Mooney Wing Tanks and Water

[GeeBee]

9 minutes ago, M20F said:

Go blue, it will fix your problem.  
 
Water is annoying.  When it freezes at the bottom  of your tank, that’s when the real fun happens.  
 
@Gee Bee Aeroproducts to the rescue. 

They are blue and have been for years. Replaced annually.

[ArtVandelay]

I made some fuel tank covers recently and tried them out this past weekend. I parked outside in north Arkansas for the weekend where we got plenty of rain. My covers stayed on and kept the water out perfectly. 
I used magnets that stick to the steel center post of the fuel cap. I cut 1/16" abs plastic which I heated to form a concave shape. I tested it in place with a 200mph blower. 
https://www.amazon.com/dp/B085NP6SQY?ref=fed_asin_title
 
-David

I used painters tape to cover the fuel caps, speed brakes slots and wing fuel gauges. An ounce of prevention….

[PT20J]

5 hours ago, N201MKTurbo said:

i have found that opening these holes is tedious. You cannot open them by just poking something through the holes. If you do the sealant will close the hole when you pull out the poker. You have to surgically remove the plug with the tip of an exacto knife like the SB says.

How big are the holes? I wonder if a deburring tool would work.

[N201MKTurbo]

8 minutes ago, PT20J said:

How big are the holes? I wonder if a deburring tool would work.

I don’t think so. Most are about 1/4 inch and against a flat plate. And you are not supposed to take it down to the metal.

[McMooney]

what is this pressure test

[PT20J]

28 minutes ago, McMooney said:

what is this pressure test

https://mooney.com/wp-content/uploads/2020/12/SBM20-229A.pdf

[PT20J]

I’ve had my J outside during numerous heavy downpours and it has never leaked water even though the depressions in the caps fill with water.  The Shaw caps have 10 year-old fluorosilicone o-rings that look like new. I keep them lubed. I do a pressure test every annual. I have no idea why some leak and mine don’t. But it is pretty easy to get the cap slightly cocked when closing it and I don’t know that it will seal in that condition, so I always check them. 

[MikeOH]

@PT20J

What do you lube them with?  Would DC4 be accepatable?

[DCarlton]

I'm hoping these do the trick and stay bone dry.  They're slightly raised.  Before these, I had nursed my Shaw caps to satisfactory performance with the o-rings mentioned above.  

[PT20J]

1 hour ago, MikeOH said:

@PT20J

What do you lube them with?  Would DC4 be accepatable?

I don’t think it matters much. The SB calls out Tri-Flow or petroleum jelly for the big ring and Tri-Flow for the small one. Petroleum jelly doesn’t last long. I tried EZ-Turn but it is too sticky. Lately I’ve been using Parker O-ring lube. I think DC4 would also be a good choice.

[Ragsf15e]

2 hours ago, PT20J said:

I’ve had my J outside during numerous heavy downpours and it has never leaked water even though the depressions in the caps fill with water.  The Shaw caps have 10 year-old fluorosilicone o-rings that look like new. I keep them lubed. I do a pressure test every annual. I have no idea why some leak and mine don’t. But it is pretty easy to get the cap slightly cocked when closing it and I don’t know that it will seal in that condition, so I always check them. 

I wonder if there’s any chance tightness on the castle nut can encourage leaking.  It can be “tight” or “loose” and still lock seemingly fine.  Someone pointed out that there’s a spec for how hard to push down the tab.  Fwiw, mine haven’t leaked either (at least that I’ve caught).

[gabez]

5 hours ago, ArtVandelay said:

I used painters tape to cover the fuel caps, speed brakes slots and wing fuel gauges. An ounce of prevention….

mmm that is an interesting idea, I am going to try to 3D some attach the magnet and maybe put some teflon tape on the edge to create a seal. the blue tape is a pain in the butt

 

[jeremyc209]

I'm still getting a few drops of water in samples out of my right tank and it's been hangared/dry for well over a month with quite a few flights and top offs since it last saw any rain. Some steep turns seemed to work some more out early on. I haven't experienced any engine roughness on that tank that I could detect though. 

 

[00-Negative]

I've never had my caps leak, and I have the fluorosilicone o-rings from Gallagher. They work well.  But the pool of water that collects in the recessed cavity bothers me. If the plane sits for a day or so after a rainfall, the water will evaporate  except for some that collects below the cap on top of the o-ring which will inevitably spill into my tank when I remove the caps during preflight. I did glue a rubber edge to my fuel cap cover that creates an adequate seal, I just don't have a picture of the final product. I tried several different ideas prior to what I'm using now. Everything else would get blown off of the wing... not by storm winds, but by prop wash from planes turning to park. Blue painters tape is an effective solution, but it shows up in the pictures when I'm grabbing candid pictures of my girl. 

 

-David

[Pinecone]

14 hours ago, ArtVandelay said:

I used painters tape to cover the fuel caps, speed brakes slots and wing fuel gauges. An ounce of prevention….

There are no holes with the wing fuel gauges.  They connect magnetically to the in tank portion.

[Pinecone]

The OP mentioned water entrained in the fuel.  Not liquid water in the tank.

Water entrained in the fuel will not come out from any sumping, unless you sump all the fuel out of the tank, as the OP did.

The isopropyl alcohol will remove it.

As was stated, the entrained water is not a big deal except for freezing into ice crystals that can clog the fuel system.

[M20F-1968]

After reading this threat, I think I might consider taking my wing covers with me on any long trips away from home.  Need to check the weight of the covers.  If in place, they should protect against water.  The weather seems to be getting worse in the middle of the US, with weather then coming east.  Finding hangar space is unpredictable.

John Breda

[A64Pilot]

A few comments

First be extraordinarily careful doing a pressure test, Gulfstream used to have a G-550 I think it was behind a curtain in their completion center, a mechanic made a mistake pressure testing a wing and ruined the wing. The area of a fuel tank is huge, even just a tiny pressure over such a large are is enormous force

Second I’m convinced that fuel when warm will hold in suspension quite a lot of water, then this water can come out of suspension at altitude and cause problems, but it wasn’t there on the ground. Military before we could refuel the truck had to do an “Aqua Glo” test, if the water was above the threshold, they had to recirculate the fuel through the filter that was water absorbing, it would absorb water that was dissolved in the fuel until it was below the max acceptance point. I don’t think that’s done in the civilian world?

Lastly My C-140’s factory fuel vents are two 1/8 holes in the fuel caps, of course rain will get water in the tanks so you must cover them. Two problems, cover must stay on in the wind and being on top of the wing it’s possible you may forget them. My answer was to buy two cheap red rubber toilet plungers, unscrew the handle and simply place them onto the top of the caps, they are heavy enough the wind won’t blow them off and if you forget them, being rubber they won’t hurt the tail etc when they fall off on takeoff.

These things, cheap and easy

 

Edited April 30 by A64Pilot

[PT20J]

Clarence suggested attaching a length of tubing to the vent and blowing into the tube to pressure test the tanks. That’s what I do. It’s easy to regulate the pressure to avoid damaging the tanks.

[Marc_B]

4 hours ago, 00-Negative said:

But the pool of water that collects in the recessed cavity bothers me. If the plane sits for a day or so after a rainfall, the water will evaporate  except for some that collects below the cap on top of the o-ring which will inevitably spill into my tank when I remove the caps during preflight.

I've had this happen a couple of times and I've never have seen a drop of water at any point in the sumped fuel.  I always make an attempt to soak up as much as I can with a paper towel before opening the cap.  Makes me wonder how much water, specifically, does it take to first begin to see water when you sump.  vs. what concentration of water is "tolerable" and won't show engine issues.  The second value likely has a temperature component as freezing water to clog screens/filters probably has a lower threshold than warm fuel in summer rains.

[GeeBee]

When pressure testing the tanks, I don't use a gauge, I use a manometer. Much more precise.

[A64Pilot]

1 hour ago, GeeBee said:

When pressure testing the tanks, I don't use a gauge, I use a manometer. Much more precise.

We tested every wing tank at Thrush after manufacture of course. We used a home made water manometer connected to the vent line and the air pressure line to the fuel inlet. Advantage of homemade water manometer is it was just a clear plastic tube in a U shape filled with colored water and a ruler on one side. If you accidentally applied more pressure than you wanted it would just blow the water out and of course the air would then free flow, you couldn’t bust a tank.

Many home builders here use a balloon, idea being too much pressure will blow up the balloon. Balloons are cheap and easy. Not as precise of course.

The home made water manometer was so precise that you would see pressure build as the morning warmed up by just a couple of degrees.

When we built the Military aircraft with hard points that penetrated the tanks we had more leaks, we switched to testing with helium as helium is a smaller molecule and will leak more than air. Ask NASA how hard it is to keep helium from leaking, Boeing anyway.

Edited April 30 by A64Pilot

[GeeBee]

4 minutes ago, A64Pilot said:

We tested every wing tank at Thrush after manufacture of course. We used a home made water manometer connected to the vent line and the air pressure line to the fuel inlet. Advantage of homemade water manometer is it was just a clear plastic tube in a U shape filled with colored water and a ruler on one side. If you accidentally applied more pressure than you wanted it would just blow the water out and of course the air would then free flow, you couldn’t bust a tank.

Many home builders here use a balloon, idea being too much pressure will blow up the balloon. Balloons are cheap and easy.

Yep that's my view too. Manometer makes it stupid simple and precise.

[ArtVandelay]

There are no holes with the wing fuel gauges.  They connect magnetically to the in tank portion.

But they can get moisture inside the gauges if left sitting in water.

[Ragsf15e]

32 minutes ago, ArtVandelay said:

But they can get moisture inside the gauges if left sitting in water.

And then depart the aircraft.  And they are hard to find…