REFLECTOR: Leaking sump float switch

[Laurencw W. Coen]

I had the same problem and no hard point.  As far as the fuel epoxy 
compatibility, not to worry, your sump is glass cloth and epoxy.  Seems to 
work.  Your plan should work just fine and I would recommend a sealant 
between the switch and the hard point.  Teflon tape or if you're paranoid 
about Teflon getting loose and stopping your engine, permitex #2 will work.

A word of caution about screwing or unscrewing the switch with the sump 
attached to the firewall.  I have a retract and the sump is narrow.  When 
you rotate the switch to unscrew it, the float will drop down and lamb 
against the side of the sump and break.  I solved this problem by shimming 
the float stop so it wouldn't drop so far but plenty far enough to function.

Larry Coen
N136LC SE/RG Franklin

----- Original Message ----- 
From: <wurzel at alumni.caltech.edu>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Sunday, October 09, 2005 12:01 PM
Subject: REFLECTOR: Leaking sump float switch


> So, I started noticing blue dye down the side of (and on the
> floor right underneath) the sump tank.  Turns out fuel is
> leaking either through or around the float switch.  D'oh,
> the one-day annual condition inspection morphs itself
> into a full-on project.
>
> Unfortunately, my float switch isn't screwed into a hard point
> as seems to be the standard these days.  I'm not sure if
> Rick L rolled his own low fuel sensor, or if Velocity
> used to recommend just glassing the switch directly into
> the side of the tank, but in any event it is, in fact, just
> glassed right into the side and providing a lovely 100LL
> aroma to my cabin.
>
> So, I'd like to convert this to a threaded installation.
>
> 1) Any ideas on the easiest way to do this?  My current
> thought is to remove the current switch while taking as
> little of the surrounding material off as possible.  Then,
> sand the outside of the sump tank so it's flat in the area
> where the switch was.  Next, coat the hard point and the tank
> with epoxy and press them together... finally put some glass
> over the outside of the hard point as well (making sure not to
> get any in the threads!)
>
> 2) What do I need to know about fuel and epoxy?  Is there a
> particular epoxy I need to use for this application?  Flox?
> Micro?  Do I have to put some kind of sealant on the inside
> after the epoxy has cured to prevent leaks or deterioration?
> I saw some comments in old posts on using a shop vac to draw a
> vacuum and suck the epoxy in around things, and that sounds
> like a good idea as long as I'm using the right epoxy and it
> doesn't dissolve as soon as the fuel hits it.  :-)
>
> Thanks in advance for the help!
>
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