Comments inserted into Dennis's text.
If there is enough interest I can show the full calculation so you can do it yourself at altitude. I can also expand the interesting part of the chart and put in some additional diagonal lines to allow one to resolve speed better. Remember: with log scales, the line for 275 mph is NOT halff way between the 250 and 300 lines.
If enough are interested, I will write a little monograph for the archives that has the data on atmospheric density, simple calculation methods, conversion factors, and all that jazz so you can do it yourself.
Fred
Fred can you tell me the units on the chart you put on the lml. Is it statute miles per hour or nautical miles per hour?
[Statute miles per hour which equals knots times 1.15]
If statute my IV results are not believable.
[Read closely: Chart is for sea level. One has to correct for lower air density at altitude.]
At 8500 4 way gps wide open (2700 rpm) I am getting 243.5 to 245 knots (two different days runs) on my 310 hp stock factory reman continental with hartzell scimitar. The HP was 80% per the G3X calcs. So taking 80% of 310 times 0.85 and chasing that down to speed I am about 1.5 sq ft if statute and 2.1 if sq feet if nautical.
[You need to correct for altitude, that is why. Similar conditions for my ship late last year, one flight only short test just to see what would happen, 8000 feet but a warm day, I recorded 238 knots, but I have not calibrated for a couple of years. Also, the power computers are frequently way, way off. Only way to be sure is to operate lean of peak and then use fuel flow and compression ratio to get a reasonable power number. Rich of peak at full throttle, the engine to engine variation from the factory is 5% as Greyhawk has noted, plus effects of water vapor and on and on.]
BTW, I have not put on the cowl flaps or plenum yet. I keep tweaking the design in my mind and I keep flying the plane too much. But I did improve cowl alignment and install gap seals to take me from 239.5 knots to the current speeds. My CHT's are very cool. I need the cowl flaps. I am about 280 CHT in cruise and 220 in descent (thats if LOP). I wanted to not modify my cowl outlets but I cant come up with a design that looks as slick as yours closed. Mine cowl flap design looks assymetric with the cowl outlets. It would likely work but it would not look as good as yours. I may be replicating yours. Any idea of current draw of your linear actuators? I have a 24 volt bird and limited capacity on my 12 volt power supply.
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