Dave’s RV-7A Building Log

I spent most of the evening helping out at Adele’s swim team meet, but spent a little time starting the long process of countersinking the cabin frame.

I guess it was a day for spending big money. In addition to confirming my engine order, I put money down on a condo hangar. Ideally, I would like to keep my plane at Boeing Field (KBFI) or Renton (KRNT). They’re both within 30 minutes of my house. However, hangar availability at either one is very limited. I’ve been on the waiting list at Renton for 1.5 years, and they’re no indication one will be available any time soon.

The next closest airport is Auburn (KS50), about 45 minutes from my house in clear traffic (a rarity around here). They have pretty good availability on rental hangars and a condo hangar project is just finishing up. I don’t really need a hangar quite yet, but there are only 5 T-hangars left in the condo project. The ability to finish out the hangar with insulation, drywall, plumbing, electrical and even a loft is very appealing. I decided to take the plunge and buy one. Take a look at Andy Karmy’s hangar pictures to see an example of what can be done with them. The company building the hangars is called Aviation Properties.

The engine is now officially ordered. I emailed Mahlon last week asking a few questions. He informed me that Mattituck was going to be raising prices soon. I decided it was time to place the order to lock in the lower prices. I’ve been putting off ordering the engine for two reasons. First, it’s an expensive investment in this project. The second thing I’ve been waiting for is the timing. I don’t want to get the engine sooner than I need it. I ideally want it to arrive within 6 months of completion, because that’s how long the engine preservative lasts and when the warranty clock start ticking. According to Mahlon, the 1 year parts and accessories and 2 year cylinder warranty starts 6 months from shipping or when the engine is first started, whichever comes first.

I ordered Mattituck’s TMX-360 engine equipped for a constant-speed propeller with fuel injection, forward facing horizontal induction and FADEC. This engine is a clone of Lycoming’s IO-360 engine, built using new parts that are the same as Lycoming’s or have been improved slightly. I added fuel injection for better performance and to avoid the hassles of carburetor heating/icing. I added the forward facing horizontal sump for better performance and so the cowl doesn’t need the lower scoop. I added FADEC (full authority digital engine control) for better fuel economy and so I won’t have to deal with constantly adjusting the mixture. In most airplanes with an internal combustion engine (i.e. not a jet turbine), there is a knob for adjusting the fuel/air mixture. The pilot must adjust this knob to account for altitude, air temperature, engine heat, etc. I’d rather let the FADEC computer handle that for me.

On the FADEC system, I’m probably going to use the dedicated battery back-up. It’s an expensive option, but provides for continued operation in the event that the airplane electrical system quits. I also added the serial bus interface so the engine monitor can get data directly from the FADEC system rather than having to duplicate many of the probes and sensors.

I chose to use a clone engine over a Lycoming, because they have many minor refinements and are also less expensive. I had narrowed the engine manufacturer down to AeroSport Power and Mattituck based largely on their reputations in the RV community. Of the two, only Mattituck was able to pre-install the FADEC system. Plus, Mahlon at Mattituck has been very helpful in helping me understand these confusing engines.

Mahlon estimated an engine build date of October 6. I might delay that a bit.

I finally finished the cabin frame drilling today. I placed the frame carefully against a straight edge and measured the height. Using the band saw I trimmed off just a tiny bit from each leg to get it to the correct height. I took the parts outside for deburring to keep Julie company while she worked on the brick patio.

It’s been kind of a low-productivity week on the plane. Other things have taken priority.

I managed to do some more drilling on the cabin frame today. I found out it’s much easier to pilot drill the frame parts to #40 and then assembly the thing for drilling to #30. I got about half way through the drilling.

Yesterday was Julie’s birthday, so I took the night off from the project.

Tonight I worked on drilling the aft cabin frame sections to the inner strap. I had a hard time getting the strap to nest nicely inside the bend of the frame. I kept using the Scotchbrite wheel to round down the corner, but it just wasn’t removing enough material. I finally just used the belt sander on it. That worked.

I spent way too much time trying to lay out the drill pattern with rulers, fractions, and a calculator. I finally figured out an easy way to do it. I marked where I wanted the holes to start and end on the cabin frame. Then I laid some tape along where I wanted the holes and marked the start and end points on the tape. I peeled off the tape and put it on a flat surface. Using the rivet fan, I marked out 19 evenly spaced holes. And finally, I put the tape back on the frame and transferred the marks to it. I was able to use the tape on both sides of the aft half of the cabin frame, and should also be able to use it on the front half. Easy.

Using lots of clamps and the long #30 drill bit, I drilled through the frame into the strap. It would have worked better to pre-drill the frame to #40 and then drill the frame and strap together to #30. I’ll do that for the remainder of the frame. This thing sure has a lot of holes in it.