Recently completed QB RV-14 painted by a professional 10 months ago. Spectacular paint job. Both fuel tanks bubbling along the same single rivet line (top only). Anybody have any history with this?
Can you elaborate what is the cause/poor workmanship and what would prevent it?Yes, not on a 14 but on a -10. It has to do with the poor workmanship done in the Philippines. Unfortunately, this is the price you pay for having someone else assemble part of your aircraft.
-Marc
Can you elaborate what is the cause/poor workmanship and what would prevent it?
What we have seen is inadequate use of proseal on mine and other QB wings. In one of my wings there was still a paper sticker on the aluminum INSIDE the fuel tank! Vans instructions say to test the fuel tank for leaks but those leaks don't always show with the slight pressurization recommended.
If I were going to buy a QB kit I would try to have it done sans tanks and do them myself. Otherwise your only option is to use the Vans tank repair kits and personally seal each tank bay.
-Marc
Paul, I agree completely. I have had two sets of QB tanks that they did not leak at all but they did have the bubble under the paint. I have also seen slow build tanks that had bubbles so it is not necessary limited to the QB tanks.This has been a big topic of discussion here on the forums over the years - it goes back to the very beginning of VAF, so you should be able to do a search and find some great threads. A lot of data collection has been done in the past, and while folks like to throw out specific causes for it, the data has ben somewhat inconclusive when actually analyzed - there are a number of causes that have been cited, and some specific fixes.
The factory is well aware of the issue as well, and has contributed to the discussions in the past - if it had a simple solution, it would have been solved - but apparently, it is still elusive.
Just some background from an “old timer” (who has had one or two suspect bubbles, but nothing extensive).
Paul
A lot of data collection has been done in the past, and while folks like to throw out specific causes for it, the data has been somewhat inconclusive when actually analyzed
Paul, "inconclusive" is hearsay, or personal analysis? And what database?
There are a few clear conclusions. First and foremost, it's not solely "poor workmanship in the Philippines". The blister database included a high percentage of owner built tanks.
Recently completed QB RV-14 painted by a professional 10 months ago. Spectacular paint job. Both fuel tanks bubbling along the same single rivet line (top only). Anybody have any history with this?
That's true, but the OP referenced QB tanks and those were only made in the Philippines. Certainly a home builder could muck up the tanks on a slow build but that wasn't what the OP was asking about.
In the case of my airplane I spoke with the builder and was told "The tanks leaked like a sieve" when they were tested. Examination of the quality of the tank-build showed poor workmanship.
Now I would think that after assembling a few QB tanks the quality would improve but reports here indicate otherwise.
In dealing with my own tanks I spoke with Paul of Weep No More and he told me that they offered to build the tanks for the QB wings but Vans turned them down. I expect that the price point didn't work for Vans but I really don't know.
-Marc
the old saying goes "good, fast, cheap - pick two."
Paul, "inconclusive" is hearsay, or personal analysis? And what database?
I'm only aware of one, covering 18 builders and a bit more than 30 variables. Very few have seen it. One who did, a lawyer named Robert Brunkenhoefer, threatened to sue Vans, so it's been buried a long time. Thank him.
There are a few clear conclusions. First and foremost, it's not solely "poor workmanship in the Philippines". The blister database included a high percentage of owner built tanks.
Anybody have any history with this?
Anybody have any history with this?
It is interesting to note that in all the cases I know of, only the top of the tank rivets bubbles and I wonder if sun has any affect on it. I can't understand why not the bottom of the tanks.
Several wild theories like needing to encapsulate rivet shop heads in proseal. May help for rivets inside the tank but does not make sense for rivets outside the tank, like along rear baffle.
Unfortunately, none of this is of any help for owners of QB tanks
It's not a wild theory. It's an aerospace standard, straight from AIR4069 Rev.A, reproduced below.
The rearmost rivet line, outside the tank, is fay and filet seal only. Apples and oranges. Unlike the rib lines, there is no intentional fuel contact at the rivet location.
Again, this was never a QB-only problem...and solving the riddle meant finding factors common to failed QB and owner-built tanks.
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Makes sense - except that I carefully encapsulated all my stringer and baffle rivets, and I still have bubbles - top and bottom.
The standard relates to liquid leak paths, not blisters.
The evidence says blister formation requires gasoline vapor as one of several factors. Fully cured polysulfide sealant is vapor permeable. Although additional thickness helps mitigate vapor permeation, it does not eliminate it.
If that were true, then every painted tank built with proseal would have blisters.