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  #1  
Old 08-18-2006, 02:26 PM
David-aviator David-aviator is offline
 
Join Date: Feb 2005
Location: Chesterfield, Missouri
Posts: 4,514
Default Paint Blisters/Fuel Tank Rivets

Six or seven reports been filed on another thread on the problem of paint blisters over fuel tank rivets. I sent a summary of those reports to Van's in an attempt to determine what is causing the phenomenon. This is an on going issue that started on my airplane over 2 years ago. I thought I was alone with the problem but that is not true as others are seeing the same thing.

I believe Van's would like to solve the problem but they do not have enough data points to begin an investigation. This was essentially where we left it 2 years ago. What follows is a response from Gus Funnel today on the subject.


We don't have any info on the subject other than what you sent
here. Be assured that if we had an answer, we'd let you know. I
realize that may not satisfy those who believe Van's knows the whole
story, but keeps it locked in a safe with the really good instructions
for the sliding canopy.

These are anecdotal reports, not data that can be analysed. The
paint types and methods of prep and application are mostly
unknown. It references only 6 airplanes out of 4700+ flying, so the
sample is very small. Not all the airplanes are QBs. I guess what one
would like to see is a common thread to distinguish these from other
RVs. I don't see that any conclusion can be drawn from what we
have here, other than that apparently < 0.2% of RV builders have
problems with paint on tank rivets.

Vans


If there are just 6 airplanes out of some 4700+ flying, we have a problem. If there are more, we need to know about it and the circumstances in an effort to determine what is causing it. So, if you've got blisters over tank rivets, please report it.

Thanks.

David Domeier
Troy, Missouri
RV-7A N707DD
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  #2  
Old 08-18-2006, 05:34 PM
casper casper is offline
 
Join Date: Jan 2005
Location: Derby Kansas
Posts: 146
Default Tank Blisters

Quote:
Originally Posted by David-aviator
Six or seven reports been filed on another thread on the problem of paint blisters over fuel tank rivets. I sent a summary of those reports to Van's in an attempt to determine what is causing the phenomenon. This is an on going issue that started on my airplane over 2 years ago. I thought I was alone with the problem but that is not true as others are seeing the same thing.

I believe Van's would like to solve the problem but they do not have enough data points to begin an investigation. This was essentially where we left it 2 years ago. What follows is a response from Gus Funnel today on the subject.


We don't have any info on the subject other than what you sent
here. Be assured that if we had an answer, we'd let you know. I
realize that may not satisfy those who believe Van's knows the whole
story, but keeps it locked in a safe with the really good instructions
for the sliding canopy.

These are anecdotal reports, not data that can be analysed. The
paint types and methods of prep and application are mostly
unknown. It references only 6 airplanes out of 4700+ flying, so the
sample is very small. Not all the airplanes are QBs. I guess what one
would like to see is a common thread to distinguish these from other
RVs. I don't see that any conclusion can be drawn from what we
have here, other than that apparently < 0.2% of RV builders have
problems with paint on tank rivets.

Vans


If there are just 6 airplanes out of some 4700+ flying, we have a problem. If there are more, we need to know about it and the circumstances in an effort to determine what is causing it. So, if you've got blisters over tank rivets, please report it.

Thanks.

David Domeier
Troy, Missouri
RV-7A N707DD
I have blister on the rivets of my tanks on RV7A slow build, Who do you suggest I report it to.
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  #3  
Old 08-18-2006, 10:58 PM
David-aviator David-aviator is offline
 
Join Date: Feb 2005
Location: Chesterfield, Missouri
Posts: 4,514
Default

Quote:
Originally Posted by casper
I have blister on the rivets of my tanks on RV7A slow build, Who do you suggest I report it to.
Good question.
Kahuna started this thread with "Question on tank vent pressure at high speed", this forum.
Perhaps, to get things organized, we should tack the blister story to his thread answering the following questions.

1. Brand of paint and primer used.
2. Was the surface acid etched.
3. What cleaner was used to wipe down proseal.

Add anything that might point toward a cause of the gas out, extreme temperature swings, etc.

We need to identify a common element.

For example, my skins were acid etched and washed down before paint. For sure some acid came in contact with proseal at some of the rivet heads. We do not know what effect an acid etch would have on proseal, but if every airplane with the problem did an acid etch, it is a valid area to investigate.

There is a common thread. We need to find it.

dd
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  #4  
Old 08-19-2006, 07:17 AM
ronoc74 ronoc74 is offline
 
Join Date: Jan 2005
Posts: 72
Default

Just a thought: maybe solvent from the paint seeps into the tiny gap between the rivet head and the skin (if not filled with proseal), is trapped when the paint cures, then is heated by the sun and blows a bubble. For a bubble to grow there must be something to fill it under pressure.

Conor McCarthy
RV-9A 90990 fuselage
QLD, Australia
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  #5  
Old 08-19-2006, 07:29 AM
robertahegy's Avatar
robertahegy robertahegy is offline
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Location: East Troy, WI
Posts: 2,010
Default

I did a QB kit and do not have any blistering on my tanks (or anywhere else). They have been painted for nearly 3 years. My plane is usually hangared, but has been tied down, outside, during trips out west and down south during hot summer months.

I prepped for paint using scotch brite to scuff the surface. No acid was used. I cleaned using laquer thinner, MEK, then finally Polyfiber Paint Cleaning Solvent C-2210. The exterior surfaces were primed with Polyfiber EP-420 white primer. The top coats were done using Polyfiber Aerothane (white and red).

It is very important to let any solvents gas out during painting. Let your epoxy primers cure for 7 days prior to top coating. Lightly scuff the primer coat with scotch brite and clean with C-2210 prior to topcoat.

This worked for me.

Roberta
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Built/Flew an RV-7A
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Ford Expedition and TRICE "Q"
Built Glen L "ZIP" Classic Outboard Runabout and Super Spartan Hydroplane
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  #6  
Old 08-19-2006, 02:33 PM
David-aviator David-aviator is offline
 
Join Date: Feb 2005
Location: Chesterfield, Missouri
Posts: 4,514
Default

Thank you for the post, Roberta.

This helps because we know what did not cause the annoying blisters.

I am wondering about the acid etch process. Not many people do it. Did any of the blister reporters use this process?

dd


Quote:
Originally Posted by robertahegy
I did a QB kit and do not have any blistering on my tanks (or anywhere else). They have been painted for nearly 3 years. My plane is usually hangared, but has been tied down, outside, during trips out west and down south during hot summer months.

I prepped for paint using scotch brite to scuff the surface. No acid was used. I cleaned using laquer thinner, MEK, then finally Polyfiber Paint Cleaning Solvent C-2210. The exterior surfaces were primed with Polyfiber EP-420 white primer. The top coats were done using Polyfiber Aerothane (white and red).

It is very important to let any solvents gas out during painting. Let your epoxy primers cure for 7 days prior to top coating. Lightly scuff the primer coat with scotch brite and clean with C-2210 prior to topcoat.

This worked for me.

Roberta
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  #7  
Old 08-21-2006, 02:56 AM
RudiGreyling's Avatar
RudiGreyling RudiGreyling is offline
 
Join Date: Jan 2005
Location: South Africa, Johannesburg
Posts: 1,324
Default

Quote:
Originally Posted by robertahegy
<Snip>

It is very important to let any solvents gas out during painting. Let your epoxy primers cure for 7 days prior to top coating. Lightly scuff the primer coat with scotch brite and clean with C-2210 prior to topcoat.

This worked for me.

Roberta
Hi Roberta,

very interesting, I have "read" that typically you need to topcoat the epoxy primers within 24 hours, before it Cures. By lightly scuffing I guess you recreate a key.

Regards
Rudi
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"Science, freedom, beauty, adventure...what more could you ask of life? Aviation offers it all" - Charles A. Lindbergh

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  #8  
Old 08-21-2006, 10:05 AM
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osxuser osxuser is offline
 
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Location: Pasadena CA
Posts: 2,490
Default

Does anyone have pictures? This sounds like fuel leaking around the rivets to me. Very common on Mooneys, wet-wing Cessnas, Commanders, and especially Piper PA-28 series. Rivets will start to seep fuel, which bubbles the paint. If it goes on long enough, sometimes the bubbles will crack, and the blue dye will come out. Someone should cut the paint bubbles to see if there is fuel on the inside, if there is, the solution is to pull the tanks and reseal them.
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RV7 emp built
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  #9  
Old 08-21-2006, 10:54 AM
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rvpilot rvpilot is offline
 
Join Date: Jan 2005
Posts: 343
Default Blisters!

Just discovered this problem on my plane a few weeks ago. Been flyin a little over a year. Quick build tanks. Kit serial number 81217. Only a few at this tme. Do not completely cover the rivet head in some cases, in fact, one starts at the edge of the rivet and migrates out. Busted one open about a week or so ago, no fuel from this cut so far. Seems to be another layer of paint or primer visible under the cut.
Other info to throw in the pot-
Three color paint scheme.
Washed wings with purple stuff, wiped down with prep solv before primer was applied.
Did not acid etch , but did use an etching wash primer.
Blisters are only in the red color on the tanks so far, not in the blue or yellow.
Blisters are only on top of the tanks.
Plane is hangered most of the time, but did spent some time outside a few months back, very hot at the time.
Rocket style fuel tank vents.
May try to get some pictures to post tonight.
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Based KCVC (Covington, GA)
RV6A - Gone, but not forgotten!
RV8 - Gone too, now winning races in the RV Gold Class!
RV4 - Flying!!!

Last edited by rvpilot : 08-21-2006 at 11:17 AM. Reason: Added note about vents after discussion with Kahana
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  #10  
Old 08-21-2006, 11:52 AM
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Kahuna Kahuna is offline
 
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Location: Gold Hill, NC25
Posts: 2,425
Default

Used Siken paint system.
COlor is DARK red
Did not use etching acid.
Normal scuff, wipe with MEK, then prep with 2 solutions provided by paint shop. Degreasers I believe.

I have cut a dozen of these blisters and there is no fuel, nor has there been any in the blister. No evidence of fuel ever being in the blister. And after sanding them off, no fuel vents out of the rivet.

I do think this is pressure related. Question for the physics buzzheads. If a 1/4" vent line goes 1' above the tank level, how much pressure builds up in the tank to get that fuel pushed up and out? I have never seen anything come out my vent line. My ventless caps are sealed tight with fuel lube on both the center o-ring and the outter big ring (I hate to see fuel streaming out of my cap on a full tank). Nothing ever vents out of the caps even when very full. So perhaps my very dark red paint heats up the air in the tank and creates pressure, not enough to push out the vent?

Talked to barefoot Billy earlier who just posted before me and he has the 'rocket' style vent tube curled in the wing root and dumping there. So maybe Im off base here. But Im still thinking this is tank pressure related.

Need answer on the tank pressure required to vent.
THanks
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