Calibrated Fuel Sticks?

[DaV8or]

Does anybody sell calibrated fuel level dip sticks for Mooneys?

[Hank]

     Just get any dip stick and a hand file. Drain one tank [fly it as low as possible first], then put in two gallons at a time. Dip the stick, use the file to put a notch in it; add two gallons, dip and file. Then at your leisure, make the marks bigger and add numbers--use an engraver or a Dremel tool. Some people use a wooden dowel and a pocket knife, then transfer the marks to the dip stick. Quick, easy, cheap and guaranteed to be accurate.

[knute]

My archive has a post I salted away from Rob Hoyle, who graciously provided the measurements and markings from the dipstick he (and the prior owner) calibrated for his 1964 C model, and which seems to be VERY well calibrated to my '66 E model.  I stick the tanks before filling to see what I expect, and compare the result to my fuel totalizer and the numbers off the gas pump-  the stick is usually right on the money.

Get a wooden paint stir stick from Home Depot or similar, then mark it with a finepoint sharpie.  The fuel soaks into the wood just enough to make it easy to see the level when you pull it out, but is dry enough to be easy to measure the next tank by the time you've walked over and pulled the cap.

Inches       Gallons
9               26
8 1/2           25
8               24
7 5/8           23
7 1/4           22
6 7/8           21
6 1/2           20
6 1/16        19
5 3/4           18
5 7/16         17
5 1/16        16
4 13/16      15
4 1/2           14
4 1/8           13
3 7/8           12
3 1/2           11
2 11/16       9
2 3/8           8
2 1/8           7
1 3/4           6

I can't remember the last time I procured ANYTHING for the airplane that was this cheap and useful. 

Regards,

Knute
'66 M20E - KSQL (San Carlos, CA)

[Immelman]

I bought a 'universal' fuel hawk dipstick. I calibrated it by running a tank dry, adding fuel in 2 gallon increments, plotting the results, and (yes, I am going overboard here) doing a curve-fit in an excel spreadsheet to get accurate numbers. I can dig up and post numbers as Knute did (I have a 66E with standard tanks), but I imagine you'd want to make certain, if you use someone else's numbers, that they are based on the same exact tank design (i.e. model & year).

If you make your own, rather than draining the tank, I suggest (not all people like this) running a tank dry. That way you know your starting point is zero usable fuel.

 

[knute]

If you don't mind posting your measurements, I'd love to see how close we ended up!  If nothing else, it helps clarify how consistent the tanks are on these planes.  (I would expect them to be very consistent on this particular measurement for standard tanks)

Regards,

-Knute

[Petehdgs]

Universal Fuelhawk M20E

I have a 1964 Super 21 and the fuel dipstick that came with my airplane proved to be inaccurate by more than 2 gallons.  I did some research and found a 2010 post by knute that gave fuel level heights for making a dipstick using a paint stir stick.  I tried that but fuel on sticks tend to wick some and makes precise readings difficult so I decided to get a 16-inch universal fuel drop tube from J-Air inc.  They call it a Universal Fuelhawk.  It comes with a set of instructions, table, and graph for calibrating the fuel tank on your airplane. 

The instructions say to start with the fuel tank nearly empty and add 5 gallons at a time to plot a calibration graph.  Since my tanks were just filled I elected to start full and drain the tank 2.5 gallons at a time instead.  It took me a couple of hours to set up collect my data, then I transferred all of it to the graph attached here.  Here is what I did:   

I started with 5 clean 5-gallon buckets that I had bought previously.  5-gallon buckets are tapered, so I used a caliper to get the exact dimension of the diameter of the bucket at different heights.  I extended the caliper inside the bucket at the height desired, locked it and measured it with a tape measure outside the bucket.  The bottom diameter was 10-¼ inches, at 12 inches height was 11-¼ and 13 inches height was 11-5/16.  From these dimensions I calculated average diameter at 0-12 inches, 0-6 inches, 6-12 inches, 12-13 inches, and 0-13 inches.  I then calculated fuel amounts for each average taken.  I compared the partial bucket volumes to the total volume calculated to determine how much error I had.  The total average was 10.78125 dia and for 13 inches that calculated to 5.1376 gallons.  Av Dia squared divided by 4, times 13 divided by 231.  ((D^2)/4) x 13 / 231 = Gallons.  The partials added were 2.2491 + 2.4684 + 0.4327 = 5.1502.  5.1502 / 5.1376 = 1.00245 or 0.245% error between the two methods. 

As best as possible I marked the 2.5 gallon mark with an equal sign so that light shining from the outside of the bucket will highlight a space between the lines.  I used a 5/16 rubber fuel hose to siphon fuel out of the tank into the bucket and stopped at the mark.  After doing this twice and pouring both into the same bucket I found they added to less than 5 gallons.  The mark ended up being 2.445 gallons and I used 2.44 in my calculations.  I measured the fuel height at 26 gallons (full) then 23.56, 21.12, and so on down to 6.48 gallons.  I took 9 measurements.  I put the fuel back in the tank through a strainer, making sure it remained clean.  I then packed up and went to the office. 

Using the calibration graph provided I plotted the fuel level and gallons remaining on the graph.  I then connected the dots with a smooth line.  I extended the line down to 5 gallons and created a height – gallons table in one gallon increments.  I put all the data on the graph and added my bucket measurements and calculated volumes.  The fuel level on the tube is marked every 1/4 inch and it is easy to read to the nearest 1/8 inch.  The smallest 1 gallon increment is 3/8 of an inch, so a 1/8 error would be about 1/3 of a gallon.  So now when I measure my fuel level I should know within 1/3 of a gallon exactly how much fuel I have.  All that is left to do is to scribe level lines per gallon on the drop tube. 

Hope this and the chart attached helps. 

PS: I am working on scribing the lines on the tube and found the scale on the drop tube is actually 7/8 of full size.  Go figure!  Since I used the tube to measure the fuel levels in the first place, the chart is correct as long as the scale on the tube is used. If you are using a ruler to mark the lines then 9-1/2 on the tube is 8-5/16 on a ruler.  

 

N1935Y Mooney M20E Fuel Level Measurements.pdf

Edited May 10, 2020 by Petehdgs
clarification

[carusoam]

Nice details, Pete!

Great update for a decade old thread too. 

The 52gallon tanks are so predictable.  Compared to some extended or odd tank variations...

Got any pics?

Best regards,

-a-

[Petehdgs]

You mean the chart wasn't enough?  LOL

Thank you for "nice details" comment.  I do try...

Here are some pics of the tube... I made a couple of small mistakes, but nobody is perfect. 

 

 

Edited May 10, 2020 by Petehdgs
add pics

[RobertGary1]

Funny all these fancy sticks and no one had equaled they free Home Depot wood stir sticks. The glass sticks are the worst since if you don’t get your thumb on them right they read wrong. 
The wooden sticks are perfect  

-Robert 

[BDPetersen]

Just finished installing bladders in my “C”. On initial fueling I stood by with the large paint sticks and a marker, assuming a definitive dipstick would result. Alas, the 5, 10, 15 & 20 marks were about 3/4” apart starting from the bottom end. Then 25 gal was another 4”! The new outboard location of the filler makes the dipstick method a bit sketchy. It’s the 6 bag system, 54 gal. I wonder if other bladder folks concur.

[bradp]

I just made a new Home Depot style stick.  I’m going to make a 3D print based off that calibration. 

[carusoam]

Way to go Pete!
Pics and everything... 

Level 1 MSer: (VFR rule)

We need to put in the extra effort required to not run out of fuel....

 

Level2 MSer: (IFR rule)

Same effort to not run into thunderstorms...

 

Flying is so much a easier when we are prepared... 

The reason why we select the tank with the most fuel in it for landing...

When we point the nose towards the runway... Fuel runs away from the pick-up...

The more empty tank has a higher probability of allowing the engine to run extra quietly....

PP thoughts only, not a mechanic...

Best regards,

-a-

[ijs12fly]

Forget the stick, read the rivets!!!  

I have never had a need for calibrated fuel sticks.  When I got checked out (2006) by John Pallante (used to be a MAPA president, CFII, M20J owner....) he taught me how to check the Fuel Level (in my M20C) by reading the Rivets inside the tank.  If you are on the Pilot side, looking into the fuel tank opening, the Rivets are at about the 2 O'Clock position (with 6 O'Clock facing  in front of the plane)  - on the back wall of the fuel cell.  The top rivet is 1.5 Gal down from Full,  Each Rivet below that is 3 Gal.   So lets say I see the fuel is 2/3 the way down between the 4th and 5th rivet I would count:  1.5 + 3 + 3 + 3 + 2 = 12.5 Gal's used. 

I have a JPI Fuel Scan 450, and I am within 1/4 Gal of accuracy for both tanks combined on every fill up.  Once the fuel gets below 15-18 gals used in one tank (my tanks hold 26 gal each) then the accuracy gets a little worse.   However after a lesson learned I wont take off on a tank if it has less then around 10 gals (1hr of fuel) in it anyway.  I had a bucking issue after taking off with around 7-8 gal's in the tank.  The guy at the FBO had an Ovation and mentioned in his POH it says not to take off with less then 12 Gals.  M20C POH does not mention a limitation.  Once I topped off the bucking stopped.

The only challenge is on really bright sunny days - sometimes tough to see in the tank with glare - but  you can always shade the view with a checklist, baseball cap, etc and if needed grab a LED flashlight to see better.

I have been doing this since 2006 and have never had a need or desire to purchase a fuel stick. 

I can't speak for other models that have different size tanks. But you could take your time one day and calibrate the Rivets as you would a stick, and you will never misplace your Rivet trick, its always installed in the tank!!!

Good luck.

 

[carusoam]

Interesting technique, IJS!

I use something similar for the 100g tanks...

More of a go/no go measurement.... 

Look in the tank... see the dry tank floor... get fuel... no matter what the mechanical fuel level indicator says...

The M20R fuel cap is slightly more up hill from the M20C...

I’ll be looking for rivets next time I Look down the hole...

Thanks for sharing that detail...

How is the lock down going by you?

Best regards,

-a-

[Andy95W]

And if anyone wishes to make their own fuel stick, these numbers have been posted many times before.

Just use a standard paint stirring stick and mark it with a regular black ballpoint pen.  Nothing special, just a cheap pen works well.  I made mine 8 years ago and it has yet to fade, run, or dissolve.  These markings are actually a bit conservative, meaning if the stick says 10 gallons, you probably have closer to 11.

Inches       Gallons

9               26

8 1/2           25

8               24

7 5/8           23

7 1/4           22

6 7/8           21

6 1/2           20

6 1/16        19

5 3/4           18

5 7/16         17

5 1/16        16

4 13/16      15

4 1/2           14

4 1/8           13

3 7/8           12

3 1/2           11

3 1/16         10

2 11/16       9

2 3/8           8

2 1/8           7

1 3/4           6

 

[Wildhorsetrail]

On 5/9/2020 at 10:47 PM, Andy95W said:

And if anyone wishes to make their own fuel stick, these numbers have been posted many times before.

Just use a standard paint stirring stick and mark it with a regular black ballpoint pen.  Nothing special, just a cheap pen works well.  I made mine 8 years ago and it has yet to fade, run, or dissolve.  These markings are actually a bit conservative, meaning if the stick says 10 gallons, you probably have closer to 11.

Inches       Gallons

9               26

8 1/2           25

8               24

7 5/8           23

7 1/4           22

6 7/8           21

6 1/2           20

6 1/16        19

5 3/4           18

5 7/16         17

5 1/16        16

4 13/16      15

4 1/2           14

4 1/8           13

3 7/8           12

3 1/2           11

3 1/16         10

2 11/16       9

2 3/8           8

2 1/8           7

1 3/4           6

 

Should be the same for the J model as well?

[kortopates]

Should be the same for the J model as well?

Wouldn’t expect so. M20C’s hold 48 or 52 usable based on serial number whereas J’s hold 64 usable.

The only stick or gauge i would feel comfortable using is the one i personally made measuring my actual tanks.


Sent from my iPhone using Tapatalk

[Pinecone]

I would think that in these times, SOMEONE has a CNC engraver.  So people could measure the levels in several of a given tank capacity and develop a CNC program to engrave a clear acrylic tube with the proper lines and numbers.  Wipe a little bit of black model paint and you have a dipstick for your tank capacity.

Hmm, might be a retirement job for me.

[midlifeflyer]

Not for a Mooney, but I went through the process of calibrating a Fuelhawk for an LSA where we are severely weight limited. In my case, I didn't use their chart but ran the numbers in an Excel spreadsheet and graphed them too.

i tried the paint stirrer method too. Problem was that because if the way it would soak into the wood, a single stirrer was pretty much useless for the second tank. It was easier to use the Fuelhawk.

 

[A64Pilot]

Only advice I have is use a stick that’s too long to be accidentally dropped into the tank

[Fly Boomer]

4 hours ago, A64Pilot said:

Only advice I have is use a stick that’s too long to be accidentally dropped into the tank

I'm a fan of sticking the tanks, and I usually tend to imagine the worst possible outcome, but had not thought of that.  Thanks!

[Utah20Gflyer]

I once spent an hour at an out of the way airport adding 1 gallon at a time to my tank and then measuring it.   At the time I had INOP fuel gauges, not just a little INOP I mean completely bad.  That project gave me a little objectivity in determining fuel quantity until I got CIES senders and a digital fuel gauge installed.  If anyone out there needs a nudge I would very strongly recommend the upgrade.  It really has increased my piece of mind while flying and the stats seemed to back up my relaxation as fuel starvation accidents are exceptionally rare with accurate fuel gauges but one of the more common accident causes for planes with older systems.   

[Zippy_Bird]

Hi All,

Decided to mark-up a single fuel stick today based on the above measurements and had a question for the community.

Two sticks came with my bird clearly marked R & L.  I tried to seek guidance from the previous owner about this but was unable.  The marks are sparse and not useful, but the question I have is are the two tanks so physically different (1966 M20E) as to call for two different calibrations, one stick per tank?  I have yet to find a thread in the forums that supports this idea, yet the here they are.  Thoughts welcome.

Thanks, Z

[Hank]

I'd be shocked if there's much difference. 

Very timely posting of the photo with measurements, as my stick just came up missing . . .

[Igor_U]

Yes, I agree , It would be unusual to have noticeably different LH and RH tank.

When I bought the plane I used HD large paint stick and marked with lines every 5 gallons. It is still dosing strong and is quite accurate.