Dave’s RV-7A Building Log

I was re-arranging stuff on the shelves to make room for the harnesses and noticed the cowl intake ramps. These things are attached to the underside of the top cowl in order to smooth the air flow. Since the baffles are trimmed to the ramps, I decided it would be a good idea to install them.

The first step was to do the final, final trim on the cowl inlets. I figured I might as well to the top and bottom and long as I was donning all the safety equipment. I trimmed the bottom inlets back from the baffles 3/8″ and used a sanding block to finish them up. I left as much material as possible along the top of the inlet and just drew a straight line in between. It turned out quite well.

Borrowing Walter’s idea, I marked on the cowl where the side and inner baffles line up. I then used that to align the ramps. I held it in place temporarily with duct tape and then drilled a few holes for clecos. The ramp will be held in place with epoxy. The clecos are just used to hold it until it dries. According to the instructions, the ramps will stiffen up the top cowl and essentially fix its shape. Thus, I installed the cowl on the plane to drill the holes. I just need to rough-up the surfaces and then it’s ready for epoxy.

It seems that I’ll need to extend the ramps inboard in order for the front baffles to have something to seal against. I’ll investigate the situation on some builder logs.

I worked more on bending and fitting the custom-made piece for the baffle jog. It fits pretty well. It ended up being kind of close to the oil cooler hole, but I want to make sure it’s at least an inch tall to provide enough material to attach the baffle seal.

I wasn’t quite ready to drill it, so I picked up something else. I was looking at the FAB and noticing how rough it was inside. I spent a few minutes sanding the inside smooth. That’s not exactly easy on such an ackward part.

Also today, I received the Princeton capactive fuel sender converters and Hooker harnesses. The harnesses look great. They’re a little heavier than I expected, but they look extremely well built. The colors were black for the belts and dark gray pads with black edging.

The Princeton units look straight-forward. Comparing them to the units Dan C described, they now leave off the cover from the BNC connector to make it easier to get them through the side of the fuselage. That’s an improvement. However, in retrospect I wish I would have just installed the float fuel senders in the tanks.

I’m finally back at building after our trip to Sun Valley. We had great weather and a great time skiing/snowboarding.

I’m still wiped out from the trip, but did a tiny bit of work after dinner. Using some scrap sheet, I did a first cut at the box that will fill the jog in the left rear baffle. I bent the box following my cardboard template, but it just didn’t fit well. It was too long and too wide. Instead of trying to unbend and rebend, I just made a new one from scratch. This time, I’ll be a bit more careful about how I bend it.

I’ve also been trying to make some final decisions on the avionics. Until I place the order, I guess I’m going to keep waffling. I’m pretty set on the Dynon EFIS/EMS. I looked again at the transponder. Using Stark’s prices including wiring and shipping, the GTX-327 is $1750 cheaper than the GTX-330. I’d love to have traffic display, but it’s only going to last another year or two because the FAA is too cheap to pay for it as the terminal radar sites are upgraded. I’d rather save that money and apply it to an ADS-B system, which is better and should continue to be supported in the future.

The next decision is between the GNS-430 GPS and GNS-480. The 480 has more flight management functions and is WAAS capable, allowing precision GPS approaches. The difference in price is $2400. I’ve downloaded both simulators. It’s really cool to be able to interact with the user interface for both units. Personally, I find the 430 much easier to use. It would be nice to have WAAS, but I doubt I would use it very often. I don’t plan on flying IFR approaches on a regular basis, and if I did I could always find a nearby airport equipped with a localizer/glideslope. Also, Garmin is supposedly working on a WAAS upgrade for the 430.

Next up is the SL-30 vs. SL-40. The only difference is that the -30 includes a VOR receiver. Actually, they’ve done the interface so well it’s like two VOR receivers. However, the 430 includes VOR, so the -30 would be redundant. Especially since the 430 can automatically tune the VOR receiver from the database. Plus, I expect I’ll use the GPS 99% of the time. The VOR is just a back-up. The difference in price is $1800.

All of those combined add up to $6000. That’s a big chunk of change. I might be giving up little things here and there, but for 99% of my VFR flying and even 90% of my IFR flying I don’t think I’ll notice the difference.

I didn’t get anything done on the project last night as we had another Seattle Eastside EAA chapter meeting. It’s fun being on the ground floor of forming a new group. Everybody seems to be enjoying it so far.

I’ve been going back and forth with Ross at Experimental Air a few times on the panel. He’s doing a fantastic job of laying out the parts. This is what we have so far:

I’ll need him to tweak the switches just a tiny bit more in order to have a spot to attach the throttle quadrant mount. Other than that, it’s looking pretty darn near done.

The two large screens are a Dynon EFIS-D100 on the left and EMS-D120 on the right.

I deburred all of the parts that I drilled yesterday and cut out a hole in the back baffle for the oil cooler. I drilled the corners to get a nice radius, connected them carefully with the jig saw, and then filed with the Vixen and sandpaper.

A common customization that I’ve seen is to make a little box for the area above the oil cooler so that it’s easier to attach the baffle material. I’m also hoping that the box reinforces the area a bit. The back left baffle doesn’t attach to the cylinder like the back right does. I made a trial box out of some cardboard from a shoe box. I’m glad I did this as I would have screwed it up a few times trying to make it first out of aluminum. I want the box low enough that the baffle seal has plenty to grip, but high enough so that it doesn’t disturb the air flow into the cooler. It’s a little difficult to see, but here’s a picture anyway.

I also sent back some changes for the panel layout to Ross. I decided to ditch the vertical card compass, and to try to move switches around a bit to make a clear area under the EFIS for a portable GPS like the 396.

I also decided to go for the throttle quadrant. At one time I was going to install it, then decided against spending the time on it. Now that I’ve seen Dan’s install, I want it again. The standard knob set up is just not intuitive. I remember when I was first training actually moving the knob in the wrong direction. It seems weird to push it in to go faster. The levers on the quadrant make much more logical sense and look 1000% cooler. For “only” $180, it’s worth the mony and should only take an hour or two to install.

I spent the morning helping my friend Steve put a new VHF antenna at the top of his mast. It was great to work outside in the sun for a change.

After an afternoon bike ride with the family and dog, I spent a little time positioning the oil cooler reinforcement. This is about as high up as I could get it without risking some interference with the baffle seal. A tiny bit of the top corner had to be removed. It looks like only the bottom 1/4 of the cooler will be blocked by the cylinder. That seems about typical from other installations I’ve seen. I drilled a few holes with the reinforcement positioned on the baffle.

I then took it off and drilled the rest of the holes on the bench where I had better access. I cleaned up all of the holes on the angle parts and managed to give them a quick shot of primer before it got too cold outside. The next task will be to make a big hole in the back baffle.

The final thing to do on the baffle trimming was the front bulkheads. In the post I read, it was suggested to leave these off to make it easier to mark the other baffles. I’m not sure that was really necessary. It was easy to mark and trim them, though. The access to the front bulkheads is really good.

With the trimming finally done, I could complete a few other tasks. I fabricated the angles that reinforce the back left corner of the baffles where the oil cooler mounts. My first attempt at the diagonal angle didn’t go up high enough, so I made another. I’ve gotten pretty good at quickly whipping up various aluminum parts. The band saw and deburring wheel are my friends.

The reinforcements needed at this corner is not exactly clear from the plans. The oil cooler drawing shows the spacer, but not the angle. The baffle drawing shows the angle but not the spacer. I put both in, as I figured it couldn’t hurt. The spacer is definitely needed otherwise the two sides of the baffle don’t meet correctly.

I also started to contemplate the location of the oil cooler. I want it as high as possible, but I don’t want it to interfere with the cowl or baffle seal.

I did a tiny bit more baffle trimming. There were a couple spots on the left side that still didn’t have a finger width of space.

I used the band saw to trim the right side baffles. I put the top cowl back on and noticed the gap is still not quite large enough on the left side and it got larger than I was shotting for on the right side, about 9/16″. I guess the cowl wasn’t sitting completely level. I put the bottom half of the cowl on just to make sure the top cowl was correctly positioned, and it was. While I had the bottom cowl on, I marked the left cowl inlet where I need to do a little more trimming. The position of the filter dictates the amount that the left floor extends forward. In order to get a 3/8″ gap, I’ll need to trim the inlet a little more.

I did a bit more trimming on the left side baffles, and called it quits for the night. Hopefully the trimming is about done.

I received the first draft of my panel drawing from Ross at Experimental Air. It’s looking great. One thing I didn’t account for in my mock-up is the fact that most of the instruments take up more room than just their face plate. For example, the avionics stack need a strip on the left and right for the supports. That’s a good example of why it’s helpful to have someone like Ross do the layout for you.

I also got the price tag from John Stark on the avionics that will go into that panel. He’s got great prices, but ouch! Time to cut a big check.

I finally went down to Sears and picked up a strap wrench to tighten the timing gears on the P-mags. The torque for the AN6 nut is 160 in-lb, but I could only get it up around 120 in-lb. That should be good enough. There’s a key that keeps the gear from turning anyway.

I next turned to the final baffle trimming. I used the band saw and Scotchbrite wheel to do the final trimming on the left side and back baffles. Since I have to remove the baffle to do this trimming, it’s taking a little longer.