NetHeads, Since it gets a little quiet on these lists sometimes, please feel free to post tidbits that might be helpful to others in constructing their airplanes or engines. Most of us have discovered some things that others probably don't know about, and I'm still learning plenty in my 50's. So here's something that is a real problem solver...when you need it, nothing else will really do.
I hung a new air reel on the wall about five years ago, and it didn't come with a swivel where the air connection is made to the supply line side, so I had to sort of screw the whole reel around to tighten up the NPT connection. As you might imagine, the connection never really got tight enough and the hose was beginning to kink, and the end result was an air leak at that connection, despite the Teflon tape. Being the lazy scud that I am, I just starting turning the air off at the nearby ball valve, and only turned it on when I wanted to use the air hose. I've had a tube of Loctite 290 for probably 30 years, but was out, and it took me five years to remember to buy some. Loctite 290 is "wicking grade", which means it can be applied after a connection is bolted together. It's "medium strength" as a locking agent, but it's also quite useful as a sealer, because it will suck up into the threads and seal any leaks. I finally ordered a tube from McMaster Carr along with some other stuff (valve guide reamers, etc) and two days ago I put a few drops of it on my air fitting. The next day I applied full air pressure to it and it was dead silent. I love this stuff! Here's another example (and where I finished off my last tube). On my most recent Corvair engine, the crank, cam, and case were assembled by Mark Petnunius, rather than me, because William and Mark wanted to ensure that if something happened to William's prototype fifth bearing, it couldn't have been something I did during assembly to cause it. That worked fine, until I started flying it. After the first flight I noticed an oil leak. It took several rounds of pressure washing the oily mess and flying it again to discover that the oil leak originated at the top front of the case in the case seam between the case halves. I couldn't find any evidence that the case had any sealant applied between the case halves, and a conversation with Mark verified that. It turns out he wasn't wild about the lack of control he had over the case seam sealant's thickness, and he told me he puts his engines together with no case sealant as a result, assuring me that it wouldn't leak. I assured him it DID leak, and set about trying to figure out how to fix it. I sprayed some carburetor cleaner down in the crack (it was actually a visible gap), blasted it with pressurized air to dry it, and then laid down a little bead of Loctite 290. It disappeared down the crack, so I let it cure and then a few hours later put a little more down there. Next time I flew it, it was perfectly dry, and proceeded to fly another 450 hours that way. It's also good for locking fasteners that would be a hassle to disassemble if you forget to lock them. It's good to have your bolts and nuts relatively clean, but it'll work either way as a sealer. I'd hope you have cleaned your fasteners when you assemble aircraft parts anyway. So next time you have a similar problem, keep this in mind. One place you can get it is http://www.mcmaster.com/#loctite-290/=jsw4dy . The guide to other Loctite products is located at http://www.loctitesolutions.com/files/AN09/Threadlocking_Guide.pdf . McMaster Carr is a secret in itself. They have just about everything you could need to do anything mechanical, and they only charge "real" shipping costs without a bunch of extra fees piled on top. If you call in an order by something like 5PM EST, it goes out that day, and they are never out of stock on anything. Mark Langford ML at N56ML.com website at http://www.N56ML.com --------------------------------------------------------
