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Contra Rotating Propeller Drive for f3a 2m Pattern Planes

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Old 05-27-2012, 06:42 PM
  #776
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

I just got back from the contest in Hemet, CA. I'm happy to say that the Contra performed exceptionally well in a variety of conditions. On Saturday we had pretty stiff winds and some moderate turbulence. I would have to say the Contra powered Onas handled it extremely well. Plenty of speed when needed and excellent power in the vertical. Today for the last two flights of F-13 we had near perfect weather. Calm and smooth. I made no changes to my set up and again the system performed very well. I won the contest winning 3 of the 4 P-13 rounds and 1 of the 2 F-13 rounds. I was pleased considering I was flying against a Nats finalist, Matt Kimbro, along with his dad Jim and Steve Hannah. Matt had beaten me earlier in the year at the Bakersfield contest. He's such a good flier and he is really upping the quality of F3A flying in this District. Sneaking by him at this meet really was a pleasant surprise for this old dog.

My set-up is a Neu motor, E-Flite 5,000 mAh 30C packs, the 10.15 ratio and the Contra carbon props. I have the 20" pitch on the front and a 22" pitch on the back. They have been clipped to 21.5" dia. and shaped into APC style tips. Average power consumption in the high winds and P13 was 3,500 mAh. Flying F13 today it was 3,800 to 3,900 mAh.

Now to finish my Nuance and get that going. I've finished a pretty nice mod to the nose of the Nuance for the Contra. I'll post pics as I get it done.
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Old 05-28-2012, 06:49 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Tony,

Congratulations on your win in Hemet California!

If you can keep the wins coming on the West Coast, AC Glenn, Dave Snow and Bill Ahrens have the Midwest covered, and Dave Lockhart has good control of the East coast, so all we need is representation in the South and we'll have a clean sweep. (Hey Bryan, how's the Allure coming? ...)

Your battery consumption seems to be just perfect. 3,800 mah to 3,900 mah in calm winds gives you just enough reserve for those days when the wind kicks up, and if the winds get so bad that you need even more speed, you can always clip the props even further for higher speed and less battery consumption.

Brnner ...
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Old 05-28-2012, 07:03 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brenner
If you want the south you had better figure out a way to get Brett Wickizer to use one on his new bipe Bryan is building! Either that or make me 40 years younger!
Good luck on both.
Dick
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Old 05-28-2012, 07:06 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Good point...
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Old 05-28-2012, 07:24 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

or you could convince Andre Bouchard
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Old 05-28-2012, 07:31 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

I don't dare hope ....
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Old 05-28-2012, 11:49 AM
  #782
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

The Allure is moving along fine, lots of stuff to engineer into this bird.
I will be updating My,website soon.

Can`t wait to try the Contra ,, don`t think your gonna have any luck with Brett
Although he will be doing some flight testing for me
Bryan
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Old 05-28-2012, 07:41 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

cough cough
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Old 05-29-2012, 01:44 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi all, has anyone done any noise testing as per FAI rules? Particularly over Tarmac ? Is the noise level lower with trimmed shaped tips than the normal tips etc. ? Is noise testing done at your comps in the US ?
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Old 05-29-2012, 03:56 AM
  #785
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

We haven't had the chance to do this yet, but we will as soon as we get the chance. We're hoping that higher pitched props with mismatched diameters and rounded tips, will show considerable improvement.

According to our calculations, higher pitch props should increase current draw from the packs when they unload in the air, which will hopefully result in lower sound on the ground for equivalent power absorbtion in the air This effect has the potential to reduce wattage on the ground by several hundred watts, which should result in less sound.

We are hoping that this, coupled with reduced diameter on the rear prop, and rounded tips on both props, results in several Dba reduction, but we haven't had the chance to verify and validate yet.

Brenner ...
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Old 05-29-2012, 04:59 AM
  #786
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Sounds good Brenner. I am running with the rounds tips and the rear prop 1/4 shorter each end. This is with the mixed props 20 pitch rear and 18 front.
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Old 05-29-2012, 09:08 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

If anyone has a DB meter I can use to measure, send it to me and I'll get some numbers.
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Old 05-29-2012, 11:14 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Tony (and others) you might try an android app for a smart phone and see what numbers you come up with. Be aware not all phones can reach 100db and are limited to mid 80's.

App is free and might be interesting.

Chuck
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Old 05-29-2012, 12:45 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes


Quote:
ORIGINAL: TonyF

If anyone has a DB meter I can use to measure, send it to me and I'll get some numbers.
The contra set-up is one electric you can definitely hear in the air. It isn't annoying or anything like that; I like the sound of the beats in flight. Personally, I want to be able to hear my plane and the contra doesn't disappoint in this regard. Of course, neither does internal combustion so that's why I use that type of powerplant.
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Old 05-29-2012, 01:27 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

The noise measurement for Fai is done on the ground before flight, not really to do with noise while flying.
The contra noise is very distinctive and hard to describe.
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Old 05-29-2012, 01:43 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

The "beats" that people hear are a synchopating rhythm that is created when two sound sources are very close to each other in frequency. What's happening is that the sound waves from each source are adding and cancelling, but with slightly different frequencies. The resulting frequency is the sum both sources.

This resultant frequency slows down and stops as the frequencies from both sources become matched. It's much less apparent with the APC props because the front and rear props have mismatched diameters. You can also get rid it when flying carbon fiber props if you trim the rear prop so that it's about 12mm to 15mm smaller in diameter than the front prop. This reduces the load on the rear prop so the planetary gearset equalizes the power loading by spinning the rear prop faster than the front prop. This raises the frequency of the synchopating rhythm enough so that it's no longer noticeable.

Making the rear prop smaller than the front prop helps in another regard as well. It keeps the tips of the rear prop away from the vortices that are shed from the tips of the front prop, which also reduces sound.

Then in addition, rounding the tips so that the round is oriented in the direction of rotation reduces the size of the vortices that are shed from the tips, which reduces sound even more.
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Old 05-31-2012, 06:14 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes


Quote:
ORIGINAL: Brenner

Hey Tony,

Congratulations on your win in Hemet California!

If you can keep the wins coming on the West Coast, AC Glenn, Dave Snow and Bill Ahrens have the Midwest covered, and Dave Lockhart has good control of the East coast, so all we need is representation in the South and we'll have a clean sweep. (Hey Bryan, how's the Allure coming? ...)

Your battery consumption seems to be just perfect. 3,800 mah to 3,900 mah in calm winds gives you just enough reserve for those days when the wind kicks up, and if the winds get so bad that you need even more speed, you can always clip the props even further for higher speed and less battery consumption.

Brnner ...

Sent me one. I'll take a shot at the title!!!

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Old 05-31-2012, 06:23 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Late
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Old 05-31-2012, 06:32 PM
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Quote:
ORIGINAL: RC_Pattern_Flyer

Late
Better late then never...LOL
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Old 06-06-2012, 02:50 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes



Brenner,



What is the current version of the Contra unit today that You sell?
Do You have any in stock today?
If not when is next production planned and for sale (I assume one has to be in a preorder que then)?
Can You post todays price for the unit, gearset, motor adapter+mounting plates and props please.
How many Contra units has been sold to customers to this day (If you do not want to tell I understand).



I have read whole thread and I have counted to about 20 different planes that has this Contra unit and that is really impressibe.



I'm a little weak for Sebart planes since I have two Sebart planes already and know they fly good. Wind S Pro all composite is a plane I'm thinking of could suit my needs.
Anyone have a Wind S Pro all composite with Contra unit? Anyone using Neu F3A motor with this plane and what gearset and props should be selected to start with then for this plane?
The APC props I read about here that fit Contra - where do You buy them and what diameter x pitch are availabe?



/Bo

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Old 06-06-2012, 04:53 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Bem,

I will do my best to answer your questions.

The current version of the Contra Drive that we sell today is our new VIII design. We have enough parts in stock to make about fifty units.

The prices are as follows:

Contra Drive (Includes 10ml of Rheolube 374A Grease, one gearset, Hub Puller, user manual, and tools ..) $1,000 USD
Adapter Manifold (Neu f3a and Hacker C50 Motors supported ..) $100 USD
Carbon Fiber Propellers (22x18, 22x20, & 22x22 front and rear available ..) $100 USD each
Replaceable Gearsets (includes planet gears, bearings, ring gear, and driveshaft - 9.89:1, 10.15:1, 10.33:1, 10.56:1 available ..) $200 USD
There are approximately 90 Contra Drive Units in circulation right now.

APC props are available from us, or direct from APC. They are $45 USD per set, and I believe the sizes are 20x22 for the rear, and 20.5x20.5 for the front.

I just flew a new Contra Powered Wind S Pro with a Neu f3a motor at a contest in Chicago this last weekend, and I highly recommend it. When I first flew it, it didn't "lock in" like my Integral would, but after I ironed the bubbles out of the black monkote on the leading edge of the wing, and adjusted the trim out of my stab, it locked in perfectly. The rolling performance is the best of any plane I've flown, and the speed range is very broad. Initially I think I had a little trouble picking up visual cues from the mid wing-arrangement, but now I don't have any problem at all. (These problems weren't all that bad, because I was still able to cop first place in Masters in Chicago..)

However, in my view the absolute best thing about this setup is the way the Neu motor is working. I'm running a 9.89:1 gearset with 22x20 front and rear props, and I am drawing from 3,000 mah to 3,500 mah for an AMA Masters schedule, (similar to P13..) and the motor and controller is running "ice-cold". I measured the motor case temperature with an infrared thermometer, and the temperature immediately after a flight is 46C. (115F) (This is with a 25C ambient temperature ..) Based on my experience with my Contra/Hacker (13XL) powered Integral, this is about 500 mah less per flight, and about 30C less heat rise.

It's a little hard to directly attribute these performance improvements to either the plane, or the motor, because both are changed from my Integral, but the Wind S Pro does have a lot of extra venting around the nose that directs air over the case of the motor, and it is definitely a much less "draggy" design than my Integral.

All in all, I am extremely pleased, and if anyone asks me personally for a recommended Contra setup, this is it.

Brenner ...
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Old 06-13-2012, 08:15 AM
  #797
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Brenner,
I flew my Asyuler with the Contra drive V3 this week for the first time and all I can say is WOW. It takes a flight or two to get used to the throttle response but the overall pace of the entire schedule is so much more consistent and the model appears much better behaved. I'm still dialing in the movements but I'm really happy with the switch,

Many thanks for your efforts

Niall

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Old 06-13-2012, 08:31 AM
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Hey Niall,

All that purple is absolutely gorgeous!! I love how the purple cockpit matches the color of the Drive.

Brenner ...
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Old 06-13-2012, 11:27 AM
  #799
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Some one needs to take the props off a pattern plane, balance it ... chunk it off a hill and see if the knife edge mixing changed. I think California is a great testing bed for this.... no spiral slipstream there. No need for cameras.

Just thinking aloud.
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Old 06-13-2012, 06:38 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Tony and/or Pippy,
Would love to see some pics and/or text on how the nose jobs on your Nuances went.

Thanks, Dan
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