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HomeAircraftHelicopterHelicopter Main Discussion › Blade performance/design ?
10-10-2012 10:16 PM  6 years agoPost 1
honda411

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Surprise, AZ USA

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So i have been thinking today about something. We notice that the bolt hole is on the leading edge on the main blades.
What if there was a design that put the hole in the center of the blade, and would help with lead and lag problems.

Kind of like adjustable paddles on a flybarred heli. Two holes/ one in front of center of paddle and one at center of paddle(which makes quicker response).

So if a main blade was bolted on with the hole in the center of the blade, wouldnt this make more performance?

HeliDirect Field Rep, Synergy N7 w/ OS 105, Torq Servos, Cyclone/ Rail blades

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10-10-2012 10:47 PM  6 years agoPost 2
Rafael23cc

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Junction City, KS

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Not an aerodynamics expert, but I have anecdotal experience.

have you ever lost a grip link in-flight? What happened? What would happen if the blade was neutrally balanced (as in the CG in line with the attacment point)? What would happen if the attachment point was BEHIND the chordwise CG as in your suggestion?

Rafael

Keep your feet on the ground, but your eyes on the sky.
Team Heliproz.com

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10-10-2012 10:54 PM  6 years agoPost 3
Havoc

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Ky.

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You want the aerodynamic center. Not the chord-wise center. It's the point where the pitching moment is constant regardless of the angle of attack (within reason).

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10-11-2012 12:10 AM  6 years agoPost 4
honda411

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Surprise, AZ USA

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rafael: i can see your point in your statement. Your saying that the blade would either pitch up or down from the forward force put on the surface.

HeliDirect Field Rep, Synergy N7 w/ OS 105, Torq Servos, Cyclone/ Rail blades

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10-11-2012 12:52 AM  6 years agoPost 5
G-Limo

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Europe

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You need the hole about the blade centre of lift, else the servos will always be fighting the blade aerodynamics.

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10-11-2012 10:34 AM  6 years agoPost 6
HeliPhil

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Brentwood, Essex, UK

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a few years ago NHP made blades with an eccentric adapter for the blade bolt hole so you could move the bolt hole backwards and forwards to suit your taste as such - never really caught on...

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10-11-2012 11:15 AM  6 years agoPost 7
G-Limo

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Europe

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I run a pair of those very blades on my KKK FBL Robinson..

I have tried moving the holes back and forward, but only makes minimal difference in the response on the head.

Fast forward flight is affected by the bolt hole position, but then again I don't tear around the sky with a Scale Robinson R22!!

/DG

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10-11-2012 09:35 PM  6 years agoPost 8
AirWolfRC

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42½ N, 83½ W

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25% . . . that's where you want the blade bolt hole. Maybe just a bit aft to account for blade lag during flight. The blades we use are in the NACA00xx series. I have verified that by actually measuring a blade.
See http://airwolfrc.com/NACA%204%20digit.png The blade pitching moment does not travel fore or aft from that position with changes in blade angle of attack.

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10-12-2012 04:21 AM  6 years agoPost 9
AWittleWabbit

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O.C., CA

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The hole lines up with the center of lift. That's where you want the pivoting about. Just think of a plank. Cg too far aft, pitchy and unstable. Too far forward, nose heavy and slow about the pitch axis. It's the reason why blades have weights in the leading edge. To get the chordwise cg even with the center of lift.

Heli-itis sufferer.

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