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czbbflier
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Winglets On Propeller Tips

Wed Apr 03, 2013 2:06 pm

I was just perusing the thread asking about the possibility of 90-seat turboprops and admiring the image of an ATR aircraft that had winglets and 8 bladed propellers.

The aircraft had winglets on the wing and it looked odd enough that it made me stop and think- would putting small winglets on the propeller tips achieve the same result?

I imagine that the tips are more like points and that they are swept back to minimize the vortex and shockwave but would bending the tips into actual winglets at say, a 30-degree angle, make them more efficient?

With propeller tips pointing toward the forward end of the plane it would look really odd but would it work?

Any aerodynamicists out there?

Cheers!
Brian

 
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vzlet
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RE: Winglets On Propeller Tips

Wed Apr 03, 2013 4:22 pm

Google "q-tip propeller". They've been in use for a while, usually as refitted upgrades.

(Even on blimps.)
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Pihero
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RE: Winglets On Propeller Tips

Wed Apr 03, 2013 4:23 pm

First, a propeller blade is just an airfoil - like a wing - and the nbasic aerodynamics are no different than a wing .
But the rotation of the blade creates more phenomena than a wing, in particular the helicoidal vortex one sees behind the prop and causes all sorts of * propeller effects*.
In theory, nothing would prevent us from having winglets at the prop tips :
the advantages would be 1/ making the prop more efficient by reducing the induced drag ( sama same as a wing ), 2/ reduce noise, 3/ keep the prop ti subsonic by decreasing its length...
Big problem is in aerodynamic streeses and AFAIK, there had been some quite spectacular failures during testing, so the solution is now to give a greater sweep to the tips ( see that as equivalent to the 777 wing tip compared to the 787 for instance). Try and find articles on the *Hartzell Q-tip*.
As naval propellers are wider and capable of deealing with bigger torque stresses, modern ones do have winglets. You could find some pictures on the web.
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vikkyvik
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RE: Winglets On Propeller Tips

Wed Apr 03, 2013 8:20 pm

Sometimes pilots decide to add them:


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czbbflier
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RE: Winglets On Propeller Tips

Thu Apr 04, 2013 2:37 am

Thanks all! I guess the scimitar props essentially achieve the same thing without the structural issues.

Quoting vikkyvik (Reply 3):
Sometimes pilots decide to add them:

I had to look. Thanks for the chuckle of the day.  
 
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Starlionblue
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RE: Winglets On Propeller Tips

Thu Apr 04, 2013 2:59 am

Quoting czbbflier (Reply 4):
Thanks all! I guess the scimitar props essentially achieve the same thing without the structural issues.

The equivalent of raked wingtips I suppose.
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KELPkid
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RE: Winglets On Propeller Tips

Thu Apr 04, 2013 5:28 am

Quoting vzlet (Reply 1):
Google "q-tip propeller". They've been in use for a while, usually as refitted upgrades.

Q-tip props were all the rage on high end piston singles and twins in the 1990's. They used to drive me nuts on the ramp, as it looked as if someone did a low pass down the runway before realizing the gear wasn't down   Don't think I've seen a Q-tip prop in at least a decade...
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TWA772LR
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RE: Winglets On Propeller Tips

Thu Apr 04, 2013 6:28 am

http://en.wikipedia.org/wiki/Winglets#Use_on_rotating_blades
They have even been used on wind power farms.  
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vzlet
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RE: Winglets On Propeller Tips

Thu Apr 04, 2013 9:38 am

Quoting KELPkid (Reply 6):
looked as if someone did a low pass down the runway before realizing the gear wasn't down

There was allegedly an incident where an FAA inspector grounded a q-tipped aircraft on a ramp check until the "damaged" props were repaired.
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KELPkid
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RE: Winglets On Propeller Tips

Thu Apr 04, 2013 7:56 pm

Quoting vzlet (Reply 8):
There was allegedly an incident where an FAA inspector grounded a q-tipped aircraft on a ramp check until the "damaged" props were repaired.

   I could totally see that happening in real life. Especially with one of the older, crustier inspectors  
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m1m2
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RE: Winglets On Propeller Tips

Fri Apr 05, 2013 4:43 pm

Q-tip props are still used on the Piper Cheyenne III. Well, at least they were 8 years ago when I last worked on one, I'd imagine it's still the same. On the Cheyenne III, they were "bent" toward the rear of the aircraft.

I often thought it looked odd, kinda like a "pilot addition" like someone jokingly suggested earlier. But, it was proven when we had the props sent for overhaul and they came back the same way.

[Edited 2013-04-05 09:49:47]

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