Fuselage « Matt's RV-7 Project

Archive for the ‘Fuselage’ Category

Riveted transponder doubler

Sunday, August 9th, 2009

Al Stuber put his CH 750 project on hold long enough to drop by and hold the bucking bar against the belly skin while I crawled inside and backriveted the transponder doubler. Thanks Al.

The brown discoloration in the above photo is alodine, by the way. Don't want any surface corrosion forming here and messing up my antenna ground plane.

Here's a shot of the transponder antenna bolted to the bottom of the fuselage… nothing to it, just a plastic shark fin thingy:

One more thing checked off the to-do list.

Posted in Fuselage |

Elevator/aileron speed controller

Sunday, July 26th, 2009

One of the things that always annoyed me about my last RV was that the electric elevator trim was incredibly sensitive at normal cruise speeds… trying to trim out control pressures would always turn into a game of "how fast can I press and release the trim button so the airplane doesn't get out of trim in the opposite direction". So to improve that situation with this airplane, I bought a Safety-Trim two-speed trim control unit, which gives you the ability to slow down the trim servos when flying faster than a preset airspeed threshold. It also provides some protection against trim runaway due to a stuck switch, which is nice.

To mount it, I made some little standoffs from scrap alclad:

I attached it to one of the ribs under the pilot-side baggage floor. It's a pretty short run forward from there to the control sticks, and the wires to the servos can go fore and aft through the center tunnel. I'll run the wires to it later – right now I'm just trying to get all my boxes mounted where they need to go so I can plan my wire runs.

In the photo above, you can also see that I've riveted a bunch of plastic tie wrap anchors to both sides of the left and right tunnel ribs. They'll get put to use soon when I start running wires through the tunnel

Posted in Electrical/Panel, Fuselage |

Transponder antenna doubler

Sunday, July 26th, 2009

I bent a doubler for the transponder antenna out of 0.050" alclad and drilled a bunch holes for rivets and mounting studs and antenna connectors through it:

Then I crawled into the fuselage and match-drilled the doubler to the belly skin and the F-729 bellcrank rib, about a foot behind the baggage bulkhead. In terms of the length of coax needed to reach this location, I'm right at the limit of what the Garmin install manual allows, but I couldn't find a better place to put it. Not to mention, I hope the transponder-rays won't do anything weird to the pitch servo. Also, I shortened the doubler slightly between these two pictures, since I'm thinking about moving the ELT back here and I wanted to be sure to leave plenty of room.

A view from the outside. I need to deburr, dimple, and alodine the mating surfaces, and then see if I can coax Mary into helping with the riveting duties.

Posted in Electrical/Panel, Fuselage |

Flap motor wiring

Sunday, July 19th, 2009

Since I had one of the required components in hand already, I decided to also work on the flap motor and associated wiring this weekend. Here I've mounted the flap positioning system control box on the new backrest brace:

Here's another view to show how it stands off from the underlying rivets, thanks to a few nylon washers. That dimpled hole in the foreground is for mounting an adel clamp.

As I previously threatened, I cut the wire harness between the control box and position sensor and crimped on some connectors. Now the motor and control box don't have to both come out of the fuselage at the same time.

Since the flap motor is now no longer permanently tethered to anything else, I couldn't think of a reason not to (semi) permanently attach it to the flap actuator channel. This photo is proof that I did put the cotter pin in:

Then I spent several hours running wires to the flap switch and pulling wires back to the flap motor. Properly bundling and securing new wires takes me about ten minutes per linear foot per wire (longer if I have to drill new grommet holes or install new clamps or tie wrap anchors) so consequently this took all afternoon. I left the flap switch hanging from the panel for now, since there's no need to go to the trouble of bolting it in place for an electrical test.

Once I had all the connectors installed, I plugged it in and gave it a floor run… it works! Bump the switch, and the flaps move one notch up or down. Nice. I'll clean up the wires in a future work session.

Posted in Electrical/Panel, Flaps, Fuselage |

Made new backrest brace

Saturday, July 18th, 2009

At some point in the last year I managed to bend my F-785 backrest brace – that's the vertical piece that goes between the F-705 bulkhead and the baggage floor, and forms the aft end of the flap motor housing. I'm not sure if I accidentally put too much weight on it from above, or inadvertently kicked it while crawling around inside the fuselage, but I definitely buckled one of the flanges. I bought the parts to make a new one many months ago, but only got around to building it this weekend.

Similar to Bob Collins' idea, I decided to reinforce the new backrest brace by riveting some angle-aluminum doublers on the inside:

The finished product, after several hours of fabrication… note how the rivets at the bottom end tie the doublers into the attach angle. Compared to the old one, the new brace is a couple ounces heavier and a heck of a lot stiffer.

Installed in the fuselage for final fitting:

Pneumatic squeezer and beer… you can theoretically build an airplane without either one, but why would you want to?

Posted in Fuselage |