REFLECTOR: Fuel Tank Fitting

[Andy Millin]

Craig,
 
FWIW.  I'm not flying yet.  Mine test fine, but, I'm still on the ground.
(gulp)
 
Microglass can be porous.  I potted aluminum hard points as well.  The
inside of the tank was coated with Jeffco.
 
Where I potted the hardpoints, I painted the inside skin with Jeffco as
well.  Then the hardpoint was potted with Jeffco and cabo (no glass)  When
the hardpoints were cured in place I put on a fillet of micro and two plies
of bid.  I'm not sure this was necessary as the Jeffco is structural as well
as an excellent sealant.
 
The only other thoughts would be in further diagnosis of the leak location.
My greatest hope and wish is that you have truly located the source and are
just finding a way to make it seal.  Is there any way to isolate the
suspected hardpoint (remove fuel) and then go fly?  Verify that if this
location is sealed the leak is gone?
 
Andy

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Craig and Denise Woolston
Sent: Wednesday, March 07, 2007 9:15 AM
To: 'Velocity Aircraft Owners and Builders list'
Subject: REFLECTOR: Fuel Tank Fitting



I'm embarrassed to even ask this question, but frustration leads me no
choice.  Some how John and I have managed to build an airplane in our garage
that actually flies, but somehow can't manage to make a vessel which will
hold liquid without leaking.  So I'm looking for suggestions and trying to
get a feel for whether we did something odd or not.

 

We made our tanks, sealed with Jeffco, bonded AL hardpoints to the inside
fuselage wall, drilled and tapped for AN fittings for both vent and feed
lines.  Is this not what other people are doing?

 

It appears that we have gotten three out of the four sealed.  We have been
able to confirm (soapy bubbles) that one of the feed lines is leaking where
the thread cut through the fuselage side.  The fuel then travels b/t the
layers of glass until it shows up outside the fuselage at the gear leg
penetration.

 

We've been working on this since Nov. without success.  I've lost track of
the number of fixes we've tried, in summary, we replaces the hardpoint, we
re-coated from the inside, we've glue the fitting in, etc.  It appears that
every fix tests okay on the ground, but fails after we fly.   The latest fix
that has failed was a complete fill of the hole (minus the threaded AL
part), covered with BID, re-drilled and tapped because it appeared that some
of our threads actually cut through fiberglass layers so we ground the
fiberglass away and backfilled with microglass.

 

What are we missing?

 

Craig

N541SW "Blue Streak"

 

 

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