Archive for November, 2009

Map lights

Saturday, November 14th, 2009

I already mounted the dimmers for my cockpit map lights, but I didn't get around to wiring them until today. So here's what one of the LED map lights looks like:

I discovered that the inside diameter of the mounting base is exactly the same size as a cleco, which is really handy for drilling the mounting holes.

I dug the rollbar out of storage, clecoed it to the fuselage, marked and drilled pilot holes for map lights, and clecoed a light mounting base to each of the trangular gussets.

I match drilled the three mounting holes to the rollbar, then enlarged the center hole to 1/4" and drilled the mounting holes for miniature nutplates. I'll rivet these to the rollbar gusset once it's been re-powder-coated.

I like this location… it's out of the way and not likely to get broken off by passengers' feet, but still in a good location to be useful for reading a chart or for illuminating dark corners of the cockpit.

I used a very small grommet to pass the wires through the rollbar gusset:

The dimmer modules came with some miniature potentiometers. I soldered leads to the terminals:

…then used heatshrink over the joints:

…and finally put a piece of bigger heatshrink over the entire component, which should help prevent the wires from breaking off.

I drilled holes in the F-721 canopy decks to mount the dimmer pots:

I used some anodized aluminum knobs that match the ones I used for the panel light dimmer knobs. Eventually I'll make little placards to identify the function of the knobs, which will have the added side effect of covering up the holes for the anti-rotation tabs.

I finished up the wiring for the little dimmer modules and closed up the connectors. The power and ground wires that go to the lights themselves are not connected permanently yet, since I need to do a little further work to route them properly.

However, I did hook up each lamp with alligator clips just to make sure everything was wired correctly. Yup, seems to work:

I have something special in mind for making the connection between the lamps and dimmers, but it's not ready to show off just yet.

Posted in Electrical/Panel |

VOR antenna

Sunday, November 1st, 2009

A forum thread convinced me to buy and install a traditional cat whisker VOR/ILS antenna on the bottom of the fuselage, rather than the hidden wingtip type often seen on these aircraft. I'm happy to give up half a knot for reliable navigation performance.

I decided to mount the VOR antenna just aft of the F-710 bulkhead, which is just barely accessible when the empennage is attached. A doubler ties into the bulkhead and the F-779 bottom tail skin.

The doubler is made out of 0.063" alclad. Here it's drying after having alodine applied, although in retrospect I'm not exactly sure why I bothered to do this – the "puck" part of the antenna is plastic, and the mounting fasteners don't make electrical contact with anything in there. Oh well, at least it won't corrode.

Here it is riveted in place with the antenna attached via nutplates. The brown stain is alodine that ran downhill while it was drying.

It would be pretty easy to use driven rivets here during the initial build of the tailcone, but on a nearly finished fuselage with the empennage installed it's essentially impossible. Cherry Max rivets to the rescue.

Test-fitting the VOR antenna using some random bolts… when I go to install it for good I'll use AN525 screws instead:

When the rudder and elevators are installed, you won't be able to step on the VOR antenna, so no danger of tripping over it while walking around the back of the airplane.

Yeah, it's hanging out in the breeze, but the airflow down there will be pretty disturbed anyway, so it shouldn't cause too much drag (he said, despite having only a journeyman's understanding of aerodynamics). At least the nav radio reception should be pretty good!

Now that all seven of the antennas on the fuselage are mechanically installed, it's time to move on to wiring them… but that will have to wait for a future work session.

Posted in Electrical/Panel, Fuselage |