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02-03-2015, 01:06 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Quote:
Originally Posted by BillL
Depending on the answer -the question is - will ALL tanks eventually have leaks at the top where the fuel does not touch when parked?
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No, or thousands of RV's would now be leaking (and that is not the case).
If there is a leak or seep where sealant is always being exposed to evaporating fuel, the sealant will become soft.
If you want to know the chemistry explanation you will have to contact the sealant manufacturer, but they will tell you the same thing
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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02-03-2015, 01:37 PM
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Join Date: Jun 2006
Location: San Jose, CA
Posts: 1,125
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Thanks everybody. It seems like this is a normal phenomenon and maybe not the result of an improper mix ratio. Who knew?
I'm in the middle of cleaning up all the soft stuff and fuel and should have ample amounts of new sealant in place in the interior of the tank in the next day or two. I'll also lop some more on externally just for good measure.
Thanks again!
__________________
Kelly Johnson
San Jose, CA
RV-9A
Pink slip issued: 5/7/12
First flight: 5/28/12, Memorial Day.
Phase I Complete: 8/18/12!
2020 donation: complete
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02-03-2015, 01:58 PM
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Join Date: Jan 2005
Location: St. Paul, MN.
Posts: 4,792
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So I presume the takeaway here is : See a leak? Drop everything and fix the leak?
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02-03-2015, 02:57 PM
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Join Date: Jun 2012
Location: Frederick, MD
Posts: 821
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There are a lot of variants of "Proseal". At least 3 different manufacturers and 2 or 3 varieties for each manufacturer. What stuff are you using on the fuel tanks?
__________________
Dan Morris
Frederick, MD
PA28-140
Hph 304CZ
RV6 built and sold
N199EC RV6A flying
Learn the facts. "Democracy dies in darkness"
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02-03-2015, 04:32 PM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by BillL
What are the bench/lab validation results for dipping in fuel, what are the quantified acceptable parameters for long life?
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There are no standards specific to 100LL exposure. All the standard tests use JRF:
http://standards.sae.org/air4275/
Quote:
Originally Posted by rvbuilder2002
If you want to know the chemistry explanation you will have to contact the sealant manufacturer, but they will tell you the same thing
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Oddly enough, a few years ago my contact at Flamemaster said he knew nothing about it. Mind getting the full explanation for us?
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Last edited by DanH : 02-03-2015 at 04:36 PM.
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02-03-2015, 05:28 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Quote:
Originally Posted by DanH
Oddly enough, a few years ago my contact at Flamemaster said he knew nothing about it. Mind getting the full explanation for us?
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Dan, I have not ever personally talked with anyone at Flame Master about this, but in response to people inquiring with tech support regarding this issue, at least someone at Van's has.
Since I have seen it numerous times (once a very mild case on my own airplane), and the word that someone at Flame Master acknowledged it can happen, that has always been enough information for me.
They way I look at it... I don't need to know why.... I just need to know to always be inspecting for fuel leakage, and then fix it as soon as it is detected.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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02-03-2015, 06:18 PM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by rvbuilder2002
Dan, I have not ever personally talked with anyone at Flame Master about this...
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Sure, sure, but you know how it is...sometimes a vendor will honor a request from an OEM when the rest of us poor schlubbs get blown off. Yet, the schlubbs, being dedicated to education and recreation like we are, would really like to know the chemistry. You could ask 'em to write it down for us, and then post it here. That would be great.
BTW, oxidation is a maybe, but I soaked a cured sealant sample in 3% hydrogen peroxide nearly 4 years without softening. It did eat the metal can.
And I recently examined a softened polysulfide sealant sample taken from inside a tank. It wasn't fully reverted (more like not very sticky week-old chewing gum, or old-fashioned window glass glazing putty), but certainly not normal-as-cured. The owner removed the rivets and easily peeled the skin off the ribs. Samples from the top of the tank (vapor/splash exposure) and the bottom of the tank (submerged exposure) were similar. Samples of the same sealant from outside the tank (zero fuel contact) were solid/normal. Built circa 2005, sealant brand unknown; checking now.
Postscript: Sealant was Chem Seal (Flamemaster) 3204-B....same stuff common to RVs.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Last edited by DanH : 02-06-2015 at 05:48 PM.
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02-03-2015, 06:37 PM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,687
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Maybe it just a coincidence, but everytime I've seen this it was with the flamemaster stuff.
__________________
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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02-03-2015, 08:46 PM
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Join Date: Oct 2005
Location: Highland Village, TX
Posts: 1,520
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Quote:
Originally Posted by Walt
Maybe it just a coincidence, but everytime I've seen this it was with the flamemaster stuff.
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So taking Walt's advice, this is what I just purchased to do the tank on my -12. http://www.skygeek.com/prc-desoto-ps...lant-pint.html
__________________
Rick Aronow,
A&P
Flying 7A Slider;
RV-12 SOLD
Jacksonville, FL
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02-04-2015, 06:38 AM
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Join Date: Jun 2012
Location: Frederick, MD
Posts: 821
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Quote:
Originally Posted by Walt
Maybe it just a coincidence, but everytime I've seen this it was with the flamemaster stuff.
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So this was my point in asking what people were using. The company "Proseal" hasn't existed for years, it was purchased by Courtaulds, then Courtaulds (former PRC) was purchased by Akzo then PPG. or at least something like that. PPG now has the products of both former companies. PS890 is the common and original "Proseal" product that meets Mil-S-8802. PR1422 and PR1440 are of the old PRC products for fuel tank sealant, but there are many others. This could be a product specific problem.
I have some work experience (more than 30 yrs) with PS890, PR1422 and PR1440 and never heard of this problem with avgas. Problems from inproper mixing and curing in an environment that was to cold, yes, but not properly mixed and cured.
__________________
Dan Morris
Frederick, MD
PA28-140
Hph 304CZ
RV6 built and sold
N199EC RV6A flying
Learn the facts. "Democracy dies in darkness"
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