I'm curious as well. I've been running a Prince 64 x 34 with great results. I haven't heard much about the Kool prop.
I'm curious as well. I've been running a Prince 64 x 34 with great results. I haven't heard much about the Kool prop.
Mike Bentley
Model IV-1200
Jabiru 2200A #438
Rotec Aerosport LCH Heads
Ellison EFS-2 Throttle Body
Prince Prop (64x34)
My SPOT Page
I have a model 4-1200 speedster. It weighs 641 empty. My engine is s/n 204 which is the oldest version with 572 hours.
The top speed yesterday was 105 indicated level flight 3150 rpm it was a little bumpy so I didn't hold it there long. Could have crept up if I had smooth air.
Should I pitch for 3300 level flight? I'm new to the adjustable pitch family.
Any idea how accurate your ASI is? I did a bunch of math, figuring tip speeds, and then googled tip speed and found this info on the warp drive site.
http://www.warpdriveprops.com/propspd2.html
You might be at a better (more efficient) tip speed at the 3150 rpm. Also, if my memory is correct, you have aluminum connecting rods on the earliest engines, later ones are steel. Maybe the lower rpm is less stressful on the engine?? JImChuk
I haven't checked my asi accuracy.
I was also wondering about increasing pitch a little and keeping the engine at a lower rpm for longevity. The old prop wouldn't let the engine rev past 2800 and it has been trouble free for 570 hrs.
I just hated the noise and vibration. I wanted a longer prop because I'm more interested in stol capabilities than speed. I will look into the tip speed efficiency info. Maybe I should limit rpm to 3000.
Using that tip speed calculator you loaded shows my tip speed is Mach .818
It says maximum performance is .8 to .92
Seems that I'm good at 3150 max rpm.
Fourth paragraph says that best performance is at or below 700 fps or 475 mph. At 3150 rpm, your prop tip speed is 628 mph. I think our Jabirus are in need of a gearbox to be most efficient. Nobody wants the extra weight or complexity though. JImChuk
Ok yes I went back and read that paragraph. I will need to do some more testing to see if I can get the same performance with more pitch to slow the rpm down some.