Jamie
Well Known Member
As is often my custom, a couple of weeks ago I snuck out to the hangar during my lunch break from work and was going to go up and get some therapy, as my wife calls it. The first thing I noticed when opening the hangar door was a big blue puddle under the wing! Doh!
Here's a crummy iPhone photo of the bottom of the wing.
I pulled the wing root fairing that day but of course blue dye was all around the wing root and it was near impossible to determine where it was actually leaking from. Plus fuel stains were present all the way up to the middle of the tank along the tank skin/fuselage skin joint, so to be 100% sure I was going to need to pull the tank.
I ordered up some proseal and finally made it out to the hangar to work on it this weekend. I pulled the tank, rigged up the balloon, lightly pressurized the tank and found the culprit almost instantly.
This is the lower, aft-most corner (probably the most common place for fuel leaks on these tanks). Of course the tank was a bit dirty with the fuel splashing around in there.
Now, for the interesting part. The sealant in that area was coming off with just my finger. Yes, nasty, uncured sealant. It smelled like sealant, it did the finger-to-finger booger-like transfer that proseal is famous for, etc. There was 'wet' sealant along that corner and along about 6 inches of the rear baffle. The rest of the sealant was of course hard and cured as expected.
Using MEK I was able to remove that uncured sealant very, very easily. After doing some searching here on VAF I found a couple of posts where other people were reporting the same thing with uncured sealant.
I resealed these joints and I don't suspect that will be leaking any more in this location. This experience does leave me slightly concerned though and with the following questions:
1) What causes the uncured sealant? Improper mixture would be the most likely explanation, although I don't think this is the culprit (I was quite careful measuring sealant back then).
2) What is the effect of this uncured sealant breaking down into the fuel and making it's way into the engine?
Here's a crummy iPhone photo of the bottom of the wing.
I pulled the wing root fairing that day but of course blue dye was all around the wing root and it was near impossible to determine where it was actually leaking from. Plus fuel stains were present all the way up to the middle of the tank along the tank skin/fuselage skin joint, so to be 100% sure I was going to need to pull the tank.
I ordered up some proseal and finally made it out to the hangar to work on it this weekend. I pulled the tank, rigged up the balloon, lightly pressurized the tank and found the culprit almost instantly.
This is the lower, aft-most corner (probably the most common place for fuel leaks on these tanks). Of course the tank was a bit dirty with the fuel splashing around in there.
Now, for the interesting part. The sealant in that area was coming off with just my finger. Yes, nasty, uncured sealant. It smelled like sealant, it did the finger-to-finger booger-like transfer that proseal is famous for, etc. There was 'wet' sealant along that corner and along about 6 inches of the rear baffle. The rest of the sealant was of course hard and cured as expected.
Using MEK I was able to remove that uncured sealant very, very easily. After doing some searching here on VAF I found a couple of posts where other people were reporting the same thing with uncured sealant.
I resealed these joints and I don't suspect that will be leaking any more in this location. This experience does leave me slightly concerned though and with the following questions:
1) What causes the uncured sealant? Improper mixture would be the most likely explanation, although I don't think this is the culprit (I was quite careful measuring sealant back then).
2) What is the effect of this uncured sealant breaking down into the fuel and making it's way into the engine?
