rt handed vesis lft handed props

[bob whitney]

i have been flying electric stunt for about two years now  i have been using 12/6 and 13/4.5 lft hand carbon APC copys on my Scorpio i now have a Formula -S. on a lft hand 12/6  i wanted a smaller prop and had a rt hand  12/6 trimed to 11 in so put it on and i started having problems with the upper right corner of the hr glass . it would get light.  today i went out and ran two 11/6  one left and one right back to back.  ran the rt one first and it got lite at the top as it has been,  put the left handed prop on and had no trouble with the hr glass  did 3 consecative manuvers with no trouble has anyone else tried a back to back test to see the diff

[Steve Helmick]

I would bet pretty good money (to me) that such tests have been done at the WSR.  Steve

[Larry Wong]

TRY VG'S it help me on the 3rd turn on the hourglass

[Dennis Adamisin]

i have been flying electric stunt for about two years now  i have been using 12/6 and 13/4.5 lft hand carbon APC copys on my Scorpio i now have a Formula -S. on a lft hand 12/6  i wanted a smaller prop and had a rt hand  12/6 trimed to 11 in so put it on and i started having problems with the upper right corner of the hr glass . it would get light.  today i went out and ran two 11/6  one left and one right back to back.  ran the rt one first and it got lite at the top as it has been,  put the left handed prop on and had no trouble with the hr glass  did 3 consecative manuvers with no trouble has anyone else tried a back to back test to see the diff

My initial experience with RH versus LH props was just as you described. 12x6's on a Pathfinder.  With the RH prop the tops of the Vert-8, hourglass, & 3rd leaf of clover were prone to go light, with the LH prop the bird stayed TIGHT in all those places.  Since then I have not bothered with any back to back comparisons - I use the lefty props exclusively.

[Chuck Feldman]

Right hand props are know as tractor, right?

Chuck Feldman

[bob whitney]

yes ,rt is tractor

i was happy with the lft hand props but had a rt had already trimmed so gave it a try rather than trim a new prop

[Bob Reeves]

First thing I noticed when I started running reverse Saitos was the top of the hour glass.

[Chris Wilson]

I have always considered 'tractor' props to pull and 'pusher' props to ........... well push regardless of their rotational direction.

[Steve Helmick]

RH tractor Props turn top blade toward the starboard side of the plane. LH tractor props turn top blade toward the port side of the plane. I'll let you figure out which side is port and starboard... Steve

[Kevin Ferguson]

For those who get confused over Right Hand Vs. Left Hand pitch:

Hold your hand with the thumb extended and the fingers curved.  If the prop spins in the direction of your curved fingers. It produces thrust in the direction of your thumb.  Use right hand or left hand as appropriate.  Amputees may need assistive technology.

Our engines' default rotation is chosen so that normal right hand pitch fasteners (prop nut or bolt, it matters not) will tend to tighten as a result of the torque of the engine.  When you pull the reverse rotation trick with a reed or piston valved engine there is often a problem with the prop coming loose.

[Howard Rush]

You can get quadrotor carbon props that work dandy for stunt.  They are cheap and pretty.  Orestes used one at the team trials.  They come in matched pairs: one in each direction.  Similarly, the Cox-Resinger props come both ways.  If anybody wants to go to the bother of balancing and pitching a pair and trimming his airplane for each, he could determine the difference.   

[Steve Helmick]

Right hand props are know as tractor, right?

Chuck Feldman

Actually, the real deal is that if they're mounted on the front of the plane, they're tractor props, whether they rotate clockwise or counterclockwise. Just as with right wing or left wing (regarding airplanes here), the view from the pilot's seat is what determines the answer. This isn't that hard to grasp, if you look at a picture of a Spitfire or Bf-109 sitting on the ramp, engine off, and compare it to a Mustang in the same situation. All three have tractor propellers, two are left handed, the other right handed.  Steve

[bob whitney]

i also have a ,09 size E-ringmaster that i have been fighting the same problem . picked up a lft hand prop of the same pitch 8/6  and flew it in some good winds yesterday and wola it will do an hr glassfor the first time

[Ted Fancher]

Thought I noted PW using smaller diameter RH props.  No?

Ted

p.s. how much variety of LH props are available?  They all seem to look like the same APC to me and my RH experience has been that the right prop for a given airplane is sort of elusive, thus a garage full of different ones.  Does on size fit all for the volts and amps crowd?

Ted

[Dan McEntee]

Thought I noted PW using smaller diameter RH props.  No?

Ted

p.s. how much variety of LH props are available?  They all seem to look like the same APC to me and my RH experience has been that the right prop for a given airplane is sort of elusive, thus a garage full of different ones.  Does on size fit all for the volts and amps crowd?

Ted

     I'm interested in that answer also Ted. I see a lot of 13-6 props on electron burners, and just wonder why? Is it because of the new fangled throttles that they run? With or without the accelerometer, does not pitch mattter some when fine tuning an electric model? Would not they also bennefit from a some what of a high RPM-flat pitch set up when flying in the wind?

   Type at you later,
    Dan McEntee

[Ted Fancher]

     I'm interested in that answer also Ted. I see a lot of 13-6 props on electron burners, and just wonder why? Is it because of the new fangled throttles that they run? With or without the accelerometer, does not pitch mattter some when fine tuning an electric model? Would not they also bennefit from a some what of a high RPM-flat pitch set up when flying in the wind?

   Type at you later,
    Dan McEntee

Can't answer that, Dan.  I've no personal experience with testing such things.  Just noted that Paul appeared to have transgressed the current gospel winning the nats with a right hand rotation, smaller diameter prop.  I could be wrong, however, as I didn't, at the time, feel the need to investigate more thoroughly.  My  personal experience (almost ancient history now) was that I wasn't sold on large diameter stuff and never flew with a bassackwards pitched prop.

Ted

Ted

[Alan Resinger]

I'm going to jump in and add a little input.  This past summer when Chris Cox and decided to make some 3B props for electric models it was not done without spending quite a bit of time contemplating the subject.  Flying with Paul a lot over the years we've both come to appreciate the fact the Paul does not do things without a firm idea of what he is trying to accomplish.  So who better to look to for guidance.  First off lets talk prop diameter.  With an electric the prop of choice has seemed to be some version of the APC props. These work very well for the majority of flyers.  For competition flyers, always looking for the best performance, this can present a problem.  When I first started flying about 60 years ago the two brothers who taught me and my friends to fly flew in a clockwise direction.  I kind of remember asking why we flew clockwise when all the magazines and kits seemed to show models set up fort counter clockwise rotation.  The answer made perfect sense in that we were taking advantage of the torque of the motor to help with line tension.  I've been ask about flying clockwise for years and most people think that it's because I'm left handed, which I'm not.  With the advent of electric and being able to turn the motor in the opposite direction it's become clear to all that have tried it that there are some advantages.  When you make that first outside corner of the square loops you understand what I've known for years.  The top of the hourglass is also a lot easier.  As to prop diameter we have to go back a few years when Mr. Walker was flying his OS40VF Impacts.  His prop of choice was always a modified Bolly 2 blade that had a maximum diameter of 11.3".  Even with the small diameter, his plane never lacked pulling ability nor did it lack corner.   When Paul showed up last year with a 3B tractor prop on his model I took notice.  Even though it was a tractor instead of a left hand APC like he had been using, the first thing I really noticed was the quality of the corners he was presenting.  All of the top level flyers can turn square corners, but not all square corners are quality corners.  Ask any top line judge and he might not be able to describe it but he knows it when he sees it.  When we started making props this year we decided to make both right and left hand props but have kept the diameter small with 3 of the props being only 11" and 1 being 12".   

[Mark Scarborough]

well,, I am far from the stunt expet,, but I think one of the reasons that the APC seems to be such a universal fit has more to the power delivery, with a glow motor, you had to match the blade area, pitch, and other facets of the design to give the right kind of thrust in concert with the power delivery,, with electrics its not the same set of issues, at least thats my observation,, certainly not in counter to what Alan or others said, but the torque curve is different, more linear ( from my nderstanding) so matching that isnt as critical,,
please redirct me if my observations are flawed,,

[Dennis Adamisin]

I believe the basic APC electric is already a darned good prop.  People who have tried the APC compared to other electric props generally come back to the APC. The prop artists will have a challenge to improve on an already good design.

Referring to Dan M's comment about prop speed:
The most popular 13” E-prop for stunt is the 13x4.5EP-F2B pusher, followed in popularity by the 13x5.5EP pusher.  The 4.5 is thin, the 5.5 is thicker, both props usually run in the 9300-9500 RPM range.  This RPM range is also about 85% of APC’s recommended max speed.  These props produce spectacular thrust & braking.
 
APC also makes a 13x4 that needs to run around 11k and a 13x6.5 that runs around 8k but these are really too slow or too fast for our app.

Since "discovering" pushers we have worked with APC to bring out the 10x5.8EP-F2B, 11x4.5EP, 11x5.5EP, 12x6EP-F2B, 12x6.5EP-wide, 13x4.5EP-F2B and the 13x5.5EP.  APC will not make a 3-blader; they feel they are too inefficient and are also difficult to properly balance in a prodution environment.

Stepping into that void,    Alan & Chris from up in the Great White North are launching some 3-blade pushers that sound very promising.  Anyone who reverted to a tractor prop to get 3 blades will now get to come back to the pushers.

Quadcopters with RH & LH props will also be a source for new blades - problem is that these are generally VERY flat in pitch, however the are thin, very light and very stiff.

Back to Bob W's original post - another case study:
I recently used a pusher prop to overcame an otherwise un-trimmable condition.  I have a Sheeks classic “Swinger” swept wing - a really cool looking bird - with issues!  I have the leadouts as far forward as possible but still had problems with line tension above 45 degrees – I contemplated “surgery” to get another ½” to ¾” forward movement but that was a lot of work including running the leadouts through the LE (ugh) so I put it off.  I had only flown it with a tractor prop.  Late last Fall I flew the bird for the first time with a 10x5.8 pusher.  The line tension is now spectacular in all regimes. Purist will (rightly) argue the bird is still "out of trim", however the symptoms (not the cause) have been appeased.

 

[L0U CRANE]

A thought no one has mentioned so far... Precession effects...

First, let's simplify the pusher v tractor wording? "Standard" rotation props turn counter-clockwise as seen from in front. And vice versa. SO, "pusher" props can be called CW (clockwise), and "standard" (tractor) props called CCW (counter-clockwise.) Unless you take special pains to adapt your glow engine to operate CW - factory 'left-hand' shaft, 90° rotation of the front end on engines like ENYA with a suitable bolt pattern, or whatever... (I did that with a Fox 35 LH shaft on an All American, Sr., back about when VSC got going. Only difference noted was that NO tip weight was needed. Engine ran identically to CCW characteristics...)

Gyroscopic precession - we're (mostly? all?) familiar with 'toy' gyroscopes, and how they react when you change the axis direction while they spin. They resist turning, and try to turn instead in the direction 90° "later" in the direction of flywheel rotation.

Our props cause an effect like the flywheel on a gyroscope with the shaft as axis. A CCW engine wants to turn RIGHT on tilting the shaft UP, AND to turn LEFT when tilting the shaft DOWN. Apply that to prop-as-flywheel on a stunter. Inside turns and corners 'try' to yaw the nose away from the flier; to increase "pull." Outside turns and corners 'try' to yaw the nose in, towards the flier.

In the hourglass, the second turn is a tight outside corner, high on the hemisphere, where we've lost speed and pull already. A CCW 'flywheel' tends to nose-in, to reduce "pull" up there. ...Or is that what everyone said was the problem they ran into, that did not occur with a CW 'flywheel?"

Two other factors may be involved:

- we don't as much notice the right-yaw effect on inside moves because we've been adapting to that since we first learned level, upright flight. It may well have become learned-reflex 'natural.' BUT, a reversal - e.g., outside moves - makes the yaw tendency much more noticeable. It goes against our most basic, ingrained expectations. And, I don't care how many laps or years a practiced stunt flier has flown inverted, upright flight is more comfortable and natural...

- APC props are not lightweights. Their weight is a small matter because they are generally so good for our needs. However - rotation rate (RPM) and mass (weight) affect the gyro precession 'couple' force.

(Don't let me get started on THAT -except to say that what I understand 'resolves' the gyro precession couple is a slight yaw shift of the model, to aim the 'pull' force ahead or behind the CG enough to counter, if not cancel it.)

So, finally (and I can hear the sighs of relief), a CW prop applies a nose-out tendency on sharp outside turns. ...Like the second turn in the Hourglass... Which happens to be where we most appreciate, and notice, the difference.
 
(Just for info, a Dutch flier. J. van Hattum I think, offered a way to estimate the forces in the gyro precession couple, in an Aeromodeller Annual about 40+ years ago. I wrestled with that - which was in metric, a language I don't speak well. IF it worked well, and IF I translated it into my more comfortable "Imperial" units, it implied a possibility of totally controlling the gyro-yaw results by the spacing of the leadout guides! Seemed to work for me, at my humble level of skill and sensitivity to the model's response.)