I have an aircraft with a baffle that is not currently airworthy. One option we're exploring is using a machine shop to produce a one-off replacement per the FAA rules for owner-produced parts. Does anyone know where I could find the specification/drawing for the baffles?

Thanks,
Rob Glenn

Have u tried Matt?

You can use the old one as an example to duplicate from. This is allowed by the owner produced parts rule.

Zach

Along the lines of this post, does anyone have some good photos or details of the rubber baffle seals for a N/A Twin that has been cooling well for them? I'm having some trouble getting the newly overhauled left engine to stay below 410 degrees on climb and high power settings according to the new Insight monitor. I'm not sure if the engine was running like this pre-overhaul or not, because the #3 cylinder with the factory probe has been the coldest on both engines and we wouldn't have noticed the engine CHT's being a little too high.

Kevin,
Don't worry about 410 in the climb at all! If that's your hottest cyl then you are in good shape. Not that your baffles couldn't be better, they probably could, but don't get hung up on that 400 number that gets shot around. Is it desireable, yes, but you are not hurting anything at the higher temps. Now, the way the temps are being read make a big difference. If you still have the factory probe in #3 and you are using a spark plug gasket type thermocouple it is going to read high! The cyl head is hotter there than where the bayonet probe screws in. Also, #3 cyl needs space behind it to get air around the back side of it. The fins are short and the airspace between fin edge and barrel is almost nonexistent. As for the rest of the baffles, think air pressure. The idea is to keep as much pressure on top of the engine as possible. Anywhere the air can get from on top of the engine to the bottom of the engine with out going through the cyl is wasted air. If your soft baffles are not set onboard of the hard baffle, or sececured outboard with a solid bar to keep it from gapping (many are just pop riveted and the baffle gaps between the rivets making big gaps), and all of the soft baffle is in good shape, overlaps to seal at corners, and positively contacts the upper cowling and cheek cowls, then you are in good shape. RTV any gaps and holes that you can't get any other way and you will have the best cooking/least drag you can get!

Here are some links to other reading on the subject.
http://lycoming.prpl.rs/content/more-cy ... emperature
http://11hc.44rf.com/manuals/engine-pro ... prints.pdf

Zach

 

Kevin,
Feel free to give me a call and we can talk about this. Keep good airflow (cowl flap open, rich mixture, wide open throttle during climb, and cruise climb speed.) and keep it under 500 during break in and you will be fine It will start to run cooler as it breaks in but you can help it with baffle work. You are seeing information you have never seen before. If you flew it to tbo with the stock gauges, go back to looking at them and use the supplementary info that your new GEM provides to fine tune the installation, not to panic that something is wrong...

Zach