Fly like Aldrich, Schaffer, and Phelps

[frank williams]

I didn't want to hijack Rich's thread, but on the subject of backwards flying.........

Given that some really great flyers did their flying “backwards” with “regular” rotation motors, were they taking advantage of something that the “normal” flying direction might still be overlooking?

Am I missing something, but isn’t a plane flying backwards laps with a normal cw rotation prop (ala Aldrich)… the same as a plane flying in a normal direction with a “pusher” ccw rotating propeller?

The pusher prop on an electric gets so much bad press by some as being a “hunter” and “does funny things at the top of the hourglass.  Is this the result only of the greater GP effects of the out-runner electric motor?
 
However, many flyers do like the flying characteristics of the pusher prop on a regular airplane.  The GP moment is opposite that of a tractor prop.  The overhead eights, vertical eights, and hourglass seem easier to perform.

There are few reverse rotation ic motors.  However, if we were to run a reverse rotation ic in a normal flight direction, with a “backwards” prop, we might feel the performance that Aldrich and the others felt.  Unless I miscalculated somewhere,

[Howard Rush]

What’s the moment of inertia of an electric motor with a wimpy prop compared to a real engine with a heavier prop?

[Brett Buck]

The pusher prop on an electric gets so much bad press by some as being a “hunter” and “does funny things at the top of the hourglass.  Is this the result only of the greater GP effects of the out-runner electric motor?

   As previously noted, I don't think the inside-out motor inertia is different enough from a crankshaft to make any consequential difference in the angular momentum.  Almost all the moment of inertia comes from the prop.

   The "funny at the top of the hourglass" effect is due to the spinning backwards, and the precession going in a different direction. As a discriminator, "outrunner" motors spinning the conventional way don't do anything particularly different from IC engines.

     Brett

[L0U CRANE]

Brett and Howard,

In another topic, - Bellcrank Placement -  I posted some thoughts about the lines, their shape and the pull they carry.

I'd appreciate any thoughts on my comments. I offered them because they are usually NOT included in discussions.

I did a draft about flying right to left, which may exist in the "ether" somewhere or got timed out for delay in posting, or something. It did not post in here anyway. It included-

Aldrich, Hal deBolt and several others, "back then" flew clockwise. Reason? IMHO, the conventional prop rotation (CCW from where we flip it) basic engine torque load on the mounts tends to lift the inboard wing that way. deBolt's  All Americans all had excessively long inboard wing panels. Rough intuitive reason? The inboard wing panel flies slower than the outboard, so more area would 'balance' lift left and right of the fuse. Correct, but without valid numbers way too much.

(His Speedwagon used an intuitively correct trick, also way in excess of proper. He curved the body to "fit" the circular flight path. But it was too much curve! When a speed model has any forward speed, pull is absolutely NO problem. It may have served to reduce the pull on the flier, but would still not be faired, streamlining, to the path flown.)

I may have said this in the other posts- I have flown an AA, Sr with a 'factory lefthand shaft' Fox 35. Ran identical to the conventional layout.
The model did not need tipweight, and takeoffs were VERY simple. Many using CCW prop rotation for CCW flight complain of difficult takeoffs and need for a wart or some other disfigurement to fly.

BTW, I haven't looked at available props much lately, but the "pusher" APCs I DID see did not look as correctly done as I'd have liked. Hope they've improved that, and not just for the e-power flimsy looking props.

[frank williams]

I calculated the angular momentum difference between ic  and electric some time back.  However I used a diameter instead of a radius somewhere in the process and the numbers were garbage.  But, I believe that Brett's numbers showed a bigger GP for electric, but not too much.

I must admit that I have a reverse Fox35 that is in a Still Stuka.  The difference in flying feel is real.  At 45deg and above the line tension is much more constant.  Vertical eights and overheads are improved feel.  I think that the "advantage" of the pusher prop for ccw flying is that of the prop swirl  effects.  The GP effects of the pusher are probably somewhat detrimental.

The prop swirl for a pusher produces a yaw that is nose out.  As the plane slows down, the outboard yaw due to swirl increases.  good.  The other side of the coin .... for a tractor prop, as the plane slows, inboard yaw is increased. not good

So, I challenge you .... take a plane, fly a regular pattern and then switch the handle over and fly an inverted pattern.  You should find the second pattern easier to fly (if the plane survives)  ..... yeah right I'm gonna try that!  better yet .... find a reverse crank

[FLOYD CARTER]

Sorry, but there a whole bunch of world-class flyers who take off counter clockwise.  There doesn't seem to be much difference, in the big scheme of things.

[Brett Buck]

What’s the moment of inertia of an electric motor with a wimpy prop compared to a real engine with a heavier prop?

     There's a calculation somewhere on SSW.

    Brett

[Tim Wescott]

What’s the moment of inertia of an electric motor with a wimpy prop compared to a real engine with a heavier prop?

C'mon Howard -- you know the answer.  For same-diameter props, about the ratio of their masses.  For different-diameter props, it's proportional to diameter squared times mass.  For wacky props that change the mass distribution toward or away from the tips -- it's complicated.

[Brett Buck]

C'mon Howard -- you know the answer.  For same-diameter props, about the ratio of their masses.  For different-diameter props, it's proportional to diameter squared times mass.  For wacky props that change the mass distribution toward or away from the tips -- it's complicated.

   Use an assumption of radius of gyration = .226*diameter. I got this from Pete Soule's site, and didn't believe it until I tried doing several props manually with bifilar and torsion pendula, and it was pretty good for any prop I tried, 2-blade, 3-blade, etc.

     Brett

[Lauri Malila]

[quote author=frank williams

There are few reverse rotation ic motors.  However, if we were to run a reverse rotation ic in a normal flight direction, with a “backwards” prop, we might feel the performance that Aldrich and the others felt.  Unless I miscalculated somewhere,
[/quote]

Frank,

In that case you would get the same benefits and problems than with a normal model with a pusher prop. In my opinion a classical model with classic layout flies better and is easier to trim with a tractor prop. That little extra tension in top of hourglass is not worth it when you look at all the other trouble it causes.
But changing running direction also tends to turn many issues affecting engine running symmetry upside down.
Been there, done that L

[frank williams]

Hi Lauri
The props are beautiful.  I like the mirror image logo on the pusher.   Very appropriate.

My thesis here is that normal flight direction with a pusher prop  E Q U A L S  clockwise flight direction with a tractor prop.  Just a mirror image.

So why didn't the problems we face with the pusher props appear for the "legends" that flew backwards with tractor props, since both scenarios are equivalent.

Frank

[Air Ministry .]

In non-vector terms: at a given rate of rotation of the observer, the magnitude of the Coriolis acceleration of the object is proportional to the velocity of the object and also to the sine of the angle between the direction of movement of the object and the axis of rotation.

The vector formula for the magnitude and direction of the Coriolis acceleration is derived through vector analysis and is[20]

{\displaystyle {\boldsymbol {a}}_{C}=2\,{\boldsymbol {v\times \Omega }}} {\displaystyle {\boldsymbol {a}}_{C}=2\,{\boldsymbol {v\times \Omega }}}
where (here and below) {\displaystyle {\boldsymbol {a}}_{C}} {\boldsymbol {a}}_{C} is the acceleration of the particle in the rotating system, {\displaystyle {\boldsymbol {v}}\,} {\boldsymbol {v}}\, is the velocity of the particle with respect to the rotating system, and Ω is the angular velocity vector having magnitude equal to the rotation rate ω, with direction along the axis of rotation of the rotating reference frame, and the {\displaystyle {\boldsymbol {\times }}} {\displaystyle {\boldsymbol {\times }}} symbol represents the cross product operator.

The equation may be multiplied by the mass of the relevant object to produce the Coriolis force:

{\displaystyle {\boldsymbol {F}}_{C}=2\,m\,{\boldsymbol {v\times \Omega }}} {\displaystyle {\boldsymbol {F}}_{C}=2\,m\,{\boldsymbol {v\times \Omega }}}.
See fictitious force for a derivation.

The Coriolis effect is the behavior added by the Coriolis acceleration. The formula implies that the Coriolis acceleration is perpendicular both to the direction of the velocity of the moving mass and to the frame's rotation axis. So in particular:

if the velocity is parallel to the rotation axis, the Coriolis acceleration is zero. (For example, on Earth, this situation occurs for a body on the equator moving north or south relative to Earth's surface.)
if the velocity is straight inward to the axis, the acceleration is in the direction of local rotation. (For example, on Earth, this situation occurs for a body on the equator falling downward, as in the Dechales illustration above, where the falling ball travels further to the east than does the tower.)
if the velocity is straight outward from the axis, the acceleration is against the direction of local rotation. (In the tower example, a ball launched upward would move toward the west.)
if the velocity is in the direction of local rotation, the acceleration is outward from the axis. (For example, on Earth, this situation occurs for a body on the equator moving east relative to Earth's surface. It would move upward as seen by an observer on the surface. This effect (see Eötvös effect below) was discussed by Galileo Galilei in 1632 and by Riccioli in 1651.[21])
if the velocity is against the direction of local rotation, the acceleration is inward to the axis. (On Earth, this situation occurs for a body on the equator moving west, which would deflect downward as seen by an observer.)

NEWZEALAND is of course optimimly placed for the full advantage in acceleration flying counter clockwise . & full restraining force flying clockwise .

( I just made that up actually . ) .

Theres more tecnicaly mathmatical calculus type tripe here ; https://en.wikipedia.org/wiki/Coriolis_force

Sounds like its of some mathmatical relevance .

[Alan Resinger]

As one of the few clockwise flyers around I can speak with authority on the subject.  First off the I am not left handed.  In the mid fifties I  learned to fly from a fellow that lost his job at the local glass factory giving him the oppurtunity to open a hobby shop jin our small town.  This guy had been in the army air force during WW II.  A tail gunner in a B-17, he got shot dow twice, once bailing out over France and being found by the Frence resistance.  After getting back to England he flew more missions and got shot down agin over the channel.  He and his older brother both flew as they had seen Hal DeBolt fly All Americans.  That turned out to be their choice for what I  would call speed freestyle stunt.  My friends all learned to fly clockwise as they did.
I flew a lot until the mid sixties when I went in the service where I  did a little flying during my seven years in the Air Force.  When I
 moved to Canada in 1981 I  started flying and competing again. 

Flying clockwise has some drawbacks.   As there are so few of us flying clockwise and even fewer that compete, on only one occasion have I  been able to fly another competitive model.  That is one flight in close to forty years.  Takeoffs with clockwise flying models are easy with RH props and clockwise motor rotation.  As I use electric power when Chris Cox and I first started  making LH  props for electric, I though I  would  try one to see how everyone ellse lives.  After two flights I  went back to the RH prop.  Scared the heck out of me. 

Another thing that is detrimental is everything is backward.  I flew at the Reno nats in 1984 and the first Tri city Nats in Pasco, Washington.  Think I finished 14th in Reno.  At the 89 Nats as I  was walking back to the pits after an early qualifying flight. I  was within earshot of the judges when I  heard one judges of the say "I  can't judge an airplane going the opposite direction".  My jaw dropped and I  stopped walking.  Set my bandle on the ground and went over and confronted the judge. I  was not happy and later made it known to the event director.  I really wanted a reflight with that judge removed but nothing happened.

Another problem conceerns equipment.  4 years ago I started using Igor Burger's active control system.  After instaling the equipment in a new model I  followed Paul Walker's instructions and got the model trimmed before turning the sensitiviy up to get some reaction from the system.   I started doing some loops and got a surprise.  The model slowed going up and sped up on the downward leg.  I stopped flying and sent Paul a text to get his opinion when I  got home from the field.  I sent an emai to Igor as soon as I  got home prior to calling Paul.  The drive home got me thinking that because i fly clockwise maybe Igor's unit needed to be installed upside down.  Paul wasn't sure but as I  was talking to him, Igor replied saying of course it needed to mount upside down.  My model that year worked fairly well although I  thought something wasn't quite right with the system.  The next years model wasn't as happy with the system.  Several parts of the pattern were problematic.  I put my thinking cap on and realized that the accelerometer unit has a specific top and bottom, which I  discovered when I first started using it.  It also has a specific inboard  and outboard side.  I have to trick the unit to think it is flying in the opposite direction.  Igor is specific about having the wires from the unit go toward the front of the model.  I had to not only mount the unit upside down I also have rotate it 180 degrees.  My lead wires go initially toward the tail and then fold over toward the front to connect to the ESC.

In short tnere is no benifit to flying clockwise.  We few flyers are cursed.

[Lauri Malila]

[quote author=frank williams

So why didn't the problems we face with the pusher props appear for the "legends" that flew backwards with tractor props, since both scenarios are equivalent.

Frank
[/quote]

Frank

I think in the old days and smaller, lighter models it was not such a big issue. But I found, that in strong wind it was more difficult to have good control of outside corners (other than hourglass).
Otherwise there is no other issues, hunting etc. Just a little difference in handle neutral.
That being said, maybe with help of active rudder one could end up in a better result.
If you ever need big pusher props, 13...14x5...6, I have plenty. Both 2 and 3 bladed. L