Sun Feb 20 2011

Fuel line tubing

I did some looking around to determine the correct location for where the fuel line will penetrate the firewall. It was shown on drawing OP-32, but there seemed to be some controversy about whether that drawing is for the parallel valve IO-360 or the angled valve IO-360. Looking at the drawing and reading some other builders' posts gave me the impression that the location of the engine fuel pump was the critical factor in determining where to drill the firewall. I slid the cover on my engine crate aside enough to verify that the location of my fuel pump seems to match that of the drawing fairly well, so I can trust the drawing. Hah! Who want's to bet that'll bite me in the keester? Trust the drawing?! Pfffttt!

Oh, by the way...this little plate is the doubler for the fuel line pass through. I think I'm going to need to make a larger doubler since I'll be passing through both a fuel line and the purge line.

As a side note, I find it very troublesome to determine things like this firewall penetration location. There are a lot of factors that can influence it (engine mount, control cables nearby, exhaust, etc) all of which are not well documented, nor will they be complete for some time, yet making the incorrect decision here can almost guarantee I'll have interference problems later. Sigh.

In order to make the routing easier for the line going from the high pressure boost pump up to (and through) the firewall, I changed the design of this line so that it angled 45 degrees aft and to the right.

I temporarily put the cover in position to verify there's no interference with the corner of the cover. It had about 3/16 clearance (no image with cover on, sorry). Sweet.

The output from the high pressure boost pump clears this line pretty well.

And with the 45 degree angle, it doesn't interfere with the loop in the line either.

I decided to start working on the outboard line and did this simple drawing.

After the outboard line exits the fuselage, I bent it 90 degrees to run forward through the tank support bracket. The drawings don't show it, but I'll try to put a grommet in the bracket hole before it's all said and done.

Here's what it looks like inside the fuselage with the gear weldment removed. Not bad so far. Time will tell if this is the final solution.