« Archives in July, 2012

Cowl and foam

4 hours.

Yesterday I glued the sub-ramp I made the day before to the cowl. Today, I shot my marine foam into the space underneath the ramps in preparation for glassing in the sides and blocking travel of high pressure air through the spaces underneath the ramps to the low-pressure area to the sides and below the baffles.

I may have used too much foam. It just keeps growing.

Tomorrow I’ll carve out the excess foam and glass in the tunnels.

I also took a crack at filling the area around the oil door. This might turn out badly, but it’s just resin and micro, so I can always sand it off and start over.

Cowling ramps

2 hours.

This is two hours of puttering over the last several days. I go the cowl ramps glued on, and tonight I made the contoured part that interfaces with the governor baffle. Next is to fill the cavities under the ramps with boat foam, shape them, then glass them over.

Gluing the ramps on turned out to be more or less a non-issue, but I did have to take the front baffles off, which is a PITA.

I got my ignition harness back from Bill’s Air Center. That was only $80 worth of stupid, so I consider myself lucky. Oh, I didn’t tell you about that? OK. I was pulling on the wire end of one of the starboard plug wires at the harness cap, for some reason, and it slid out of the casing. Plug wires work like a Chinese finger trap. The outer shield expands or contracts depending on where the tension is, so it allowed a bit of wire to slide out of the casing. One thing led to another, bad went to worse, and the next thing I know, the whole wire is in its separate components on my bench.

After a frustrating couple of minutes, I resigned myself to taking it up to Bill’s Air Center at SMO. Bill’s a great guy and he’s been there forever. They fixed it, but said it was a major headache to source all the parts, since Skytronics doesn’t actually sell them. They want you to send your harness back to them for repair. Phoo on that. Anyway, it’s all better now.

Baffles 15 – Almost done!

6.5 hours

Today was fairly significant, even though it might not look it. I finished attaching the airseal material to all the baffles, drilled the holes for the spark plug wires, and more or less permanently attached the baffles to the engine.

Since I did the aft left baffle last time, I figured I’d do the aft right baffle, that way I could at least get both of them on and done. this one actually proved to be pretty easy, with no surprises. After all, it was more or less about doing the spark plug wire grommet holes, deburring everything, and attaching the airseal with rivets.

The connection in the middle where the baffle connects to the bracket got changed a little. Originally, I had the bracket pinning the airseal between it and the baffle, but that looked stupid and distorted the baffle, so I cut some slits in the baffle to get around the bracket. It should seal fine, and eventually the rubber will mold itself around the bracket with hours of heat and use.

With both sets of aft baffles on, I installed the oil cooler. This was one of the items that’s been bugging me for a while, and now it’s finally done. I’m still not happy about the amount of flex in the aft baffle where the inboard oil cooler attaches, but I’m not exactly sure what to do about it right now. Any reinforcing strut that picks up a convenient attach point on the engine would interfere with the fuel injector lines, which is no good. This shot shows the beefy angle bracket I installed last time to reinforce the connection between the side and rear parts of the baffle, and gives the oil cooler bolts a more solid structure to hang from. Lots of people report problems in this area, but this, and a strut for the other side usually fixes it.

So here it is, the bane of my life, nearly finished. I recut the governor baffle, because the governor hole didn’t seal well enough for my taste, and this time around, I left a big dog-ear flap on the front to aid in sealing with the cowl, should the need arise. I didn’t take a lot of photos of the process of installing the governor baffle seal, because it’s difficult to shoot pictures while you’re using both hands to wrestle with airseal. The end of the governor is bigger than the housing where the seal sits, so you have to cut the hole big enough to get over the end, but small enough to seal on the governor housing.

This process also revealed a small flaw in my governor baffle design: I can’t actually take the baffle off without removing the governor. I can live with this, I think. But what I have to do to get at the governor nuts is take the left front baffle off, which can’t be done with the governor and its baffle in place. But there’s always a way. It’s messy, and it’s a hack, but disconnecting the oil line from the #2 cylinder allows me to drop the left front baffle out of the way and slip it out past the governor baffle.

I also put the airbox on, just to see everything in place, and make sure it all still fits. What you see in the photo is essentially the final configuration of the baffles and intake.

I still have a few minor things to do. I need to drill the duct holes for the mags and alternator, but I don’t want to do that until I’ve figured out control cable routing. I also need to make the rods securing the baffles at the bottom where they wrap around the cylinders. Once that’s all set up, I’ll need to squidge some red RTV in where the airseal meets the baffles, and around the engine-baffle interface in various places, plus around the corners of the oil cooler so I get maximum efficiency from the airflow through that.

Baffles 14 and Oil Cooler

8 hours.

I haven’t been working on this a lot lately, because my motivation is low, and I’m traveling for work. But I can report this time that the project is sucking a little less. Last time, I’d gotten the baffle seal material trimmed. Since then, I’ve been knocking items off my list, one by glorious one. At this point, baffle seal material is riveted to both front outboard baffles, and left rear baffle.

In addition to that, the oil cooler bracket is done, and the left rear baffle parts are all riveted together. This went surprisingly well, except for the fact that I initially installed the oil cooler double upside down, which sucks, because just flipping it over doesn’t work: The damned holes don’t line up on the sides anymore. I managed to fix this without making a huge mess, but there were a few too many extra holes for my comfort, so I beefed up the section in the corner with a piece of angle running down the vertical where the side and rear join up.

This is a shot of the rear baffle section before I cut out the hole for the actual cooler.

Making the hole for the plug wire grommet was also fun. Not that big a deal though. And finally, everything became a more or less unified piece of equipment that will hopefully serve its purpose as part of the cooling system. With the angle going up the vertical on the outboard corner, this thing is really solid, and hopefully stands up to all the engine vibration. I’m not crazy about the fact that the inboard side of the cooler is attached directly to the baffle, so I’m going to look at options for transferring the load to the engine case somehow.

Here’s everything riveted together, except the baffle seal. I’ll try to find a better photo. When I was doing this, I didn’t take a lot of photos, because I’m experimenting with a new workflow that involves periodically stopping to clean up the mess that accretes around the work area, such as tools, clecos, harware, and cast-off bits of aluminum. At some point, I’ll roll photos into that process. Yeah, I know, seven years on is a little late to be experimenting with new methodologies, but that’s why it’s called “experimental” aviation.