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Author Topic: Prop turning direction  (Read 2512 times)

Offline Carl Cisneros

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Prop turning direction
« on: June 02, 2015, 10:52:26 PM »
Folks;

I have seen the props used on the Electic planes here at our flying field all running reverse rotation.

Is there anything wrong with them running in the standard rotation like the IC engines?

Thanks

Carl R Cisneros, Dist IV
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Offline Howard Rush

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Re: Prop turning direction
« Reply #1 on: June 02, 2015, 11:35:35 PM »
I assume you fly clockwise, looking from the top of the circle.  If you let them come up to speed before launching, the torque makes takeoffs a little sportier with standard rotation.  Other than that, standard rotation works better on one of my airplanes and just as well on the other.
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Offline Motorman

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Re: Prop turning direction
« Reply #2 on: June 03, 2015, 07:38:54 AM »
Check the avatar.

Offline Carl Cisneros

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Re: Prop turning direction
« Reply #3 on: June 03, 2015, 09:09:30 AM »
Howard

we fly anti clock wise as per the norm for most folks.

Carl R Cisneros, Dist IV
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Offline Randy Powell

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Re: Prop turning direction
« Reply #4 on: June 03, 2015, 10:05:23 AM »
Some fly deosil but I prefer widdershins.
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Offline John Cralley

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Re: Prop turning direction
« Reply #5 on: June 03, 2015, 11:12:15 AM »
Some pilots feel that they have better line tension especially in the overhead maneuvers when using pusher props  (clockwise viewed from the front). I'm not good enough to tell one way or another!
« Last Edit: June 03, 2015, 04:10:47 PM by John Cralley »
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Offline Howard Rush

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Re: Prop turning direction
« Reply #6 on: June 03, 2015, 02:41:27 PM »
Some pilots feel that they have better line tension especially in the overhead maneuvers when using pusher props  (clockwise viewed from the front). I'm not good enough to tell one way or another!

The perverted stuff my new plane did at the top of the hourglass caused me to switch to standard rotation (counterclockwise viewed from the front).  You'd figure that torque yawing the airplane out in those outside corners would favor the "pusher", but it didn't in that case. 
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Offline Dennis Toth

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Re: Prop turning direction
« Reply #7 on: June 04, 2015, 08:39:54 AM »
Carl,
There are pro's and con's to "pusher" setups. On the con side, if you have a ship that is set up for normal counter clockwise IC and convert to E power all the trim settings have to be almost reversed. For IC many build in a 1/16 -1/8" positive incidence (leading edge up) to the stab (this counteracts the downward piching moment do to circular flight with the counter clockwise rotation of the prop), we use reverse bellcrank installation (i.e. front line down). We carry more outboard wing tip weight. Some of these you can't easily change when converting. If the ship was built zero/zero then the only issue would be the reverse bellcrank which you could live with as long as the leadout position is adjustable.

On the plus side - if you build E power from the start the conversion is not to bad. For my ships I have found that I needed to be able to get the at least 1/2 the battery pack over the leading edge to hit the proper CG without adding tail weight, not to hard in the build stage. Also if you are going to go pusher prop you can use the old standard bellcrank installation with the front line "UP", this makes the control installation a little simpler. The stab should be at zero to 1/16" negative incident (to counter act the upward pitching moment due to circular flight path and the clockwise prop rotation). You will likely need a little less tip weight but this is minimal.

During flight what you normally notice is on take-off it holds the nose down a little more with the "pusher prop" then the standard rotation. You will likely feel more tension on the outside maneuvers (a little more solid feel) particularly the corners and last outside loop of the clover. I have two ships that are running pushers and for me it made them feel better.

Best,         DennisT

Offline bob whitney

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Re: Prop turning direction
« Reply #8 on: June 04, 2015, 10:16:10 AM »
i thought that with a flapped plane and standard bellcrank set up the front lead out is down
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Offline Dennis Toth

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Re: Prop turning direction
« Reply #9 on: June 04, 2015, 12:16:09 PM »
Bob,
Todays approach, for ships set up for counter clockwise flight, is to set up for the bellcrank (on IC CC rotation prop) with the output arm set up on the inside (leadout side) to give back line down. This gives a slight out yaw on outside turns (prop yaw in moment on outside turns) to help line tension.

For the clockwise rotation (pusher prop) the bellcrank goes in with the output arm on the outside (away from the leadouts) giving up line back to again give a slight yaw out. This is the opposite of the IC conventional counter clockwise rotation, thus the reverse leadout convention.

If the prop is very light the impact is minimal and some don't bother, but for heavy props or high rpm setups it makes a difference.

Best,         DennisT

Offline Howard Rush

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Re: Prop turning direction
« Reply #10 on: June 04, 2015, 09:00:48 PM »
On the con side, if you have a ship that is set up for normal counter clockwise IC and convert to E power all the trim settings have to be almost reversed.

Yes, the sign almost has to be changed, but not quite.  My experience has been quite different than Dennis's.  I built the same design I'd been flying as IC, and made it electric. The most notable change from IC to electric was that the CG had to move forward and UP for the electric, much farther than just the increment required for fuel.  My electric planes both started with CW props (looking from the front) and ended up with CCW (looking from the front) props.  I made no stab incidence change, and I don't remember making any elevator bias change, either when going from CCW IC to CW electric or when changing prop direction on the electrics.  The rear leadout is up on one dog; the front leadout is up on the other.  The biggest change I had to make going from the CW prop to the CCW prop was to bias the right flap down relative to the left flap: the opposite of what you'd do to balance the torque change.  When I switched props on both planes, I went from a CW 11" CA 3-blade to a CCW 11" CA 3-blade, so both props were aerodynamically and inertially the same. 

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Offline Curare

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Re: Prop turning direction
« Reply #11 on: June 04, 2015, 10:08:03 PM »
Howard, I also recall you saying that the CCW prop was giving you a lomcevak at the top of the hourglass. My stunt pig was doing the same, and so I decided to switch to a CW prop, and found similar outcomes to you swapping from one way to the other.

Truth be told I've not got it dialled in just yet, but the initial trim changes are pretty well in line with yours.
Greg Kowalski
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Offline Carl Cisneros

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Re: Prop turning direction
« Reply #12 on: June 04, 2015, 10:59:52 PM »
Folks

Thanks very much for all your inputs.

I pretty much just have to weight the pros and cons for each direction and then go from there.

Carl
Carl R Cisneros, Dist IV
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