RE: Lanier 94" Yak help
Sorry I have been gone guys, but busy is not the word around here, swamped is.
For cooling purposes you are supposed to have at least 1.5 to 2 times the opening on the bottom as you do for the air inlet, I know it is a Yak and all opening. But we are not running a 480HP 5 cylinder radial so we do not need all of the opening. I have made the engine baffles out of everything from fiberglass to 4mil foam core, you close the opening and cut it out for your cylinders or cylinder and output shaft then make it duct back to the motor. It is rather simple to duct it this way and the Midwest foam core you can get at your LHS is very light and works just fine, then the hard part, you need to make the air hole on the bottom of the cowl that is 1.5 to 2 times the opening to let the air out. I will attach pictures of my big 260 where you can see one of the ways I do this, but on the Yak the cowl is round and if you make one opening it looks like carp. I have seen people spend hours opening all the louvers in the cowl and then still have to make more opening on the bottom that looked pretty good, but that solution is for someone with no life, LOL. On my Lanier Yak I ran a ZDZ 80 and only had a duct on the bottom of the cowl, I opened the bottom of the cowl just enough where the air would escape around the top and rear of the head and back to my Pitts style outlets which didn't look too bad, but for those running a twin you can make strips like I did here from mid way to the body of the plane on the bottom 1 on the outside of the exhaust outlets and a few in between to get the proper air flow.