Al.. Is 2350 rpm all you can get in cruise?
You should see at least 2500 if not 2575, which then would indicate best performance... for a C-85. On the other hand, a C-90 engine that shares the O-200 crankshaft will be redlining at 2475, a hundred revolutions slower than a C-85, but due to the higher torque will still develop 5 horses more than a C-85. Interestingly enough the McCauley 71/52 is considered a normal prop on a C-90, while a cruise prop on the C-85. It is all torque related I guess. Confusing? Sure. Last note, 105 MPH is slow in a Coupe that has 85 or more horses. I see 110 or more depending on environment with a C-85 and a McCauley 71/52. Hartmut To: [email protected]; [email protected] From: [email protected] Date: Mon, 25 Jan 2010 11:00:49 -0600 Subject: Re: [ercoupe-tech] Re: PROP PITCH Donald, I have a 1947 415CD. It's engine is a C85 with the 0200 STC. It now has 12 hours on it since major OH. Hartmut recommended I put a 71/52 prop on it for best cross country cruse. I am happy with the 71/52 performance on this engine. I gave up just a little bit of climb in order to gain just a little bit of speed. I am with you, a stickler for not having a draggy plane. SO, I removed the large venturi, Installed a new round windshield and waxed it to a military bootcamp shine. It now indicates 105 MPH at 2350 RPM. Before the improvements it indicated 105 MPH at 2350 RPM. My ASI was checked with my GPS. SO, no matter what I do the numbers just keep comming out the same. Let us know how your wheel pants work? Al Flora N94748 (HYR) ----- Original Message ----- From: Donald To: [email protected] Sent: Sunday, January 24, 2010 8:35 PM Subject: [ercoupe-tech] Re: PROP PITCH That makes sense. I am a stickler for not having a draggy plane, plans already to put the sissors fairing back on, wheel pants going on, venturi horn comes off etc. I have the round windshield, somewhere I heard that is even a help too. Anybody have any more ideas to make it slide thru the air easier? I have even found that a good coat of wax helps. --- In [email protected], "Ed Burkhead" <e...@...> wrote: > > > Besides what Hartmut said, a heavy Coupe with a cruise prop (7151 or > 7152) may not be able to get up to cruising speed due to load and > insufficient horsepower to turn that pitch of prop adequately. > > While a 1260 pound Coupe might cruise 112 mph with a 7152 prop, a 1400 > pound Coupe may only cruise at 90 mph at near full power with the same > prop. > > So, if you want the fast cruise, either you need the horsepower to do it > or a plane light enough to do it with the engine/prop you have. > > Each airframe, just like each boat/ship hull, has a range of speed it > can reach with moderate power. Past that speed, the power requirements > go up steeply. > > Ercoupes and Forneys get to that elbow in the graph somewhere around 110 > mph. The guy who mounted a 135 horsepower engine didn't go much faster > than that - he just got humongous climb and fuel consumption (and a very > ugly plane). > > Mark in Wisconsin (who used to work for a previous owner of Skyport and > who designed the 30 gallon fuel tank system) is one of the few who has > made a higher power installation effective and he really worked at it > intelligently. > > Me, I was happiest with my C-85 engine and a 7146 prop that gave me > adequate climb even though my 2400 rpm cruise speed was only 100 mph. > > Ed > _________________________________________________________________ Windows Live Hotmail: Your friends can get your Facebook updates, right from Hotmail®. http://www.microsoft.com/middleeast/windows/windowslive/see-it-in-action/social-network-basics.aspx?ocid=PID23461::T:WLMTAGL:ON:WL:en-xm:SI_SB_4:092009
