Improving the main rotors performance

royden

helikopter befok
Joined
Jul 20, 2005
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93
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springs
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Fly Citation Excel for work, Fly everything else for pleasure
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Hi everyone.
If I wanted to improve the performance of the main rotor, would it be better to widen the chord of the rotorblades or to increase the length of the rotorblades ?
 

Chaingang

Newbie
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Nov 4, 2022
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2
Location
NC
Hi everyone.
If I wanted to improve the performance of the main rotor, would it be better to widen the chord of the rotorblades or to increase the length of the rotorblades ?
I have the exact same question. I wonder if the width actually helps after you go past the density ratio, at that point it seems like only length would help. also was wondering how much the inner 1/3 offers in lift because I see sone bars that come to the 1/3 length of the blade and it seems that much loss, even thoght offers little lift, cound be significant. Also, if you added the seconf set of teeters like one model did for a breif time, was that any good after you go past the density ratio.
 

MikeBoyette

Gold Member
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Oct 30, 2003
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2,476
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Plant City, Fl
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Dominator
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My old man experimented with doing exactly this. He discovered that the inner third of the blade virtually does nothing. By widening the cord the entire length of the blade you increase disk solidity which does help with over all ability to lift more weight for same disk size but not as much as increasing the length of the disk. He even tried a criss cross four bladed system with some success. This allowed him to reduce the disk size from 27 feet down to 24 feet on the same machine. The problem was the scissors affect. Dad put a device that allowed some in plane compliance to reduce this affect. The machine flew it on was a very light 618 two place and it worked very well. He actually flew a fella that was almost 400 lbs in the back seat with plenty of power left over. The two bladed system he could only put someone about 340 in the back seat and was full power to fly them. The one issue we found was the left to right speed of the controls was almost twice as fast without affecting the fore and aft. He was happy with the system until we put it on a larger heavier machine. We put it in a rotary powered machine that was quite heavy and after about three flights all four blades suffered from the trailing edge of the blades ripping. It was determined that the amount of in plain compliance needed to increase with the amount of weight of the machine. It was abandoned. I wrote an article about it in the Rotorcraft magazine in I think 1996-1997? It was quite an interesting experiment.
 
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