Matt's RV-7 Project

I had previously put the rudder back on the airplane to demonstrate something to another builder, so while I had it on I decided to work on the forward ends of the rudder cables. They're connected to the pedals via small 4130 steel links that you make from raw stock, and since I'm the one building this contraption I get to size them in such a way that the pedals' neutral position is set up just for me. I put the seat cushions in and spent a fair amount of time playing with pedal positions and angles until I was happy. Using tie wraps as temporary stand-ins for the F-6119 links was a good way to quickly experiment with different link sizes.

In a rare example of intelligence and foresight on my part, I drilled out this rivet on both sides of the firewall. I'll put an eye bolt in each hole to provide a place to anchor some pedal return springs, should I need them. It's much easier to plan for this now while I still have decent access to the back side of the firewall. The springs will go between the eye bolts and the pivot bolts on the two innermost pedals, to keep the rudder from flopping around on a windy ramp. I should also be able to size them appropriately to dial in a bit of rudder trim if I need it.

Because they're installed in pairs, I wanted to ensure that the hole-to-hole spacing was the same for all four links. I drilled them together so they're all identically sized.

Deburring ferrous material makes little magnetic whiskers. Science is fun!

One more test to make sure these are the right length. The pedal angle is good and I have to point my toes slightly to get up on the brakes, which should help prevent inadvertent braking (especially unwelcome in a taildragger!).

I rounded off the corners all nice-like, and then because these are steel pieces I primed them and gave them a coat of enamel to protect against rust.

Here's the finished product, with cotter pins installed. Note that they have you use AN23 clevis bolts here, presumably because the low profile head has less of a chance of catching on your shoe.

It took a surprisingly long time to make these four little pieces. I spent a lot of time fooling around with different rudder pedal positions, which involved repeatedly unbolting, repositioning, and re-fastening the pedal mounting blocks. In the end I wound up using the middle of the three available positions, which was where the pedals were mounted before I began this exercise. Oh well.

For reference, I'm about 6'1" and I made the pedal angle fit me well by using the middle pedal attach position and using a hole-to-hole distance on F-6119 of 1.5 inches.

The last thing I did on the rudder cables today was to pay some attention to the bushings through which they pass as they head from the pedals to the tail. All RV's make a kind of sawing noise as you work the rudder pedals – that's the sound of the cables sliding through the plastic bushings. Other aircraft use pulleys for this, and the bushings Van's uses are a little cheesy but they work. A recent issue of the RVator suggested cutting a slot in a smaller bushing, slipping it over the cable, and inserting it into the bigger bushing – the idea being to provide more material for the cable to saw through before it starts eating into the bulkheads. Of course, you inspect these every year during the annual condition inspection, and they last for years, but I thought it seemed like a good idea anyway. I used an Xacto razor saw to slit a dozen or so bushings and popped one into every bushing from the pedals to the tail.

I mounted the power supply for the red belly strobe next to the main one, using basically the same type of bracketry as I used to mount the ELT:

Astute readers will recall that this box is designed for ultralights, so as such it has less power output than a real-airplane strobe power supply. In this case that's exactly what I want, since I don't want my belly strobe to be quite as blinding as the real three-point anticollision strobe lights. I actually hooked up the 70821 strobe head and gave it a try before I installed this thing permanently. The flash rate is lower than the main strobe power supply, and the pulses seem less intense. Excellent.

Mary helped me rivet two little brackets to the longeron between the F-708 and F-707 bulkheads. These secure the static line as it runs forward from the tee, and keep it from rubbing on the seatbelt bracket. I know it's probably overkill to use rivets and threaded fasteners here, but I wanted to avoid using those self-adhesive tie wrap mounts because of all the problems I've heard about. Apparently they tend to come unstuck over time, so I'm doing the extra work to make sure my static line will stay put.

Just after the tee, the line transitions from 1/4" ID silicone tube to the 1/4" OD Nylaflow tubing that's standard issue for aircraft pitot/static plumbing. No adapter fitting necessary – I just slipped one tube inside the other for a length of about four inches.

While I was back there I gooped some RTV between the static line and the rivet at the top of F-708. After it cured I removed the popsicle sticks, and now the RTV keeps the rivet from rubbing through the tubing.

Between F-707 and the F-706 baggage bulkhead, the line angles downward to parallel the F-786B-L stiffener, then disappears through a snap bushing behind the baggage sidewall cover. Two more little angle brackets are pop riveted to the stiffener here to hold the line in place. (The grey blotch is an area that got a shot of primer after I scratched it up a bit.)

The static line runs forward through snap bushings beneath the baggage sidewall covers, then goes through another snap bushing through the F-705 seat back bulkhead and emerges under the armrest.

This routing for the static line is nonstandard – I got the idea from Dan – but it will make the tubing totally invisible as it travels from the tailcone to the instrument panel. In the baggage area it runs behind cover panels, and in the seating area proper it will be hidden beneath the armrest and behind the interior upholstery. I still need to figure out how to bring it through F-704, but that job will wait for another day.

After properly anesthetizing myself against the inevitable painful cramping, I crawled way back into the fuselage and installed the first few feet of static plumbing. The two static ports are now tied together, and the line will eventually run forward from the tee along the left side of the fuselage to the instrument panel. Notice that the tubing goes uphill from each of the static ports – that's to help keep water out of the system.

Most people use tie wraps to secure the tubing to the bulkhead, but in my airplane it's held in place by some neat little cable/tubing clamps I found at Ace Aircraft Supply. They are like minuature adel clamps, but made of nylon and not padded, intended to secure household wiring and the like. Each one is fastened to the bulkhead with a #8 screw and nut. As an extra bonus, they also provide enough of a standoff so that the tubing never actually touches the bulkhead anywhere – except for that one rivet at the very top, to which I need to apply some RTV to keep it from chafing through the tube.

Here's a better view of one of the nylon clamps. I made a handful of these little angles with nutplates on them, to be riveted to the longeron at strategic intervals to provide support for the tube as it runs forward into the cabin. Didn't have a chance to install them tonight, though.