Today's Message Index:
----------------------
1. 02:39 AM - Re: Data points to wing leak (John Bolding)
2. 03:23 AM - Thanks for the input. (MPPalmer@aol.com)
3. 10:03 AM - Re: Vapor pressure and the case of the missing fuel? (John Grosse)
4. 10:51 PM - Still no culprit in "The case of the missing fuel" (MPPalmer@aol.com)
Message 1
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| Subject: | Re: Data points to wing leak |
Mike, Robin
The fix is to pack mill fiber around the bolt heads then a couple layers
of cloth over the whole assy. Easy to say but you gotta be inside the
tank to do it. John
----- Original Message -----
From: RObin Young
To: glasair-list@matronics.com
Sent: Friday, July 11, 2008 11:38 PM
Subject: RE: Glasair-List: Data points to wing leak
I'll plan to pull the inspection panels and hope something obvious
(and easy) shows up.
Anyone know (like Bruce) where fuel leaks tend to occur most
frequently? I'm guessing more in the middle of the tank, where pressures
are highest.
Thanks,
Mike Palmer <><
Mike, the forward attach brackets for the wing are through bolted to
the spar. Early builders had a problem of seepage around the bolts and
a fix was added to the manuals but, at #36 to fly, I don't know what the
fix is. You might check under the seat pans for stains but you would
have noticed the odor if a is stain there.....this leads me to think
there may be a siphon due to low pressure under the wing fairing and
fuel is being pulled from around the attach bracket outside the cockpit.
It is a long shot but worth a look; first at the top of the brackets
and then under the fairings. Godspeed, Robin
Message 2
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| Subject: | Thanks for the input. |
Thanks for the many responses about my missing fuel problem.
For Bruce: After an early failure of the main fuel drain on a freezing cold
morning while in Texas on business (just as Lyle Powell had once written would
happen), I now prophylactically replace the o-ring fittings in the drain every
3 to 4 years or so. They always come out with cracks starting. (The early
failure was due to a sliver of fiberglass jamming the drain. That was around the
first 100 hours or so.) The current drains seem tight. Was at all of them
yesterday.
For Robin: While I always griped about how long it was taking us to build,
all things work together for good... for some. We got the SB in time about
coating the heads of the bolts with lots of glass and resin to minimize leaking.
(As I write this, I think we got the SB after the bolts were in, but before the
wing was closed. I think you were supposed to dip the bolts in resin while
inserting. We didn't do that, but did glass over the heads.) But I forgot that
was a classic failure point, so I'll plan to look there too.
For James: Yeah, I'm hoping the blue stain will be obvious. We have an
Emergency Gravity feed that's fed by a ball valve. We had some leaking with a
fitting there at about 500 hours. (I could smell it back then.) It wasn't much
of a
blue stain, and it's gone now, but I've seen it before, so know what to look
for in the wing. Nothing seen on the hangar floor.
I'm hoping the leak isn't in the middle bay. Should have more data after
Saturday evening.
Mike <><<BR><BR><BR>**************<BR>Get the scoop on last night's hottest shows
and the
live music scene in your area - Check out TourTracker.com!<BR>
(http://www.tourtracker.com?NCID=aolmus00050000000112)
Message 3
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| Subject: | Re: Vapor pressure and the case of the missing fuel? |
When I pressure tested my wing I had leaks that I absolutely could not
find using any of the usual techniques. I finally bought a combustible
gas detector to sniff out the leaks. My tank was dry and I didn't want
to put fuel in it so I pressurized the tank with propane then used the
detector to find the leaks. (I had two in very inaccessible places and
had to cut holes in the wing to fix them, but that's another story.) The
instrument I used was a TIF8800A Combustible Gas Detector that I bought
on ebay for $100. (Mine was new, but used ones are less. Retail is
$200.) It has a probe on the end of a flexible wand that's about 18
inches long so you can get it in some pretty tight spaces. The
sensitivity is adjustable, and it works very well. I was able to
pinpoint the source of my leaks to within an inch or so at pressures
less than 1psi. I'm sure if you have a tank leak you will be able to
find it with this instrument.
Here's a link to one that's on sale on ebay right now:
http://cgi.ebay.com/TIF-TIF8800A-COMBUSTIBLE-GAS-DETECTOR_W0QQitemZ150268327575QQihZ005QQcategoryZ50965QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
John Grosse
Message 4
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| Subject: | Still no culprit in "The case of the missing fuel" |
Basically, nothing found.
I pulled the inspection panels this evening and peered all around the inside
of the inner and outer bays. (I felt like a cancer surgeon, trying to make
sure he hadn't missed anything.) The closest evidence I could find to a leak was
two spots near each other on the roof of the wing, adjacent to the main spar
cap, that I call a "ring spot." You know, like you see in acoustic ceiling tile
when there's a rain leak in a roof. But in my case, the stain is white, not
blue. And there's no corresponding stain on the wing floor.
Hint: When inspecting the wing internals for fuel leaks, do NOT use a new
fangled LED flashlight. Use a conventional bulb. The "white" in an LED flashlight
is too blue. In addition to making the whole wing look like one big fuel
leak, the blue light may actually hide a bona fide leak, as you may not be able
see the blue dye in 100LL. I prefer to use a mini-Mag light with the old
hi-intensity bulb. You can unscrew the lens cap to put the thing in "candle" mode
and
put it in the wing to flood the interior with broad spectrum light. (Don't
forget to take the flashlight out when you're done! I left one in once.
Fortunately, I caught it before buttoning up, but it had been a day later and the
battery died. May be best to leave a long string on these things... )
I also inspected the seat pan areas for leaks, with particular attention to
the wing attach fitting bolts. No leaking evident.
I did not detect the smell of fuel anywhere while sniffing around the panels.
This is getting stranger and stranger.
I checked the fuel level in the mains today again visually. It's gone down a
bit more in one day, but nothing like the first time. On the assumption I may
have made a bad assumption about the wing being full the first time, I will
plan to top it off again on Monday and see what happens with the level after
that. If it goes down, I must have a leak.
I left a sample cup of fuel out on the wing yesterday. It's one of those old
style ones - 1 1/2" diameter, about 1 3/4" tall. To my amazement, a full
sample cup was nearly empty in a little over 24 hours!
Still, that's not 4 gallons in 2 day and I suppose if AvGas were suddenly
evaporating more than it used to, then all sorts of people would be falling out
of the sky due to fuel exhaustion.
I don't know if this indicates a medical condition on my part, but I can't
smell the fuel fumes more than 3 inches away from the sample cup. It doesn't
seem as strong as it used to. (I'm not a smoker, nor have I ever been.)
If the fuel level goes down after a second top off, then my leak must be in
one of the middle bay. (Murphy's Law.) But before cutting into the wing, I'll
plan to do what John did and buy/borrow a propane sniffer and confirm/find the
leak that way before cutting.
My question to those who have had wing leaks... were you losing enough fuel
to where it cut your endurance by an hour?
Mike Palmer <><<BR><BR><BR>**************<BR>Get the scoop on last night's hottest
shows and
the live music scene in your area - Check out TourTracker.com!<BR>
(http://www.tourtracker.com?NCID=aolmus00050000000112)
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