RunRyder - What makes the blades FAI?

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Aerobatic FAI F3C Contest > What makes the blades FAI?

Angelos
Key Veteran
Location: nr Oxford, OX11, UK

What are the FAI blades? Sumetrical/semi-symetrical? special weight?
Cheers,

12-03-2003 Over year old.

Dr.Ben
Elite Veteran
Location: Richmond, VA, USA

Definition of an FAI blade:

Could be either semi or fully symm.

Auto's well.

Allows model to sit well in windy conditions with predictable response to gusts.

Responsive to collective and cyclic inputs without being jumpy or pitchy.

Good balance.

Good finish.

Quiet in aeros.

Fast in FFF.

Torsionally rigid, MAYBE rigid spanwise or MAYBE not, depending on the rotorhead

Reliable supply, because once you're trimmed and accustomed to a blade, you DON'T want to switch.

With no sarcasm intended, I'd fly a 2 by 4 if it fulfilled most or all of the aforementioned criteria, whether it was an "FAI" named blade or not. I can think of several "3D" blades that are superb for contest work.

Ben Minor

12-03-2003 Over year old.

Wally
Veteran
Location: San Diego, CA

Dr.Ben is right on the money.

Talk to 12 different FAI gurus and see 12 different blade manufacturers and styles.

I do see more and more pilots leaning toward fully symmetrical blades however; they seem to be more solid in the hover with unpredictable winds.

The Big Wally

12-03-2003 Over year old.

Heli-Driver
Elite Veteran
Location: Arlington, TX

I have a set of MS 680 FAI blades, they are 210grams compared to the same set of MS 3D blades (185gram).

I'm sure the extra weight makes the FAI blades track smoother in FFF and hovering and it certainly holds more energy for autos.

Raymond

Predator Gasser SE/231 X 2
Century Helicopters

12-03-2003 Over year old.

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RappyTappy
Elite Veteran
Location: Las Vegas, NV

Quote
Ok why?

The washout is used to distribute lift evenly. The tips of the rotor blades have a greater velocity than the root, therefore, if pitch of the blade was the same all the way from root to tip, the blade would actually be producing more lift on the tips of the blade. Kinda like a propeller on an airplane.

Chris
Rex 500 A123 Power

Forever Brothers
Mickey Tylo

12-03-2003 Over year old.

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jonasl
Senior Heliman
Location: From Denmark, but live in Hong Kong

so...

On the box it say washout, so why don´t we just call it that???

Jonas

12-03-2003 Over year old.

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Angelos
Key Veteran
Location: nr Oxford, OX11, UK

Thanks for the replies everyone. The reason I asked the question on the first place is because I am after a set of blades that generate more lift and auto easy. These are for my camera ship. Not that I really have a problem now but I would like to see if I can make it better. FAI blades seem better for the purpose. Any recommendation for good semi-symmetrical FAIs?

Cheers,
Angelos

12-03-2003 Over year old.

Dr.Ben
Elite Veteran
Location: Richmond, VA, USA

I forgot one other thing about FAI blades vs 3D ones. Some companies will play with the chordwise CG a bit. For FAI, we almost can't get the CG too far forward within most limitations of blade construction. The further forward it is, the more the blade lags in flight, and the better the model tracks ("grooves"). If you shift the CW CG aft a little, you can create a blade which bites a little more with cyclic inputs, which some pilots might prefer for some styles of 3D.

Ben Minor

12-03-2003 Over year old.

Andi G
Veteran
Location: Switzerland

Hi,

interesting things to learn here...

For the Henseleit NT you don't want the CG fore or aft, the MFS head won't like blades like that (for example BBT FAI aren't a good choice on NT and Joker).

Andi

12-03-2003 Over year old.

Dr.Ben
Elite Veteran
Location: Richmond, VA, USA

Andi,

What does the head do...............flutter or wobble or otherwise act unhappy if the CG is fore or aft of the pivot point of the blade?

I do like these threads. With blades and heads, somone has always had a different experience.

Ben

12-03-2003 Over year old.

Andi G
Veteran
Location: Switzerland

Hi,

I don't know first hand. I think it won't fly well in FF, and might vibrate, the flutter problems were mainly with the first batch because the flybar could get in resonance. It would move up and down and swing itself up till the heli explodes in the air (blades 20cm and more out of track) - this was solved by changing the swash plate direction (swash down -> more pitch). It had something to do with the weight of the moving flybar. With the reversed direction it will dampen the response instead of swinging itself up.

Regards,

Andi

12-03-2003 Over year old.

AirWolfRC
Elite Veteran
Location: 42½ N, 83½ W

Not going to say much about FAI vs 3D but;

Symetrical blades are for 3D flying for only one reason; they fly the same right side up or up side down.

Asymetrical or "S" shaped (reflex) blades produce more lift right side up than up side down.

Asymetrical blades produce more lift, when right side up, than symetrical blades.

Asymetrical blades can have washout. This helps make more of the blade disk produce lift compared to no washout where the tips produce most of the lift.

Camera ships want asymetric blades with washout for best lifting ability. This can be twice as much lift than symetric blades.

Asymetric blades and/or washout is not good for 3D flying where negative lift (inverted flight) is involved.

Wolfgang

12-03-2003 Over year old.

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KC
Elite Veteran
Location: WA

Angelos, a blade that might just work is a special order through MA, SAB has listed a 70mm chord high lift 710 blade. it should fit on a R90 real well and lift a lot.

12-04-2003 Over year old.

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