PPU.

[asra]

As I said before Birdy, very interesting.Did you take any before and after pics ?Be interesting to hear how it performs with the new hart.Will you use the same rotors ?Robert DunnMackay. Qld.Growing old is good while it lasts.

[birdy]

Plenty o pix of the ferel around[ can't think why].I did the 2 pic thingy to get an idea of where the COM was, maybe I'll get a chance to do it again .........in the next 10 years.I'll let you know bout the rotors after the first days mustering in the next dust storm.Ignorance is bliss............but only till you realise you were.You can always get the answer you want, if you ask enough experts.

[asra]

Sam, you seem to be getting a bit mixed up?The HS on a low thrust line machine is at a negative AOA,ie leading edge down,it pushes the nose up further with application of power and or airspeed,its not to "trim" it out.Why on earth would you have a positive pitched HS on a low thrustline machine,or any machine for that matter?.The whole idea is to keep the nose up, not put forces on the airframe to push the nose down.As I said previosly a sudden loss of power in a correctly built LTL machine is a non event,something every student in my machines can vouch for.M Barker

[asra]

Murray you may want to read "Gyroplane Stability Misconceptions- Part 1" or the "Rest of the Story" By Greg Gremminger.He probably explains it better than me.Regards Sam.

[asra]

Just curious Murray, how low are your thrust lines, could you post a photo of your CofG and thrust line calcs.Sam.

[asra]

Sam,I have flown about 10 or 12 gyros with thrustlines from about -2inches (Dominator) and plus about 12 inches (modified Raf)and I can assure you none of them had a positive set horizontal stab.The second low thrustline gyro in OZ (Front cover Gyro news c96)was one I built in about '93/94.I made the mistake of not measuring the AOA on the tall tail after some modifications and did a low pass at a private strip,there was a photo of this in the Pacific ultralights magazine.The photo showed how much the tail was pushing the nose down and in this configeration the gyro was dangerous at any speed.After moveing the tail to 1 degree negative AOA(Leading edge down) it flew perfectly.This gyro was fully streamlined and capable of 95 KIAS. If Greg Greminger is advocating putting positive AOA on HS's then he is pushing dangerous practises.All gyros Iv'e had anything to do with have either Tall Tails -1',engine level,or Benson type tails 0' engine -3'.Anyone deliberataly having a device,or thrustline that continualy try's to nose you over into the dirt is in my opinion an accident waiting for a convenient place to happen.M Barker

[asra]

The US forum is down, so I found my way to this interesting forum down under.Chuck and Birdy - when birdy moved his (heavy) engine 6" down, he increased the moment of inertia (MOI) in the roll and pitch axes. I don't know how meaningful this is (too lazy to calculate right now), but it could account for some of the sluggishness that Birdy is reporting.Cheers mates.Udi

[asra]

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[asra]

[Tim]

quote:Originally posted by Udiwhen birdy moved his (heavy) engine 6" down, he increased the moment of inertia (Udi, Birdy's engine is a 912.Chuck:- "The UK forum seems to be dying a lingering death; perhaps we can give the Ozzy forum some mouth to mouth resuscitation (not literally)". Please do Chuck and Co. You are more than welcome.Tim McClure

[birdy]

Just cum back from bout 5 1/2 hours of ........... in lousy air.[my request for a dustorm was granted.]Good thing it was only a small paddock.It still has the 'feel' of be'n over rotored and the 'responce' from the rotors to inputs is still slower, but nuthn I can't handle.The biggest gain is in power efficiancy. IOW, it feels like I'v already put the bigger donk on.Also, a couple o times it developed a resonat frame shake????Sumthn I'v never felt before.It seemed to appear when the rotors where momentarily unloaded by an airhole.[ as opposed to a 'pothole'.]Ignorance is bliss............but only till you realise you were.You can always get the answer you want, if you ask enough experts.

[asra]

Birdy, how much heavier is the new engine? Maybe it will bring enough weight with it to speed your rotor up some. What kind did you choose?Flying the right side up in Canada

[birdy]

Only replacing an old 80hp 912 with the new 100hp 912s.Not alota weight difference.Ignorance is bliss............but only till you realise you were.You can always get the answer you want, if you ask enough experts.

[asra]

Same cooling system and prop? When are you going to put it in or are you waiting for the old one to time out?Flying the right side up in Canada

[asra]

quote:Originally posted by Chuck BeatyAccording to Gessow & Meyers (Aerodynamics of the Helicopter) Udi, a taller mast does not alter control sensitivity. Both control power and rotor damping increase proportionately, maintaining a constant ratio.Writing from Kentucky today (having driven 3200 miles over the last 10 days)...I understand control power, Chuck, but what mechanism do you (or G&M) refer to when saying "rotor damping"? My understanding that more control power is achieved by having a longer moment arm. I assume the damping you are talking about is the reduction of lift (control power) due to the velocity of the rotor in the roll direction, similar to the damping of a control surface due to the movement of the control surface, and resulting change of AOA.I don't want to be too presumptuous, but may we consider the possibility that Gassow & Meyers were assuming a constant MOI in their analysis of a taller mast?Tim - the 914 is a fairly heavy engine, compared to a 582 or 503. The mass of the engine is a significant fraction of the whole gyro.Udi