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Dick Maddux
Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl
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 Posted: Sun Sep 06, 2009 4:52 am Post subject: bubbles under the skin |
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You know, it's always something! Yesterday I noticed some very large and small bubbles under the skin of my aircraft located over my right fuel tank. Some of them were about 4 inches in diameter. These protruded about 1/2 inch above the surface. Now my question is, "what caused that ?" The only thing I can think of is fuel vapor passing thru the top of the tank but after 15 years ??? Anyway I stuck a pin in each one to let the air out and the bubbles dropped flush with the rest of the skin. I quess at this point I will put a damp rag over each "bubble" that I pricked and apply a hot iron in order to shrink the fabric a little and possibly reactivate the glue. Any body ever have this happen? It is only on the right tank and is spread pretty much across the tank area. I was pretty much mentally preparing to yank these tanks out sometime after the first of the year and install new tanks because of the gasohol that is mandated after the first of the year but I hate to do it sooner. In fact I don't want to do it at all. Anyway I will keep a jaundiced eye on it (as I have the Kream in my tank) and prick and iron as necessary (sounds bad huh Lynn )?
Dick Maddux
Fox 4
Milton,Fl
[quote][b]
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Lynn Matteson
Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan
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| Posted: Sun Sep 06, 2009 5:31 am Post subject: bubbles under the skin |
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Sounds bad, alright, but how 'bout injecting some of the proper
"glue" into those pricked holes? In the model planes we would just
prick the holes and run an iron over the area, activating the
adhesive. But in our "real" planes, maybe the person who applied the
covering over the tank area didn't apply enough Poly Brush over the
area. At least that's what I recall doing to mine. I know I applied
Poly Brush over the ribs and the false ribs (yes, I made up false
ribs to go over the tanks), but have to admit that I don't recall
whether I applied it over the whole tank or not...I'll have to look
at my pictures or re-read the directions which I followed to the
letter (those that made sense, anyway..: ) ).
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 758.3 hrs
Sensenich 62"x46" Wood prop
Electroair direct-fire ignition system
Rotec TBI-40 injection
Status: flying
On Sep 6, 2009, at 8:50 AM, Catz631(at)aol.com wrote:
| Quote: | You know, it's always something! Yesterday I noticed some very
large and small bubbles under the skin of my aircraft located over
my right fuel tank. Some of them were about 4 inches in diameter.
These protruded about 1/2 inch above the surface. Now my question
is, "what caused that ?" The only thing I can think of is fuel
vapor passing thru the top of the tank but after 15 years ???
Anyway I stuck a pin in each one to let the air out and the bubbles
dropped flush with the rest of the skin. I quess at this point I
will put a damp rag over each "bubble" that I pricked and apply a
hot iron in order to shrink the fabric a little and possibly
reactivate the glue. Any body ever have this happen? It is only on
the right tank and is spread pretty much across the tank area. I
was pretty much mentally preparing to yank these tanks out sometime
after the first of the year and install new tanks because of the
gasohol that is mandated after the first of the year but I hate to
do it sooner. In fact I don't want to do it at all. Anyway I will
keep a jaundiced eye on it (as I have the Kream in my tank) and
prick and iron as necessary (sounds bad huh Lynn )?
Dick Maddux
Fox 4
Milton,Fl
www.matronics.com/contribution _-
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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM |
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Lynn Matteson
Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan
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| Posted: Sun Sep 06, 2009 1:24 pm Post subject: bubbles under the skin |
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Now that I look at the tank areas of my wings, I see that the fabric
IS bonded to the tanks, but only because the Poly Brush soaks through
the fabric, and where it touches the tanks, it is bonded to the
tanks. Where it is not in contact with the tank....where it lifts
away to tangent up and over each rib....it is of course not bonded
there. So I guess if I was not going to remove the tanks, I would
either inject some Poly Brush under the bubble, which might soften
the color coat, and therefore require some finish work, or MEK the
whole area down to the bare fabric, and then apply Poly Brush
liberally through the fabric, thereby bonding the fabric to the tank.
But before doing this, I'd make sure that the fabric was shrunk with
the iron.
Then do the normal spray coats of Poly Brush, Poly Spray, etc. At
least that's the way I THINK it should happen....I've been wrong
before though....once. : )
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 760.3 hrs
Sensenich 62"x46" Wood prop
Electroair direct-fire ignition system
Rotec TBI-40 injection
Status: flying
On Sep 6, 2009, at 9:27 AM, Lynn Matteson wrote:
| Quote: |
Sounds bad, alright, but how 'bout injecting some of the proper
"glue" into those pricked holes? In the model planes we would just
prick the holes and run an iron over the area, activating the
adhesive. But in our "real" planes, maybe the person who applied
the covering over the tank area didn't apply enough Poly Brush over
the area. At least that's what I recall doing to mine. I know I
applied Poly Brush over the ribs and the false ribs (yes, I made up
false ribs to go over the tanks), but have to admit that I don't
recall whether I applied it over the whole tank or not...I'll have
to look at my pictures or re-read the directions which I followed
to the letter (those that made sense, anyway..: ) ).
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 758.3 hrs
Sensenich 62"x46" Wood prop
Electroair direct-fire ignition system
Rotec TBI-40 injection
Status: flying
On Sep 6, 2009, at 8:50 AM, Catz631(at)aol.com wrote:
> You know, it's always something! Yesterday I noticed some very
> large and small bubbles under the skin of my aircraft located over
> my right fuel tank. Some of them were about 4 inches in diameter.
> These protruded about 1/2 inch above the surface. Now my question
> is, "what caused that ?" The only thing I can think of is fuel
> vapor passing thru the top of the tank but after 15 years ???
> Anyway I stuck a pin in each one to let the air out and the
> bubbles dropped flush with the rest of the skin. I quess at this
> point I will put a damp rag over each "bubble" that I pricked and
> apply a hot iron in order to shrink the fabric a little and
> possibly reactivate the glue. Any body ever have this happen? It
> is only on the right tank and is spread pretty much across the
> tank area. I was pretty much mentally preparing to yank these
> tanks out sometime after the first of the year and install new
> tanks because of the gasohol that is mandated after the first of
> the year but I hate to do it sooner. In fact I don't want to do it
> at all. Anyway I will keep a jaundiced eye on it (as I have the
> Kream in my tank) and prick and iron as necessary (sounds bad huh
> Lynn )?
>
> Dick Maddux
>
> Fox 4
>
> Milton,Fl
>
> www.matronics.com/contribution _-
> ============================================================
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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM |
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n61kf
Joined: 27 Aug 2006
Posts: 23
Location: Waynesville Ohio
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| Posted: Sun Sep 06, 2009 3:33 pm Post subject: Re: bubbles under the skin |
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Dick,
I have the same thing going on the surface over my tanks. I have not attempted a cure yet, but was leaning toward injecting some thinned polytac under the bubbles.
I had this same thing happen with poly-fiber over fiberglass leading edges on my Skybolt, so I'm not so sure that fuel has anything to do with it.
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Keith Schneider
Red Stewart Airfield
Waynesville Ohio
KF IV 912ul |
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lcfitt(at)sbcglobal.net
Guest
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| Posted: Sun Sep 06, 2009 6:44 pm Post subject: bubbles under the skin |
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Lynn,
Got a question. Are the bubbles under the fabric, or between the fabric and
finish coat?
I had very small bubbles - to 1/4", most much smaller between the fabric
and finish coat, and they were all filled with fuel. I resloshed the tank,
and lived with the bubbles. I was able to reduce the larger ones by shaving
with a razor blade and touching up the aerothane with a touch up brush.
If they are larger and under the fabric, maybe one suggestion. I found once
that using one of the Polyfiber adhesives - solvent based, caused an ugly
wrinkling of the paint layer - sort of like crinkle paint. I then tried
injecting unthickened structural adhesive and moving it around under the bad
area with a roller. That worked fine and no change to the surface.
Lowell
---
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Lynn Matteson
Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan
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| Posted: Sun Sep 06, 2009 7:07 pm Post subject: bubbles under the skin |
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Lowell-
I assume you meant to address this to Dick...he's the one with the
bubbles. : )
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 760.3 hrs
Sensenich 62"x46" Wood prop
Electroair direct-fire ignition system
Rotec TBI-40 injection
Status: flying
do not archive
On Sep 6, 2009, at 10:31 PM, Lowell Fitt wrote:
[quote]
<lcfitt(at)sbcglobal.net>
Lynn,
Got a question. Are the bubbles under the fabric, or between the
fabric and finish coat?
I had very small bubbles - to 1/4", most much smaller between the
fabric and finish coat, and they were all filled with fuel. I
resloshed the tank, and lived with the bubbles. I was able to
reduce the larger ones by shaving with a razor blade and touching
up the aerothane with a touch up brush.
If they are larger and under the fabric, maybe one suggestion. I
found once that using one of the Polyfiber adhesives - solvent
based, caused an ugly wrinkling of the paint layer - sort of like
crinkle paint. I then tried injecting unthickened structural
adhesive and moving it around under the bad area with a roller.
That worked fine and no change to the surface.
Lowell
---
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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM |
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Dick Maddux
Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl
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| Posted: Mon Sep 07, 2009 4:39 am Post subject: bubbles under the skin |
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Thanks for the replies Lynn,Keith and Lowell ! Got another flight in yesterday. After pricking the bubbles,they are staying flat to the surface so, so far so good. It's nice to know that I am not the only one who has had this problem. I may or may not use the adhesive under the skin depending on how it goes. It looks nice now and you can't tell where I put the hole in the bubbles. They have not reinflated.
Dick Maddux
Fox 4
Milton,Fl
[quote][b]
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