The Co8
The latest creation from Reinhard Sielemann and Dr Hans-Jurgen Unverferth
Well, finally, the details and drawings are finally finished. Sorry that I don't have any actual pictures of this machine yet. They may appear in time.
Hans-Jurgen says that the C08 is like a racehorse compared to the C07, but they are having problems with getting servos strong enough to go in the slim wing. Maybe a slightly larger version, scaled up to take good microservos?
Here is the text from the 1/98 Aufwind about the Co8.
Once again translated by my good friend Klaus Mittendorf.
The construction hints for a competitive swept flying wing, by the example of the development of the CO6 to the Co8.
As always in the home construction of a swept flying wing, to be competitive in the fields of slope, winch launch and F3j, a considerable amount of thought is required. This has nothing to do with voodoo magic, but more or less. The whole thing is made out of one piece and nothing can change the section or washout once it is built, unless you use a bandsaw.
So there are a lot of questions to be considered when constructing a flying wing.
Firstly, what is it to be used for?
Secondly, what handling qualities do you expect?
Thirdly, what specific task do you want to use your flying wing for?
Speed, slow flying, distance thermal, slope or everything together?
Basic outlines,
and that has to be clear to everybody that will construct such an apparatus, is the sections that you use, the amount of sweep, washout and winglet dimensions.
With all that goes only one position of control surfaces for one particular task and you have to decide on it and if you want to change it, I refer to my comment on the bandsaw.
Any changes after construction can only be achieved with the position of the control surfaces.
The attempt to come up with a formula for the successful construction of a flying wing disappears into nothing. It seems more sensible to use known basic constructions of creative builders and moderately modify those.
The airfoil section.
Everything is now possible on a swept flying wing. I remind you on the Cmo=0 sections, the Mh, the Eh sections, the Eppler and our own RS. Not to forget the CB sections of Christian Behrens!
Our team has decided to use our own creations after tests for years with the Cmo=0 sections.
Our creation, the Rs004a.
(These section coordinates are available from AIRFOIL coords)
The question of the correct sections cannot be answered. Cmo=0 sections only need a small washout and with that, the basic Ca is only small. To increase the camber with flap is therefore a necessity, Cmo negative sections need quite a bit of washout to enable a realistic stability, but unfortunately with that, you also fly it in a region of High Ca, so how do you get that on its best glide angle and how can you fly it fast?
The Sweep.
The sweep of a flying wing is only a secondary problem, for example, with what angle of sweep do I need no more ballast in the nose? The answer is with 25 degrees sweep, it also means it is becoming V-form effective, the higher the sweep the more negative the anhedral.
The Winglet.
The winglet is a continuation of the wing, but it is working as a disc and as such should reduce the induced drag of the wing, at the same time it should add directional stability like a rudder on a normal tailed configuration. And the creator is well advised to lay out his wing so that the winglet only has a directional stability effect, but also here there is no formula and a reasonably designed wing can handle any winglet.
After all these negative statements, lets put some light on the subject. We are now showing you our new design.
First off, the critique on the CO7:
Too big(3.3m), too heavy(2.2kg), Ca selection is too high, (0.65) so in reality, to fly fast we need 1.5 kg ballast, but still a nice machine if you just want to stay up.
Now the light, the CO8.
Span 2.6m, Chord 18cm, Weight 1400gm, Sweep 25 degrees, Wing section RS004a.
In the tables (Not shown. Look on the article pg 52 in Aufwind 1/98) you can find the calculations to realise this design. As for many years now, responsible for the calculations is John Yost. Without his help we would not have been able to construct a decent flying wing since the CO2.
The Co8 is designed around the third section of the half span. That means that the first third is washed out from 0 to 3mm, the second third from 3 to 8mm and the last from 8 to 14mm. This washout represents a Ca of .35 with a stability measure of 7.5 percent. This results in the following: Min sink with 30g/dm is .365 m/s best glide is 22.5. The neutral point is at 34cm behind the leading edge.
The handling.
(Sorry, these curves aren't shown)
The enclosed curves explain the following situation. The spanwise lift along the wing.
Secondly the lift distribution under the situation when the wing is release crooked to the launch line. (+-5 degrees)
What happens when the wing suddenly rises its nose during the launch and "bites" into the air.
What happens when it goes sideways.
To interpret these calculations, we must advise that you must always calculate with the extreme handling problems. If the lift curve crosses the Ca Max curve at the outer wing, you can expect the outer wing to stall, which will create problems during the launch and slow flying phases of the model which would implicate the handling of the model. These calculations were based on a winglet configuration which was designed as a plane which enclosed the whole outer panel.
The C08 here described promises fantastic all around capabilities. It is shown here, and it is an exception, before we have tested him for at least one year minimum, and with that we like to stay at least one step ahead of the critics, who accuse us of releasing our new constructions only after 2 years.
For construction of the CO8, I would use the same method as recommended for the C07. One surface layer of tissue, or the lightest glass you can find over a layer of 190gm plain weave carbon fibre oriented at 45 degrees and a spar of your favourite construction method.
YOU WILL NEED THESE DETAILS WHICH ARE NOT ON THE DRAWING!
The fuselage is not shown on the drawings.
Both wings have ANHEDRAL of 1 degree.
(yes, the wings slope downwards from the middle)
If you have the excellent COMPUFOIL
you can download my zipped template files (with my kerf compensation and no skin thickness) by clicking here
The washout is introduced in the Version 1 at the ends of the control surfaces which correspond with the thirds of the half span!
Version 1 has washout as the following:
R00T = 0 washout
END OF FIRST THIRD = 3MM OR -1 DEGREE
END OF SECOND THIRD = 8MM OR -2.5 DEGREES
END OF WING = 14MM OR -4.5 DEGREES
ANHEDRAL OF 1 DEGREE OR 23.0MM AT THE ROOT
THE NEUTRAL POINT IS 340 MM BEHIND THE LEADING EDGE AT THE ROOT.
THE STABILITY MARGIN IS 7.5 PERCENT.
THIS GIVES A CALCULATED C.G OF 326.5MM BEHIND THE LEADING EDGE AT THE ROOT.
The wing area is 46.8 dm2
The weight should be about 1400gms
The Version 2 has some slight differences, namely, different washout giving a lesser Cl, 10 cm more span and slightly different control sufaces. It also weighs a bit more.
Version 2 has washout as the following:
R00T = 0 washout
END OF FIRST THIRD = 2MM OR -0.6 DEGREE
END OF SECOND THIRD = 5MM OR -1.6 DEGREES
END OF WING = 9MM OR -2.9 DEGREES
ANHEDRAL OF 1 DEGREE OR 24MM AT THE ROOT
THE NEUTRAL POINT IS 360.5 MM BEHIND THE LEADING EDGE AT THE ROOT.
IF THE STABILITY MARGIN IS 7.5 PERCENT, THE C.G WILL BE 347MM BEHIND THE LEADING EDGE AT THE ROOT
The wing area is 48.6 dm2
The weight should be about 1500gms
Don't forget that you can scale these things up to whatever size you like, if you can build them stiff enough. I think that a 3.3/3.5 meter C08 would be an excellent choice for an F3J wing.
Here also is the product information sheet for those who would like to buy a Co8! ( I am not quite sure where you can get them yet, but they will be available in America)
C08, the next step.
A high performance fourth generation FLYING WING, forged in Germany.
This plane is the latest WING design from the Sielemann/Unverferth team.
The design of the CO8 is based on their 12 years of experience in FLYING WING development.
Uncompromised construction and quality meet your high standards.
As every development depends on communication, all members of the CO8
generation have the opportunity to use the "CO-Hotline" to exchange their
experiences with the designers themselves via email
The WING:
A high aspect-ratio (15:1) wing with two-step wash-out, designed for excellent duration and distance performance.
An optimised lift distribution for simplified handling and low-drag flying over a wide speed range.
Setback symmetricaly profiled winglets for optimum launch and circling stability.
Streamlined fuselage,for low drag, shaped for easy handling when winch launching or slope soaring.
Four control surfaces, for simple programming with a modern radio. Elevons and Flaps/Brakes.
Constructed of Carbon fibre/Fiberglass over foam cores with Carbon fibre Spars on a plywood shear web.
Enough long lasting strength for extreme winch starting and whatever aerobatics you can think of (g-load = 91) combined with very low wing loading (3o g/dm, <10oz sq/ft) thermal performance.
A three piece wing with one centerpiece, two outer wings and carbon joiners with optimum force distribution for ease of transport in the backseat of your new Porsche. (Not necessary, but a fantastic option!)
Exact directions how to adjust the elevons and flaps.
Last but by far not least: The new RS 004a, a profile with gentle stall characteristics, wonderful flap efficency, gorgeous low-drag flying over a wide angle of attack and as a result, a wide speed range on a low wing loading.
OPERATIONAL SPECTRUM
A good swept back FLYING WING has always had excellent thermalling characteristics combined with non compromising aerobatic qualities in one airframe.
Leaving thermals vertical without brakes from the edge of your vision to hit-your(-own)-
head distance poses no problem.
That's what makes the fascination of flying a WING.
The CO8 generation combines all these characteristics in an unbelievable manner.
Tight circles on the winglet, excellent sink rate, very good glide and it's flight
stability make it stand out from the bunch of "normal" thermal soarers.
With high maneuvrability, in positive as well as in negative flight, coupled with a wide
speed range, the CO8 is a hot hint for slope pilots used to tails (on their wings).
An aerobatic plane that stays aloft when the going gets calmer. Isn't that what you
were always looking for?.
Pilot qualification
Model airplanes can cause injuries to people and damage to objects, especially
when flown at the high kinetic energy level this plane is capable of!
One of the duties of the makers and distributors of this plane is to tell the customer
which piloting abilities he must have to get safe fun out of our
construction.
Like each really good swept back FLYING WING, the CO8 poses no problems to the pilots
skills.
You don't need aileron experience. Some RC-HLG flying will give you the sufficient skill.
Don't skimp on this practice, because the WING gets r e a I I y fast!
The elevons feel just like a very efficient rudder for stabilising the circles.
Here in Osnabruck we train beginners on WINGs. Except for the winch launch.
Everything goes faster and harder so you must have experience with launching model airplanes with that kind that kind of launch technique.
This way you get fun out of it, no matter what branch of our sport you practice.
This product information is more extensive than others for two reasons:
FLYING WINGs still need more spacious descriptions anyway.
We want to document that the designers, makers and distributors identify themselves with the CO8 philosophy:
We do not want to make a fast dollar, but want to market a great product with exceptional quality.
That's what we, the C08-generation, stand for, Be a part if it.