jnred123

Hi
I'd like to know what everybody thinks is the best out of the box aeroplane for the Contra, about six months ago I think the concensus was the CARF Valiant and the Wind S Pro needed the least tweaking to fly great, any other Contra natural airframes out there.
Cheers
Greg

Dsnow

Hi Peter, so far the rudder throws are grouped in three ranges, less than 5 deg, between 10 and 15 deg and more than 25 deg. From the test report I post earlier and their conclusions I believe the best initial rudder throw should be around 13 deg or maybe equal to the elevator throw for the plane, I did not compare the elevator and rudder throws but I think most elevator throws are in the 10 to 13 deg range. I’m still waiting for a few pilots to help out but I did ask one of the high rudder throw fliers to try reducing his throw, he went from 25 deg to 14 deg, and he said it worked great.

The less than 5 deg group was two biplanes, so if anyone is planning on using a biplane this would be a good starting point.

Also from the test report we could use slightly weaker rudder servos since it takes less force to move the rudder but it should have great centering and zero backlash and no play in the linkage. This would help reduce the chances of the plane from initiating the yaw instability with small yaw angles. One other change that we could make, I only have one data point on this, is to reduce the chord of the rudder to make it smaller.

From the information posted here over the last few months I think most of the yaw instability issues we have seen last year could be self-induced and not so much the design of the plane if we are using too large of rudder throw and have too much play/poor centering of the rudder. I hope several of the high rudder throw guys would try the reduced throw and give us a report if the yaw instability issues are solved or reduced any.

Hi Greg, I think almost any current design will work very well with the contra.

Dave Snow

Brenner

Good work Dave,

I definitely agree about a smaller rudder chord being an option. This also compensates for any increase in length due to the Contra spinner as well.

Brenner ...

Hans Meij

Anyone with Amps usage on the 13XL?
This week started to use the CD again after the winterbreak. Used it only for a few flights last autumn.

C5013XL, - 22*18 front 22*20 rear, Schulze 32.80KA, 10.15 gearset
On the first flight I noticed that the controller throttled back when hitting full power for more than about 5 seconds.
The Schulze is rated 95A cont. 115A peak. Mailed Schulze about it and they confirmed that it is the overload mechanism that throttles back.
I could not believe that I was using 100A so today measured it. The controller was right I'm hitting 100A.
Allready have clipped the tips about 1cm. Motor gets too hot.

The 13XL is rated 1250Kv, The Neu 1300Kv.
According to the amp. usage table of Brenner the Neu does not consume this amount of amps.
Is the Neu that more efficient? Or are the Kv values not comparable?

Does perhaps the internal resistance of the drive when new cause this extra amount of amps?

OhD

Hans, now you have to worry that the motor may have been demagnetized by the high temperature. In that case it will pull more amps for a given load. You might want to test it with a Hacker gear box and a single prop to see if it is still okay.

Jim O

Hans Meij

Don't think that it got that hot. Measured about 70 degrees. Thats still fine but the outside temp is 10 degrees. It wont be fine in the summer.

serious power

Hi Hans,
I know that Brenner ,and others are running the Hacker 14XL and are happy.
Maybe run a little hot.
However we have run the 13XL x 2 and found them very hot compared to the Neu.
The difference is a matter of motor load rating.
Hacker is rated at 2200W and the Neu 3000W.
We flew them the same day the Hacker was too hot to touch 70+ C while the Neu was just warm 40C.
The Neu was also a lot more powerful , it was obvious - both pulling Oxai bipes - same gearset/props as you.
A hot motor is an inefficient one - maybe 10+ Amps to heat.
Also we are now using YGE 90's - I have two of those Shulze's on the shelf - not efficient.

Brian

Hans Meij

Hi Brian,
Thanks, so have to ask Brenner for a Hacker to Neu conversion.
Just bought the Schulze l-32.115 to tackle the power problem so that one that must do the job.
The YGE must then be very efficient because once I did an efficiency comparison from Spin 99 to Schulze 32.80.
Here the Schulze performed a little better than the Spin.

Brenner

In answer to jnred123,

The CA Visa looks to be pretty good as well. Here in the American Midwest Bobby Satalino flies one with a Contra, and it looks rock solid.

Brenner ...

pattratt

My Feedback: (1)

Hey Dave
I got your PM and I had intended to reply to your earlier post but "stuff" [defined as anything other than Pattern] is getting in the way, so your PM "shamed" me into setting down and catching everyone up on my changes and experiments on the Wind S Pro. So here goes!
First of all I have removed all of my Futaba BLS Servos and replaced them with lighter, slower, less torque, corless digital BB nylon gear servos. The result was absolutely amazing and it made a huge difference in how I flew the F-13 Schedule. It really calmed me and the aircraft down! Prior to switching out all the BLS Servos I was using 70 to 80 mah's per F-13 flight. With the Corless BB Servos I am down to 53 mah's per flight allowing me to go from a 730 lipo to a 480 lipo on the receiver! All this has added up to smoother performance and reduced weight!! Thanks to Chip for heading me in that direction.
Now for the rudder discussion. This is not a simple discussion as there are a number of factors that go in to the rudder "Feel" an individual is looking for and obviously everyone has there own idea of what that is! This is a short list of the items that effect the "Feel" of the Rudder, obviously lamanar airflow from the contra drive is a huge one. : Size, Shape, Trailing edge shape & width. Throw, Type Servo, Linkage, and last but not least Expo setting. Now to answer the questions, here is what I am using:
Futaba S9151 servo with pull/pull linkage to 2mm bb ends.
Winds S Pro has a 5/8 wide flared rudder trailing edge.
Throws normal rate = 1 5/8" 45% expo high rate = 2 3/8 60% expo
One other thing I failed to mention that really effects the rudder feel and that is the c/g setting. I use 25% MAC which requires a lot more throw on down elevator and less expo on down elevator. This is required to get a light down elevator feel for inverted flight. A more nose heavey c/g gives the rudder more power and less sensativity at netural and vise versa with a more rearward c/g.
So in closing I hope this info helps and as you can see obtaining the desired rudder "feel" requires a lot of work and experimenting with many parameters to get it just right!
Dick

Dsnow

Hi Dick, was the rudder throw taken at the top or bottom of the rudder? Without the rudder chord I cannot calculate the deflection.

Thanks,
Dave Snow

pattratt

My Feedback: (1)

Dave
Sorry about that it's 4 1/4" at measurment.
Dick

Malcolm H

Well we put the first four flights on one of the Scottish based Contradrives today.

Its early days yet but the results were very encouraging. The model exhibited no significant trim changes, knifedge and vertical flight still neutral having been set using the Triangulation method.

We didn't detect any obvious lack of directional stability but this requires more confirmation. The Asyuler has a flaired rudder trailing edge as standard so this may contribute to this. The model definitely has increased rudder response as noted by others but there wasn't enough downline braking with the motor freewheeling at least not in this airframe and with these pilots!

More as the learning curve progresses.

Malcolm

Brenner

Hey Malcolm,

The Asyular looks very sharp! One thing to mention is to be careful not to confound the effects of any mixes you may have defined when the plane was set up for a single prop.

Brenner ...

Malcolm H

Hi Brenner,

Only mix on this one is a smidgen of down elevator with low throttle for the downlines.

Completely neutral everywhere else.

Malcolm

Brenner

Hey Malcolm,

It sounds like your Asyular was very well setup from the beginning. By the way, there is a tradeoff between horizontal speed and downline braking. The most braking is with the 22x18 props front and rear. The least is with 22x22 props front and rear.

Brenner ...

pattratt

My Feedback: (1)

Brenner & Malcom
I am sucessfully using 30% brake on my CC Phoneix Ice HV 80 II ESC. I am using the 22x20 rear and the22x18 front Carbon props. What I have determined is that anytime the props are turned in opposite direction thay are engaged with the motor therefore an applied brake torque should be felt at the windmilling props slowing them down if you are completely off the throttle stick.
Dick

Malcolm H

Dick,

I'm not sure what you are saying. Are you suggesting that setting up a brake doesn't slow the model on down lines because it slows the props and causes less drag or are you saying it does work?

Malcolm

pattratt

My Feedback: (1)

Hey Malcomb
Yes, it works.
Dick

pippy

to Dsnow, I am flying a Nuance with contra and my my normal flying rudder throw is 15 degrees and I may reduce that some more. I have put a flared edge on the back of the rudder for the Yaw stability. The rudder was 17mm thick its whole length and the flare I have put on doubles this to 35mm.As you can see from the photos I have tried to make the flare as long as possible to smooth the airflow over it.
When I was experimenting with flares I tried different sizes, bigger ,smaller and at one stage I took it of and flew without one, I didn't like the feel of the model without the flare but as you point out maybe I had too much rudder throw at that time. It certainly was more than I am using now. I may never know.
My Nuance is flying really well with the Contra and what I am finding is it's easier to get smoothness into a schedule with rolling and speed more controllable. I can keep up with the model.

pippy

Hi Malcolm, great to see the contra on your Asyuler and glad it is flying well for you.Good colour choice BTW.

Hans Meij

40mm wide on my Gaudius rudder. Makes the plane very stable, no complaints.
However the drag it generates makes me hit the throttle too much to reached my preferred pace.
Have to experiment with less wide rudders and give Neu a try cause the C5013XL gets overheated.

pippy

Very nice paint job on your flair. It makes me think I should do mine also.

Hans Meij

No paint, it's Oracover. Photo's do smoothen things up.

Brenner

Hey Hans,

I just took my 13XL apart to change the bearings, and I noticed that there was a lengthwise score mark on the Kevlar covering on the rotor magnets that looks like it was made when the rotor was new, except that now there is a 1mm or so jog in it near the end of the rotor. Also, there is a circular break in the Kevlar that goes around the circumference of the rotor and passes through the jog in the score mark that could only be there because the rotor magnets on the end have rotated relative to the remaining magnets.

To me this looks like a classic case of "slipped rotor", which has happened to me once before, and one of the effects of something like this is increased current draw, and overheating.

Anyhow, before you give up completely on your Hacker, maybe this is something you can check for as well.

Brenner ...