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Author Topic: Why do left hand props work?  (Read 1894 times)

Offline Larry Renger

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Why do left hand props work?
« on: June 11, 2014, 07:02:39 PM »
As noted in another thread, a left hand prop solved my line tension problems in outside overhead maneuvers. The torque driving the prop should be causing problems, not solutions. What am I missing?  ::)
Think S.M.A.L.L. y'all and, it's all good, CL, FF and RC!

DesignMan
 BTW, Dracula Sucks!  A closed mouth gathers no feet!

Online Brett Buck

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Re: Why do left hand props work?
« Reply #1 on: June 11, 2014, 07:55:43 PM »
As noted in another thread, a left hand prop solved my line tension problems in outside overhead maneuvers. The torque driving the prop should be causing problems, not solutions. What am I missing?  ::)

   It yaws nose-out on outside maneuvers instead of nose-in. First time I saw an electric with a backwards prop, I was startled to see it do that in the hourglass, they look completely different than regular direction motors.

    Brett

Offline Dean Pappas

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Re: Why do left hand props work?
« Reply #2 on: June 11, 2014, 08:51:01 PM »
Hi Larry,
Spiral airflow. It's the 900 lb gorilla among the prop-related asymmetries that plague our ships.
Every time the governor "throttles up" or the airspeed drops under near constant RPM conditions, it kicks the tail inboard with a pusher prop.
take care,
  Dean P.
Dean Pappas

Offline Igor Burger

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Re: Why do left hand props work?
« Reply #3 on: June 12, 2014, 02:36:02 AM »
I aways got better trim and cleaner flights with CW prop (right hand, tractor) then CCW prop (pusher) ... I mean ususal airplane - left flying, with thrust line over the wing and landing gears down :- ))) ... and it is also theoretically better compatible

yes it solves mentioned troubles, but they should be solved other way by usual trimming methods
« Last Edit: October 22, 2014, 12:45:39 AM by Igor Burger »

Offline RyanYoung

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Re: Why do left hand props work?
« Reply #4 on: June 12, 2014, 09:01:56 AM »
Is this not an effect of P-Factor?

Offline Larry Renger

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Re: Why do left hand props work?
« Reply #5 on: June 12, 2014, 12:25:28 PM »
P-factor is the yaw induced by the plane flying at a high angle of attack. The effective pitch on the blades becomes different on the two sides. On a flapped model, the fuselage pretty much tracks true through the turn while the flaps provide the angle of attack.
Think S.M.A.L.L. y'all and, it's all good, CL, FF and RC!

DesignMan
 BTW, Dracula Sucks!  A closed mouth gathers no feet!

Offline Dean Pappas

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Re: Why do left hand props work?
« Reply #6 on: June 12, 2014, 01:22:35 PM »
Is this not an effect of P-Factor?
Hi Ryan,
Spiral airflow has much more effect to our flying, when it comes to line tension issues.
There is more P-factor in level flight due to out-thrust and flying yawed outward than there is during all but hard corners, with a flapped ship.
That's because flapped ships fly the rounds with the wing centerline almost tangential to the loop.
On the other hand, that constant out/right-thrust induced p-factor is trying to bend our motor shafts into a bow, all the time.
The bow is canopy-ward or wheels-ward depending upon the rotation.
Take a metal rod, bow it and make it rotate, and eventually it or the bearings supporting it will fail.
Anybody out there remember the old Pontiac Tempest with Rope-Drive?

take care,
  Dean Pappas
Dean Pappas

Offline Igor Burger

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Re: Why do left hand props work?
« Reply #7 on: June 12, 2014, 02:02:49 PM »
P-factor is the yaw induced by the plane flying at a high angle of attack. The effective pitch on the blades becomes different on the two sides. On a flapped model, the fuselage pretty much tracks true through the turn while the flaps provide the angle of attack.

That is right, at AoA we fly (aproximately 10 degrees) and usual radius in corner, prop is aproximately tangent. However as Dean already wrote we have relative side wind and it makes moment pitching fuselage up (CW prop) and it adds to precession (both have the same direction). Fortunately we have landing gears drag and wing drag bot under thrust line, so that is reason why I thin CW prop is better compatible with models we use, so we not need to pull down all the flight.


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