Does anyone have Experience with Making Fuel Dipsticks for an M20C?

[Fusco]

I am currently in the process of buying a 65' M20C and like many older airplanes, the fuel gauges are pretty much useless. Just about all my flying experience is in Cessnas and I really liked being able to verify my fuel quantity using a plastic dipstick. I assumed that all airplanes had this and I now realize that is not the case. I am making this post because I would very much so like to make one and was wondering if anyone on here has a similar year Mooney that has done this same thing. I think I will use some sort of plastic tubing and make markings on it and would appreciate if anyone could share markings or dipstick designs that they have found to work with their Mooneys.

This is my first post here and I really appreciate any replies!

[hammdo]

I did one for my 66 C with 52 gallons. There is a post on here that gives the markings. I did mine on a couple of Lowes paint sticks. I will say they are conservative. I’ve found they can show less than you have but are close enough.

I’ll see if I can find it again…

edit:

E and C have the same tanks — if yours is 52 gallons…

-Don

[Hector]

Paint stick. Empty/drain tank, add two gallons at a time and mark with a sharply. I keep the original as a master and make duplicates from the original.


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[cliffy]

1/4 inch wooden dowel rod about 2 feet long

Drain tank (by flying::-)

Add 5 gallons at a time - dip in tank by holding against the inboard side of the fill hole 

          and mark where it is wet with fuel  MARK with a pencil so fuel doesn't dissolve the marks

Don't let it sit in the fuel too long or it will capillary up the stick and give a false reading 

Just a quick dip to touch the bottom of the tank. Pull it out and mark it

Now- Why the 2 feet long? Hold the dry end and wave the stick around like a flag to dry it off for the next test

You can very easily interpolate between 5 gallon marks. 

Stick sets just inside the baggage door along the right wall of the compartment

Dries off very nicely (and no smell) because its long and easily dried.  

Always check fuel by putting the stick against the inboard side of the fill hole as you did when you made the stick. 

 

[Hank]

Use the paint stick as described above to take measurements. Then use a Dremel or powered engraving tool to transfer them to a typical hollow fuel dipstick. I'll take a picture of mine and post un a day or two, right now it's 17°F with winds NW at 15G21. I'm not leaving the house!! 

[Fusco]

Thanks for all the replies! The weather is pretty awful here in NJ so I'll have to try next week. I'll give an update if it works out, thanks again!

[Fly Boomer]

13 hours ago, Hector said:

I keep the original as a master and make duplicates from the original.

Clever!

[laytonl]

You don’t really need to empty the tank.  You know the usable fuel level, so just keep a log of stick reading before filling vs. the amount of fuel added. You do need a couple of readings with the tank low on fuel and then with readings from several fill-ups you can extrapolate the data to determine the markings.  Lee

[Fly Boomer]

5 minutes ago, laytonl said:

You don’t really need to empty the tank.  You know the usable fuel level, so just keep a log of stick reading before filling vs. the amount of fuel added. You do need a couple of readings with the tank low on fuel and then with readings from several fill-ups you can extrapolate the data to determine the markings.  Lee

Spoken like an engineer!  :-)

[DonMuncy]

1 hour ago, laytonl said:

You don’t really need to empty the tank.  You know the usable fuel level, so just keep a log of stick reading before filling vs. the amount of fuel added. You do need a couple of readings with the tank low on fuel and then with readings from several fill-ups you can extrapolate the data to determine the markings.  Lee

In theory, you are absolutely correct. In practice, there are a couple of problems. I think there are some variations in the capacities of tanks due to minor variations in the production. Also it is very hard to establish where "full" is, both when you are looking at published useable fuel and when you are measuring your own. The extrapolation is also a little tough to be super accurate. It is not as liner as we would like. But this is not much of a problem at the lower fuel levels, as it takes a few gallons before it begins to show on the stick

But overall, this method will get you awfully close. We all like to know, down to the ounce, exactly how much fuel is there, but in practice, nobody (with good sense) ever flies that close to the limits.

I still think the best way is to fly one tank down to where the engine sputters. (And no, there is no real danger here. It is only a little spooky the first time you feel that loss of power. Remember, the early POHs approved the process) Land and add fuel in one or two gallon increments, marking your stick as you go. I also suspect to be super-duper accurate, you would have to have a separate stick for each side. 

[Utah20Gflyer]

1 hour ago, laytonl said:

You don’t really need to empty the tank.  You know the usable fuel level, so just keep a log of stick reading before filling vs. the amount of fuel added. You do need a couple of readings with the tank low on fuel and then with readings from several fill-ups you can extrapolate the data to determine the markings.  Lee

Yes, the last 3-4 gallons are below where you are dipping so you just have to get the fuel level below where you are dipping, add fuel until full, then extrapolate backwards to determine actual fuel levels.

[N201MKTurbo]

The tab in the tank has a hole in it near the bottom. If you made careful measurements, you could fashion an aluminum strip that you could bolt onto the back of the tab. You could engrave the graduations, then you would have a permanent dip stick. If any crazy IA gave you crap about it, you could unbolt it and take it out until after the inspection.

I would rivet a nut plate in the top of the strip so it wouldn't be to huge of a PITA to screw it together. If it was easy, it wouldn't be a Mooney! Keep your magnet handy to retrieve all the hardware you drop into the tank.

[Hank]

28 minutes ago, N201MKTurbo said:

The tab in the tank has a hole in it near the bottom. If you made careful measurements, you could fashion an aluminum strip that you could bolt onto the back of the tab. 

The tabs began with the Js, ar some point. The C models don't have them on any year.

[N201MKTurbo]

16 minutes ago, Hank said:

The tabs began with the Js, ar some point. The C models don't have them on any year.

Well, that's a bummer. My F had tabs. Maybe they added them when they went to the 64 gallon tanks.

[MikeOH]

1 hour ago, N201MKTurbo said:

Well, that's a bummer. My F had tabs. Maybe they added them when they went to the 64 gallon tanks.

Hmm, my '70F doesn't have them.

I made my fuel stick by running the tank low then adding 5 gals at a time until full and then back marking the stick.  Sure, you can argue that may not be perfectly accurate but if I'm ever down to worrying about counting on the last 5 gallons I've screwed up big time!

[Jim Peace]

this all seems like a lot of work and you guys still say they are not that accurate....

I did this and all is well:

https://ciescorp.net

[N201MKTurbo]

51 minutes ago, Jim Peace said:

this all seems like a lot of work and you guys still say they are not that accurate....

I did this and all is well:

https://ciescorp.net

Paint sticks are a little cheaper...

You are on a Mooney forum after all.

[hammdo]

Free is always good ;o)..

-Don

[Hank]

On 12/23/2022 at 9:03 AM, Hank said:

Use the paint stick as described above to take measurements. Then use a Dremel or powered engraving tool to transfer them to a typical hollow fuel dipstick. I'll take a picture of mine and post un a day or two, right now it's 17°F with winds NW at 15G21. I'm not leaving the house!! 

Here is mine. It sits on the hatrack with the sample cup.

Here is a closeup showing the marks every two gallons. It will be easier to mark a paint stick, then transfer the marks to the tube.

[Yetti]

Nice big paint stick from Sherwin Williams.  Sharpie.   Stick the tank.  Mark a line with sharpie.   Fill to top.  Do some math.  Write the number down by the line.    I think I have about 5 lines like this on my stick and makes for good.   On my 75 F I also have tabs.

[FlyingDude]

12 hours ago, laytonl said:

just keep a log of stick reading before filling vs. the amount of fuel added.

I’ve been doing that to verify the stick that was calibrated by adding known increments to an empty tank, but the only problem is you don’t always fill it to the exact same level. That introduces 1-2 gl variations which are not big, but big enough to be annoying…

[BDPetersen]

After installing the bladder system I hoped to recreate the dipstick as I filled the tanks. The results were puzzling. May have been the tanks expanding on first fill, but something seemed off about the idea. To make matters worse, the freshly overhauled quantity transmitters seemed worse than before ( the right one, at least). I haven’t revisited the dipstick idea, but strive to have good calibration on my JPI. Anybody with bladders have a stick solution?

[takair]

33 minutes ago, BDPetersen said:

After installing the bladder system I hoped to recreate the dipstick as I filled the tanks. The results were puzzling. May have been the tanks expanding on first fill, but something seemed off about the idea. To make matters worse, the freshly overhauled quantity transmitters seemed worse than before ( the right one, at least). I haven’t revisited the dipstick idea, but strive to have good calibration on my JPI. Anybody with bladders have a stick solution?

I had my bladders installed by O&N when they were still around. They included a stick that I still use today. Fairly accurate. I can get measurements next week if needed. The gauges ended up very non linear, even with the STC sticker combinations. I made new ones and they are generally within 1 gallon with old style senders. 

[BDPetersen]

Thanks. I should have tried again when I pulled a bladder for repair (clamp on quick drain created a small tear). Don’t often have empty tanks.

[takair]

On 12/25/2022 at 8:04 AM, BDPetersen said:

Thanks. I should have tried again when I pulled a bladder for repair (clamp on quick drain created a small tear). Don’t often have empty tanks.

Finally remembered to get the stick out of the plane.  This was from O&N and seems to be fairly accurate.  If there is fuel just at the bottom of the tank it is about 7 gallons.