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C. Beaty
Gold Supporter
Last Activity: Today, 07:28 AM
Joined: 04-16-2004
Location: Florida
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  • C. Beaty
    replied to Tall Tail size choice
    Jake, the only way that propeller torque can be eliminated as a coffin corner is by untwisting its slipstream. Issac Newton understood this when he published his Principia in 1687.

    Tinkering around with rotorhead offsets is essentially a feel good measure....
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    Last edited by C. Beaty; Today, 07:26 AM.

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  • C. Beaty
    replied to Tall Tail size choice
    Sideways flapping resulting from coning showing coned and unconed rotor. ...
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  • C. Beaty
    replied to Tall Tail size choice
    Perhaps the attached sketch will eliminate some of the confusion about offsets. Angles and offsets are exaggerated for the sake of illustration. ...
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  • C. Beaty
    replied to Tall Tail size choice
    Offsetting the rotorhead to one side and offsetting the roll pivot to one side are two different, unrelated effects.

    Offsetting the rotorhead to one side of the airframe is for purely aesthetic effect; it makes the airframe fly level but does not compensate for propeller torque. Unload...
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  • C. Beaty
    replied to Tall Tail size choice
    Sad but true. Most “"designers"” of "“modern"” gyros simply copy a design that’ has proven successful in the marketplace and add their own decorations.

    Lateral trim is required to reduce stick pressure resulting from coning angle. A coned rotor tilts sideways during...
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    Last edited by C. Beaty; Yesterday, 11:59 AM.

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  • C. Beaty
    replied to Tall Tail size choice
    You’re right, Chris; providing torque balance without removing the offset of the rotorhead would spoil the aesthetics. But I don’t think it would affect the flying qualities....
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  • C. Beaty
    replied to Tall Tail size choice
    JM, you might obtain torque balance with your all flying vertical tail by the use of large, full length trim tabs. The upper ½ set in the opposite direction from the lower ½.

    Tie your gyro to a tree, place main wheels on bathroom scales and adjust tabs for equal readings while engine power...
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  • C. Beaty
    replied to Tall Tail size choice
    JM, anything that removes the rotation from the propeller slipstream will eliminate torque.

    First of course is contra rotation of propellers; the slipstream does not rotate if the pitch of the propellers is adjusted for equal and opposite torque. Powered parachutes use contra rotating propellers...
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  • C. Beaty
    replied to Tall Tail size choice
    A competently designed gyro with correctly located propeller thrust line and torque balance will tolerate zero G for a short time.

    From the book, Cierva Autogiros by Brooks about the first fatal Autogiro accident:

    “This was the first Autogiro fatality. Up to this time, more...
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  • C. Beaty
    replied to Tall Tail size choice
    You’re right, Jake. Cierva set out to solve the stall problem of FW aircraft and in the process, solved the problem of rotors moving edgewise by the invention of flap hinges and thus paved the way for the helicopter. The helicopter proved to be nearly indispensable but the Autogiro was a dead end, going...
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  • C. Beaty
    replied to Tall Tail size choice
    Brilliant! One must never let scientific fact interfere with opinion.

    But Friedrich Nietzsche, a well known 19th century German philosopher said; “There are no facts, only interpretations.”

    I suppose you’re a Nietzscheite, Vance....
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    Last edited by C. Beaty; 10-13-2017, 02:21 PM.

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  • C. Beaty
    replied to Tall Tail size choice
    You may be right Vance, that the downhill flow of water is only an opinion and not a scientific fact.

    Perhaps down under in the Land of Oz where everything is upside down and people drive on the wrong side of the road, gravity is backwards and water runs uphill....
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  • C. Beaty
    replied to Tall Tail size choice
    But that statement is well known scientific fact, not merely opinion.

    It is also one of the questions on the test for obtaining a journeyman plumber’s certificate....
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    Last edited by C. Beaty; 10-13-2017, 05:37 AM.

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  • C. Beaty
    replied to Tall Tail size choice
    I think Vance is on to something when he says; “In my opinion, water flows downhill.”...
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  • C. Beaty
    replied to Tall Tail size choice
    Short vertical tails, dipping in the lower ½ of the whirlwind coming off the propeller get swatted in whichever way the lower ½ of the prop is moving; requiring the rudder pedal toe dance during the takeoff roll.

    Once mastered, nothing to it; most people may not even be consciously aware...
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    Last edited by C. Beaty; 10-12-2017, 08:10 AM.

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  • C. Beaty
    replied to Tall Tail size choice
    Poor Cierva; without Vance to guide him, centered both vertical and horizontal tail surfaces in the propeller slipstream.

    Vertical tail surfaces were equally disposed in the propeller slipstream, eliminating throttle-yaw coupling.

    Horizontal tail surfaces were also centered...
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  • C. Beaty
    replied to Tall Tail size choice
    My guess is that those “designers” who opt for a keel mounted horizontal stabilizer don’t understand that the propeller slipstream is the vector sum of free-stream and propeller induced velocities, believing it is something like the exhaust from a rocket engine. ...
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  • C. Beaty
    replied to Tall Tail size choice
    Normally, an all flying tail is designed with its hinge line set a bit ahead of its aerodynamic center so that it trails downwind feet off the pedals; in which case, you have something that tries to swap ends “feet off.” It is also a bit wobbly “feet on.”

    That’s the reason an anti-servo...
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  • C. Beaty
    replied to Tall Tail size choice
    In the gyro land of make-believe, Jean Fourcade is one of the very few real engineers.

    Tail surfaces are roughly 2x as effective when located within the propeller slipstream. The reason for locating the horizontal stabilizer slightly below the propeller center is that the slipstream velocity...
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    Last edited by C. Beaty; 10-10-2017, 11:33 PM.

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  • C. Beaty
    replied to Tall Tail size choice
    Make a scale drawing of your gyro’s side profile on cardboard and cut out with scissors or whatever is convenient.

    Balance on pencil point and the balance point is approximately the aerodynamic center of your gyro (technically, it’'s the “centroid of area”).

    The aerodynamic...
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