X-Mozilla-Keys:                                                                                 
Ed Anderson wrote:

Thanks for the comparative data Ed, this kind of stuff is hard to find.I
was surprised at the numbers though.  My RV-4 is a bit lighter but the
difference in performance should not be that much.  Last week on a rare 75
degree, 60% humidity day I did some ROC tests and got 2100 FPM at 100 MPH.
This was solo at a gross takeoff weight of 1220 pounds, engine rpm 5300 rpm,
WOT,  prop  68 x 71.  This was starting from an altitude of 100 ft. above
MSL.

You mentioned it once but I've forgotten what your empty weight was. Also,
what was your WOT rpm during the climb?   You might want to try using a
slightly higher airspeed.  I find that mine is best around 100 - 110 mph.
The higher speed allows the engine to turn up more rpm and the increase in
power more than makes up for the increased drag.

Tracy

Ed Anderson wrote:

 Hi Tracy,

  My empty weight is 1170 lbs, but I agree that something does not track.
I am turning approx 100-200 more rpm than Jim, but performance is
considerbly less.  I was climbing at 85 -90 so that could account for a
little of the difference, perhaps higher airspeed in climb would be the
ticket. The only other difference is Jim's prop is about 1" wide in chord.
But, I know you are using a Performance Prop as I am so they are practically
identical.

 I am fairly certain that I am only producting 150 hp and get 5000-5100
rpm at static run up.  Get slightly more on cooler days. As I recall that is
about what you get with the 68x71 last I heard.  Guess you may be getting
more now that the new engine is producing 185 or more HP.  I don't have a
fuel flow meter, but I have flown it full throttle for over 30 minutes and
carefully measured the fuel used (9.8 GPH) which would indicated I am
producing considerably less HP than you (17.5 GPH).

 I changed the timing a little today, after it was pointed out by Neil
that the point of my timing indictor was (apparently always has been)
pointed off by 30 degree or more which could account for approx 10 degree on
the eccentric shaft or so.

 In anycase, I plan on attending the Thomasville flyin next week end so
hope to see you and Laura there.

Ed

9.8 gallons per hour translates into about 107 engine HP max 
at a BSFC of 0.55. 

As I recall Jim's airplane grosses about 1500 pounds
so Ed's airplane must be about 1400 pounds. (Sounds like a high school
math proplem :-)) 

So Ed is climbing at 700 FPM and Jim is climbing
at 1000 FPM. Ed is doing 11.66 FPS vertical and his climb HP is therefor
about 30 HP out of the prop. If we figure a prop eff. of 80%
Ed engine HP for climb is roughly 37.5 HP. 

Jim's climb HP is 45.5 out of the prop and engine HP is about
57 HP. It sounds like Jim has more HP than Ed.  

Tracy on the other hand is climbing at 2100 FPM or 35 FPS vertical
and his gross weight is 1220 so his climb HP out of
the prop is 77.6 or about 97 HP out of the engine.

All three airplanes are mostly pretty close in overall aero drag.

Sounds like Tracy has a lot more HP than both Ed and Jim.

Ed what about that intake manifold?

What brand of prop is Jim using?

Paul Lamar

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