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Thread: Restoring a Soarmaster

  1. #11

    Pusher vs. Tractor effect on stability

    Quote Originally Posted by Norman Langlois View Post
    While every aircraft has individual differences by additional counter measures. Tail size distance from wing etc. Do all pusher aircraft share these adverse effects in the same way ? While one aircraft may be more or less susceptible. Would they suffer from trying to push against the drag force resistance rather than as a tractor aircraft pulling through a drag force. The processions you describe are they enhanced by pushing VS pulling ?

    I am struggling to understand what caused my plane to crash . Did I violate a never do this kind of thing as you described. It is possible that what you described coupled with a wind direction was the cause.


    I've never thought that the location of the propeller before or behind the center of mass makes any difference in the stability of the aircraft.

    The case I'm describing is very extreme. In the Soarmaster/Rogallo system, the thrustline is 2 foot 9 inches above the center of mass -- in a tail-less aircraft this is EXTREME. Then the propeller disk is a full 7 feet behind the center of mass -- and again, in a tail-less aircraft this is EXTREME. And third, the thrust is 60 pounds applied above a total mass of only 270 pounds -- and this ratio of thrust to total mass is EXTREME.

    If the prop. disk was 7 feet in front of the center of mass, rather than behind, I can imagine that being even WORSE in it's destabilizing effects.

    I'm very reluctant to try to apply any of my observations and lessons to a conventional form of aircraft.

    Soarmaster

  2. #12

    Join Date
    Jan 2012
    Posts
    278
    Soarmaster: Your post #9 is excellent and I can agree with your analysis. Thank you very much.

    Your analysis begins with the offset thrust line. Please review more Soarmaster characteristics. Prop rotation CCW? I believe the extended drive shaft was rather flexable. If one applied say a 10# side load at the prop, how far would the prop center line displace.

    I do not know if you have any "normal" airplane experience. It is said that 90 percent of a flight instructors job is to say "Right Rudder". Sounds like that would contribute in your case except with a CCW rotation it converts to left rudder which of course you did not have.

    PS: I always thought the Sea Gull was a great glider but never had one. I am pleased to see that you survived. Great job!!

  3. #13
    Quote Originally Posted by jedi View Post
    Soarmaster: Your post #9 is excellent and I can agree with your analysis. Thank you very much.

    Your analysis begins with the offset thrust line. Please review more Soarmaster characteristics. Prop rotation CCW? I believe the extended drive shaft was rather flexable. If one applied say a 10# side load at the prop, how far would the prop center line displace.

    I do not know if you have any "normal" airplane experience. It is said that 90 percent of a flight instructors job is to say "Right Rudder". Sounds like that would contribute in your case except with a CCW rotation it converts to left rudder which of course you did not have.

    PS: I always thought the Sea Gull was a great glider but never had one. I am pleased to see that you survived. Great job!!

    The rotation was CCW from the 'point of view' of the the pilot ( he can't actually see the prop. when flying). So the torque is trying to lower the right wing when under power, and the pilot holds himself slightly to the left of center to hold the right wing up. There is no yaw effect in normal flight under power -- the yaw thing only happens at stall under power, otherwise the wing flys straight ahead.
    The Soarmaster driveshaft is not at all flexible. The driveshaft is a 5/8 inch chrome-moly steel tube centered in a 1.75 inch alum. housing shaft. There are bearings every 3 feet within this housing. There is nothing flexible about the system, and it is bolted to the apex of the control bar and the rear of the glider keel. A ten pound side load would do nothing but yaw the entire glider -- the prop. disk wouldn't deflect in any way.

    Soarmaster

  4. #14
    A clarification to this Thread:

    I am NOT advocating a return of this flying system, or that anyone anywhere ever develop a similar system. The Soarmaster plus Rogallo system was a very problematic concept and there are no realistic solutions to the instabilities it causes. Pilots soon abandoned the idea and moved on to other concepts with fewer problems and greater potentials. It was right that they did this, and God forbid that the Soarmaster make any kind of ' comeback'.

    I am restoring the machine I own as a piece of Aviation History. As an Antique Aircraft, and an artifact of American History. The days of the soarmaster/rogallo were NOT the ' good-old-days'. I do not advocate for it's return.

    Soarmaster

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