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Old Jun 14, 2013, 07:02 PM
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The New Concept-X4 Ultamate Wind Plane

Looking great King Roland
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Last edited by rcgeorge; Jun 14, 2013 at 08:50 PM.
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Old Jun 14, 2013, 07:46 PM
SCSA - Nick Wu
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China, Guangdong, Guangzhou
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wow, looks like back to cx2 layout with smaller wingtip.
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Old Jun 14, 2013, 08:00 PM
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Ultimate Wind Plane?

I live in an area with a lot of wind SoCal High Desert. Please explain?
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Old Jun 14, 2013, 08:50 PM
usaf3kteam
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Hope Roland will fill us in tonight well USA time
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Old Jun 14, 2013, 09:02 PM
Team ATX Pilot
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Sweet!
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Old Jun 15, 2013, 05:13 AM
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Higher Aspect Ratio and super thin airfoil...I like
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Old Jun 15, 2013, 11:15 AM
G_T
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I'm always interested in details of course - what people try and how it works out. Roland does beautiful work. Nice flying site too...

Gerald
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Old Jun 15, 2013, 05:32 PM
or F, J, K, or even TD
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Email from Roland on the CX4

CX4 a new member of the CX family

The original background for the development was a new wing which should replace the CX2 wing in near future....
The primary target was the further reduction of induced drag and even better penetration at lower weight, without sacrificing too much of floating efficiency.
Therefore I have chosen a high L/D geometry which touches already hard the border of being feasible, especially in combination with new very thin foils, designed for that sole purpose.
The All up weight is 255g including 5g Trim lead in the nose and 2g for lateral balancing.
Penetration and ground covering shows improvement against the CX3 (even at this very low weight. Flight is very stable and even more "hands free" but still indicating very sensitive. Very stable circular flight without the tendency to dive in like the CX2 does,
Very good climb rate at 2 positive flap. Very high speed in negative flap.....


...Sounds great Roland, can't wait to see one in person. Sounds like that will be in Denmark since, as you said, it will give you an advantage

See you soon.

Mike
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Old Jun 15, 2013, 06:05 PM
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How thin is very thin

I have been thinking along these lines - any more details you can share?
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Old Jun 15, 2013, 10:15 PM
usaf3kteam
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Just got off the phone with Roland he is going flying right know, he will try to do some write up and answer questions. I hope to fly one at the worlds. But for know contest tomorrow with CX3 a formal fun contest. Roland and Mong and the Concept team you are the best cheers and beers.
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Old Jun 16, 2013, 01:40 AM
Zeus
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CX4 a new member of the CX family

For sure, GMo catched me by surprise this morning on the phone....
Actually I prepared already some brief overview, and just finalized it after return form today's test flights......

Here is the story....
The nearly impossible came true... finalizing the many month ongoing design work and in the end, the build of a new mold for the newest wing evolution Which I call the CX4.

Synopsis....
Why creating a new CX4 wing, after the CX2 and the CX3 are proven top performers?
Well, the answer is quite simple: For the reason to replace the CX2 mold in near future, because the mold is starting to "age", but not necessarily the cause, after a heavy damage during an earth quake, which just happened for the 2nd time during our last quite strong quake. Still the mold can and will be repaired soon, ready to produce as many CX2's as needed, or better, as long as the mold will last.
The 2nd and perhaps a good reason, is a derivative new development to implement any new thoughts coming from practical experiences during the last 3 years and newest findings in development of wing sections, to make it worth the trouble and investment into a new mold anyway.
Last not least, as the 3rd reason, it might give an old man some slight advantage in Denmark....

Design background.....
1.5 meter of wing span is an insuperable limitation of aerodynamically efficiency, when it comes to the reduction of induced drag by high L/D, if i.e. winglets can't be used for either practical reason, or the wing chord can't be reduced to keep efficiency otherwise. Therefore I was trying to increase L/D as much as it will be feasible in terms of composite layout and in terms of aerodynamically efficiency while still maintaining reasonable RE numbers distributed over the wing span. To reach this goal, a set of especially matched wing sections was prerequisite, I was working on for over 3 month.

Flight testing and first experiences....

The CX4 wing follows the trend of low lift airfoils, which already have proven the right way to go since the existence of the CX3 wing. Therefore I was trying to build the whole airframe weight as low as possible. At the end, the CX4 prototype came out at a weight of 250g without an additional CG trim of 5g.
Right now, I can't verify the projected CG of 76 mm, I will do it later, back in Taichung. It seems that the actual CG is pretty close to the calculated location.
Already during the first flights I could feel that the wing allows for an increased velocity despite the very low total weight of the plane, giving the plane really nice legs and ground covering, which is quite astonishing for this weight class.
Furthermore it was amazing to see that this new wing showed very good efficiency in slow going as well, opening up the speed range to lower velocities as well. In the words of JW, now the plane covers a complete set of Golf clubs, including the putter AND the driver and therefore the whole possible speed range from very slow to very fast.
My personal throw height matches up with the CX3, perhaps a little more, since the total weight is about 15g lighter (using RDS-265 Yellow caps [MKS DS65K] servos exclusively).
My personal and provisional flight experience so far after about 3 hours of stick time.....:
The CX4 showed very good performance under a wide variety of conditions, from dead calm air to stronger turbulent winds before a thunderstorm.
Unfortunately I didn't have the chance yet to compare with other planes flying at the same time under the very same conditions.
However, if I would compare to the rest of the CX family, I would use horses as a comparison example:
1) CX2 = Work horse
2) CX3 = Hunting horse
3) CX4 = Race horse

I will continue to post soon as I can collect more test data......

Roland
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Old Jun 16, 2013, 02:44 AM
Zeus
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CX4 Wing Geometry

Quote:
Originally Posted by nickbox View Post
wow, looks like back to cx2 layout with smaller wingtip.
Yes, there is no way around if the highest possible (feasible) L/D is desired. It will always go into the very similar direction by keeping a nearly elliptic lift distribution. An other reason is to keep the spirit of the legendary CX2 wing....

In compare to the CX2 wing, the CX4 wing has a reduced sweep back to enhance performance in circular flight as primary target and also to bring the CG more forward to provide a broader range of CG trims, especially if you fly a more backward CG under use of more heavy servos.
Now the use of 2 pcs. 9g servos is possible.

Cheers, Roland
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Old Jun 16, 2013, 03:04 AM
Zeus
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Quote:
Originally Posted by socaldave View Post
I live in an area with a lot of wind SoCal High Desert. Please explain?
So do I.... Taiwan is an island and there is always wind, the more, the closer you are to the see. Therefore a good wind penetration is a must in my designs. The difference is, the latest development target since the CX2 and even more the CX3 is to provide maximum penetration at lowest possible weight, without the use of ballast, if you don't try to fly in a turbulent storm. The CX4 wing should be the state of the art coronation of this development.....

Cheers, Roland
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Old Jun 16, 2013, 03:10 AM
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Looks sexy . Roland, do you mind me asking what software you use for your foil and wing design/analysis?
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Old Jun 16, 2013, 03:39 AM
Zeus
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Quote:
Originally Posted by bwill6 View Post
Looks sexy . Roland, do you mind me asking what software you use for your foil and wing design/analysis?
Basic 3D-design is done in SolidWorks. For wing parameter design and analysis, I use my own developed software. For structural design and analysis I use partly my own software and FEA analysis in Solidworks.
After predesign of my foils in own software I use Mark Drela's X-foil for detail compare as an easy and quick to use solution. Also I found, that X-Foil results are pretty close to reality, even a bit more pessimistic, but at the end, the compare result with what you know, bears at least the same fluctuation but true compare results for interpretation.
How ever, After so many years of experience in airfoil design, Calculation becomes secondary and mostly used for verification and comparison only.

For Mold making I use MasterCAM software. Molds are CNC milled in my made in Germany High-Z S-1000 /T machine which I upgrated especially for the CX4 mold with new close loop Hybrid servo drives and WinPcNc Professional controller software. Mold blocks are casted from "Golden Gate" Tool cast Epoxy resin.

Cheers, Roland
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Last edited by KINETIC; Jun 16, 2013 at 09:00 PM. Reason: forgot one....
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