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Paint Blisters/Fuel Tank Rivets

rvbuilder2002 said:
Quick build kits have been available for RV's since about 1994 (15 years). I have seen teh inside of many of those tanks over the years and can tell you that they didn't just stop encapsulating rivets in the last couple of years of production.
If not, then why does this problem seem to have just started up in the last couple of years?
This is the type of question we need to answer.
Click to expand...

And it's a darn good question too.

I'm not an old-time RV guy, so please excuse me if I'm being dumb. We all say "proseal", but am I correct in thinking the Proseal brand is a product of PRC-DeSoto, a division of PPG?

Am I also correct in thinking Vans did sell/specify the PRC-DeSoto product at one time, but now sells a Flamemaster Corporation sealant?

So when did they switch?
 
Hello.....

My name is Pete and I suffer from...

Freaking Unbelievable Tank Blister and Leaking Syndrome (FUTBALS)

My instance of FUTBALS is somewhat interesting. Like many cases, it was incubated in the warm, wet climate of the Phillipines, and lay dormant for several years. As with many, my case of FUTBALS struck when the host was most vulnerable, while admiring his bird during a post flight wipe down. The first step is denial........

Next comes acceptance, then agony. In my rare case, written up in several journals(don't look - you can't get them), the effects were far more insidious. You see, I have blisters on only one tank. Not only is the raw beauty of my bird now unbalanced, but she was so perfectly rigged, the extra drag from the blisters disturbed the laminar flow, costing me 3kts and causing me to add an ugly rudder wedge to the rear of the bird(where no blisters can be found) to make her fly straight. Oh, the humanity! I now have Freaking Unbalanced Tank Blister and Leaking Syndrome (FUTBALS-2)

Don't weep for me VAFinistas. I categorically deny building or painting these tanks. As any good politician will tell you "Mistakes were made. We will get to the bottom of this" To paraphrase my good friend Chico Escuela "FUTBALS not been berry, beery goot to me!!"

==========================================

All kidding aside. I have blisters(pass side only). 2005 vintage QB tanks. Scuffed, cleaned, epoxy primed, and painted by a hot rod shop. (Valspar car paint system) Very interesting that I seem to have them only on one side. I have not stuck a lit match in there to check the rivet tails and fay seals yet. I will check soon. Any thoughts?
 
Captain Avgas said:
Kahuna, did you fully encapsulate all your shop heads with proseal when you built your tanks ?
Click to expand...
No I dont think I did. Ill have to confirm that.
MEK was my primary weapon of choice in cleanup of tanks and tools after riveting.
Coleman stove fuel(cheapest alcohol based product by the gallon) for generic cleaning and wiping all parts before paint. Then a product called "770 normal degreaser" (Thats what the can says), used by my local paint shop, to wipe before prime, and again before Sikens paint. Googling it turned up nothing so I dont know what it is but Ill poke around on that some more.

I have also been known to thin proseal on occasion with MEK, at least on other tanks I have built. Cant remember if I did on these or not to be honest. Would not surprise me. I discard that item as a possible culprit, MEK in the proseal mix, cause I have blisters in all various places and I did not mix MEK in my proseal in all those various places.
Bubbles get bigger in the sun on any given day.

My dark read paint on my wings gets HOT in the summer. THe size of the bubbles double in the baking hot summer sun.

Also been known to NOT measure accurately at all on the pro seal mix. Never. Always errored on the side of more black than needed. Always check for set up and hardness with the mixing cup afterwards. I now have a nice little digital scale for my new wings which Im building now.
 
RE: Points

Jamie said:
I built a standard kit and have been flying for 2 years, 2 months and so far no blisters.

I am however hesitant to place the blame on the QB factory if for only the following fact: The problem seems to be all-or-nothing. We seem to have tanks with many blisters or tanks with no blisters. To me this is inconsistent with placing the blame on weeping rivets.

Given the number of rivets in a pair of tanks and the fact that most tanks are built by first-timers, it is highly probable (approaching the point of certainty) that each pair of tanks has at least one rivet that is not sealed perfectly. Therefore if the blisters are caused by a bad seal in the tank, it stands to reason that a large number of customer-built tanks would exhibit the behavior with a limited number of blisters -- and that simply isn't the case.
Click to expand...

I agree with Jamie!!!

In the old days of my MBA training we studied a pretty simple process of business analysis of "what is different now from before"....or in other words what are the difference between the no blister tanks and the blister tanks. I will admit to gather the info on each blister tank and non blister tank would be an undertaking!!!!! How each was built/painted with the specific info in spread sheet form might just give an indication of similar indicators between each blistered tank and each none blistered tank. WHAT A JOB!!!!!

Considering I gave up painting my plane

http://www.vansairforce.com/community/showthread.php?t=33556&highlight=painting+begun&page=10 (Check out 2nd to last comment in the thread)

and did stay at a Holiday Inn near Van's in August doesn't make me qualified to answer this complex...seemingly unreasonable outcome...mystery as to why......blisters happen or don't happen situation.

Frank @ 1L8 and SGU ...RV7A... Phase one
 
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Only one cause

Blisters happen because ribs and skins were not prepared properly, lack of scuffing, lack of cleanliness, and because proseal was not applied properly! If one tank can be blister and leak free, this is a testament that it can be done right. I mixed up a batch of proseal that was over 2 yrs out of date, but kept in the fridge. When it hardened I cut up quarter size samples and submerged it in straight MEK, lacquer thinner, 100LL and acetone for a couple weeks. I removed the samples and none were soft, sticky or showed any loss of integrity. This is a QC problem! Believe or say what you want, this is a QC issue. Rick Galati is dead on with his thoery.
 
Problem

Guys,
I am not trying to personally attack any of you or your theory's. We all agree there is a problem with some QB and slow build tanks. The thing I have a problem with is the lack of acknowledgement (yeah right) that mother ship contends. The NEW QB7 tanks I have in my paint shop now are evidence of poor workmanship. MS needs to realize there is a problem and try and help us through. I had the owner of the QB7 in my shop call MS on this problem today. MS response was basically what are you talking about, we don't have a problem. Are they going to continue offering us a defective product or fix the problem? They should stop offering QB tanks until a reputable builder is found or add a disclaimer that they are not responsible for QB tanks if you want to gamble with them. Go to the MS website and read all the positive's about a QB kit, including not having to hassle with tank building. Believe me, at this stage I would have loved the hassle of the tanks.
 
Jamie said:
I built a standard kit and have been flying for 2 years, 2 months and so far no blisters.

I am however hesitant to place the blame on the QB factory if for only the following fact: The problem seems to be all-or-nothing. We seem to have tanks with many blisters or tanks with no blisters. To me this is inconsistent with placing the blame on weeping rivets.
Click to expand...

Jamie, with all due respect, I don't think that this is correct (all or nothing). In fact the opposite seems to be true. Most of the pix that I have seen show partial blistering of the tank's rivets (and additional written comments support that). In fact if you go right back through this thread you'll find that partial blistering is the norm....complete blistering of every rivet in the tank seems to be rare.

Incidentally, you state that you have no blisters in your SB tanks. Did you encapsulate your shop heads. It would be handy if from now on every builder, whether they have blisters or not (slow build or quick build), would state whether they encasulated their shop heads or not. We are more likely to see a trend then.
 
This is ridiculous.

The goal is to find a cause for tank blisters.

The proceedure is methodical process of elimination based on fact.

Report fact. Demonstrate logic. Skip the nit-picking, emotion, and opinion, please.
 
Captain Avgas said:
Jamie, with all due respect, I don't think that this is correct (all or nothing). In fact the opposite seems to be true. Most of the pix that I have seen show partial blistering of the tank's rivets (and additional written comments support that). In fact if you go right back through this thread you'll find that partial blistering is the norm....complete blistering of every rivet in the tank seems to be rare.
Click to expand...

You are right. I am aware of what you are saying and simply misspoke (mistyped?). What I meant to say is that people having this issue have a lot of rivets showing the problem...it's hardly ever, if at all, one or two rivets. That was my point.

For what it's worth, I guess you can say I encapsulated the rivets in sealant. It was a mess. The internals of my tanks are not neat. I did use lots of sealant though.
 
DanH said:
And it's a darn good question too.

I'm not an old-time RV guy, so please excuse me if I'm being dumb. We all say "proseal", but am I correct in thinking the Proseal brand is a product of PRC-DeSoto, a division of PPG?

Am I also correct in thinking Vans did sell/specify the PRC-DeSoto product at one time, but now sells a Flamemaster Corporation sealant?

So when did they switch?
Click to expand...

I think proseal gets thrown around as a generic term for fuel tank sealant just like cleco does for temporary skin fasteners.

I don't think any documentation ever specified a specific sealant but for many years Van's did sell the tank sealant product distributed my Morton Thiokol.

I believe the change to the Flame master product was about 5 years ago but I am not sure of the exact time.

I have personal experience with the flame master sealant on about 6 fuels tanks. Two of those tanks have had extensive use with auto fuel containing 10% ethanol. The mixing of the sealant assembly of the tanks, and performance of the tanks in service since being built has all been the same as my experience with the Morton Thiokol sealant.

Thanks Dan...
This is the type of analysis that needs to be done to gain an understanding of what has caused some tanks to do this and many others not do it.
 
FWIW, some of the QB proseal was tacky on the one tank closeout.
Incidentally this tank is the one with the leaking rivets and lots of blisters.
So maybe the prep or mix is wrong on this tank. The other tank had far fewer blisters and absolutely no leaks.
Also note that when I systematically popped the blisters, some had blue goo inside which is avgas residue.
I drilled out the several leaking rivets, mixed proseal and used cherry max in the holes. Leaks gone.
The blister rivets have had the paint removed . The rivet head has been touched up with a fine brush.
The above has sorta fixed the problem.
Every 6 months or so I have to touch up a rivet that blisters or sweats blue dye.
 
rvbuilder2002 said:
Rick,
I fully understand all of the points you make above but as you said your self in the above quote. These are your standards. I am not saying their is anything wrong with them. In fact they are good standards for builders to follow to help minimize the chance of any leaks.

Where I disagree is the implication that because you have seen Q.B. tanks that obviously do not meet your standards, that that is the reason for paint blisters happening on RV tanks....
Click to expand...
Scott,

I agree the points I raised are good standards for builders to follow but it is unclear to me why you would suppose they are my standards. Thanks for giving me the credit but just so we are clear, they are NOT my own particular self developed standards. Those standards I cite are based upon FORMAL training with proseal, not stuff read on forums, not passed down folklore, not personally developed techniques, but real honest to goodness classroom training with a pass or fail written examination and practical lab experience. Just so we are clear....

In at least one case of paint blisters, the poster has eventually admitted that he might have thinned the proseal with MEK. I am virtually certain (as you probably are) that Morton Thiokol the likely manufacturer of the proseal would not approve. Still, as that example shows, people continue to do things based upon hearsay and an example of why quality control can be all over the map when it comes to homebuilding.

Now I have offered...not just words but photographs when possible to support my contentions. I loathe to repeat myself, but here it is again as it relates to those very same QB tanks. A set rivet can be measured and is either acceptable or unacceptable. No matter what my personal standards are, these rivets are not acceptable yet like everything else, there are going to be a certain number people who will challenge and deny anything wrong at all. So be it. But it does not take a rocket scientist to suppose that if this QB rivet quality existed INSIDE that same fuel tank and not encapsulated with proseal as a last resort, (remember the builders manual?) fuel will almost certainly seep down one side of the rivet hole and eventually find its way to the painted surface. Given the "quality" standard that is outwardly visible here, who am I to suppose that same level of quality does not exist elsewhere, unseen within the dark confines of that same fuel tank? Whether one chooses to agree or not, I am only working with information I have at hand.

Maybe by way of explanation there is something to be said for a particular formulation of proseal or solvent reaction, or sanding issues or priming issues or whatever else has been tossed out there to explain paint blisters. Age and life experience has taught me (and sometimes painfully) to never categorically rule anything out so I don't. But until that day comes, I can only work with what we know so far. From my vantage point, misapplied proseal continues to remain highly suspect. The good news is that for those builders who have yet to build the fuel tanks...I believe they can be reasonably confident that correctly applied proseal continues to remain the most highly addressable solution put forward thus far.

nvyud5.jpg
 
rvbuilder2002 said:
...for many years Van's did sell the tank sealant product distributed by Morton Thiokol. I believe the change to the Flame master product was about 5 years ago but I am not sure of the exact time.
Click to expand...

Thank you Scott. Can the two products be identified visually, ie different shades of gray or some other property?

BTW, the technical bulletin for Flamemaster/ChemSeal CS3204 can be found here:

http://www.flamemaster.com/TechnicalsPDF/cs3204.pdf
 
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I suspect a lot of the folks following this thread are doing so in anticipation of building their tanks.

Trying to learn as much as they can, to insure no leaks/paint blisters etc.

Here is a well written, detailed description of what to do when building your tanks.

Not gonna help us QB types, but if it helps you slow builders, well, I am glad I brought this back.

Good luck, enjoy.
 
Took a look in my tanks.
My rivets are encapsulated and a bead on both sides of the rib seams.
They start as a pin and eventually overcome the rivet entirely.
blister1sm.jpg


blister2sm.jpg
 
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Pete's one-tank only raises interesting points

There is some trend evidence before us that seems to have gotten missed in the discussion.

First, a point someone made above - why do tanks get either widespread blisters, or no blisters at all?

Second, Pete above in post #153 has one tank with blisters, one without.

Both of these points suggest that there is something in the particular patch of proseal that allows the fuel vapor to propogate through.

Kahuna admitted to thinning proseal. I'm thinking that a worthwhile hypothesis is that sometimes, the QB guys do something to the proseal. Whether it is out of date, mixed wrong, thinned with a solvent, left too long after mixing, something.....
When they do it, you get blisters. When they don't, no blisters. Whatever it is, they do it often enough that it seems to be considered 'normal' to them.
And sometimes slow builders do it too.

No doubt the surface prep, fillet technique, rivet squeeze, rivet encapsulation are all contributing factors that would make some areas have problems, even with good proseal. And it shows a general lack of QC. And sometimes the tanks even leak in a few spots. But when hundreds of rivets get blisters on a tank, and a different tank, built at a different time, gets none....to me this says something more systematic in the proseal itself.

One example picture in a previous post was of the fuel cap flange with blisters. It was on a beautifully painted blue wing. Here is a part that is very simple to install with good proseal squeeze-out, so even the poorest workman in the factory ought to be able to get that installed so it doesn't leak. Yet it is forming blisters. I think it is important to consider that something may have been done to the proseal to degrade its performance.

Also just to state the obvious - the fact that many folks find blue dye inside the blisters, and one with mogas found yellow dye - well this blows out of the water the suggestion that it is surface prep solvents that can't escape. That argument is clearly specious. Fuel vapor is getting between the rivet head and the paint.
 
Kahuna said:
Took a look in my tanks.
My rivets are encapsulated and a bead on both sides of the rib seams.
They start as a pin and eventually overcome the rivet entirely.
Click to expand...
Kahuna,

Here's my take and I'll use an analogy many homeowners know all too well. Sometimes a ceiling on one side of a house will drip water when the hole in the roof that is actually allowing rain to enter is located some distance away.

How can such an analogy apply to that undeniable blister shown in your fuel tank photo? A possible explanation for that blister is that a void exists somewhere in the fay sealed boundary between the filler flange and the skin and fuel has found its way through it. If that is true, rivet shop head encapsulation will be of no help.

2m81f01.jpg

2j5ckz4.jpg
 
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That drawing illustrates just how difficult it can be to eliminate ALL paths for vapor, especially on things like the rear baffle that get slid into place. It seems to me that maybe the solution we should be looking for is a primer that will not lift when exposed to fuel vapor.
 
You might be on to something----

szicree said:
It seems to me that maybe the solution we should be looking for is a primer that will not lift when exposed to fuel vapor.
Click to expand...

Or, maybe a barrier material that can be applied prior to the paint primer.

Someone mentioned epoxy and a small round of glass cloth, but I would think that would take a lot of work to keep it from being visible in/under the finished paint job.

For all you painters out there, any bullet proof, impervious primers available??
 
Upon further review........

I have small blisters just beginning on the pilot side as well. We popped a bigger one on the passenger side tonight and it was interesting:

Paint%20Blisters%20013.jpg


It contained some thin, brownish liquid that oozed out. Maybe a faint petroleum odor, but not avgassy. (never used mogas) Notice the rivet behind it looks just fine, but the one ahead is starting to blister.

Taking a borescope inside shows the same rivet line from the inside:

Paint%20Blisters%20032.jpg


Everything is covered - draw your own conclusion. 3..2..1.. Speculate!
 
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RE:Type of paint

Hi Pete

Great Info. What type of paint system on your airplane???

Frank @ 1L8 ...RV7A... Phase 1


petehowell said:
I have small blisters just beginning on the pilot side as well. We popped a bigger one on the passenger side tonight and it was interesting:

Paint%20Blisters%20013.jpg


It contained some thin, brownish liquid that oozed out. Maybe a faint petroleum odor, but not avgassy. (never used mogas) Notice the rivet behind it looks just fine, but the one ahead is starting to blister.

Taking a boroscope inside shows the same rivet line from the inside:

Paint%20Blisters%20032.jpg


Everything is covered - draw your own conclusion. 3..2..1.. Speculate!
Click to expand...
 
Dumb Questions ?

In post 166 (Kahuna) and 168 (RickG), it looks like both blisters are clear as if there is lifting between a clearcoat and basecoat. So that raises the dumb questions:

If there is no clearcoat, then why can we see the painted rivet through the blister?

If there is a clearcoat, that would explain the transparentcy but it would also make it highly unlikely that anything could ease in between a clearcoat and basecoat and separate it unless the contaminent itself was between them at the time of application?

Probably missing something but thought I would ask?

BTW, my 7a tanks are mid year 2003 and have a full fillet of Proseal covering the entire rib(s) as far as I can see just looking through the tank gauge plate. Neatly done but a LOT Of wasted Pro-Seal. The Pro-Seal on the outside rib is still flexible and shows no degradation after being in a hot warehouse for the past 6 years. I "think" Vans told me this is from the Philliphines Serial #71444

Thanks
Bill S
7a finishing
 
Another variable MAY be important

with QB and some SB tanks. That is the position of the vent line and it's proximity to the top/outboard edge of the tank. I have QB wings, but they are not painted yet. I have, however installed Andair fuel caps, and though I love them, I've had some weeping of fuel or fuel dye from the caps after a fillup. Investigating, I found that the QB internal tank vent line was not chamfered and placed as close as practical to the top outboard edge of the tank. When I fill the tanks, and a few minutes later reopen the cap, it burps quite a bit of fuel. Blowing on the vent outlet near the firewall clearly clears a slug of fuel in the vertical part of the vent line. My theory is that PART of the blister issue could be poorly placed vent lines (inside the tanks) that results in higher tank pressures as the tank heats up. This of course would be a tougher test of the riveting and proseal job done on the tanks. This MIGHT explain why one tank would exhibit blisters while another (even on the same plane?) would not.

Maybe those with the futbol syndrome could check their vent lines to see if they get more pressure buildup than necessary due to the position of the vent line inlet inside the tanks.
 
petehowell said:
It contained some thin, brownish liquid that oozed out. Maybe a faint petroleum odor, but not avgassy. (never used mogas)
Click to expand...

Pete, would you say the blister was full of liquid, half full, or or just had a trace of liquid?

Everybody else with blisters; you see what Pete did, just a pin prick does the trick. Let's get a few more quantity indications, and it would be nice if you collected some samples on a clean media.
 
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No Pattern

DanH said:
Pete, would you say the blister was full of liquid, half full, or or just had a trace of liquid?
Click to expand...

Hiya Dan - one was nearly full(the one in the pic), one was half full - the biggest one I popped was empty:confused:

No pattern - we did not pop all of them, only about 6. I was expecting blue dye - none to be found.....

Sorry for the bad steer on the one side only - I should have looked better in good light like we did tonight. They are starting on the other side, too.

Good thing I planned for my next plane to win the Grand Champion;)

Alex and I decided I just have to keep flying and putting fuel in it to see what happens. I fully respect the guys with great paint that this is a big deal to. I am not happy, but then again, I haul dogs in my plane. I am still amazed that I built it and it actually flies.....
 
Mike S said:
Or, maybe a barrier material that can be applied prior to the paint primer.

Someone mentioned epoxy and a small round of glass cloth, but I would think that would take a lot of work to keep it from being visible in/under the finished paint job.

For all you painters out there, any bullet proof, impervious primers available??
Click to expand...

I think the gold standard for gasoline resistance is a specialty epoxy called novolac epoxy. Commercial underground gasoline tanks are made with the stuff. It comes in various viscosities. Some companies sell thin stuff as a high quality slosh.
http://www.caswellplating.com/aids/epoxygas.htm

For new construction, I suppose one could recess the rivets more than normal and fill the recess with the epoxy.

For old tanks, does someone want to try sloshing with the stuff? :eek:

I wonder if one could use the thick stuff instead of proseal? Might have to add some cab-o-sil to thicken it up.

I suppose one could "prime" the entire outside of the tank with it, but I think they recommend at least 20 mils thickness. That tank is going to stand a little proud. ;)
 
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Pete, I wouldn't necessarily expect a visual indication of blue dye. Dye quantity in liquid fuel is low. We see obvious blue stains from continuous leak paths where some quantity of fuel has evaporated and concentrated the dye. Assuming the brownish mystery substance is liquid fuel, the blue could easily be masked by pigment from the CS3204 sealant. If it is condensed fuel vapor it might not contain any dye at all. And yes, at this moment we have no proof of fuel involvement.

Reminder; we're still looking for any report of a blister at a prosealed rivet NOT on a fuel tank. Would all readers kindly examine those areas when you visit your airplane this weekend?
 
petehowell said:
Hiya Dan - one was nearly full(the one in the pic), one was half full - the biggest one I popped was empty:confused:

No pattern - we did not pop all of them, only about 6. I was expecting blue dye - none to be found.....

Sorry for the bad steer on the one side only - I should have looked better in good light like we did tonight. They are starting on the other side, too.

Good thing I planned for my next plane to win the Grand Champion;)

Alex and I decided I just have to keep flying and putting fuel in it to see what happens. I fully respect the guys with great paint that this is a big deal to. I am not happy, but then again, I haul dogs in my plane. I am still amazed that I built it and it actually flies.....
Click to expand...

Pete,
Sorry to hear the blister gremlin has paid you a visit.
Whatever is going on here, it is occuring at random time. The first blisters here began in 2004 and there are a couple new ones this year. All are at the fuel tanks, none anywhere else.
You haul dogs, I go on imaginary combat missions patroling for the enemy (large birds, non RV airplanes). The blisters do not affect the operation. You can't see them from 10,000'. The engine runs great. :)
 
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petehowell said:
Everything is covered - draw your own conclusion. 3..2..1.. Speculate
Click to expand...
I look at all that real estate your photo encompasses and what do I see? The only place a blister occurs is (surprise, surprise) at a fuel tank rivet hole. I think most of us agree that fresh, correctly mixed proseal is compatible with most paints and I think most of us agree that most paints are not compatible with fuel. Without ruling out any other possible scenario such as "surface contamination" in whatever way you wish to frame it, is it possible the blister shown in the photograph may be the result of a paint and fuel or fuel vapors introducing themselves to one another even if only in the slightest trace amount? I wholeheartedly agree with Dan. I would be especially interested if someone...anyone...offered up photographic evidence of paint blistering....not so much of a single, random isolated hole but rather a considerably more compelling argument might be framed IF documentary evidence exists showing a whole series of prosealed rivet holes on an RV that are NOT occuring on the fuel tanks. By way of example, I am thinking maybe some builder out there decided to REALLY fume seal his firewall and wet-installed rivets around its perimeter. Anyone? Well then, if not rivet holes perhaps someone out there has fay-sealed the footsteps, data plate, rudder cable fairings, or other airframe details. Any evidence of paint blistering through the proseal around those areas?
 
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ProSeal / paint data point

[Well then, if not rivet holes perhaps someone out there has fay-sealed the footsteps, data plate, rudder cable fairing, or other airframe details. Any evidence of paint blistering through the proseal around those areas?[/QUOTE]

My steps on the 6A were installed with screws and proseal, with edges nicely filleted. Sealant was slightly out of date tank sealant used by FEDEX in Memphis, so it was not what VAN's sells (I don't think). Paint is AIRTECH Urethane. No issues in 4+ years.

Tanks were assembled in California by Evan Johnson - don't know the type of sealant - whatever Van's had at the time (2001). No issues there either.
 
Just thought of another thing

I did on mine (I have some blisters/no leaks). I recall using a special tank rivet dimple die set (from Cleaveland) that dimpled a little further to allow for the proseal around the rivet head. How many people with blisters remember using this special dimple die set?

http://www.cleavelandtool.com/catalog/sqzsets.html

DIE4263T - TANK DIES 3/32" RIVET - $34.00
Tank dies make deeper dimples to allow for the layer of tank sealer between the rivet and the skin.
Rivets will sit flush with the top of the skin and you will not have to shave them off.

Also, one other thing from the Flamemaster spec for their proseal:

CURE
Specified application and cure schedules are based on the standard conditions of 77°F and 50% relative humidity.
Increased temperature and relative humidity will reduce the work life and speed up the cure while reduced
temperatures and relative humidity will extend the work life and slow the cure. Cure may be accelerated by heating up to 120°F. However care must be exercised to avoid the entrapment of solvent when heat is applied.
 
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Kahuna said:
Took a look in my tanks.
My rivets are encapsulated and a bead on both sides of the rib seams.
They start as a pin and eventually overcome the rivet entirely.
blister1sm.jpg


blister2sm.jpg
Click to expand...

So is it just an optical illusion that the lifting appears to be between a clearcoat and basecoat. Perhaps the whole surface is lifting but it appears that you can clearly see the rivet and a basecoat under the clear blister which would mean that something got between the two. Don't think there is any way fuel or contaminent could get between a basecoat and clearcoat unless it happened at application?

Just wondering why this looks the way it does?

Bill S
 
Everything Lifts

Definitely an illusion, clear and basecoat lifts. Single stage paints without clear also lifts.
 
Leak Paths

Some builders report paint blisters are occuring on the rear baffle of the fuel tanks
yet many people continue to have great difficulty understanding how fuel can be
the culprit because the rivets are located outside the fuel tank (pressure boundary).
Having completed a formal training course working with proseal, I pulled out
some of my old training materials and thought some of its information may be
relevant or at least mildly interesting to some. If nothing else, the definitions
underscore not only the importance of rivet shop head encapsulation but a
high quality fay and fillet seal are vital to insuring long term leak proof security.

DETERMINING LEAK PATHS:

A. Leak Source is defined as the point inside of a pressure boundary
where the leak point originates.

B. Leak Path is defined as the distance a liquid or gas travels from the source to the
next possible exit.

C. Leak Exit is defined as the point outside of a pressure boundary where a leak appears.

2uetuzs.jpg
 
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David-aviator said:
The first blisters here began in 2004 and there are a couple new ones this year. All are at the fuel tanks, none anywhere else.
Click to expand...

David, If blisters are occurring on your tanks years (in this case presumably 5 years) after they were fabricated wouldn't it be fair to assume that this is not a case of trapped solvents. I think we can probably discard that hypothesis. What do you think.
 
hecilopter said:
Also, one other thing from the Flamemaster spec for their proseal:

CURE
Specified application and cure schedules are based on the standard conditions of 77?F and 50% relative humidity.
Increased temperature and relative humidity will reduce the work life and speed up the cure while reduced
temperatures and relative humidity will extend the work life and slow the cure. Cure may be accelerated by heating up to 120?F. However care must be exercised to avoid the entrapment of solvent when heat is applied.
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The point about heat and humidity and accelerated "proseal" cure (read reduced work life) may be very relevant. I lived in the Philippines for 2 years and I can state quite confidentally that the daytime temperatures in Manila (where the QB kits were made up until very recently) are consistently well above 77 degrees F for most of the year and the humidity is WELL over 50% virtually all year around.

You can bet your booty that the QB factory in the Philippines WILL NOT be airconditioned or humidity controlled. That alone may make fabrication of wet wing tanks problematic.

I had a friend who was fabricating composite parts in the Philippines when I was there and he consistently had quality control problems which he attributed to the high temperatures and oppressive humidity.
 
Treatment?? 3rd try--What now??!!

While the causation seems to be the focus here--reasonable enough--what about the treatment?

I have qb tanks, 50ish blisters per tank, no dye, no streaks, no fluid. Just a bunch of tank only blisters.

What do I do to seal this thing up?
 
We have two parallel blister threads at the same time. Those interested in the blister problem should make an effort to follow both.

Chuck, finding a cure here is pretty the same as the MD business; we can't proceed with a treatment until we clearly define the cause.

I've proposed we quit fooling around and get some hard evidence via a test lab. First step is to confirm or eliminate fuel as a contributor to the blister problem. If we confirm fuel components in a blister, we know we have a liquid or vapor leak from inside the tank. If there is no evidence of fuel, we concentrate on factors external to the tank. Internal/external will have very different cures.

Hang loose; the lab has asked for more information so we can plan a test course. Basic stuff....they're not airplane people, so they don't know anything about rivets, wet wings, and proseal.
 
Dan I have a couple of un popped bubbles.
If I pop it, there will be no fuel there, no evidence of fuel.
Let me know if there is some procedure you might like me to do on these un-popped blisters.
 
Kahuna said:
Let me know if there is some procedure you might like me to do on these un-popped blisters.
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Exactly right. Proceedure and packing may be important and I'll be talking to the lab about it. Just sent them a general info document this AM. Everybody hang loose.
 
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DanH said:
First step is to confirm or eliminate fuel as a contributor to the blister problem. If we confirm fuel components in a blister, we know we have a liquid or vapor leak from inside the tank. If there is no evidence of fuel, we concentrate on factors external to the tank. Internal/external will have very different cures.
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O.K., to add a bit to what you are saying.

I can think of at least 3 types/conditions of riveting that could be identified so as to develop a pattern of blistering.

1. Riveted skin, no proseal, no exposure to fuel.

2. Riveted skin, with proseal, exposed to fuel.

3. Riveted skin, with proseal, no exposure to skin.

As was mentioned in the other thread, proseal is used for other things than tanks.

As of yet, I dont recall hearing of any bubbles on rivets not in the tank area, proseal or not.

Areas I can think of where a riveted surface is also prosealed, but not the fuel tanks------ RV 10 elevator and rudder trailing edges, firewall to side skin.

Any others ????

Todd S did his entire plane with it, IIRC.

I am going to stare a thread with a poll to gather this data.
 
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Plenty to sample.....

I have plenty of tank rivet blisters to sample, top and bottom, but not one anywhere else.

The ones I have opened have never had fluid or wept blue since.
 
chuck, as i see it vans sold a product(QB wing with finished sealed tank ). if it cannot be painted because it bubbles the paint around , and only around the tank rivets , any lay person, such as would sit in judgment of this issue would deduce that vans sold a wing with a leaky tank. what should happen is vans should step up and provide a replacement product that doesn't leak and the cost to replace and repaint. probably short of some action to compel this sort of appropriate response there is no fix and people who have been complaining for years about this condition of their pride and joy will be no further along in solving the problem they never created in the first place, and should never have had to deal with. the cavalier response to date from vans leaves me cold. people paid a lot of money for these QB products and in spite of all the complaints, i do not hear much coming from vans. i do not intend to let the matter remain unresolved. N661G / ugly bubbles
 
Please forgive what may be a stupid question, but if fuel vapors under pressure are what are creating the blisters, couldn't I just pop the first one to avoid more?
 
One thought to start forward....

I think I will sand the paint off a strip of several, maybe 10 bubbles and do a little test. The first 2 I will clean with acetone only, the next two clean and apply green loctite, next two clean and apply some epoxy. Not sure what to apply to the last 4.....suggestions??

After appropriate dry time then apply some good quality, high adherence vinyl trim tape to this row and see what happens?

Opinions?

Suggestions?

Odds for side bets???
 
szicree said:
Please forgive what may be a stupid question, but if fuel vapors under pressure are what are creating the blisters, couldn't I just pop the first one to avoid more?
Click to expand...
I have thought about the very same thing. If yours is a stupid question, then here is a stupid answer. If it were MY airplane, I would give it a try because it seems to me that a simple pin prick to lance a developing baby blister would be sufficient to relieve outward pressure. Who knows? Caught in time, you may get lucky and the paint might eventually settle down.....just like a lanced air bubble in a freshly applied vinyl graphic causes the vinyl to eventually settle down and conform to the surface. Pure 100% speculation on my part, but what can it hurt?
 
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