DP asks- >Anyone have experience "dropping" a lip from the lower cowl >to let heat escape?
No experience here whatsoever... just from what I've read about it and know from theory. What you have inside the engine cowling is air that has entered at a relatively high pressure and has gone through a set of cooling fins on the engine cylinders and heads, baffles, oil cooler, whatever- and has lost some of its pressure. The air on the underside of the airplane is at a high velocity, zipping by in the slipstream, and at a relatively higher pressure than the air inside the cowling. That difference in pressure tends to prevent the air from wanting to exit the lower lip of the cowling and enter the slipstream under the airplane. The small 'lip' on the trailing edge of the cowling air exit tends to add resistance to the slipstream (pressure loss), to allow the air inside the cowling to more easily exit. The pressure of the air inside the cowling has to be greater than the pressure outside for the air to exit, so we have to drop the pressure of the slipstream air by introducing the "lip" to add drag. As noted in many tech write-ups on engine installations, engine cooling is usually a major teething problem and folks have even found that air is tending to go up into the cowling through the "exit" opening on the bottom, so they make the opening even larger... which lowers the pressure of the airstream trying to exit... and hinders the cause. But don't try a 'lip' unless it's necessary due to high engine temps or other indications of insufficient airflow through the cowling. And if you're experimenting with a 'lip', make it something you can remove in case it doesn't work out after test flights. Some of this is "black magic" and we don't really have the answers ;op Oscar Zuniga San Antonio, TX mailto: taildr...@hotmail.com website at http://www.flysquirrel.net _________________________________________________________________ Fast, faster, fastest: Upgrade to Cable or DSL today! https://broadband.msn.com
