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4 Bladed RASA Folding prop

Old 03-22-2010, 05:24 PM
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RC_Pattern_Flyer
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Default 4 Bladed RASA Folding prop

if someone was to try a 4 bladed folding RASA Prop... which one to use?

20X13 2 bladed converts to ?????


AND... what are your thoughts of a 4 bladed electric prop?

Chuck Hochhalter
Old 03-23-2010, 03:30 AM
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Default RE: 4 Bladed RASA Folding prop

AND... what are your thoughts of a 4 bladed electric prop?
First thought is "Why"...

I have brief experience of a Pletty/Rasa 21x15 set-up in a Leviosa,by recommendation as the nearest(NB not the same) in performance to the fairly commonly-used APCE 21x14/20.5X14.
The Rasa is smooth,quiet,OK in calm weather,but a little slow for the usual breezy UK weather....and it needs about 1/2 as much again ,dialling into the braking program on the ESC, to get the same downline brake as the APC.
From 4-blade (fixed) experience with IC pattern motors,I'd guess that braking would be improved quite a lot cf 2 blades....but with the loss of efficiency, you might struggle to get enough vertical performance,and/or outright speed,especially round the top corners of manouevres into a headwind.....
Old 03-23-2010, 03:19 PM
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Default RE: 4 Bladed RASA Folding prop

Why? you ask... well, no particular reason, had some time to think about things, looking for advantages and weighing different configurations and wondered what the advantages/disadvantages might be with a setup like this.

I am sure others asked why with the original folding RASA setup and here some have used it successfully.

If no one asks the question, one will never find the answer.

Pattern to me is not accepting what is out there, yes it works but we are always looking for that one thing that might set us apart and aide us in our endeavor.


Fly 10's and don't look back.

Thanks for your reply, i will let everyone know if I decide to try it out.

I may play with apc's back to back and see what amps look like etc.

Chuck Hochhalter
Old 03-23-2010, 05:03 PM
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Default RE: 4 Bladed RASA Folding prop

I couldn't innovate to save my life, so Good Luck and Best Hopes to anyone who can.....but,it seems to me,that current electric set-ups with 2 blades,fixed or Rasa-type,already have whatever you could want,in terms of thrust, braking, and lack of noise.
Just my opinion, of course, but where improvements could still come, is in the area of countering the effects of the inevitable spiral air flow off any rotating-blade-type propulsion system.
So, flow straighteners/canalisers/shaped bits on the fuselage, or simpler/much cheaper contra-rotating blades(than those used by Mr. Silvestri for example) without too much loss in efficiency, might be a more likely route?
Old 03-23-2010, 06:50 PM
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Default RE: 4 Bladed RASA Folding prop

All other things equal, a single wing is more efficient than 2 wings summing the same area.

Change from a 2 blade to a 4 blade, and you will lose efficiency, which means higher amps and more mah used to accomplish the same flight. Not a good direction to move to (IMO), unless you are forced to do so by lack of ground clearance, to reduce noise, or lack of the correct sized prop for your needs in a 2 blade. Adding blades only increases downline braking when the total blade area increases.

Regards,

Dave

Old 03-26-2010, 12:01 PM
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Default RE: 4 Bladed RASA Folding prop

I was also thinking about the 3 and 4 bladed props for E power, but not because of better braking etc, I was hoping to have a smaller diameter.
With 21 inch props, longer gear legs are needed to achieve the ground clearance, it would be an advantage to be able to run a small diameter, but like it has been said earlier, it would not be as effecient. Matt13

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