Dave’s RV-7A Building Log

Today I’m offically an airplane builder. After nearly 2.5 years of working on the plane nearly every day, I finally drilled a hole in my finger. It’s certainly a dubious milestone in the project.

I finally had the energy today for some serious work on the baffles. I tweaked the support for the right front floor and shaped the tab to cover the prop govenor oil line slot. I suppose if one cut the slot just right, the tab wouldn’t be necessary. Here are two views from below and one from above.

One thing I just don’t get about the baffles is how the sides are supposed to seal against the sides of the cowl inlet. Even if I pull the sides in tight, it seems like there’s still going to be a big hole there. I’d especially like to keep the left floor as wide as possible for the engine intake filter.

I cut up some thick paper to simulate the seal material. Along the sides, the material pushes against the cowl. Along the cowl inlet bottom, the seal kind of bridges the gap from the cowl to the baffle floor. I guess the two overlap enough to make a decent seal. The instructions say to center the sides in the “slot” of the cowl. I guess this is what they are talking about.

I shaped the angles that attach the right floor to the right side baffle and drilled them in place. The drawings and instructions are a bit contradictory on how to deal with the aft part of the junction. I just kind of faked it as best I could. It all feels solid. The aft-most side rivet goes through the bolt reinforcement. The drawings kind of indicate using one of the existing holes in the reinforcement, but I couldn’t make that work. I just drilled a new hole.

I also riveted together the bracket and tab contraption and added some nut plates for #8 screws. It also feels quite solid. I figured out which rubber grommet I need from Spruce to seal the gap around the oil line.

I pulled out the front bulkheads and spent a little time trying to figure them out, but I’m done for the day.

Spent more time on the right front baffle floor fit. I made a little tab to secure the slot of the prop governor line.

We’re back from skiing/boarding at Mt. Bachelor. Great place. We had great weather, great snow, and the view from the mountain was incredible.

I spent a little time just getting back into the swing of things. I messed around with the right front baffle floor.

I didn’t spend too much time on the plane, but Julie was nice enough to allow me an hour with the mistress on Valentine’s Day.

Mattituck installed an alternator on my engine by mistake. They were nice enough to let me keep it if I could use it. Well, I can’t use it. It’s much larger than Vans 60 amp alternator and is interfering with the FAB intake to the fuel servo. I could modify the servo, but I’d rather just swap out the alternator.

I pulled out the parts and instructions for mounting the Vans alternator. The Mattituck alternator was apparently in an aircraft-style housing, so it fit the standard mounting bracket. The Vans alternator is straight off a car, and so needs a different mounting bracket. The bracket that Vans includes in the kit is made from aluminum rather than steel, but looks beefier. It also attachs at 4 spots rather than just 2. I had to file a bushing on the alternator (as mentioned in the instructions) in order for the bracket to fit properly. There’s also a strut that ties the starter to the alternator. I don’t know that it’s required, but it couldn’t hurt. I started fabricating that out of aluminum bar stock also provided in the kit.

I received a letter from Vans confirming my propeller order from Hartzell. They’re going to ship direct. The expected ship date is May 10, 2006!! I know they said to expect a 12 week lead time, but holy cow. I hope it gets here before that. I’d like to confirm the fit of the cowl before then. Assuming shipping takes a week or two, I might not see it until the end of May.

This just confirms that I need to order the rest of what I need for the plane. I was trying to pace out the purchases and buy things only as I need them. But I don’t want manufacturing delays to hold up my project. I’m going to confirm my avionics choices at the aviation trade show in Puyallup next Saturday, and then it’s time to do some major ordering.

I worked a bit more on the parts that attach the FAB to the baffle floor. The drawings are not very accurate. The side parts need to be much shorter than what is called out. Also, the corners don’t fit together very well unless you cut an extra jog in the flange. I’m having a little trouble figuring out how this whole thing is supposed to be sealed. At least I think the idea is to have a pretty good seal between FAB, the filter and the baffle floor.

The main point of figuring out the parts was to help determine the location of the filter on the floor. It looks like I can position the filter so that the aft edge of the filter frame is right at the bend line.

I worked further on fitting the forward left baffle floor to the cowl inlet. I had to trim quite a bit more off the inboard edge of the floor so that it could slope down to the cowl inlet and not hit the crankcase. That involved several iterations of installing/removing the bottom cowl (not an easy task solo) and installing/removing the floor and grinding it down with the Scotchbrite wheel. I eventually got the forward floor edge to line up nicely with the cowl inlet. I then worked on the bracket that holds the inboard edge of the floor in position. The part comes flat with a large bolt hole in it. Not helpful. It would be much better to have the bend but no hole. Putting a bend in a small piece of .063 sheet exactly where you want without a bending brake is not fun. I used the vise, the hand seamer, a board, a hammer, and some colorful language. Surprisingly, it turned out pretty good.

The FAB instructions say not to install the angle the connects the left floor with the side baffle. The FAB kit replaces it with a different piece. I guess I move on to the right floor now.

I didn’t do anything on the project over the past two days. Took a little break for some computer projects. Today, I worked more on the front left baffle floor. I positioned and drilled the 2R stiffener angle at the front of the cylinder and part 14 that holds up the right side of the floor. I had to do a lot of trimming in the process, but it’s starting to fit pretty good.

I test fit the cowl and it’s obvious that the cowl inlet needs to be trimmed back in order to make enough room for the air filter.

I trimmed the cowl and re-installed it.

I took a few iterations of trimming back the left side baffle before the fit was looking good. I need to study a bit more how the filter and FAB gets attached to the baffle floor before I can figure out if I need to trim the cowl more or not. I’m not sure if the edge of the filter can go right up against the bend just forward of part 2R. If it can, I have about 1/4″ between the cowl and filter right now. That looks pretty good.

After dinner I went back out and started making the parts that connect the FAB to the bottom of the left baffle floor. Getting these figured out will help me determine how to position the filter.

Took last night off for a meeting with the group of folks getting a new EAA chapter started on the Seattle Eastside. The meeting went great. We split up the tasks, which should make it easy to get it all done. I think we’re going to have a good group.

Tonight I worked on fitting the left front baffle floor. Following René’s advice, I flattened the diagonal bend a bit and increased the bend at the back of the floor. Once I trim back the cowl inlet, I think it’s going to work out just right.

It’s a little difficult to determine where the floor is supposed to be relative to the cylinder it attaches to. There are no pre-drilled holes and there’s no drawing that shows the right angle. Following the casting marks on the cylinder leads right to a little fin on that crankcase, so that’s the position I’m using. I trimmed the inside and outside of the floor a bit to get it fitting well. For now, I have the left side baffle pointing outward. I’m not sure if that’s necessary in order to get enough room for the filter or not. Doesn’t hurt to start out that way. I roughly positioned the front left bulkhead a few times just to make sure it was going to fit OK with the floor angle. Looks fine.

I also fabricated the angle 2R that stiffens the back of the left floor and holds it to the front of the cylinder. That gets riveted to the floor with the part 14 support that attaches to the crankcase. I have it all pictured in my mind how it goes together now. Some spatial ability is definitely required for these baffles due to the lack of good drawings.

Earlier in the week, the spring arrived that ordered from McMaster-Carr. Unfortunately, it doesn’t have enough torque to make the oil door stay open. Not sure if I’ll try to order a different one, or just live with it. I also received the Hartwell latches from Wicks. They look great, but the two don’t match. On one the latch part sticks up more than the other. On the back one has “-.025″ imprinted on it and the other says “-.115″. That appears to be how much they stick up from the attachment plate. I called Wicks and they’re sending out another matched pair this time for free, and they’ll reimburse me for sending back this pair.

I did a bit more fitting and tweaking on the rear bulkheads. I’m pretty confident I know how they’re supposed to go together now. I was going to drill some holes, but it seems like the hole layout is dependent on the eventual height of the baffles. I won’t know the height until I trim the baffles to fit under the top cowl. I’m getting caught in a catch-22, and might have to just forge forward.

I moved on to the front floors. I installed the lower cowl to see where the floors needed to be. I trimmed the front of the left floor just a little bit, so that it would fit under the cowl inlet. I’ve read in a few places now that I don’t want to trim the front floor too much.

The floors need a fairly severe angle in them. The drawings indicate two bend lines, one parallel to and just and of the cylinders. The other bend line is sort of diagonal across the floor. I started with a slight bend at the parallel line and a more sharp bend along the diagonal. That was obviously not going to work well. First, the front of the floor is at too much of an angle relative to the cowl inlet. And secondly, the filter for the engine intake needs to fit in the floor. That’s going to be much more difficult with a diagonal bend going through it.

After quite a bit of messing around, I was getting more and more confused. Time to hit the web building logs. It turns out, not many builders go for the 180hp, horizontal/forward induction engine. At least I couldn’t find many. Walter has this set up, but made a custom intake plenum. I want to use the standard one. Pete James sent me some pictures a while back, but it looks like he had to do some customization of the plenum because he cut too much off the side of the left floor. I finally looked at René Bubberman and friends’ site. He’s got some good pictures and tips on there. He basically trimmed the cowl inlet way back, enough so that the filter has room on the flat part of the left floor. I also emailed him and he sent me some more tips that I’ll walk through in my log as I work on that part.

There have been many tricky parts in building this plane, but so far this is the worst documented area. I’m using an engine that is a clone of one (IO360-M1B) that Van’s fully supports. However, the instructions leave out so many details that you’ll end up ordering new parts (as René had to) if you follow them.

The main thing I did was to make a spacer for the rear left inner bulkhead. The plans say to make a finger spacer or use washers. The problem is that the bulkhead is at an angle relative to the attachment point on the engine. I tried using a flat spacer, but that tweaks the bulkhead quite a bit pushing it against the top left engine mount. Instead I made a spacer out of some .125 stock and filed it down until it angled down to .080 on the lower side. I ended up using an additional .040 spacer with it. It took a while to make, but should work pretty well.

I trimmed the front of the side baffles just enough to get the bottom cowl on. They’ll need more trimming later, but I just want to do some rough fitting at this point. I also started figuring out all of the various angles and brackets that hold the front floors in place. I deburred the right front floor, which took quite a while with all of the corners and relief notches. I measured and rough cut a slot in the front right floor for the prop oil line. I’m trying to make it so the bracket will cover the slot once installed.

I’m starting to get the feeling that these baffles are going to take a long time.