Rigid head v's floating

[Jamin_00]

Been reading on HF about the benefits of each head and how they work best with certain types of flying.

It appears the floating head (black bushes) is better for ffff and the rigid head (white bushes) is better for sports etc flying.

I have both types here and just wondering what your thoughts are as I have the rigid head currently in Spunky and the floating in the other. Apparently they also say you get less pitch ups with the floating head?

May swap them over and try to see what I find just thought I'd ask you lot too.

[KevDavies]

I was always of the impression that a floating head was better for stability and the softer the dampers the better. And the solid head was for a crisp precise response for aerobatics?

I could be wrong

[Guest]

In Spunky I'd go floating as alows more flapping which is a benefit in FFF, delays retreating blade stall which will result in pitch up. Rigid good for 3D.

MJ

[Jamin_00]

In Spunky I'd go floating as alows more flapping which is a benefit in FFF, delays retreating blade stall which will result in pitch up. Rigid good for 3D.

MJ

Cheers M. Will swap them over during the week

[scallybert]

In Spunky I'd go floating as alows more flapping which is a benefit in FFF, delays retreating blade stall which will result in pitch up. Rigid good for 3D.

I think it's 'teetering' rather than 'flapping'.

AIUI, flapping occurs either through a flapping hinge at the blade grip; or through the blades flexing.

Both teetering and flapping broadly allow the rotor disk to tilt relative to the mainshaft (giving the benefits you describe), but there are other differences.

[Guest]

It's just a central pivot (teetering head design) allowing blades to flap semi rigid system. Fully articulated would have a hinge, fully rigid would be through blade flexing.

MJ

[Jamin_00]

Well, just swapped the bushs and dampeners over now so will test tomorrow and see for myself how they feel now.

[WildWake]

Well, just swapped the bushs and dampeners over now so will test tomorrow and see for myself how they feel now.

It's going to be nice and warm tomorrow, what time are you getting there? don't forget you spade,,, I mean shorts....

[Rctintin]

Black bushes for me!!

Back to the TDR, I love the feel of the floating head, it makes for a very varied speed range to fly in. Thats from 1300 chilled flight to 1950 manic 3D with Jamiem smacking it around!

[Jamin_00]

Have you tried the other Rob?

When I got Robs TDR it had the white bushes with reds on the inner and black on the outers and it was so locked in down to around 1500 or 1600 rpm, cant remember exactly but when I got my new one even at the same headspeed it did feel nice just not as nice as the other. This combo is apparently better for the higher headspeed sports/3D flying but isnt as good for the low headspeed stuff.
But for FFFF the flappy black on blacks is supposed to be the way to go so I will see how it feels tomorrow. Hopefully I wont have to play with my vbar file to much. My gains are so low its insane but if I do have to play with it, its a piece of **** now thanks to Ian's bluetooth module fitted

[mahbouni]

In Spunky I'd go floating as alows more flapping which is a benefit in FFF, delays retreating blade stall which will result in pitch up. Rigid good for 3D.

MJ

Its beneficial for helis with a flybar. In FFF the leading blade has a faster airspeed, which causes the heli to pitch up. When the spindle teeters it inputs into the flybar, which corrects this to some extent. In a FBL system these mechanics are not present and the FBL unit does all the correction, so it is better to have a more rigid head. Manufacturers of FBL heads still use dampers so I guess it's to smooth things out.

[scallybert]

Its beneficial for helis with a flybar. In FFF the leading blade has a faster airspeed, which causes the heli to pitch up. When the spindle teeters it inputs into the flybar, which corrects this to some extent. In a FBL system these mechanics are not present and the FBL unit does all the correction, so it is better to have a more rigid head. Manufacturers of FBL heads still use dampers so I guess it's to smooth things out.

I think I disagree.

Teetering & flapping both allow the rotor disk to be inclined to the mainshaft.

The swash, linkages, etc set the blade pitch relative to the mainshaft.

However, the blades motion is in the plane of the rotor disk (by definition); so the inclination between the rotor disk and mainshaft affects the blades' angle of attack (which governs lift).

{If you want to see this demonstrated, look at the flybar itself. [You can do this by taking the blades off a small heli, and spinning it up. Carefully...] As you put input through the swash, the flybar seesaw teeters to orient flybar disk so that the flybar paddles lie in the disk. ie there's no/negligible angle of attack. Hence, nothing making the flybar disk precess.}

Back on the plot, the inclination of the rotor disk compared to the mainshaft will affect the angle of attack, regardless of whether there is a flybar or not.

Flap back - Wikipedia, the free encyclopedia describes this affect.

[Guest]

Very basically the advancing blade will generate more lift with relative wind either wind of path of travel. The retreating blade will produce less. Blades therefore flap to equality to balance this out. There is a limit and can be found in FFF. Retreating blade will suffer reverse flow nearer root and tips will begin to stall both reducing surface area to produce lift. At extreme you'll get retreating blade stall which may result in a roll to the advancing side followed by the more usual pitch up. Flapback is generally only seen by the pilot when passing etl requiring application of more forward cyclic. Many other effects are taking place read a few aerodynamic books quite intresting. I had to when going through University to attain my ATPL (H).


MJ

[mahbouni]

Flap back - Wikipedia, the free encyclopedia describes this affect.

If you read the Wikipedia link again you will see that it agrees with what I said. This is the pitching up behavior I described.

"As the blade continues to rotate, it achieves its maximum upflapping displacement over the nose of the aircraft and maximum downflapping displacement over the tail. This results in the rotor disk being tilted to the rear and is referred to as flap back, as if the rotor disk had flapped or tilted back"

Most flybar heads do not have zero delta, so when you teeter the spindle the the ball links on the blade grip arms also move up and down a little bit. As these are connected to the flybar they produce an input.

[Guest]

Fallback is as described and a result to realtive wind. There is no flapback in hover with no wind. Add a crosswind now work out where the max displacement is? It's not the nose! In FFF this in itself isn't causing the problem. Dissymmetry of lift is the problem and the other effects I described above.

Putting aerodynamics aside crank up the headspeed and use as little pitch as necessary. Also try different blades as have different properties.

MJ