# Rotor Weights

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Hi all

Regards
Mohan

#### don january

##### Well-Known Member
Log Member
Average aspect ratio (span/cord) is about 18 to 1. Exterior weight approx. 85% span from root, Trim tab approx. 85% span from root

#### TFF

##### Well-Known Member
Don't have a scientific explanation, but weights need to be out not in. Blades need the centrifugal weight to stiffen the blades. Moving weight in probably makes everything outward of it not stay as straight as it should, or sets up some kind of spot where outboard is not in frequency of some sort and is trying to dampen. .

#### henryk

##### Well-Known Member
Don't have a scientific explanation, but weights need to be out not in. Blades need the centrifugal weight to stiffen the blades. Moving weight in probably makes everything outward of it not stay as straight as it should, or sets up some kind of spot where outboard is not in frequency of some sort and is trying to dampen. .
-I dont know....

http://ovirc.free.fr/Alain_Hairie.php

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#### Swampyankee

##### Well-Known Member
If you're making a helicopter, vs an autogyro, one issue you may want to consider is that the greater the rotor's mass moment of inertia, the longer the pilot has to reduce the collective pitch when transitioning to autorotation.

#### henryk

##### Well-Known Member
If you're making a helicopter, vs an autogyro, one issue you may want to consider is that the greater the rotor's mass moment of inertia, the longer the pilot has to reduce the collective pitch when transitioning to autorotation.
-auer goal is to build autogyro-like device,much moore energyefficiant(permanent rotor
prerotation) with possibility of VTOL,simple,gearless construction...

=on the 1.5 m modell we have got >10 kG/kW thrust force!

#### stuart fields

##### Well-Known Member
If you're making a helicopter, vs an autogyro, one issue you may want to consider is that the greater the rotor's mass moment of inertia, the longer the pilot has to reduce the collective pitch when transitioning to autorotation.
And the longer it takes to recover from a low rotor rpm. The more you lean toward needing hydraulic boosted controls.

#### stuart fields

##### Well-Known Member
The early Benson gyrocopters had wooden blades with a weight mounted on the leading edge. You might try to find someone with a set and try the same dimension.

#### dino

##### Well-Known Member
HBA Supporter
I believe the wooden Benson blades had their mass balance bullet located at 70% span.

#### BBerson

##### Light Plane Philosopher
HBA Supporter
I would use a long steel round bar from say 60% to 80% or more of blade. Most helicopters are 100% of blade.

#### dino

##### Well-Known Member
HBA Supporter
Wallis blade steel strap sandwiched in wood.

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#### henryk

##### Well-Known Member
BTW= who know this formula, for rotors efficiancy comparation

(коэффициент летучести, качество Ренара или число Эверинга)

(fly coefficiant,Renard finesse,Evering number)=

K=q√p

q=F/N

F=thrust force ,N=power

p=F/s

s=rotor surface

#### pictsidhe

##### Well-Known Member
They are likely fluttering. Having them evenly balanced at 25% all the way along likely makes it hardest for them to flutter. Having the balance inboard will tend to encourage it. The suggestions of 70% and 85% should be listened to.

#### rotax618

##### Well-Known Member
Benson blades had a tapered 1/8” mild steel(Boiler Plate) spar the full length of the blade, it was attached to the ply spar using countersunk screws. The noseweight was attached at 70% span and was weighted to give the blade a 25% chordwise balance or the blade would flutter. I still have a plan somewhere amongst my stuff, I re-designed the Benson Gyro in the 1960’s to suit the local materials (here in Australia) for submission to the then DCA (equiv. FAA).