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Contra Rotating Propeller Drive for f3a 2m Pattern Planes

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Old 07-25-2012, 06:27 PM
  #851
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

There were no sound checks before the finals?

Chris
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Old 07-25-2012, 06:48 PM
  #852
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

nope...
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Old 07-25-2012, 07:31 PM
  #853
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Brenner,

Hard luck about dropping a round for not judging. Hard to believe that someone didn't give you a push to get in the chair.... Good luck in the finals anyway.

When you did the sound check was it with your carbon props or the APC specials? Even at 94dBA you still have the tolerance of the measuring device to add on top.

Cheers,
Jason.
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Old 07-25-2012, 07:44 PM
  #854
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Good luck and fly well!
Dan
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Old 07-25-2012, 07:59 PM
  #855
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Good luck Brenner! I see you won a round today. Keep it up!

Sorry to see Dave missed the finals. I really hate the idea of switching models. No matter what you do they always fly a bit different.
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Old 07-26-2012, 01:56 PM
  #856
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes


Quote:
ORIGINAL: TonyF


Sorry to see Dave missed the finals. I really hate the idea of switching models. No matter what you do they always fly a bit different.
Practicing, Dave appeared to fly the contra better in the P and the standard drive better in the F. It was his strategy to do exactly as he did.

Nevetheless, scoring 90% to the winner's score is nowhere near where Dave normally flies F. Something may have gone wrong with the equipment
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Old 08-02-2012, 06:12 AM
  #857
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Anyone out there running a contra on a Spark Evo? I measured my Spark Evo last night and from the bottom of the rudder to the front of the nose appears to be 77", and I am thinking with the contra spinner length of 85mm, this will put me over 2 meters, any thoughts?
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Old 08-02-2012, 08:14 AM
  #858
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Cut the ruder off. :-)
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Old 08-02-2012, 08:22 AM
  #859
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

I think Dave Snow cut the nose back a little bit, and also bit a new rudder for his.

Arch
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Old 08-02-2012, 11:59 AM
  #860
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Arch, I cut the nose off of a Spark Dynamic, I’m not sure if that would be required for the Spark Evo. The spinner on the Dynamic is 64mm but the contra is 82mm, if the spinner for the Evo is around 82mm then I doubt Robert would want to remove a portion of the nose. Robert could build a new rudder, I’ve done several sets of built-up rudder parts by hand but they did not have a flare at the trailing edge just a thickened trailing edge. I’ve attached a plan and several pictures of what I did for a built up Xigris rudder, since it was all straight cuts it was easy to get the rudder parts and jigs at the same time.

Dave Snow
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Old 08-02-2012, 02:01 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Thanks Dave, that what i may have to do if i want to run the Contra. I know Brenner mentioned that he was a 1/4 inch under when he was measured at the NATS. Can someone with a contra drive measure the length of your airplane from rudder to the tip of the Contra and tell me what number you get. Dave i know that you had to cut the front of the dynamic to make yours work so your measurements wouldn't count . If the contra fits the Integral without a problem, i beleive the Spark and the Integral share the same length in fuse and rudder, at least it was the last time i measure it.

regards
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Old 08-02-2012, 02:42 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes


Quote:
ORIGINAL: rgreen24

Anyone out there running a contra on a Spark Evo? I measured my Spark Evo last night and from the bottom of the rudder to the front of the nose appears to be 77'', and I am thinking with the contra spinner length of 85mm, this will put me over 2 meters, any thoughts?
Hi,
The FAI rule is 2M +/- 1%
In practice this means that up to 2020mm is ok.
ie unless your National rule is different.
Most NGB'S set up their rules so that the FAI rule takes precedent where both bodies have rulings.
At WC'S and ICC's models weighing up 5050g and measuring up to 2020mm are passed at processing.

Brian
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Old 08-02-2012, 03:21 PM
  #863
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Brian,

Here in North America the AMA rule is 2m or less for AMA classes. FAI classes get the 1% tolerance.

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Old 08-02-2012, 03:22 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Unfortunately, I am flying Masters not FAI. I will leave FAI to the really good pilots. May be in ten years
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Old 08-02-2012, 03:42 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Chuck Schone from CO is coming to your contest, I think with his contra/Spark.
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Old 08-02-2012, 04:12 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes


Quote:
ORIGINAL: Brenner

Hey Brian,

Here in North America the AMA rule is 2m or less for AMA classes. FAI classes get the 1% tolerance.

Brenner ...
Hi Brenner,
That's that so , surgery seems to be the option.
A nose job and a butt tuck .
Btw good Nat's result - well done.

Brian
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Old 08-02-2012, 04:56 PM
  #867
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Brian,

Thanks for the congratulations. The Contra Drive ran absolutely perfect for me. The combination of the Drive, my Wind S Pro, and a set of Dave Snow Spark wings was the perfect setup for the conditions at Muncie. I had huge speed range, and precise speed control on downlines.

Cutting back the nose is actually a pretty good option for any plane. I did it with my Wind S Pro by gluing in a 6mm plywood ring behind the existing plywood ring, and then fixturing my fuse relative to my disk sander so that I had the right down and side thrust. Then I just sanded the nose down until I had the new angles. Sanding and painting finished the job, and made it look like new. The whole thing only took me a few hours to complete, and then the gap between the nose and the spinner was constant.

Ideally, you want the nose ring diameter to be 83mm in order to match the 82mm spinner diameter. If it's a few mm over it's not really noticeable, but I think a diameter smaller than 83mm is going to be a lot more noticeable than a diameter greater than 83mm.

As far as the rudder is concerned, I think making a shorter rudder is also a good idea, because most Contra setups end up with the rudder throw cut pretty much in half anyway. (I only have about 25 degrees of throw on my Wind S Pro ..) However, If I was to make a new rudder for any of my planes, I would make sure to keep the trailing edge quite thick, and/or add a flaired trailing edge.

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Old 08-02-2012, 05:21 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Thanks Brenner. Underdw, I think that Chuck is coming so I will visit with him about his set up. Cutting the nose back may be the best option, along with. Butt lift
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Old 08-04-2012, 06:48 AM
  #869
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brenner,
What did you use as reference points on the Wind S to set it up relative to sander?

Gary
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Old 08-04-2012, 07:11 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Gary,

I put a pair of carbon fiber rods through the two sets of wing pin holes in the fuse so that they stuck out on both sides of the fuse, and used a straight edge ruler and a digital level to set the angle of the wing to one degree positive relative to my disk sander. I also set my fuse perpendicular to my wing sander and then sanded the nose ring until it was flat.

Then I made a 3mm plywood spacer and taped my Drive assembly directly to the nose so that it was held out from the nose with a fixed 3mm gap. Then I made mounting plates to fit, and glued them into the fuse. The resulting assembly gave me a setup where the motor was set at one degree negative relative to the stock Wind S Pro wing position, and with zero degrees of right thrust.

Then I flew the plane and used the stab adjusters to remove any elevator trim. The end result was a plane that flies a vertical upline hands-off, and requires about 1% or so of down elevator mix into low throttle to get a plumb line straight downline.

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Old 08-05-2012, 09:23 AM
  #871
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Tony, could you post a picture of the SFG's you put on your tailplane please ?
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Old 08-11-2012, 09:47 AM
  #872
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Finally finished; my new toy airplane:-)

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Old 08-12-2012, 05:58 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

It looks very sleek. Has it flown yet?

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Old 08-13-2012, 09:51 AM
  #874
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes


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ORIGINAL: br@m

Finally finished; my new toy airplane:-)

Reminds me of a wood Miss Wind. I like it a LOT. Very nice looking design.
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Old 08-15-2012, 12:58 PM
  #875
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Nice Br@m
My dad did a nice Job covering the plane in the Spark scheme.

This plane called the Indira is actually based on the little Miss Wind 50 wich I liked a lot but it's to small for serious F3A flying.
We can't afford the big Oxai Miss Wind so we scaled up the 50 size Miss Wind.
And after a few version this is the latest one.
It is completely wood built with foam wings and a carbon motor cowl.
Sorry there are no plans available.

This design flies very well with the contra drive, it seems that the small fuselage works very well with the contra drive.
I flew mine at the 2012 EC at Chateroux France and finished 47 this was my first EC.
I modified my wings with winglets like the Wind S Pro GFK version the bubble tips these seem to work better than the flat ones used on the Oxai Citrin. I also have them on the tips of the stabilizer for rock solid flight in windy conditions.
I also widened the TE of the rudder by almost 2 cm.

This was a very nice project and we had lots of fun !
The project started in the winter of 2010 there where 7 planes buildt. 1 crashed by a Emcotec DPSI switch failure.
Building and designing was done by Harry Wever, me and my dad. I've done the test flights and tweaking until it was at it's best.
The contra drive was the last and best upgrade for this plane it is a match made in heaven

Hope Br@m will enjoy the plane as much as I do.

I will post some nice pictures from the EC plane I took to France.



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