeared so non-linear... I either need to add 4 gal and mark and repeat repeat repeat or I'll have to find someone who already did it for the F with the bladders. My top to bottom only measured approx 7 3/4" to the top of the fuel it could hold but I thought the wing depths where all the same so I don't know whats up there.

[BigTex]

Andrew, it's interesting that we both have the 54.8 O&N bladders but have different graphs... I would think they'd be closer. Guess +/- a gallon is close enough for government work.

Fuel Stick Calibration.pdf

[andrew]

If you flip the axes we're actually quite close. I am normally just verifying the fuel load against the JPI readings anyways. I find it's far more accurate than my dips at tracking fuel.

[1964-M20E]

Thanks this will give me a good start on mine.

[rodney]

Here is another data point for you from my 65 E model, standard 26 gallon tanks. I use this with a fuelhawk measurement tube (from Sportys or Spruce). Interestingly, my line is pretty linear.

Rodney

[DrBill]

Here is my 65E with new O&N 54G bladders. I did this today at 5 gal intervals. You have to wait 1-2 mins for the fuel to flow even before you measure. We are all really close.

Bill

Depth Gallons

0.875 10

2.25 15

3.75 20

6.25 25