02 October 2015

Fuselage: Fuel system. Complete.

The fuel system is completed.  The fuel selector flange requires countersinking so that the screws sit flush.  It's important to clamp the part down solidly and with some backing for the countersink's pilot to avoid chattering the bit and making goofy holes.  I got the two side holes done perfectly, but the aft center hole had some chatter probably because I didn't clamp things down hard enough.  It's not too noticeable when the screw is inserted.


The fuel lines take some patience to get bent properly.  I had my friend, who build a -9A, complete the two lines from the wing tanks to the selector.  His approach was to use one section of tube as a sacrificial prototype to get the lengths, bend radii and locations correct.  He did well.  I used a 13/16" crow's foot to torque the outboard bolts.



The line that goes from the selector to the fuel filter was relatively easy for me to do.  I got it right on the second try.  The first one, per plans, was too long, though the bend is properly located.


The line that extends from the fuel pump to the firewall was exceptionally difficult for me to fabricate, probably because it requires manipulating the line precisely in all three dimensions with bends and rotations.  I tried three times and gave up, purchasing instead a prefabricated line from Aircraft Specialty  for $56.17 shipped.  One individual, posting on VAF, indicated his preference for a flexible fuel line into the firewall in case of an incident.  I have no expertise to comment.


Not shown in the pictures is that, following proper torquing of the lines, they are marked with torque seal to support future inspections.

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