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A Main Hobbies . Boca Bearings . Modefo's RC Helicopters

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Aerial Photography and Video > Non sym rotors - heavy on links?
 
 
MPA
Elite Veteran
Location: Australia

Im looking for a set of non sym or flat bottom rotors for the helicam.

Will throwing on a set of non symetrical or flat bottom rotors have any ill effect to standard linkages compared to symetrical rotors.

Its is the case in full size helis but dont know if this follow with out size heli.

if so do we need converting to dual rod push/pull linkages or beafed up ones.

The point of it all ~
Are non syms or flat bottom rotors going to provide much gain for the helicam in
less vibration off rotors
and or
greater hovering stability.

In short
Are they good or ungood for helicam?
Do we all rush out tomoorow and buy a set if we have syms on our helcams now?

~
Yeah realy!
So why's that then?

Rgds
10-06-2003 Over year old.
HOMEPAGE  
 
 
SteveH
rrProfessor
Location: Texas

Years ago when I started flying, I started with a GMP Cobra and the Gorham Model Products helis used flat bottom airfoil wood blades. They had no problems with link failures, at least no more problems than we have with symetrical blades. They will all eventually wear out.

As far as smoothness is concerned, I believe that is all related to balance and blade design, i.e. CG, lead/lag, etc., and not related to airfoil.

The semi-symetrical and flat bottom blades WILL give you more lift for a given blade area and rotor speed.

SteveH
Magnum Fuel
AMA76186
10-06-2003 Over year old.
 
 
MPA
Elite Veteran
Location: Australia

Thanks Steve.

I need a bit more lift.

I was just under the impression the syms gave off more vibration.
My thinking was
Less lift with syms = greater pitch angle to get same load up? which I assumed would cause more vibe off the rotors.
10-06-2003 Over year old.
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daggit
Elite Veteran
Location: Waseca MN

MPA,

I have heard that the semi's do give more lift but the trade-off is your heli will be prone to "pitchyness" when there's ANY wind.

I generally use NOH Razor Pro high lift blades (symmetrical) for calm or warm/humid conditions. But when it's windy these blades have too much lift and the heli is pitchy. I switch to regular Carbon Fiber sport blades when the wind's blowing hard.

10-06-2003 Over year old.
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Doug
Elite Veteran
Location: Naples Florida....

Aerodynamic forces on different types of blades are very small and of no concern

First member of Member of Bearings Anonymous
10-06-2003 Over year old.
 
 
MPA
Elite Veteran
Location: Australia

Thx daggit

NHP Razor CF 710 on it now.
They have a swept? tip.

The previous ones had a flat butt ends 680 CF

The NHP seem pretty much the same as the other on lift, I was hoping for a bit more, if they are providing more lift I cant tell the diff.

I fly a lot of windy conditions (including times I shouldnt but thats another tale) and by the beach here its always gusty wind not constant.
Ill hang with the NHP for now and save the dollars I think

Cheers
10-06-2003 Over year old.
HOMEPAGE  
 
 
MPA
Elite Veteran
Location: Australia

Doug
Glad to hear it.
10-06-2003 Over year old.
HOMEPAGE  
 
 
daggit
Elite Veteran
Location: Waseca MN

my NOH Razor Pro high lift blades have the flat ends but I bought them over a year ago and I've heard that they have since went to producing only the swept tip variety. I have not double-checked whether that's true.

If you get those blades you'll love the sound they make! very distinctive
10-06-2003 Over year old.
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ELOSSAM
Veteran
Location: Es

Hi Dave,about your flat blade considerations. More lifting power with less angle means less air resistance but the different angle between both blades (the one who goes foward and the one that cames back) should be the same no matter wich kind of blades you use and that motion is one of the main vibration surce. Then we must go deeper analyzing each type of blade and all the forces involved, the center of pressure, etc.... Not sure about vibration reduction.
I found very interesting this URL www.digital-fusion.ca/sbr/baldedesign.htm
and here something about CCPM issues than can have some relation
with vibrations (have not finished reading it as I dont use any CCPM system)
http://www.digital-fusion.ca/sbr/ECCPM.htm
About the blades that I´m using they are a 810 semi-sym ones from VARIO with a high lift auto-stable profile (like the flying wings, with the end of the profile pointed up). very stable but the heli still vibrates.

Another thing I found recently is a simple device used by ULM pilots to balance their propellers, look at www.balancemasters.com. Basically its a ring tube filled with mercury. They fit it between the propeller and the engine shaft and the mercury will run where necessary to compensate the vibrations. They have some little units to be used on driveshafts that can be adapted to a rotor head, fan, or engine shaft. May be it works or may be not but at least it seems to be a nice idea.

Take care
Elossam
10-06-2003 Over year old.
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