Tue Jun 29 2010

Fabricating vent tube bottom fittings

Well, I'm currently waiting on some parts and material to continue working on either the popup tipup mods or the fireproofing panels, so I decided to work on routing the vent lines for the fuel tanks. Here are four spacer washers I deburred. Certainly there's no functional requirement to do a top-notch deburring job on these, but hey, it's my plane. :-)

To fabricate the vents that go through the floor, Van's has you use a bulkhead fitting, chop the end off at 45 degrees, and face that into the wind. The idea is to provide some positive pressure to the tanks. I've always known I wanted to do something a bit fancier than the plain bulkhead fitting, so I decided to work on that. I'll use some aluminum from the block in the background to beautify this fitting.

First task was to trim the hex nut of this fitting down to a thinner, more aesthetically pleasing dimension. I drilled a 7/16 hole through this piece of oak to act as a holder for the fitting, then used the band saw to cut into the nut until the cut was roughly at a depth equalling the diameter of the fitting.

A cutting disc in the die grinder took off most of the meat from the nut.

With the fitting inserted back into another wood block, I used the sander to turn this down to 0.250 inch diameter.

The face of the thinned-out nut was pretty rough from the band saw, so I filed it smooth.

Looking good so far. :-)

I sliced off a piece of the aforementioned aluminum block and sketched a sort of airfoil shape on it. The rough cuts were made with the band saw, then a lot of sanding got it down to a nice smooth profile. This sucker got really hot during the sanding process. I kept dunking it in a cup of water, but the water almost got too hot to stick my fingers in for retrieval.

The scotchbrite wheel polished up the outside.

I filed one of the points of the nut down slightly and filed a notch in the bottom of the little airfoil.

The two parts pressed together quite nicely.

I still needed to angle the forward face of the tube per the plans, so I hacked off the bottom edge at a 45 degree angle.

I decided to polish the first one up to see how it would look. I'm pretty pleased with this...should add a nice touch to the plane. Took about four hours to make the first one.

The second one (on the right) actually came out even better...and only took three more hours. I'll polish that one up some other time.