Working with one 6’ piece of tubing that
requires multiple bends is scary … that is a lot of tubing wasted should there
be an error in judgment or bending procedures. Add to that, Van’s instructions
do not have a detailed 1:1 drawing for this portion of the fuel line
construction. So with that in mind, I purposely cut the length of the fuel line
oversized and made the first 90 degree bend at the firewall so there should be a
little extra material to trim when finalizing the finished length prior to flaring.
At the firewall the fuel line takes a 90 degree
bend upward (already done) and gets captured by a cushion clamp which will keep
the fuel line off the firewall by 1/8". In the vicinity of the lower
portion of the motor mount bracket, the fuel line requires an aft offset which
I made by placing two 45 degree center line bends in the tubing. This takes the
tubing aft of the firewall and vertical again to align it with the center of bulkhead
fuel fitting hole on the firewall shelf. (The first 90 degree bend was made at
a point 1/2" longer than called for to insure the forward fuel line tubing
will be slightly longer than necessary).
When you are free styling you want to take your
time and do a little math. The drawings showed the approximate location of the
bends so measurements were taken and marked on the tubing. Taking into
consideration the 1/8" gap from the firewall and the 1/4" thickness
of the tubing and location to the center of the hole for the fuel fitting … the desired
centerline offset is approximately 15/16".
Imperial
bender - the marks on the upper handle are used for various types of bends, the
45 marks are for making 45 degree centerline bends after a little math is
performed.
The Imperial tubing bender comes with the
capability of making centerline bends if the user is willing to do a little
math. Basically, you mark the location on the tubing where the first bend will
begin. Then multiply the desired centerline offset by 1.414 and add that length
onto the tubing measuring from the previously made mark and mark the tubing
again. In my case, the desired
centerline offset was 15/16" x 1.414 which yielded 1.3256" (roughly 1
21/64") to be added onto the first mark on the tubing. The tubing bender
has offset locating markings on it so the first mark on the tubing is not
located at the 0 mark as usual, but instead placed under the 45 offset mark on the
bender for the size tubing being bent … then the tubing is bent as usual. After
marking the tubing, but prior to making any bends, I noted that from the
firewall the tubing path down the tunnel was to the pilot side of where the
tubing rises up the firewall. Since there is a 90 degree bend at the bottom of
the tubing already, decide to cant that bend 45 degrees aft towards the pilot
side. The reasoning for this is it will only require one approximate 45 degree
bent to make the tubing head aft down the tunnel in line with the bulkhead grommet.
So prior to making the offset bends I positioned the tubing with the bottom 90 bend
canted 45 degrees towards the pilot side and made a line on the tubing denoting
the edge that should be along the firewall.
Just finished bending the final 45 degree bend
to head the tubing aft to the bulkdead grommet. The offset bends on the firewall
portion of the fuel return line turned out perfectly and truly look great, but admittedly
it took a long time because I had never made centerline bends before … so I took
my time and checked and rechecked and checked again before bending.
Next the tubing is curved a bit so it can be fed
through the bulkhead grommets and slowly worked aft. A piece of tape was
wrapped around the flaperon mixer arm to prevent it from scratching or being
scratched by the tubing as it is slid aft through the grommets and along the
groves on the standoff blocks.
Beginning the feeding of the return fuel line
tubing through the bulkhead grommets … the recently made 45 degree bend can be
seen nicely here.
Slowly working the return fuel line aft and underneath
the flaperon mixer arm.
End of the line … without rolling the fuselage
assembly onto its side and allowing the excess tubing to be pulled out the
inspection port the tubing can’t be feed in any further.
Could not finish off the final cut and flaring of
the tubing at the firewall because it could not be pushed aft far enough … will
need assistance to roll the fuselage assembly so the excess fuel line can be
worked out the inspection port.
