Adjustable prop

[dwightsmall]

I have the open cowl model Cub with the O-200 eng. 25 hours ago I replaced the metal prop (69-48) with the adjustable prop and am using the -46 pitch cartridge. The takeoff and climb performance is definitely better. Hard to quantify but I believe that the ROC is about 150 FPM better. The only way I have to measure this is by referencing the rate-of-climb indication on the Garmin 396 and the fact that, when lightly loaded, I reach pattern altitude while on crosswind instead of downwind. I believe the speed gain is about 1-2 MPH. I've spent about an hour on two separate occasions making shallow circles over the desert averaging the GPS GS. The previous prop yielded 89-90 MPH and the adjustable prop gives me about 90-91. This is at 2450-2500 RPM as measured using an electronic prop tachometer. I found the installed tach indicates about 60 RPM low. I recently did a 21 hour cross country and found that the fuel burn using this prop is slightly less. I have carefully checked the burn with the former prop installed and with this one and the burn went from 5.3 to 5.2. I am fairly aggressive with leaning. This prop is smoother and somewhat quieter but takes some getting used to during ground operations. Because of the very light weight blades the flywheel effect is less and I, at first, thought the engine was going to stop while at idle RPM. This prop weighs 12 pounds less than the metal prop so it gives me 2 more gallons of fuel and the trim is noticeably different in cruise. The paperwork shows a .6 inch difference in CG. So, is this prop worth the investment? As far as I'm concerned, the jury is still out. I do like the weight saving advantage. I believe the pitch on the previous prop, the metal 69-48, was a bit too much. I would like to know what the performance would be if the metal prop was a -46 pitch. I would like to hear from others using this prop. It doesn't seem that I'm getting the performance gain I expected.

 

[carlmill]