REFLECTOR: Sump Tank Design Change Suggestion

Lawrence J. Epstein,MD ljepstein at hotmail.com
Fri Aug 4 12:50:29 CDT 2006


What I have done is make 2 hardpoints on the floor of the fuselage under
the forward edge of the Sump tank. I then made "legs" using small mixing
cups as a mold and I am putting a rib on each leg to the sump. I am then
securing the sump legs to the floor. The tank is then supported @ 4
points.

 

Larry Epstein

 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Hiroo Umeno
Sent: Friday, August 04, 2006 1:30 PM
To: reflector at tvbf.org
Subject: REFLECTOR: Sump Tank Design Change Suggestion

 

After my last "incident" on first engine run related to my shoddy
craftsmanship on the sump tank, I started thinking.

 

Admittedly, it was mostly due to the crappy job I did in joining the
sump tank tub with the side wall.  However, I am thinking that the
original design also had some contributing factor to it.  My kit came
with sump tank that had two parts: the part that looked like a tub and a
flat sheet of fiberglass plate that was to be the "back wall" that was
oversized and needed to be trimmed to fit.

 

What this forces the builders to do is to lay the tub over the sheet,
mark the tub outline on the sheet, cut to fit, then lay up the edges to
join the halves.  This layup is a bit tricky since the plate is rather
thin and even after sanding the edges off, it remains a fairly sharp
radius.  To make the matter worse, the tub side wall does not meet the
plate at 90 degrees making the fiberglass tape wrap the approximately
100 degree corner as it join the pieces.  It is very easy to get
delamination or bubbles in the lay up which, as I leaned the hard way,
is a really bad thing for something that contains fuel.

 

My suggestion is to change the sump tank design such that two tub halves
are mated flat at the center much like how the nose gear pants are
joined left and right.  This will enable the joining lay up to be done
on a relatively flat side-wall and make it much less problematic for
first-time builders like me.

 

Hiroo

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