Wet Wing Longevity

[Marc_B]

@Pinecone I added unknown to the first question for you.  If not aware of any patching in your logs, that's the second question.  If your tanks were resealed at 23 years that's the third question.

[Vance Harral]

20 hours ago, MikeOH said:

At this rate, I have no issue with continuing to patch vs. a $15,000+ reseal.

No criticism of your strategy, we also paid $1-2K for patches every few years, for the last 20 years, and it served us well.  That said, your estimate for a reseal is pessimistic by more than $5K.  After about 50 years of original sealant plus patches, we decided to bite the bullet, and have an appointment with Don Maxwell at the beginning of February for a full strip and reseal on our M20F with 64 gallon tanks (roughly the same vintage as yours, I recall).  The contracted price is $9600 for both sides.  7 year warranty, for what that's worth.

The $9600 quote doesn't include travel costs.  Round trip from Denver to Longview in the Mooney will put about 8 hours on the airplane, but it's hard to say whether that should be included in the accounting or not, as we like to fly and would likely have gone somewhere else instead.  Short-notice round trip airfare from Longview home, then back for pickup, adds about $750 (anyone traveling from northeast Texas to Denver around the end of January, and/or in the other direction around end of February?)

I don't know whether to feel better or worse that we scheduled this reseal right before the recent news about G100UL and Mooney tanks.  No G100UL in Colorado for now, but it's obviously a strategic concern.  We're unconvinced bladders are a better bet on that front, and slightly prefer wet wings for other reasons as well.  The other alternative was to do nothing, but we had reached a point where we were concerned the airplane might spring a significant leak that would make it difficult to deliver it even to a shop that would patch it.  You also just get tired of looking at the ugly blue/brown stains after a while.  Even when it's not a safety of flight issue, it starts to feel like you're neglecting the airplane and creating a major sticking point for sale somewhere down the road.

[MikeOH]

@Vance Harral

Thanks.  Good to know it's only a $10,000 problem; I thought I'd read in a post that one of the other sealing guys was running $7K-$8K per side!

Thankfully, I've spent less than $1000 on the two patch/repairs over the last 7 years.  Don't have any blue/brown stains to clean up.

I'm pretty happy continuing with this strategy until it isn't!  With as old as my sealant is (54 years??), G100UL is a HUGE concern for me...it may result in my current strategy ending.  Which will piss me off, greatly...and, no doubt, I'll be told, "it wasn't G100UL it was your old sealant!"

[MooneyMitch]

21 hours ago, PT20J said:

The two women that did tank sealing that were interviewed in the Boots on the Ground video admitted that it was a challenging job and had a learning curve and that they weren’t very good at it when they started. Someone got the airplanes they learned on.

 I remember filming that segment with the 2 very dedicated women tank sealers.  I haven't watched that video in years.  There are some very wonderful segments that I loved filming though.............especially the dear Bill Wheat and the very dedicated Stanley Feller segments.  I don't know if the 2 ladies went back to Mooney with the 2014 startup.  They had been gone from Mooney since the 2008 shutdown and were most gracious to return to the factory during our filming in 2011. 

[Vance Harral]

44 minutes ago, MikeOH said:

I thought I'd read in a post that one of the other sealing guys was running $7K-$8K per side!

That's probably the correct range for airplanes with larger tanks: later models from the factory and/or those with Monroy long-range STC.

 

44 minutes ago, MikeOH said:

I'm pretty happy continuing with this strategy until it isn't!

Yep, that was our strategy for two decades, and I don't regret it.  The cost of the patches worked out to less than $5/hour for us, which is arguably in the noise of operating cost.  But nothing lasts forever.  You have to guess at how much longer you think you'll own the airplane, estimate inflation, time value of money, etc.  I kinda wish we'd ponied up for that "too expensive" paint job in 2005, when we could have had a pretty good one for under $10K.  That same paint job would be over $20K now.

As for the G100UL thing, I guess it remains to be seen the degree to which this is actually a function of tank sealant health.  We're of course hoping a fresh seal job buys us some insulation against the problem, if we use G100UL in the future.  But there isn't enough at-scale-in-the-market data to be sure, and for better or worse we're not going to wait on it.  If G100UL is a major cosmetic problem for people like us who ride the tail of the sealant curve, I can only imagine how irritated people with young sealant (and often nice paint jobs) will be if G100UL turns out to be - even just cosmetically - incompatible with wet wings.

[spistora]

Mine went 44 years on the original seal. Just patched two minor seeps this year's annual. No leaks since patch, but question 2 didn't have that option.

[Marc_B]

FWIW. When I had my tanks resealed at WeepNoMore it was $8900 for both mains.  If you needed aux tanks that added $3000 to the total (so aux plus mains around $12k).  The wait list was the long part...I believe they were scheduling a year out.  I think that since Don Maxwell picked up the Monroy aux tank STC installs, I'm guessing that might offload some backlog??

Of course it's a 2-3 week process, so depending on how far you live, you're likely looking at travel on both ends wherever you decide to go.

It's a hassle, but if you're considering that you're doing this once every 25-30 years (or more)...that context makes this much more reasonable.  If you're flying regularly, you could potentially go though 2 engines during that time!

[Marc_B]

6 hours ago, spistora said:

No leaks since patch, but question 2 didn't have that option.

added the option.

[MikeOH]

1 hour ago, Marc_B said:

FWIW. When I had my tanks resealed at WeepNoMore it was $8900 for both mains.  If you needed aux tanks that added $3000 to the total (so aux plus mains around $12k).  The wait list was the long part...I believe they were scheduling a year out.  I think that since Don Maxwell picked up the Monroy aux tank STC installs, I'm guessing that might offload some backlog??

Of course it's a 2-3 week process, so depending on how far you live, you're likely looking at travel on both ends wherever you decide to go.

It's a hassle, but if you're considering that you're doing this once every 25-30 years (or more)...that context makes this much more reasonable.  If you're flying regularly, you could potentially go though 2 engines during that time!

What year was the $8900 price?  Sorry if I missed it in an earlier post.

[N201MKTurbo]

I had my tanks resealed by Wilmar Air Service in 2006. The quote for the job was $7000 for both sides. When I showed up to pick up the plane they handed me an invoice for $9500. When I asked them why it was more than they quoted, they said it took longer than they thought it would. I said “I thought you guys did these all the time. Don’t you know how long it takes?” Then I said there was nothing in the quote about time and materials. It was a quote for the job. Anyway, it started leaking soon after and I have been fixing it ever since.

The warrantee is kind of worthless. If you want a warrantee repair, you have to schedule it a year out and take your plane back to the shop. So the free repair will cost you a couple af AMUs and your airplane will be down for a year. 
 

BTW. I don’t blame the current owner of that shop in any way…

[Marc_B]

28 minutes ago, MikeOH said:

What year was the $8900 price?

2 years ago. 

[Fritz1]

I had my 2000 Bravo resealed by Weep no More in 2019 since it had gone through multiple patch jobs, was leaking minimally, but I wanted to get it painted, think the cost was $11k, no leaks since, I kept the tanks filled to the brim whenever I can, the sealant dries out when the tanks sit empty in high ambient temp, brittle sealant cracks under hard landings on old and hard donuts, I put the Bravo on jacks whenever I do not fly it for more than a week, short bodies were almost 900 lb lighter than a long body fully fueled, donuts still the same

[Fly Boomer]

12 hours ago, Fritz1 said:

I put the Bravo on jacks whenever I do not fly it for more than a week

I have been giving this some consideration.  Does the Bravo have a jack point for the nose, or do you anchor the tail?

[Marc_B]

18 minutes ago, Fly Boomer said:

I have been giving this some consideration.

There's someone that makes something like Mooney shock disc savers.  They presented at MooneyMax this year...basically they slide inside the gear tube (like where you slide tow bar) and then you use a hydraulic jack to raise up a couple of inches and allow insertion of a clevis pin.

https://kotzur.com/products/mooney-shock-disc-savers

This was what I could find with a simple search, but isn't the vendor that was at MooneyMax... @LANCECASPER can you recall the name?

My personal thought was this might make sense for storage if you're not flying regularly, but would be a hassle for those who fly a lot.

[dzeleski]

16 hours ago, Marc_B said:

FWIW. When I had my tanks resealed at WeepNoMore it was $8900 for both mains.  If you needed aux tanks that added $3000 to the total (so aux plus mains around $12k).  The wait list was the long part...I believe they were scheduling a year out.  I think that since Don Maxwell picked up the Monroy aux tank STC installs, I'm guessing that might offload some backlog??

Of course it's a 2-3 week process, so depending on how far you live, you're likely looking at travel on both ends wherever you decide to go.

It's a hassle, but if you're considering that you're doing this once every 25-30 years (or more)...that context makes this much more reasonable.  If you're flying regularly, you could potentially go though 2 engines during that time!

The waitlist is well over a year now. Almost 2 years. I have an appointment for Jan of 2026, I called February of 2024.

I was also told it would cost $9,000 for a 64 gallon J.

[LANCECASPER]

Just now, Marc_B said:

There's someone that makes something like Mooney shock disc savers.  They presented at MooneyMax this year...basically they slide inside the gear tube (like where you slide tow bar) and then you use a hydraulic jack to raise up a couple of inches and allow insertion of a clevis pin.

https://kotzur.com/products/mooney-shock-disc-savers

This was what I could find with a simple search, but isn't the vendor that was at MooneyMax... @LANCECASPER can you recall the name?

My personal thought was this might make sense for storage if you're not flying regularly, but would be a hassle for those who fly a lot.

This is the guy:   https://htsllc.net/index.html  I believe his name is Carl Sharon.

[Fly Boomer]

28 minutes ago, Marc_B said:

There's someone that makes something like Mooney shock disc savers.  They presented at MooneyMax this year...basically they slide inside the gear tube (like where you slide tow bar) and then you use a hydraulic jack to raise up a couple of inches and allow insertion of a clevis pin.

https://kotzur.com/products/mooney-shock-disc-savers

This was what I could find with a simple search, but isn't the vendor that was at MooneyMax...

I have seen the ones your link points to, but I can't imagine what it would cost to get them here from Australia.

[Marc_B]

@LANCECASPER yes, I think that's the company.  Although I didn't see anything about shock disc savers on his website. @Fly Boomer there's a company here in the US that sells them.  I think Lance pointed out the vendor above. Not sure details of cost and availability though.  But the pictures in the Australia company looked very similar to the models that were shown at MooneyMax 2024.

 

Also came across an article from Kerry McIntire.  Pretty good overview of tanks, patching, and bladders. 

https://knr-inc.com/shoptalk-articles.html?view=article&id=24&catid=25

[Marc_B]

I've looked and can't find a specific expected life of fuel tank sealant, but I've found the round number of "20 years" used routinely regarding wet wings, bladders, and fuel cells.  So I think the general "round number spitball" of wet wing longevity is over 20 years.  So far the majority of poll responses have described that the Mooney wet wing can typically do that and then some. 

Yes, there are variances in construction (wet vs dry riveting), differences in material, differences in bladder vs wet wings vs fuel cells, etc. across the fleet; however, one can't say that "all Mooney's leak" and that's just the reason for any and every leak seen.  A leak seen a couple months after sealing (as noted above) isn't the same as a leak in a 40 year old aircraft on original sealant.  But wet wings lasting for 20, 25, 30 years or more without leaks certainly sounds like a high quality, high efficiency, low weight fuel storage solution to me!  Sounds right in line with what Mooney represents: sleek, efficient, do more with less approach that is seen throughout our Mooneys!

It's a personal judgement of patching vs. reseal, but in general if you are seeing flecks of sealant in your sumps with 30-40+ year old sealant; it sounds like it's time to consider a reseal.  All sealant has a useful life and sometimes your tanks "talk to you" just like your engine does when it's nearing time for overhaul.

...and leaks with fuels of the future vs. fuels of the past may be different or similar...correlation does not necessarily imply causation...so more data and details are needed, and hopefully will be forthcoming with field reports of real world successes and setbacks....  Details regarding age/condition of sealant may be important as well...if nothing else than to help define the condition at risk.

There's nuance to these discussions and we need to speak with details and avoid broad generalizations that don't apply.  In my mind, Mooney wet wings work pretty darn well!

[Vance Harral]

3 hours ago, Fly Boomer said:

I have been giving this some consideration.  Does the Bravo have a jack point for the nose, or do you anchor the tail?

Much as I like our Mooney, this is the sort of thing that really shows how the airframe is sliding into obsolescence.  I understand people are just trying to keep their birds viable without breaking the bank, but I cannot imagine jacking up my airplane and/or installing locks in the landing gear suspension to "save the landing gear doughnuts".  The risk of the airplane falling off jacks is pretty small if you're careful, but it's a catastrophic event if it happens, and the likelihood of it happening goes way up if you're doing it literally every time you put the airplane away.

Lots of airframe models remain viable after being orphaned by the manufacturer (and let's not kid ourselves, that's the state of Mooney).  But beyond a certain point, it becomes ridiculous.  Imagine the reaction of a potential new owner, or the peals of laughter from the local hangar crowd.  "Yeah, a Mooney is a pretty nice airplane, but the design of the landing gear is so dumb that you've gotta put it up on jacks when you're not flying it".

[Marc_B]

I suspect it's a solution looking for a problem.  Tons of Mooneys have been firmly planted on the ground compressing the shock discs that last 12-15 years.  Long bodies shock discs don't last as long due to heavier engine and higher empty weight on the discs.

None of the Mooneys need this.  But perhaps it eeks out a few years on shock discs for long bodies with full fuel tanks?

My hangar neighbor had their M20J covered in a series of Goodwill sheets tip to tail, wing to wing, and this kept their aircraft paint less covered in dust, less need to clean and scratch with dirt, and their original paint looked pretty factory fresh after 30 years.  Sometimes it seems that an ounce of prevention keeps the "pounds" of time at bay! But @Vance Harral I'm with you, I can't imagine leaving my Mooney up on jacks routinely.

[Marc_B]

Has anyone ever noticed a big difference when they opened tanks to patch or reseal with regards to the top wing sealant and the bottom wing sealant? 

It seems there are two possible reasons that sealant covered in fuel would help protect sealant...better thermal regulation with the large volume of fluid that could absorb heat, and keeping the sealant wet to keep it from drying out.  If the offered theory is that fuel is so damaging to the sealant, then it seems to reason that keeping tanks empty would be better...but I've never heard anyone suggest this...

Not sure if any studies have been done on either theory, or if keeping wet tanks full is just an OWT/tradition for "best practice" rather than actual science??

 

[Vance Harral]

1 hour ago, Marc_B said:

Has anyone ever noticed a big difference when they opened tanks to patch or reseal with regards to the top wing sealant and the bottom wing sealant?

I'll try to get a data point on this when we have our tanks resealed in February, but it'll just be one data point.

We're a good poster child, though, because the fueling policy in our partnership is to fill to the tabs (not full) after each flight, and it's been that way for 20 years.  That means we have two decades worth of having the bottom portion of the tank full of fuel almost all the time, and the top inch or two almost always dry.  We have several seeps on the bottom of the wings, and I know both tops seep a bit (right worse than left) if you fill the tanks and let the airplane sit an hour or more.

Our airplane is hangared, so we don't have the effect of sun heating the top half of the wings with air in the top half of the tanks.  But if being immersed in fuel vs. not really makes a difference, I can't think of a much better candidate for a data point than our airplane.  If there's a difference and it's visible, we ought to be able to see it.

[Fritz1]

I use 3 jack points for the Bravo, held the tail down once and realized that the door was hard to close which told be not to pull down the tail, the jacking takes 5-7 min with Meyer jacks on wheels, no idea if it really extends the life of the donuts, it just might, I keep the jacks under the wing tips and scoot them in when I need them, Lasar combo tiedown jackpoints stay in the wings all the time

[MikeOH]

With no real basis other than my own non-expert reasoning, I've always thought that the "keep the sealant wet' mantra to be an OWT. If keeping the sealant 'wet' was valid then it implies that fuel is, at least partially, 'soaking' into the sealant.  After all, if it didn't, then how would the 'sealant' even 'know' if it was wet or dry?  If it is 'soaking in' why would that make it last longer...over time I think that repetitive soaking and drying would shorten the life, not prolong it.

Anyway, that's my $0.02 and I've never worried about how much fuel is left in the tanks when I put my plane away in the hangar.

Honestly, I think having the plane hangared is much more critical as I believe the temperature cycling and direct sun exposure to be far more damaging to the sealant, especially on the top of the wings.