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Contra Rotating Propeller Drive for f3a 2m Pattern Planes

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Old 04-19-2012, 08:13 PM
  #751
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Brenner
Modified my carbon props as indicated above and was able to complete the cut and finishing in under an hour.
Had a good afternoon to test them as the wind started out around 10 mph and increased over the afternoon to a steady 15 gusting twenty. I cleared my ESC logger and made five flights with the first flight with my original setup of stock 22x20 rear and a 22x18 front. All flights were logged and down loaded. The second,3rd ,4th and 5th flights were all done with the modified set of props. Here are my observations and data with all flights being F-13 schedule and 5000 mah packs on 9:89 to 1 gear set:
1. Max current 96 amps max for only very short times with average 42 amps.
2. Max ESC temp 140 derees with average at 117 degrees. [80 degree day]
3. RPM max was 4670, previous was 4710 not much different. This was very surprising!
4. I immediately felt the increase in speed at all throttle stick positions. I would agree with Brenner when he said it was the fastest 2m pattern plane he had flown to date. So much so that it took three flights before I could get a handel on throttle stick position for normal cross box and vertical up lines. I did not get my snapp speed throttle position until the last flight! There is so much difference I am not sure it is going to be practical to switch sets back and forth for different wind conditions! It really screwed up my maneuver timing.
5. Aircraft in flight was definitely quiter but would need more testing as I had a crosswind on my back blowing sound away from me.
6. I increased my braking to 40% and the downline was still not as good as the longer props. I will test more at 50% and up to see what happens.
7. One thing I really enjoyed was the greatly increased ground clearence with the shorter props!
That's about it until I get more flights on this combination.
One thing I want to do is take 1/2 inch off the rear prop of my previous set [22x20] and reshape the tips of both front and rear props. This will give me 1/4 inch longer tips on the front [22x18] prop. The tip shaped I used was exactly the same design the APC's had as I think there is a sound and efficiency benefit to this shape tip.
That's about it for now. Questions and comments welcome and will report more when I get results.

Dick

Late note, all batteries took between 3100 and 3300 mah when charged. Will definitely be able to use my 4400's!
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Old 04-20-2012, 01:29 AM
  #752
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

How do I get one of these Hyde mounts. I can't find it on the Hyde mount web site. What part number etc.
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Old 04-20-2012, 04:38 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Dick,

Thanks for trying the cut down props. we appreciate your help.

Hey Paul,

I think guys are using the Hyde Mount for the Neu f3a motor, and modifying it.

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Old 04-20-2012, 09:48 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Won't you also have to change your up/down thrust when you change props?
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Old 04-20-2012, 10:47 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

No
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Old 04-21-2012, 06:23 AM
  #756
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

OK, I would appreciate if those who are running the gear drive would share their plane, batteries used and final weights. That would be fantastic.

Thanks

Chuck
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Old 04-21-2012, 07:35 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Chuck,

I'll look around to see if I have a spare plane. The plane that I'm flying right now is an Integral, but I'm finishing up a Wind S Pro. My batteries are Thunderpower G6 25C 5000 mah packs, and last year at the Nats I weighed in at 4920g with the stock wings and stab.

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Old 04-21-2012, 12:55 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Oh nice one Brenner, ha, love the english language!

I need a setup that is around 10 lbs 6 oz rtf... this will give the me 6 to 8 oz I need for my project that you are helping me with.

Chuck
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Old 04-21-2012, 12:58 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Chuck,

Is the spinner assembly I sent you going to work for you? Have you gotten it running yet?

You might be able to save 5 oz to 6 oz with a set of Dave Snow built up wings.

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Old 04-21-2012, 07:10 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Chuck
I am using Thunder PowerG6 4400's.
I am in the process of completing two Wind S Pros and will give weights when done
My current Wind S Prothat I did not build weighs 10 lbs 12 oz.I am shooting for 10 lbs 8 oz on the new ones!
Dick
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Old 04-21-2012, 08:48 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Dick, sound s great.

Brenner...it will work great. I have to make a small adapter but should be fairly simple.
I found an 8mm od and 6mm id shaft that I can join.

Shouldn't be long. :-)

Chuck
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Old 04-26-2012, 07:07 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes


Quote:
ORIGINAL: RC_Pattern_Flyer

Dick, sound s great.

Brenner...it will work great. I have to make a small adapter but should be fairly simple.
I found an 8mm od and 6mm id shaft that I can join.

Shouldn't be long. :-)

Chuck

Chuck, where are you installing the contra drive?

Happy Landings
Guillermo
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Old 04-27-2012, 04:11 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hope to be testing by june.
Chuck
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Old 05-09-2012, 06:54 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi All

Quick updqate on my prop experimenting.

The cut-down 22x22/22x20 set of props really turned me on to modifying and playing with all my carbon contra props. I had 14 carbon props laying around and I had a good time grinding mixing, modifying and matching these props.
Here are my findings and results in no particular order:

1. I learned that tip shape is a very important factor in prop efficency and noise.
2. On the Contra Drive making the front prop 1/4" longer than the rear prop really made the drive much smoother in performance. Although I can't prove it with hard data I feel it also made the drive more efficient.
3. I learned that matching props to specific set of wind conditions can produce very desireable results but there was a penalty as each set requires a different throttle, idle, and brake setup.

I ended up with three sets of props that I can use for three wind conditions. All props have been tip modified utilizing the APC tip pattern. All three sets have been modified in length with the front prop being 1/4" longer at each tip. This was accomplished by cutting the rear prop on two sets a 1/4" at each tip. The net results are as follows with the defined wind condition.

0 to 10 mph wind condition = 21.5x20 Rear & 22x18 Front
10 to 15 mph wind condition = 21.5x20 Rear & 22x20 Front
15 to 25 mph wind condition = 20.0x22 Rear & 20.5x20 Front

All of these are flown on the 9.89 to 1 gear set.

Some of what I accomplished speed wise could have been duplicated with gear sets but it's a lot easier to change props at a contest. Plus the diameter changes along with changing the tip shapes really quieted the props down and made the whole Contra Drive smoother! I really enjoyed experimenting with the props and learned a lot.

Now, if I could only learn F-13!!

Dick

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Old 05-10-2012, 01:12 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Dick,

Photos ???

Brian
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Old 05-10-2012, 05:27 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brian
There are no pic's as the props pretty much look the same as un modified except for the tips. What I did was take the new APC contra drive electric prop and etched the shape of the tip onto the catbon and ground it dowm and then finished with a final sanding. I then sealed the tips with thin CA. This also gives the tip a durable edge.
Dick
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Old 05-21-2012, 01:35 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Quote:
ORIGINAL: Brenner

Hey Chuck,

I'll look around to see if I have a spare plane. The plane that I'm flying right now is an Integral, but I'm finishing up a Wind S Pro. My batteries are Thunderpower G6 25C 5000 mah packs, and last year at the Nats I weighed in at 4920g with the stock wings and stab.

Brenner ...
Saw Dave Lockhart's contra driven Bravo flying for the first time at the contest this past Saturday. The drive system provided outstanding performance, especially with Dave's new props and gear ratio. The sound was quite cool, especially the beats, similar to a twin with engines slightly out of sync.

Later, Dave let me fly it. Performance to burn and it was solid down to a crawl

Nice job!
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Old 05-21-2012, 03:14 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes


Quote:
ORIGINAL: MTK

Quote:
ORIGINAL: Brenner

Hey Chuck,

I'll look around to see if I have a spare plane. The plane that I'm flying right now is an Integral, but I'm finishing up a Wind S Pro. My batteries are Thunderpower G6 25C 5000 mah packs, and last year at the Nats I weighed in at 4920g with the stock wings and stab.

Brenner ...
Saw Dave Lockhart's contra driven Bravo flying for the first time at the contest this past Saturday. The drive system provided outstanding performance, especially with Dave's new props and gear ratio. The sound was quite cool, especially the beats, similar to a twin with engines slightly out of sync.

Later, Dave let me fly it. Performance to burn and it was solid down to a crawl

Nice job!
Guys,
Spill please !!
'Dave's props and gear ratio' what's are these.

Brian
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Old 05-21-2012, 03:47 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes


Quote:
ORIGINAL: serious power


Quote:
ORIGINAL: MTK
Saw Dave Lockhart's contra driven Bravo flying for the first time at the contest this past Saturday. The drive system provided outstanding performance, especially with Dave's new props and gear ratio. The sound was quite cool, especially the beats, similar to a twin with engines slightly out of sync.

Later, Dave let me fly it. Performance to burn and it was solid down to a crawl

Nice job!
Guys,
Spill please !!
'Dave's props and gear ratio' what's are these.

Brian
[/quote]

Brian,

The props are "development" props from fall 2011, and they made the rounds in the US to a couple Contra flyers. Basically, they are 22x20" props modified by Chip. Front cut to 21" and rear cut to 20.75", and about 22" of pitch on both with APC style tips. I'm running the 9.89 gearset. I suspect the new 22x22 props cut to 21 and 20.75" will give similar performance, but I haven't gotten around to doing that yet.

Regards,
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Old 05-22-2012, 01:14 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Dave,
Ah ok.
I have to say that I'm not at all sure of this direction - high speed etc.
Though it good to see all this experimenting going on.
We have the future of F3A propulsion right here right now !!
Let us know what you think when you have enough time on the contra.
Have you tried the 22x18 front/22x20 rear mix yet at all. I would have to be dragged away 'kicking and screaming' to change from that set up.

Brian
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Old 05-22-2012, 06:11 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brian,

I find the 22x18/20 combo to be painfully slow for all weather conditions and styles - unless the goal is to crawl around the sky at 140 meters in very light winds. I find it to be very lacking in top end speed for windy conditions, and in most conditions, the downlines are much slower than needed (ie, slower than the horizontal flight).

My goal with the Contra setup was/is to be able to match the top end speed of my favored single prop setup and not give up anything in terms of efficiency or downline braking. My "benchmark" is the 20.5x14.5 Falcon on the Neu F3A motor in my Bravo - the plane I flew for judge warm ups at the 2011 WC. The Bravo has a rather thick wing TE, so it is not the lowest drag plane around. With the ~21x22 props, I find the performance to be very comparable to a 21x14 for top speed, and the Contra has slightly more authority in the climb and the downlines are slower - no brake on the Contra but with brake on the 21x14. At this point, in light winds, I rarely exceed 75% power with the Contra or a single prop....but....in heavy winds, I am running the Contra quite hard, and am looking to essentially gain a little more top end speed at the expense of downline braking (which I have an excess of).

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Old 05-22-2012, 08:42 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

It's easy to overlook the significant differences in style between the way pattern is flown in North America and the way that pattern is flown in Europe. Here in North America, flying fields are wide open, and this encourages a wide, fast style of flying, whereas in Europe, flying styles are much more compact and graceful.

This was especially noticeable at the recent WC in Muncie. I remember watching Andrew Jesky's first preliminary round, and thinking that he flew with more precision than anyone else in that round, but when I saw his scores, it was obvious that the judges had a strong dislike for how he flew. They even zeroed his spin, which I thought was flawless. What I saw was precision, but what the judges saw was a lack of gracefulness.

However, fortunately for us, thanks to the work that Dave, Chip, and others are doing, we are now showing that it's possible to set a contra powered plane up to accomodate both styles of flying, and still have all the benefits that come from flying a Contra.

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Old 05-22-2012, 11:09 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

' I find the 22x18/20 combo to be painfully slow for all weather conditions and styles - unless the goal is to crawl around the sky at 140 meters in very light winds. I find it to be very lacking in top end speed for windy conditions, and in most conditions, the downlines are much slower than needed (ie, slower than the horizontal flight). '

Hi Dave,
I just slowed down the horizontal flight to match it up.
I then have , it would appear at least, the same speed at and across the top of the vertical manoeuvres.
I have this with a cool motor and happy batteries.
I try to fly at 160m which is closer than most think.
I get it done with comfort inside the time. In fact it is interesting to take note of the times.
Fast is not as fast as one might think and slow is not so slow at all - time taken wise.

I'm sure you heard the story about the young bull and the old bull out for an afternoon stroll.
They got to the top of a hill and down in the valley there was a herd of cows - prime beef .
The young bull said 'let's run down there quickly and we can service a cow each'.
In reply the old bull said 'No !!, lets walk down and service them all'.

Regards.

Brian
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Old 05-22-2012, 11:53 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brian,

Matching the apparent speed with any of the prop sets is not a problem. For my plane, I am finding it can be flown at a very slow constant speed even with the higher pitched props, just by using less throttle, and when it gets windy, I don't make any changes, I just go faster to avoid larger crab angles. Based on the judges training at the 2011 WC...I'm flying at about 170m, and completing P13 box entry to box exit in about 5:15 to 5:30. On an 80F day, I typically see 130F on the motor and 110-115F on the TP G6 5000 Prolites. I've used as little as 2800 mah on a day with light winds.

Smart bull!!!

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Old 05-24-2012, 10:54 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes


Quote:
ORIGINAL: serious power


Hi Dave,
I just slowed down the horizontal flight to match it up.
I then have , it would appear at least, the same speed at and across the top of the vertical manoeuvres.
I have this with a cool motor and happy batteries.
I try to fly at 160m which is closer than most think.
I get it done with comfort inside the time. In fact it is interesting to take note of the times.
Fast is not as fast as one might think and slow is not so slow at all - time taken wise.


Regards.

Brian
I only have the one flight on Dave's well trimmed model to reference. I flew it at exceedingly, almost painfully slow speed on purpose at around 160 meters. Wind conditions were moderate at 15-20 mph and quartering but the model didn't ever seem to get affected by the wind as much as other stuff I fly.

It never lacked speed or control authority but I think if I flew it a dozen times I might creep the speed up as I got used to it. If I flew it a dozen times, I think I could bring it in closer which would help my aging eyes see it better. The Masters flight was respectable ......

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