28 Feb 06 - Baggage Floor Conduit, Air Vents, Wiring

Eventually, wires are going to have to get from the front of the plane back to the back - there's actually going to be a lot of stuff back there - an altitude hold, the strobe power supply, probably the ELT, and of course the nav and strobe light that are in the rudder. Knowing that this is a concern, we've been trying to come up with a nice way of getting wires from the front to the back - going under the baggage floors seems to be the best way to get back there - and the most recent brainstorm is using PVC pipe.

Yesterday, we figured out how to bend PVC pipe with a heat gun, which is going to be a necessary part of this adventure because of the shape of the seat pans. Here's the deal: The bulkhead that separates the seat pans and the baggage floor has a big structural stiffener that goes along the bottom, which you can see in the third picture below. This actually attaches to the wing rear attach point, so it's not something that we really want to mess with. We don't want to drill through that, so we've got to drill the hole for this near the top of that bulkhead, so it misses the spar/stiffener/whatever and doesn't hit anything structural. However, if we do that, the tube has to curve down to miss where the seat pans go down another couple inches forward of this point. This is why you'll need to figure out how to bend PVC (or whatever tubing you are using). Or use flexible tubing, whatever.

Oh - totally unrelated - a couple of these eyeball vents showed up in the mail today. We'll be using them to penetrate the firewall as soon as we figure out where that's going to happen, what wires need to be where, all that.
Okay - here's the PVC tube in the shape that it has to be to fit in the fuselage.
Location of the hole for the PVC - we've managed to miss all the important structural stuff, it seems.
There's the PVC sitting in there. The ends still need to be finished out so it's not rattling around in there, but at this point it seems that the concept is going to work. Nice.

This is probably worth discussing, here: air vents. I got these quite awhile ago from Ross at ExperimentalAir. They're quite nice, and seem to be less expensive than anyone else's aluminium air vents. They took awhile to come in, but we ordered them a year early, so who cares? They work well. However, since we're putting them into one of the Fabian's modular panels, the metal that they're going into is a bit thicker than what was originally planned. The way this can be adjusted is by putting in thicker or thinner felt between the base of the vent and the eyeball part that actually moves. I emailed Ross, and he dropped a few strips of thicker felt in the mail (for free, I should point out), and although the pieces of felt were fine, none of us seemed to be able to get them to stick in there. I didn't do enough arts and crafts as a kid, it seems. However, we figured out that the felt that we had bought to cover the floor of the glove box - which is sticky on the back - was just sitting around, and could probably be used for this application as well.

Sure enough, it worked. This is lots easier to get in there, and then it doesn't have the tendency to slide out. It takes a few tries of figuring out how much you need in there - too much and it won't move, or not enough and it won't stop moving - but after a few iterations, it works great, now, and if it ever doesn't, will be really straightforward to fix.

With the new sticky felt in there . . .
. . . and there it is in the plane.

At some point I'm going to run another piece of PVC down the fuselage on the other side - I have no idea if the wires that we've got will require another one, but I suspect they will, and I want to get the baggage floors in some point soon. We've got to get the PVC pipe in there before the baggage floors get riveted on.

Oh, and there was more work done on the wiring today . . . just running more wires, nothing overly interesting.

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