Tony,
Humm, your reported performance does coincide with the weight you got off your scales but I'd re-weigh the plane with a different set of scales anyway. And, I'd get some certified weights and check the calibration of the scales myself as well. I'm skeptical of scales that haven't been very recently calibrated. I don't think you want to change it to be a D model in these regulatory times. You'll cut your plane's value by $10,000 in a moment. Instead, do most of the changes for the D model (except the stainless steel panel) as part of doing the 1320 lb. gross weight STC Then, lighten the plane. Considerations: 1. With a C-85 engine, operating from a high altitude airport, you NEED an extreme climb prop. I had the McCauley 1B90 repitched to 7146 and it gave me static rpm right at the prescribed upper limit (for a Coupe) for static rpm of 2225. You list that you have the O-200 engine STC (I presume you mean the O-200 crank STC, not the entire O-200 engine STC). With that change, a 7146 might give you more than the 2225 rpm specified as maximum for static rpm. Humm, that doesn't sound like a bad thing to me for operations though an officious mechanic might give you grief sometime in the future if the AI does a static runup during an annual inspection. But, for operations at a high field with any kind of C-85, I would make sure my prop gave me a static runup rpm of 2225. In my Coupe, I could climb to 12,500 feet ANY TIME, including all summer. The one and only time I failed to get to 12,500' was over Nevada in turbulence on an afternoon when 11,500 gave me a density altitude of 14,500' and I just couldn't climb any more. On my one trip out through the mountains and Intermountain West, I was always off the ground in the first third of the runway and climbed fine before 10:30 a.m. when the turbulent thermals got going. (After that, crossing Wyoming, I found a thermal and climbed in it, circling.) Summary: make sure you've got a climb prop, either a 7146 or 7148. 2. As Bill Bayne said, you've just got to have a correctly working mixture control where you live. If yours hasn't been maintained properly, (and if it's a Stromberg) the carb should be taken off the plane and the air passages cleaned, the mixture assembly taken out and cleaned. I've heard it recommended that the two mixture plates be stropped together so they make firm, smooth contact. I still think, in spite of all those who don't see the need, that a high sensitivity EGT does a lot to help adjust the mixture. The Stromberg mixture works very well but it does respond slowly. Adjusting mixture just by looking for the rpm drop (or sound change) and then pushing it back in a bit may be OK for flatlanders or for those who don't do much high flying. With my high sensitivity EGT I was able to set my cruise EGT temps at 50° rich of peak and my climb/takeoff EGT at 100° rich of peak. The 100° rich of peak was recommended as the best power EGT. Best of all, you KNOW what you are doing, you're not fumbling around in the dark with just noise. 3. Lighten the plane. a. A mechanic I used for many years washed each plane during the annual inspection because that let him inspect the entire thing, inside and out for damage or cracks. Thus, I had a clean plane with no accumulated dirt. You probably need to follow this rule since you are based at a high altitude airport. b. The upholstery side panels, firewall panel and carpet may be nice but do you need them? Consider taking them out. Can you get a very thin, light carpet or maybe just paint the plywood floor? Is the plywood floor the original thickness (I don't know what that'd be but Bill Bayne might)? Do you have a large baggage compartment with carpet all over it? Can that be made lighter, maybe with paint replacing the carpet or wallpaper or something light? c. My original upholstery was WAY heavy. I'd bet that replacing mine with new aviation foam filled seat and seat-back could save 15-20 lb. d. My panel was full of instruments and many were heavy, old instruments. The old artificial horizon would have made a great boat anchor. Get rid of all the heavy instruments and maybe keep one gyro instrument, maybe a turn coordinator, and get the panel as light as possible and remove the venturi and tubing. If you want to keep the night flying ability, you may want to keep an artificial horizon but get the lightest you can find. e. If you are going to skip the night flying, you don't need the landing lights but you'll still need position lights and a strobe to be legal during the civil twilight period when Sport Pilots are allowed to fly. f. Get a smaller, lighter battery similar to the battery that was original on the plane. g. Consider changing to 4-ply tires. (Find out what the weight difference is.) h. Consider removing the paint and polishing the plane. i. If you have metalized wings, then sell them to someone who wants metalized wings and get a good, recently recovered set of fabric covered wings. This is usually about a 35-40 lb. weight difference. If you do those things to lighten the plane, ensure you have a good mixture and a climb prop, you should be VERY MUCH happier with your Coupe. The alternative is to either get a true O-200 engine for the Coupe or change to another plane type. Piper Colts climb like a banshee but you're sitting inside a cave looking out through little windows - depressing. Please keep us posted on your progress and success. Ed Ed Burkhead http://edburkhead.com/Ercoupe/index.htm East Peoria, Illinois ed -at- edbur???khead.??com (remove the ? marks and change -at- to @)
