Props and Blades

[Av8r3400 1178]

Does anyone over here have the courage to talk about propellers?  Apparently they don't over at Rotax.

I'd like to know more about 4+ bladed props.  Are they only for extreme low speed ('Chutes and Trikes)?

I wanna learn something, cause I's be ignorant. 

[84KF 4]

Something like this...??

[akflyer 1427]

think you need to roll it one more hole there steve... while youre at it, put the rest ofthe bolts in and safety wire it.... sumbitch, do I gotta teach you A&P guys everything  

I dont think there is a big improvement.  The most efficient is a single bladed prop with a big counterweight.  On a Beaver, the best climb prop is a big ole 2 blade canoe paddle blade.  Most of the time, if you cant use all the power your engine is putting out, the answer is to throw more blades at it.  You can load the 582 with a 2 blade or a 3 blade.  All the extra blades do is give you less pitch on each blade (less forward speed more thrust).  I am pretty damn happy with a 72" 3 blade on my 582.  I am at 2.62:1 right now, but next week will be at 3:1 and see how she does!

[jackak 20]

Leni,

Have you read message 12317 on the Yahoo avid flyer group?  Seems like most of the people there went back to a 2.62 box from the 3.0.  Just wondering?

Jack

[akflyer 1427]

I flew a buddies KF I with a 582 b box 2.58:1 and while it flew good, when we went to the C box 3:1 and more prop it turned into a rocket on take of and climb.  I dont care too much about top speed or cruise, I want  most grunt to get out of the hole on floats.  I talked to Dave (from the list) and he said he tried 3:47, 3:1 and 2:62.  He thought he would pick up more cruise with the 2.62 but loose in climb.  Turned out he lost all the way around so he went back to 3:1.  I have the IVO IFA so I can flatten out for max RPM to get off the ground, then pitch it up for cruise.

The gear puller should be here in a few days so I should know next week if ther is any significant change by going 3:1.  If not, well it is only an hour or 2 to go back to the 2:62.

Still looking at the AC 800 to put in the nose.  About the same weight as the 582 but 120 HP and 105# tq at 6800.... plus EFI.  Shold be one hell of a performer when I get it installed.  Trying to figure out now what I can do to get the C gear box on the front of the engine.

[jackak 20]

Have you been able to pickup an ac 800?  What prop will you use with that much power?  I can just see the motor mount stretching as the power comes on!  If you can use your ifa unit I guess an Ivo med would do the job and you'd come out of the hole like a rocket, and go like hell in cruise.                       

[akflyer 1427]

Well you called that one Jack.  I gave the 3:1 a fair shake, but I think I lost allthe way around.  take off, climb, and cruise.  The fuel burn went up too as I have to trun the engine faster to get the same prop speed.  You would think that I could just go with more pitch and get iut back but in real world the math just is not working out.  I did way better with the 2.62:1.  I will be swapping abck next time home.

I have not got my hands on the 800 yet, still trying to get a price from AC salvage on the engine, puter, wireing harness etc.

[akflyer 1427]

I tried AKFLYERBOB Brolga prop on my plane last Sunday.  I thought that would be the ticket and my performance would go up.. No dice.  about the same climb, and at 5600 RPM my fuel burn was 1 gallon an hour more than with the IVO with a 5 MPH speed reduction.  I am going back to the 2.62 gears and sticking with my IVO IFA for now.  I think his performance difference is because he is normaly solo, I am normaly duel with alot more fuel, plus he has almost 3' more wing than I do.

[jackak 20]

Leni,

Have you read the prop tests that the fellow who sells the feathers vg's did on his 701?  Seems that using his criteria, most of the props were quite similar in performance.  I think some may be quieter, some stronger, others lighter, but overall performance very close.  I haven't tried even as much testing as you have, but on the C model, a 70" Ivo high pitch ul prop, turning 6250 static gave great performance.  Cruise was only around 80 mph, but to was excellent.  That was after a fresh overhaul done by Mike Jacober just before his death.

Jack

[akflyer 1427]

I am liking the IFA.  when I set the prop for cruise on my brothers KF II at 5800 RPM, then left it there for landing, the result was I was only able to turn 4750 on take off.  There is alot of performance left on the table by not having IFA I.M.O.  It took all I could get RPM wise to get his plane on step with 2 fat guys on board.  This was due to the floats he had on it, but still, it was a booger.  I should be getting my new floats on my plane this time in and will see how she does!