Full tank to protect the sealant - OWT or not?

[Tommy]

Is there any truth in keeping the tanks full in order to protect the tank sealant?

v.s. the additional weight on the gear

v.s. unable to take off for that impromptu scenic flight with 4 big boys / girls!

Edited October 7, 2017 by Tommy

[rbridges]

I don't know the science behind the sealant. Is heat or lack of moisture worst for it?  Keeping fuel in the tanks could act as a heat sink to keep the sealant in a lower heat range. Especially for non hangared planes that have their wings in direct sunlight. 

[DVA]

The sealants used to create the fuel cells, according to PPG and Flamemaster, two manufactures’ of the products, say no. The products do not rely on any outside liquid to remain in-tact.

However, the natural flexing of the fuel cells do contribute to breaches, and we see that on inspection when we do repairs. Keeping fuel, at some level above empty appears as if its a good thing to help prevent quickly changing the aggregate temperature in and around those cells. The fuel acts to provide some hysteresis in the speed of heating and cooling and empirically at least, helps to keep temperature induced flexing down. But that could all be BS, it just seems to be logical.

Always keep enough fuel in the plane to be able to have fun when you want to. :-)

DVA

[carusoam]

1) When it comes to polymers, heat is usually bad for their long term health...

2) When it comes to metal boxes coated with polymers, leaving them out in the sun is ussually bad for their long term health...

3) So, looking at this way, the OWT is partially correct, but for the wrong reason....

4) keeping them wet with fuel, happens to be a great way to keep the sheetmetal temperature from exceeding the roasting temperature of an oven. Ever touch a car that has been out in the sun?  Our wings aren't much different...

5) If your plane is not in direct sunlight, like under a shade hangar or inside in a hangar, it is probably not going to be a big issue for a properly sealed wing tank.

6) putting the plane away...

• dust cover/bird crap protector while in the hangar?
• can't fill the tanks, somebody might want to fill the back seats on the next flight?
• jack the plane off the ground, to save a donut?  Added risk of injury...?
• connect the engine dryer?
• doors open or closed
• oil fill tube, open to vent moisture?

How much time does it take to put the plane away if you add all these details together..?

I like putting it in the hangar and call it done... till next time.

Much better than leaving it outside.

Best regards,

-a-

[Piloto]

+1 for Carusoam. The tank sealant is very much like rubber, too much heat cause degradation. Fuel helps to cool it down. If you store your Mooney in a hangar there is no need for fuel in the tanks, but if you store it outside leave at least half a tank full. Under heat the sealant looses it elasticity  and becomes brittle causing fuel leaks.

José

[flyboy0681]

All of these answers beg the question, while my ship is down for repairs over the next few months, should the shop fill the tanks with some kind of inert liquid?

[Skates97]

2 hours ago, DVA said:

Always keep enough fuel in the plane to be able to have fun when you want to. :-)

DVA

I keep tanks full for a different reason. We don't worry about hurricanes here in CA but there is the constant concern about earthquakes. Should there be a reason we have to "get out of dodge" the Mooney will be the way to go. The evacuation plan is driving to the airport (10 miles away), or riding bikes if need be and then flying. If electricity is out, then so are the fuel pumps. If I have full tanks I can get to family in AZ or UT easily.

[carusoam]

Flyboy, you might consider leaving the tanks empty and vented while work is being done...

Somewhere along the way, Somebody may want to check the integrity of the sealant that is currently there.

 

Richard, getting out of dodge can sometimes have additional challenges...  the one time I wanted to skip town, all the airport's got closed down for three days... 9/11...  seems like you may have it covered by biking the distance...

Best regards,

-a-

[N201MKTurbo]

1 hour ago, flyboy0681 said:

All of these answers beg the question, while my ship is down for repairs over the next few months, should the shop fill the tanks with some kind of inert liquid?

A few months is unlikely to change anything.  You have ro abuse that sealant for decades before it will go south.

[ArtVandelay]

I keep tanks full for a different reason. We don't worry about hurricanes here in CA but there is the constant concern about earthquakes. Should there be a reason we have to "get out of dodge" the Mooney will be the way to go. The evacuation plan is driving to the airport (10 miles away), or riding bikes if need be and then flying. If electricity is out, then so are the fuel pumps. If I have full tanks I can get to family in AZ or UT easily.

I escaped hurricane Irma by flying, it took people I talked to 12-18 hours to get out of south Florida/Georgia , took me 3. Of course unlike earthquakes, we had time to fill up.

[Tommy]

That also begs the question, is the sealant all 'round the entire tank or just bottom part of it? Reason asking is that if it's only the bottom part then filling to half definitely beats filling to the top, keeping it cool whilst giving you the flexibility of flying withe more weight and less stress on the gear. 

[Hector]

That also begs the question, is the sealant all 'round the entire tank or just bottom part of it? Reason asking is that if it's only the bottom part then filling to half definitely beats filling to the top, keeping it cool whilst giving you the flexibility of flying withe more weight and less stress on the gear. 

The sealant is all around the entire tank. Filling it half full is enough to provide a heat sink for all the sheet metal in the tank


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[carusoam]

The sealant is everywhere two pieces of aluminum come together in the tank.

The first failures are often at the inspection panels on top...

keep in mind, my statistics are based on n=1

The inspection panels are also a special case.  Because an easier to separate sealant is used there...

What year is your J, Tommy..?

Best regards,

-a-