« Posts tagged Airseal

Red Goo.

5 hours.

A shortish day, after Thanksgiving weekend.  But decent.   I got the pax side restraint system involved in addition to the pilot side crotch strap or “anti-submarine” restraint, as it’s called.  That took longer than I thought because of the number of times I had to hop in and out of the plane to find washers and other hardware and tools.

But now they’re both in.  This unflattering photo is just to show that both seat belts are hooked up.


So I went on to the red goo.   I’ve been putting this off, because of my usual aversion to non-solids, but it was finally time to RTV the baffles.   Squeezing a tube of red RTV into all the places it has to go is really hard on the hand muscles, especially when you have to get the nozzle into nooks and crannies now blocked by FWF equipment.

IMG_1685So I’m not the best RTV’er in the world, but I think the bases are more or less covered – a bead running along the baffle meterial, and anywhere light gets between the baffle and the engine.   OK, maybe not everywhere, but everywhere I could get the stuff in there.

IMG_1686Oops.  Didn’t get around the right magneto blast tube.  I’ll have to get that later.

But I was sure to get RTV into all the gaps between baffle and oil cooler, because that’s kind of important, and as for other leaks, we’ll have to see what happens to CHT’s in flight.

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 13

5 hours.

Lucky 13. This baffles thing is second to none the worst, most vexing part of this build yet.  However, I did make a lot of progress this weekend. I got the airseal material trimmed, for the most part, although I suspect I’ll have to iterate the left front a bit, the part that goes around the governor. This is no end of head-scratching and puzzlement. Today I was actually able to drill the airseal material to the baffle sides, which is a big step, and with the exception of what I just mentioned about the front governor, the top cowl seems to seal all the way around, which is a good thing. Never having built an airplane before, it’s hard to tell if I’m overthinking a problem. The key is to keep focused on the end result desired, and solutions will appear. On this particular task, they take their sweet time doing so, and this is the one task on this build where I’m not able to stand back and go “yeah, that’s awesome.” Instead, it’s something to be gotten through, like a prostate exam or tax forms.

I’ll post as much of a photo story as I can in a later entry, but I didn’t take a whole lot, and part of the reason for that is that it’s really difficult to see anything inside the cowl with all the parts installed, let alone jam a camera up in there and shoot comprehensible pictures.

There are also a number of things that need to get finished before this can be called “done” so I’ll list them here and hope to get at them this week.

The pain in iteration comes from having to put on and take off the baffles. This is a time consuming process, and needs to happen several times before all the finishing touches can be done, but it’s not a good idea to install things permanently because depending on various factors they’ll just have to come off again. So here’s a list of unfinished business, in no particular order:

  • Make tab for left front lower ramp to close off gap near engine case.
  • Drill rear bracket to rear baffle
  • Make/install fasteners for front/rear side baffles
  • Drill ducts for alternator and magnetos
  • Drill/install spark plug wire grommets
  • Proseal corners of snorkel at the filter bracket
  • Finish making front left baffle seal sections
  • Trim cowl for lower left inlet ramp
  • Rivet oil cooler reinforcing bracket to baffles
  • Drill/install oil cooler doubler and bracket
  • Deburr baffle seal rivet holes
  • Pop-rivet baffle seals to baffle metal
  • Glue/fiberglass top cowl inlet ramps/seal inlet ramp sides, shape ramp interface
  • Permanently install prop governor, gasket and all
  • Recut governor/front left seal material
  • Make/install lower cowl inlet seals

It’s endless, I’m telling you.  But with this out of the way, it’s time for plumbing, wiring, and control cables.  When that’s done, I’ll rivet the top skin on, put the canopy back on, and finish the interior.  After that, it’s time to go to the airport!

Baffles 12

7 hours.

If I had a time machine, I wouldn’t go back and tell 1984-me about all the cool stuff in the future, or bet on all the baseball games, or ram a pickup truck into a sleeping Mohammed Atta. OK, maybe I’d do that. But what I’d definitely do is tell 2005-me that under no circumstances should you purchase an engine off eBay, and if you do, make sure the damn prop governor is in the back.

I’ve spent more time than I care to think about figuring out just how the hell the cowl intakes are supposed to interface with the baffles via the rubber airseal material. There are no guidelines for this, here there be monsters, etc. The io-390.com site has a lot of good information, but as with all things cowl and baffle, everybody’s setup is just a little bit different, and I’m basically having to roll my own solution anyway. This is not necessarily a bad thing. I just wish I knew a lot more of what I know now back before I started.

The major issue comes from figuring out the shape of the airseal on the front baffle on the left side, the one that wraps around the prop governor. I think I have something that works, but I’m not 100% happy with it, and I wish I knew how to do it better. But it looks like what I’ve done will seal the high-pressure area under the cowl, and when I get back from Toronto, I should be able to finish cutting the airseal strips for the rest of the baffles. I should also be able to bond the inlet ramps to the top cowl and start filling in the tunnels on either side of them. The idea is to keep air from spilling out of the high pressure area into the area below the engine. The pressure differential is what cools the engine.

If I didn’t have this stupid front-mounted governor, the standard baffle kit would fit fine and I would probably be on to plumbing and wiring by now.