Ok, so now that I got your attention, you are wondering what's the punch line, right? Not so much...

So I'm watching Ed Cook fly his electric Super Clown at our club field and it looks fast to me inverted. We can talk clearly over the prop noise, and I half joking say to Ed - "Hey Ed, you look a little fast inverted".

Ed laughs and tells me to put my stop watch on it. OK... so I get 4.79 upright, and 4.62 inverted. Umm... ok, maybe a power fluctuation, tail wind or some such nonsense, I tell Ed "lets do it again, somethings not right". Same exact times... several times over... hmmm... this is odd.

All we could figure, is that the plane is flying "cleaner" one way than the other, perhaps having some down thrust in the motor or something.

Makes you really wonder about all the things on our wet IC engines we took for granted as being the motor/tank issues, don't it?!!!

Ok guys, thoughts?
EricV

close enough to be human error on the watch too......

plus I bet he can fly straighter upright than inverted

Its gotta be a trim issue, like flying an aerobatic airplane with semi symmetrical airfoil (e.g. Bellanca Decathlon) requires more nose-up pitch in level inverted flight, and results in slower airspeed (draggier) compared with upright, than a fully symmetrical airfoil (e.g. Pitts or any full-on akro plane), which flies like our stunters and has almost no pitch difference inverted compared with upright. There must be something built into the model that causes a slight pitch difference in level flight upright vs inverted.

Eric,

It would be interesting to see if the variation is the same with a pusher vs tractor prop. If its a trim effect then it should switch because the prop swirl would hit the tail opposite. When I started using the pusher the first thing I noticed was that the ship would hug the ground a little more on take off. For the initial test I think you could just switch to a pusher and see if it's lap times were different (the pushers sometimes have a little lower pitch from the package than the tractor prop). Let us know.

Best,              DennisT

Eric
Darned interesting observation - and MAYBE it also speaks to the upright/inverted differences sometimes observed with IC.

I CAUSE that problem.  Upright I tend to back up on the airplane - a habit picked up a LONG time ago, before I could even stunt.  However inverted I stand still and pivot.  That is normally a .1 to .2 kind of difference (slower inverted).

Someone mentioned a pusher prop - Is Ed using one?  With a pusher the torque is toward the outside of the circle upright - and the Speed guys have proven that is SLOWER, but I'd have a hard time believing it is worth .2 sec lap - I do not recall that anyone else flying pushers has reported anything like that.

I would bet on the control positions, I'd GUESS that flaps might be up a little, spoiling lift, encouraging a slightly nose high attitude an probably a little draggier.  Another scenario could be BOTH wings tsited the same (probably washed out) so it flies wings level but is not truly symetrical.  Probably pretty hard to SEE it.  Does Ed report any difference turning inside versus outside?

Guys,

With summer starting and temperatures increasing it has been noticed that some electrics models emit stray electrons that cling to the smooth surfaces. You could have this problem when you go inverted. To remove these annoying electrons take a "Bounce" dryer sheet and wipe down the ship, pay special attention to the wing surface and hinge lines as this is were they collect. This will give smooth flow and may reduce you battery consumption (results may variety depending on weather, sun spot activity, closeness to RF sources, earth magnetic polarity, etc).

Caution  >>> you may notice your hair standing up during this procedure. If this happens quickly check to see if there are any large dark cloud in your area as you are going to be struck by lighting. Do not hold your ship if this happens as sensitive electronics could be damaged.

Best,              DennisT 

Eric,

OK, back on topic.  I'm with Denny in that pilot input might be the cause of the laptime differential.  Assuming a right-handed flier and counterclockwise upright flight, it's much easier to lead the plane without realizing it in inverted flight vs. upright.  If Ed is slightly holding the model back upright and slightly tugging on it inverted, this could easily cause an 0.2 sec variation.

To test this, the next time you time Ed's model, have him bring the handle to his chest and just pivot both upright and inverted.  My guess is that the lap times will probably be within experimental error.

What unmitigated conjectural nonsense!

Dang it, I knew the E experts would figure out the real reason.

The battery leads exit from either the top or the bottom of the pack. Gravity is inversely proportional to the distance from the centers of mass. Hence the distance from the side opposite the leads to the center of the earth varies in upright or inverted flight. The mass of electrons = 9.10938188 × 10-31 kilograms therefore we have the same pressure head differential situation as occurs in a IC fuel tank. I further expect that times in inside and outside loops to be different due to accelerative forces on the electrons.  

Kim  


I'm surprised Kim. Such vertical thinking.

Here's the solution.  Mount your battery sideways so there is no vertical difference (thus gravity is out of the equation) between the battery leads and the motor. Solves the inverted flight problem!

Paul

This thread piqued my interest so I did some research.  In the past whenever I have been stymied Fluke has had a way to quantify my stymie.  It was no surprise to once again find the answer at Fluke. 
Simply by purchasing this piece of equipment or any of their fine instruments it will be very easy to close the gap between clockwise and counter clockwise rotation.  For you particular situation/stymie simply pay in cash and count out each rather large bill placing it on a table in clockwise rotation.  By the time you get ¼ of the way to the full amount + tax, shipping, insurance and that all-important handling charge you will have slowed down considerably.  At that point you will be able to ramp back up to the desired speed by picking up the large bills in counter clockwise rotation and stopping at an acceptable level.  After doing this just once you will be able to preemptively mitigate any future asynchronous rotational transitions by sheer will power! It is truly a case where the means justify the end.  QED

See link below
<http://us.fluke.com/fluke/usen/products/categoryegt>
Earth Ground Testing
Most facilities have grounded electrical systems, so that in the event of a lightning strike or utility overvoltage, current will find a safe path to earth. A ground electrode provides the contact between the electrical system and the earth. To ensure a reliable connection to earth, electrical codes, engineering standards, and local standards often specify a minimum impedance for the ground electrode. The International Electrical Testing Association specifies ground electrode testing every three years for a system in good condition with average up-time requirements.
Understand earth/ground principles and safety in more depth and then describes the principle testing methods: 3 and 4 pole Fall-of-Potential testing, selective testing, stakeless testing and 2 pole testing.

Bruce, I think you got it that previous post. I do not think that level flight can have so drastically different drag that it can make 0.2s difference. The drag of model in level flight is very low and trust of the prop can easily compensate any flap/elevator miasalighment or something like that.

But you are right that if you use different walk backwars, so it wil change diameter of circle, for example only by 2ft, you will easily come to that number only by shortening circle.

But it is realively easy to find - if the current to the motor shows lower power (SQUARE of power) at quicker laps, then it is drag what makes the difference, if the power is the same, then the reason is smaller diameter of circle.

Measuring of power in figures is good sign anyway, I used active power delivery on base of the input power during flight (that is true 4-2-4 simulation) and it also shows misalighned flaps if figures with positive "G" shows different input power (means different drag)

Russel - WELCOME to this forum and congrats on your recent win.  Sounds like Bruce really has the E-Firecraker working well too.

Pusher props torque to the outside of the circle in upright flight - meaning some loss of speed is possible versus inverted.  No one else has commented on HOW MUCH tho

Finally got out last weekend to fly, had a refurbished bird, we were trying to check lap times. the boys kept yelling at me to STOP WALKING as I was causing about a .1 to .15 second effect on lap time.  Old habits die hard...

That's it, Dennis,
For your birthday we are getting you a pylon! ... I could steal one from the Speed circles when nobody ain't lookin' 
Dean

HA! We were at AMA, they were flying the Xtreme Flight Champs over on the L-pad, so we flew on ... the speed circles.  As I was walking backards I kept stumbling into the hole in the ground where they put the pylon...!!!  I shoulda just stuck my toe in it and hopped around on 1 foot...