« Archives in June, 2012

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.

Baffles 11

6 hours.

Quick update: Baffles trimmed, front baffle bracket fabbed, top inlet ramp trimmed,

Pondering airseal fit. I just don’t friggin’ get it.