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Old Apr 15, 2014, 08:06 PM
Drifting off the reservation..
JumpySticks's Avatar
USA, LA, Broussard
Joined Jan 2011
2,284 Posts
If the prop nuts are too tight they might not fold back. If they are loose and the bottom one still hangs down a little the drag is negligable. The rubber band probably causes as much drag as the dangling prop. It also could cause the prop to hang on the canopy when the motor starts up.
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Old Yesterday, 07:47 AM
aka Mr.Side-Winder
Jeff Winder's Avatar
United States, OH, Cincinnati
Joined Jun 2007
349 Posts
The reason for having the prop automatically fold back when the motor is off has 2 main advantages:
1. Yes, reduced drag ...... in the air with motor off.... soaring mode, (I'm not a fluid dynamics expert, but a 3/4" wide blade dangling in the airstream has got to cause undesirable drag ).

But just as important for me....

2. The prop is not flopping around and sticking in the ground when you have the fuse tail end up assembling the tail and inserting the wings . Also a whole lot easier to put away in the box. (Yes, I could put a Velcro restraining strap around the blades for this and remove before flight, but then no #1 advantage).
Rubber bands give you both advantages and are automatic, (I just have to figure out why they keep snapping on me after about 3 flights, or maybe this is just the way it is ??)

Jeff
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Last edited by Jeff Winder; Yesterday at 08:15 AM.
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Old Yesterday, 12:07 PM
Drifting off the reservation..
JumpySticks's Avatar
USA, LA, Broussard
Joined Jan 2011
2,284 Posts
Quote:
Originally Posted by Jeff Winder View Post
The reason for having the prop automatically fold back when the motor is off has 2 main advantages:
1. Yes, reduced drag ...... in the air with motor off.... soaring mode, (I'm not a fluid dynamics expert, but a 3/4" wide blade dangling in the airstream has got to cause undesirable drag ).

But just as important for me....

2. The prop is not flopping around and sticking in the ground when you have the fuse tail end up assembling the tail and inserting the wings . Also a whole lot easier to put away in the box. (Yes, I could put a Velcro restraining strap around the blades for this and remove before flight, but then no #1 advantage).
Rubber bands give you both advantages and are automatic, (I just have to figure out why they keep snapping on me after about 3 flights, or maybe this is just the way it is ??)

Jeff
If the blade is not tight at the hub, it cannot be causing a lot of drag. The airstream pushes it back against the fuse. Very little force needed, thus very little drag.

A band is useful during assembly, but probably more of a pain and possibly a hazard when operating the model.

They are snapping because they probably vibrate like crazy when the prop is spinning. That creates drag and decreases prop efficiency.

If you really can't stand the dangling blade, you can blip the throttle until the blades align with the sides of the fuse, where they will not dangle.
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