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Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Old 07-06-2011, 06:07 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brian, you are very fortunate. This is my 6th season of enjoying electric pattern flight and most of my flights are off concrete runways. The point I was trying to make is that you/all of us cannot
rely on a clutch arrangement to minimize or eliminate prop damage. Now, if you are using $15 USD APC electric props it's not a big deal. But, if I'm not mistaken, these props you are using are approximately $100 USD a peice, correct? What the heck, it's only money! I was hoping your response was not another attempt to lead me down a "primrose lane" and thankfully it wasn't. As you know the vast number of current available pattern plane designs do not take into account the use of any of these geared units and the size props associated with their use. Sure, the problem can be overcome with the purchase of longer gear which is usually accompanied by increased overall weight. So, there is a give and take. I found it interesting that a couple of the above Contra-drive users were quick to add how great their particular plane flew regardless of whether they used the unit or not. I suppose it's all part of promotion. In the final analysis "YOU still gotta fly it". (YSGFI) Again, thanks for your response, Everette
Old 07-06-2011, 06:11 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Brian, I've too had several prop strikes on the ground, some from landing and one big one on taxi, and if it's on grass so far I've had no damage to the prop besides some dirt. On pavement I have received some tip damage but some sandpaper and reshaping of the tip all was good. The big prop strike while coming back to the pits happened when trying to get over some tall grass and the landing gears got stuck, the props hit so hard it actually broke the motor mount, the back motor support, but the props were ok. I think the real reason for the clutch is to save the gears in the unit if a prop strike does happen, so far for me it's been working really well.

I'm trying some fences or SFG's on the stab per Andrew's experience with several of his past planes that needed more yaw stability. I have about 10 flights with them and they seem to be adding slightly more stability to the plane, at minimum they are not hurting anything. I plan to keep them on for the next few weeks and see if any problems come up. The plane was almost stable in yaw before the fences, I think that's due mostly to the thick trailing edge rudder, and now the plane seems to be locking in better, I hope it's not a placebo effect. The stab has a layer of vinyl tape that the fences are ca'd to, this seems to be holding well and everything should be easily removed if needed. Isn't testing fun.

Dave

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Old 07-07-2011, 01:01 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Dave,
They seem toe 'out' in the photos.
Is this the case ??

Brian
Old 07-07-2011, 02:54 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Brian, they're actually parallel to the fuse center line but the photo does not show that well. I also tried my best to get them vertical, with the anhedral stab the fences are not perpendicular to the surface of the stab and this may give the illusion of the toe-out.

I did get some feedback from Andrew and my fences are smaller than what he used, mine 3/8" tall and his 5/8" tall. I had several more flights today and still cannot detect any bad effects from the fences and the locked on feeling still there but it was calm today so I'm still not sure what will happen in wind or crosswind. With about 15 flights now using the fences I think there are worth the effort if you are detecting yaw instability but I would make them taller than my first attempt.

Dave
Old 07-07-2011, 03:53 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Dave,
I had some,or so I thought, going vertical up or inverted going up at 45*.
The Ventura rudder is 60mm longer at the bottom than at the top.I put a flair on it that was 5mm wider at the bottom than at the top,in keeping with the rudder shape.
The rudder was giving a subtle neg,, pitch effect in those positions and was speed and wind dependant so it was inconsistant.
I removed 45mm from the back of the rudder at the bottom and 0mm at the top. I also put a paralell flair on it and it's all good now.We have had no calm weather to speak of so making accurate observations has not been easy.
However a little more locked on can't be bad, so I may try the fences at some stage.

Have you or Andrew J tried a little toe in on the fences. I think that would add stability.

Brian
Old 07-07-2011, 04:38 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brian this is my first attempt at using fences and I'm not sure how toe-in would effect the plane. In level flight it probably would work great but in knife edge flight one fence, lower, would have a greater angle to the flight path and the other fence, top, would have a lower angle, I think this would require more rudder input to maintain knife edge flight and then if the speed changes...... Just too many variables to think about, maybe some other flier has tested this but I think KISS is the best approach here since we are looking for slightly more stability without changing anything else.

Dave
Old 07-28-2011, 04:59 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi,
It looks very that Angus will make it to the WC semi's using the contra.
I hope he does and I wish him all the very best.

Brian
Old 07-30-2011, 04:11 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brenner,
Just caught up with this in the last couple of weeks and it looks the Biz.
What is the spinner dia of the standard set up.
What lead time do you need.
How about that Chip dude, turns out partying hard isn't bad for you after all.
I hope he wins it.
Cheers
Greg Hede
Australia
Old 07-30-2011, 06:17 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Greg,

The spinner diameter is 82mm and the spinner length is 85mm. I have Drives with me at the Worlds that people can take with them if they want. If these all get sold, then I can ship more Drives a few days after I get back from the Nats

You're right about Chip. He's a force of nature. Here in America we're all rooting hard for him.

Brenner...
Old 07-30-2011, 07:47 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Here are some Contra pictures from the Worlds...
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Old 07-30-2011, 12:31 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

that is really cool Brenner. You guys must be proud!! (and rightly so!!!!!!)

Volkert
Old 08-01-2011, 04:16 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi,

Of the 10 finalist in 2011 F3A WC -any of them using contra rotating props?

Christophe Paysant-Le Roux
Chip Hyde
Tetsuo Onda
Gerhard Mayr
Andrew Jesky
Berndt Beschorner
Koji Suzuki
Stefan Kaiser
Benoît Paysant-Le Roux
Wolfgang Matt


/Bo
Old 08-01-2011, 05:31 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hello

There is the Addiction of Berndt Beschorner

sorry it's a 3 blades prop
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Old 08-01-2011, 06:20 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi
None in the top 10 this time but I'm tipping that the next Worlds will have plenty.
It must be better.
Greg Hede
Australia
Old 08-01-2011, 05:53 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brenner:

I am very impressed with your system. I am a Japanese flyer. In order to minimize the price at a given demand level, I suggest that you present this system to Futaba. I have heard that the company is interested in marketing its own F3A size motor. In fact, it has announced the 110( 4 cycle) size electric motor for about $150 in Japan. It also announced speed controller for the 110 . Futaba maybe interested in marketing your product without you losing much money. If you can come up with a system that fits future Futaba F3A motor, maybe you and Futaba can make a deal to market. This would be great for flyers like us. Japan is very interested in the electrics now. One of the top notch flyer even came up with a belt drive system to reduce the rpm and T. Onda, placed in the 2nd today at the internats, flies electric as well as YS engine. So give it shot for fans like us!!!


Chuck
Old 08-02-2011, 07:03 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Chuck,

If Futaba comes out with an f3a electric motor, I'm sure that we will be able to develop an Adapter Manifold for it. As far as presenting our Contra Drive to Futaba, usually large corporations like Futaba like to develop products internally, so I'm suspecting that their interest wouldn't be strong, especially since pattern flyers are such a small market.

Brenner ...
Old 08-03-2011, 10:48 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brenner:


You are correct about large corporations like Futaba. I worked for Sony for a long time and they wanted to do something internally. However, Futaba is a later comer in the market behind Hacker. So, maybe they are interested in adding value to their product. The Japanese are very interested nowadays in collaboration. So, maybe a good chance for you. I would show this to Onda or to Akiba. Good luck.

Chuck
Old 08-07-2011, 05:10 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Slightly different topic for the contra drive:
I watched a few of these at the worlds. It certainly looks to have some real potential. However, it doesn't look like there is an airframe that is really able to match it perfectly.

What characteristics should an airframe have that is purpose designed for the contra drive?
Old 08-07-2011, 06:51 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Steve,

This is an excellent question. In fact, a lot of pilots have been asking the same thing, and so far there are several ideas and concepts that are emerging:

1/.. Airframe Drag

Airframe drag is not needed as much to control the speed of the aircraft on downlines because the Contra Drive provides more than enough downline braking to do the job. This means that an airframe with less drag will have a wider speed range, and will take less mah out of the battery pack.

2/.. Yaw Stability

Zero degrees of right thrust, and no spiral airflow over the fuselage means that additional features are required to add dampimg in the yaw axis for Contra Driven planes. This can be in the form of larger rudder fin area, sfgs on the stab or wing, or perhaps a longer tail moment.

3/.. Fuselage Side Area

The absence of spiral airflow over the fuselage changes the aerodynamics of the fuselage. This means that the amount of fuselage side area, and the distribution of fuselage side area, may have to be different from current aircraft to optimize rolling performance, and minimize mixing between the rudder and other controls.

It's been interesting to see how different aircraft adapt to the Contra Drive. For instance, my Integral needs additional damping in the yaw axis, which I accomplished with the use of triangular strips on the trailing edge of my rudder, whereas Angus Balfor's Valiant didn't need any changes at all to fly well. Dave Snow's Spark also needed additional yaw damping, but not as much as my Integral, and the Wind S Pro needed just a slight increase in yaw damping.
Old 08-08-2011, 04:29 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brenner
I PM'd you with a kinda similar question, I mentioned the Integral, Wind Spro and the Spark.
Is there a design out there that jumps out at you as THE one or is it way too early in the development path to make any informed calls on.
I mentioned that the Integral and WindSPro were the two most affordable over here in OZ, would you have a preference on either of these as more or less suitable.
I've only been flying turnaround pattern for 18 months with real Clunkers after being out of the hobby for 32 years having been pretty active in the old 70's pattern scene as a teenager.
Cheers
Greg Hede
Australia
Old 08-08-2011, 06:24 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Greg,

I remember your PM now. I apologize for not getting back to you. My excuse is that I've been totally consumed by the Worlds and then the US Nats for the last two weeks.

Right now I think it is a little early to point to a particular design and label it as "The One". If I had to buy a new plane tomorrow, I think I'd seriously look at the Valiant, and the Wind S Pro, but I think that there will be better airframes as early as next year that have actually been designed with the Contra in Mind.

My Integral is also flying pretty well right now, and I have no qualms about recommending it as well. However, with the Integral you are going to have to add damping in the Yaw Axis, by adding strips to the trailing edge of the rudder, adding sfg's to the stab, or both. You will also need rudder to aileron, and rudder to elevator mixes to get the knife performance working properly, and perhaps a very slight mix of throttle to elevator to prevent pulling to the canopy on downlines, but once you do all this, it it a very sweet flying airplane.

I actually haven't flown the Wind S Pro, so I can't speak about it with as much confidence, but it has a lot of the characteristics and features that I think we will see in the future with planes that have been designed with the Contra in Mind, and I think that with what we know now about how to make a plane fly well with a Contra, we can make the Wind S Pro fly very well.

By the way, both planes should be under the 2m length requirement with a Contra, and my Integral was 4920 grams RTF on the official Nats scale.

Also, the Valiant is the only plane that I know of that flew with a Contra without seeming to need any modifications at all. In fact, Angus Balfor from Team Ireland flew to 19th place in the Worlds with his Valiant. (However, I personally haven't flown a Valiant with a Contra, so I can't speak from personal experience...)

Brenner ...
Old 08-09-2011, 11:48 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Last weekend I tried my Indira F3A biplane with the Brenner contra drive.

All I can say is: WOW !
What an amazing system, very high quality machined and everything fits perfect.

I changed the motor mount to 0 degrees down thrust and 0 degrees side thrust.
It seems that I need a little up thrust for the biplane instead of 0,5 degrees down thrust.
Will experiment with that next weekend..

Also it sounds very nice with 22x18 prop in front and the 22x20 prop in rear.
Not that anoing e factor contra drive sound.
Speed is also excellent exactly my style of flying, calm and slow.
But with a little more throttle also very good for windy days.

Also noticed that I needed far less aileron and rudder rate.
No difference in roll speed left or right.
Stall turns are much nicer and easier.

I'm very happy with it !

Thanks for making this affordable and possible for the regular pattern flyers Brenner.

Here are some pictures:









Old 08-09-2011, 01:27 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Spark09,

Is that your own design? Looks great.

Cheers,
Jason.
Old 08-09-2011, 10:54 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Jason,

Yes, We designed and built it in the winter of 2009.
There was a version before this one but it crashed.. caused by a dead rx lipo.

The plane is based on the Miss Wind 50..
Still testing the plane looking for better and lighter solutions and making it even better.

The new one will have better wing struts, different landing gear and different stabilizer.


Cheers,

Roy
Old 09-14-2011, 11:36 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brenner - U got mail

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