Koolprop on jabiru

I replaced my wood 60x34 prop with a new 67 inch two blade koolprop with scimitar blades. I flew my kitfox with the new prop today and was pleased.
The wood prop was dynamically balanced and still shook the windshield compass so badly from cavitation I could not read it. The engine would not rev past 2800 even in a dive.

Now there is no vibration at all and much quieter. I have the pitch adjusted for 2800 static. It now climbs at 1200 fpm at 70mph and will rev to 3150 level flight

The wood prop cruised at 2250 rpm at 75mph
The koolprop is now 2400 rpm at 75mph but much smoother.

I flew for 1.5 hours today and still need to re learn the landing approach. The new prop is like a brake at idle and I lose airspeed much quicker. With practice I will figure out my finals.

My top speed is about the same but with less load on the engine. I'm very pleased with my purchase.

Congratulations!

There's a lot of positive buzz about the Kool/Luga props these days.

Which Kitfox model do you have? I've played with a number of different props since I rebuilt my Avid MK IV. Ended up back with the 64" square tip warp drive 2 blade. What kind of speed were you making at the 3150 rpm. JImChuk

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 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.

RPM = HP as well, so there is that consideration as well. What did the prop cost you? JImChuk

It was 1050 shipped

Quote:

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Originally Posted by avidflyer

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

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That also says at cruise - so if you're cruising at 3150 it's high. If you cruise at 2400 or so you're pretty close! I'm not a Jabiru guy so FWIW!

Greg

Did your cylinder head temperature change .

My cylinder head temps stayed the same. This engine has never had temp problems. It is always around 250 for all four.

Regardless of what the speed calculator says, this prop is much better than the wood prop that was on it. And I can tweak it as needed. 1200 fpm climb out of a jabiru seems very good to me.

Greg I agree on the cruise theory. I think 2400 rpm is a good number to keep the engine for long periods of time..

I usually cruise about 2950ish at about 95mph. If memory serves me, WOT is 3250. I'll verify next time I go fly.

That is the exact same prop he quoted me. I didn't dare pull the trigger on it because I thought thats way to big, Guess it does work keep flying it and keep posting. I may go that route as well

Got a chance to go flying today. Prop is performing well. Still trying to relearn my landing approach angles due to the increased drag at idle.

Level flight

I just got off the phone with a guy who has an add on barnstormers for a couple of Jabiru props. A Warp drive 62" and a Sensenich 62". They both look like new, and his price was real cheap. He is in Pa. JImChuk