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wolfy

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I thought in the case of magni, high stick forces were from the nose heavy rotors causing pitch stability and not wanting to change pitch/direction easily.

wolfy
 

XXavier

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I thought in the case of magni, high stick forces were from the nose heavy rotors causing pitch stability and not wanting to change pitch/direction easily.

wolfy

Yes, that's the reason. In the forum, there are several posts by Chuck Beaty explaining the apparent 'heaviness' of the Magni blades...
 

wolfy

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Not sure Jm other than is it just a difference in geometry, does the stick travel the same distance for head travel across the different machines?.

wolfy
 

XXavier

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Hi Javier,

what about the other gyros, my question was not specifically on magnis ( I only mentioned magni as example) .
what about the difference btw monoseaters and tandems with extruded rotors ?

I don't have enough experience. I've always piloted two-seaters. The Averso blades that I have now in the ELA are a bit heavier than the original ELA composite blades. However, the main difference is that I have now not enough forward trim when over 120-130 km/h...
Concerning the Magni, they are very 'heavy'. I don't see any advantage, but Magni says there is. In my opinion, it's uncomfortable. I prefer lighter blades...
 

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Has anyone flown a Magni with a different rotor ? That would seem to isolate the issue to the rotor.
 

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Mani's do have a heavy stick but Greg Gremmiger makes a logical case that they also add more stability than any other rotor system. IIRC
 

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Not sure over 10,000+ logged FW, 260+ ultralights, sailplane, hang-gliders
PS:
The heavy stick is not that big of a deal, even for an old man.
 

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Jean Michel,
I'll point out that tandems have LARGER diameter rotors.
Larger rotors also have more mass.
More mass spinning is harder to move than less mass spinning.
That's might opinion on your observation. :)
Brian
 

XXavier

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are they nose heavier you mean ?



do you mean that when you trim cable gets loose ( no trim at all) you have to push the stick to be able to dive steeper ?



I have flow many low profile gyros ( center of mass under the centre of thrust) in montelimar ( it is hot in summer , ultra windy and ultra turbulent) and by by far the magnis have been the more stable gyros I have flown, I flow autogyros, ela, and magnis

the only gyro I have tried approaching the magni pitch stability in turbulence is the xeeleex, but it is nearly ctl ..



one of my friends mounted aluminium extruded blades on the magni, (resisting the warnings of the hangar owner) , the result is that the controls are really softer as a matter of fact .


As I understand it, (not sure if I'm correct) the Averso blades are more tail-heavy than the original ELA blades. Hence, the advancing blade twists back, increasing its effective angle of attack. To compensate for the higher dissymmetry of lift, the flapping angle automatically rises, and the pilot has to push the stick forward to compensate for that higher blowback angle. In cruise above 120-130 km/h, and in my ELA, I have to trim the gyro 'by hand', pushing the stick, because the pitch system hasn't enough amplitude.

The ELA hasn't a trim cable as the Magni, but a compressed air piston that tilts the rotor head forward...

I'm sure that the 'heavy stick' of the Magni is due to the blades, and not to the tightness of the control transmission, as I've heard from Magni people...
 

XXavier

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all of this is far beyond my capacity of understanding rotor dynamics principles ..
as a reply I would only dare to say say that avesro blades are not tail heavy, in my opinion they are less nose heavy then the magni ones but their center of lift is still behind the center of gravity making the blades try to pitch down under lifft

Of course. It's all relative, as the ELA gyro has the trim system adjusted for the ELA blades, that may be (relatively) nose-heavy, so that –in comparison– the Averso blades are tail-heavy. But not in an absolute way...
 

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As I understand it, (not sure if I'm correct) the Averso blades are more tail-heavy than the original ELA blades. Hence, the advancing blade twists back, increasing its effective angle of attack. To compensate for the higher dissymmetry of lift, the flapping angle automatically rises, and the pilot has to push the stick forward to compensate for that higher blowback angle. In cruise above 120-130 km/h, and in my ELA, I have to trim the gyro 'by hand', pushing the stick, because the pitch system hasn't enough amplitude.

The ELA hasn't a trim cable as the Magni, but a compressed air piston that tilts the rotor head forward...

I'm sure that the 'heavy stick' of the Magni is due to the blades, and not to the tightness of the control transmission, as I've heard from Magni people...
I wish I could remember but back then I was just learning it all. As I recall Greg said it had to to with the RTV. It's not just the blades in Greg's opinion. I know he sells them but if you read all he's written on gyro dynamics it is scientific. He may sell them because he really believe they are the best.
If you can still find his posts he spells it out where I believe today I would have understood more than back then.
 
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Tyger

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He may sell them because he really believes they are the best.
If you can still find his posts he spells it out where I believe today I would have understood more than back then.
That is, in fact, the case. Magni asked Greg to represent them in the US because he understood the things that made Magnis different and thought that they were "a cut above" because of those things. He's pretty much retired and I know he doesn't really do it for the $. I understand he's retired as a CFI now, too, sadly.
 

wolfy

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For what it's worth, my last single seater had a lot of different rotors. Some heavier and some longer and some both, without anything else changing the longer and heavier rotors from memory absolutely had a heavier stick.

wolfy
 

XXavier

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In case it may be of some help, in this book:


there's a description of the control forces of an MTO gyro, stick forces included. Pages 105 ... 161 Yes, it is in German, sorry... To my knowledge, this interesting book hasn't been translated yet...
 
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C. Beaty

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Stick force for a given control arrangement depends upon the following rate of the rotor. The greater the rotor lag, the heavier the stick.

The higher the rotor inertia, the greater the lag but that’s only the tip of the iceberg; design errors along with torsional stiffness play a much greater role.

Tail heavy and torsionally flexible rotors such as Skywheels have a form of built in power steering; pulling the stick back tilts the advancing blade in a nose-up direction and the resulting aerodynamic force twists the blade more nose-up, amplifying the control input, yielding a very light stick. The built in collective pitch also increases the “float” during the landing phase. An upward gust causes a nose up pitch, an unstable response; often misinterpreted as “high lift.”

And of course nose heavy and torsioally flexible blades such as Magni produce the opposite effect. Pulling the stick back causes the advancing blade to twist nose down, partially nullifying control input, increasing lag and thereby stick force.

Correct design requires that the blade CG and aerodynamic center coincide. Professional designs, beginning with Cierva have always used rotor blades with coincident CG/AC.
 

XXavier

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unfortunately I don't speak german at all, the only thing I understand in german is the refrain of the lili marlen song (((-:

Wie einst, Lili Marleen,
Wie einst, Lili Marleeeen...
 

C. Beaty

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I, Linux and this forum just don't get along. Try as I might, I can't reduce the size of that sketch.
 

C. Beaty

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It’s a matter of blade loading, JM. If the gross weight is 2x as great, the rotor diameter must be increased by a factor of 1.414 to keep the disc loading the same but blade loading has increased by that same factor. Heavier blade loading increases blade twist.
 
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