Syd, It seems you sent the following message just to me but intended it for the group. I'll comment below.
_____ From: Syd Cohen [mailto:[email protected]] Sent: Wednesday, January 27, 2010 12:32 PM To: Ed Burkhead Subject: Re: [ercoupe-tech] Re: PROP PITCH Ed and all, I think you are forgetting the variations of drag from one Coupe to another. Some have one, maybe two big venturis, landing lights on the gear fairings, wheel pants, numerous antennas, etc. I've flown with many Coupes in our Caravan into AirVenture and to Sun N Fun, and I almost always have to throttle back to 2100 rpm so that they can stay with me. Some Coupes with 7150 props can't keep up to my Coupe with a 7148 unless I throttle way back. Syd _____ Syd, I'm not forgetting it but I don't know how to quantify it. The 95% efficiency number I got from Paul Prentice's book and found it matched my plane's actual performance. Since, I've found that it matches the performance for lots of other Ercoupes. But cleaning up those aerodynamic drag items is a great idea. I dearly wish someone could do a proper aerodynamic design of wheel pants for the Coupe's trailing arm main landing gear (and nose gear, too). I'd bet several miles per hour could be picked up if that were done right. Removing all venturis and lowering the weight of the plane are greatly beneficial to carrying capacity even more than speed. Similarly, I wish there were a way to improve the effective aerodynamics of the Ercoupe/Forney canopy area (such as a more gently slanted and rounded windshield kind of like Mark Huesden's). I'd guess a couple or four mph could be picked up there. STC and profit for somebody who, by the way, would earn the money. Aerodynamically optimal wingtip lights/strobes and lighting would also be high on my list, especially the landing lights. Actually making the Coupe a retractable would be enormous, but I think that's unrealistic. Most of the benefit could be realized with good, aerodynamic wheel pants. The biggest speed mod would naturally come from replacing the C-85, etc., with a new in-line engine and put in a redesigned cowl similar to Fred's original design - narrow nosed and nicely streamlined. Maybe the new generation of diesels will come up with one in this class. Me, I'd be inclined to skip the engine and windshield mods to keep the plane closer to original. A huge value of the Ercoupe, to me, is its wonderful virtues for a plane designed and built when it was! Most of the mods in this list bring it back closer to the original factory appearance. Ed
