Hi Jesse
Good question.
In Canada you must use at least 3/8" tubing so that an air bubble
doesn't restrict flow too much and so that an air bubble has a fair
chance of percolating back up the line to the tank. Since 3/8" tubing
matches the size of a 1/4"NPT fitting I would be very surprised if an
inspector would allow anything smaller. I would not want anything
smaller in my plane. The hole in a 1/8NPT fitting is no where near as
large as 3/8 tubing.
In regards to the other discussion on sumps. The inpector who did my
plane was very knowledgable on fuel systems and I believe has experience
designing certified fuel systems. He clearly wanted to see a drain at
every low point in the fuel line. As I understand it, it seems that
during off season storage water has been known to separate out of fuel
trapped in a fuel line, then freeze and create a partial blockage and
problems after takeoff. Personally I don't think there is much chance of
that happening or much chance of a precisely located drain collecting a
few drops during thaws so I was surprised to hear of such a scenario.
However I like to defer to folks with more experience and as has been
mentioned, we are starting into an era where alcohol is an additional
concern. As yet another possibility, a t least one Rebel ran the fuel
lines behind the doors and out the center bottom of the fuselage then
forward along the exterior centerline of the fuselage as per some of the
dehavilland airplanes.
Ken
Jesse Jenks wrote:
Ken,
Is there a reason not to just use a 1/8 NPT "T" and 1/8 NPT X 1/4 tube
nipples? That way you would eliminate the reducer and save some vertical
space.
Jesse
From: Ken <
klehman@albedo.net>
Reply-To: <
rebel-builders@dcsol.com>
To:
rebel-builders@dcsol.com
Subject: Re: [rebel-builders] belly sumps
Date: Wed, 09 Aug 2006 09:37:33 -0400
1. What came with the kit with the CAV-110 drain screwed into the
adapter and the adapter screwed onto the 1/4"NPT male AN825 "T" fitting.
The adapter has a 1/8 NPT female on one end and 1/4 NPT female on the
other end. My parts were all heavy brass and I don't like to encourage
corrosion by changing metal types if I don't have to. And I didn't want
the drain to extend so far below the fuselage.
2. Or for less vertical space I believe I screwed the CAV-110 into a 1/8
to 1/4 bushing (AN912) and the bushing into a 1/4" AN917 "T" fitting.
Then AN816's etc to bring the 3/8 aluminum tubes into and out of the
'T". It was then easy to make a couple of "L" brackets with grommets
that slipped over the AN816's and held everything. I added a cover plate
in the fuselage floor for access although some guys even bury rubber
hose without access. (I think they don't plan to keep the aircraft very
long...)
3. for even less vertical space you could always make a "T" similar to
the AN917 out of a block of aluminum and then have mounting holes to
bolt it directly to the airframe. That avoids the AN912 bushing and
makes it easier to mount but probably not worth the effort. Only
requires NPT taps and a drill to make it though.
Ken
Jesse Jenks wrote:
The recent talk of sumps gives me the prompting to ask something I've
been
wondering for a while:
What is the accepted method of making the sump? I haven't seen a specific
fitting for this. Do you just use an AN fitting with 1/8 pipe thread on
one
side and screw the quick drain in there? If so, how do you go about
mounting
it inside the fuselage? It would be nice if there was some sort of
flanged
fitting you could rivet in the belly
Thanks.
Jesse
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