Prop Rip

[Bunky.F.Knuckle]

I'm not sure yet. I have the props narrowed down to a Falcon CF 24/9 or Mej 24/9th. What do you think?


Sent from my iPhone using Tapatalk

I ran a Falcon 24x9 cf on a gp 61 with a pitts muffler. It wasnt overly loud on the ground. But i was never forced to put it on a dB meter either.

You may like the 24x10 or the 23x10. You will have the same basic load with the 23x10, just a little less tip speed with the shorter prop. I think no matter what you do and what prop you choose, it "may" be too loud for them, so to speak.

Just dont go full throttle on the ground, and you'll be ok.

 

[Eric Anderson]

I ran a Falcon 24x9 cf on a gp 61 with a pitts muffler. It wasnt overly loud on the ground. But i was never forced to put it on a dB meter either.

You may like the 24x10 or the 23x10. You will have the same basic load with the 23x10, just a little less tip speed with the shorter prop. I think no matter what you do and what prop you choose, it "may" be too loud for them, so to speak.

Just dont go full throttle on the ground, and you'll be ok.

Thanks Bunky . Fergus Lin also recommend a 23x10. I ordered a Mejlik 23x10.


Sent from my iPhone using Tapatalk

 

[Twister]

OK so far I tried
Beila 29x10 bad prop rip @ half throttle
Beila 29x12 prop rip
Biela 30x8 real bad prop rip
Mejzlik 29x10s prop rip ( really like this prop)
Mejzlik 30x10 Prop rip
Falcon 27x11 prop rip on down line (fast prop )
Mejzlik 27x12th prop rip on down line (fast prop )
Mejzlik 27x12th 3blade no prop rip tons of air over surfaces and decent pullout ( going to stay with this prop for now )

 

[Surfer Dude]

If you can 28x12 its a good load on the engine. With minimal throttle management it should be good

 

[Pancake]

Propellers rip because the tips move faster than the speed on sound. In general, a bigger diameter prop is more likely to cause rip. It's fairly easy to calculate the RPM at which a certain prop will rip.

rpm = 255780 / diameter in inches

So a 27" inch prop will rip at 9473 RPM (way above the normal RPM range), but a 32" prop will rip at 7993 RPM, which is easy to achieve in a downline or fast pass.

Great post. Exactly what I was looking for.

I want to add my 2c to the discussion. IF you want to slow a prop down, don't add an inch of dia, and take away the pitch- IE: going from a 29X10 to a 30X8. Both will put about the same load on the motor. You want to keep the pitch constant, and add diameter. Otherwise you're trading apples for more apples.

Also, and this is a side rant- most you lucky bastiges live at or very near to sea level. I'm at 6,000' ASL, and in the summer time, density altitudes routinely reach 9K. Our engines just don't have the oomph up here to swing these big-ass props! I have Vess 27A's on my DA-100's and they won't rip unless you are on a WOT downline with a slippery airplane! Everyone at sea level tells me I need a 28X10! WTF! NO way is that going to pull my plane out of a hover!. Just some food for thought...

 

[stangflyer]

Great post. Exactly what I was looking for.

I want to add my 2c to the discussion. IF you want to slow a prop down, don't add an inch of dia, and take away the pitch- IE: going from a 29X10 to a 30X8. Both will put about the same load on the motor. You want to keep the pitch constant, and add diameter. Otherwise you're trading apples for more apples.

Also, and this is a side rant- most you lucky bastiges live at or very near to sea level. I'm at 6,000' ASL, and in the summer time, density altitudes routinely reach 9K. Our engines just don't have the oomph up here to swing these big-ass props! I have Vess 27A's on my DA-100's and they won't rip unless you are on a WOT downline with a slippery airplane! Everyone at sea level tells me I need a 28X10! WTF! NO way is that going to pull my plane out of a hover!. Just some food for thought...

Wow...6000 feet? That would suck in the summer.

 

[njswede]

It's actually a bit more complicated than that. I noticed my 27" was ripping, so I did some more math and I realized you have to take the airspeed into consideration. The formula becomes rpm = sqrt(c^2 - v^2) / d * pi for metric units. OK, that's a mouthful. What it means in real terms is that if I'm doing a 60 mph pass, I only need 8395 rpm to rip.

 

[49dimes]

When DA gets these out and in different displacements may be the prop rip issue will just go away!