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TOPIC: Carbon Dragon with electric engine

Carbon Dragon with electric engine 25 Jun 2014 20:43 #821

Dear Group
I am an italian aviation enthusiast who began his career working in a Company named Caproni Vizzola in 1973 and at that time I had the chance to work on the two seats side by side Calif A21 S glider.
Now retired and presently flying for fun on a Robin DR 400, EAA member since 1975,I have been recently hit by the very light gliders family able to soar in minimal conditions and with low wing loading comparable to hang glider or paraglider while maintaining a full three axis control.
I was asking the group if nowadays, where electric brushless engines technology and lithium batteries is available while it was not when Carbon Dragon was designed, it does make sense to think about a self launching capability of the CD by installing a close to CG engine under the wing and a protruding prop on the nose like the italian electric Silent glider. Another recent example is the swiss Archaeopteryx where the engine is pushing at the end of the fuselage pod.They claim an added weight of 23 kilograms, that is 51 lbs inclusive of battery, with motor run time at full throttle of 11 minutes and with engine power of about 20 hp.
Even though the nose installation of the prop is close to the ground from what I understand from Silent pilots with a proper sitting angle of the glider, take off and landings do not pose a problem.

I realize that Jim Maupin designed also the motor glider Windrose which did not have the Carbon Dragon success, and I do not understand why, but I understand also that Windrose is a different class of aircraft and with a higher wing loading. In the Windrose the electric engine installation should be done with a foldable prop pushing form the back of the fuselage.

I am not an expert and I would like to hear some comments about my thoughts from members of the group who knows much more than me on possible modifications of the original Carbon Dragon including increase of max take off weight and some beefing up on the airframe needed.
Congratulations to all of you able to build such a marvelous glider and who dedicate also time and effort to provide for free such enormous amount of information.
Thank you for your time
My best regards
Cesare

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Carbon Dragon with electric engine 27 Jun 2014 09:45 #822

Hi Cesare,

I can't claim to be an expert in the area (either as a builder or in adding power) and I am still working on my first all-Carbon Dragon, but one of my plans (after I get it flying) is to analyse the loads and stresses associated with adding an electric motor and batteries to the CD, and what effect this will have on the centre of gravity. I am planning on redesigning the pilot pod anyway (along the lines of the Swift Lite - aluminium tube structure with clip-on fairings) and I don't think it would take much to include hard points for mounting the motor and batteries.

Icaro in Italy have recently released an electric version of the Swift Lite with a folding prop and it seems to work well... but this is a tail-less glider!



In its current configuration the Carbon Dragon pilot pod is not suited to adding power - it's too low to the ground to add a prop on the nose and the tail boom prevents installation there also. Any redesign would mean raising the height of the wing and tail boom aboce the ground to give sufficient clearance, which is certainly an option. It would allow you to place a motor in the nose more easily and have the added benefit of taking the pilot's head out from inside the wing, improving visibility considerably. I like the Silent's folding nose prop - it seems to fold back into molded recesses in the nose cone (perhaps held in by magnets?) for a very streamlined finish.

I did come across a few photos of a motorised Carbon Dragon, called the Alnair some years ago. The builder had a single pusher-prop sticking out of the trailing edge of one wing - off axis. I don't have any idea how it performed, but with the modern, compact brushless DC motors that are available today there's no reason why you couldn't mount a pair of these, on the main wing spar (after beefing it up a little) either side to keep the thrust symmetrical. It would also allow you to use smaller motors and shorter props to get the same thrust (with a small weight penalty.) In fact this might be the simplest solution all round.

Keep in touch and let us know where your research takes you!

All the best,

Phil.

www.ihpa.ie/carbon-dragon/images/carbon-...%20%28CD%20clone%29/
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Carbon Dragon with electric engine 27 Jun 2014 20:53 #823

Ciao Phil
Thank you very much for your time and your useful comments and considerations.

I am happy to understand that also in your opinion the time has come to get the benefits of the brushless motor technology and apply them to very light aircraft such as the CD.I was not familiar with the Icaro Electric Swift, I went to some videos and it looks like the system is working very well with a good size prop, 1.4 meters diameter, and about 13 hp of installed power. As a matter of fact it is more or less the total power installed on the Archeopterix and it does its job well also on the swiss machine. For horizontal flight al 70 km/h on max 150 kg the power needed is about 5 hp and the rest is required to take off and climb at reasonable rate.

I do share the opinion that as is the CD cabin is not suited for a prop on the nose installation and that it would require a redesign the pilot pod to give more ground clearance, but I did not think about a twin engine configuration on the wing or, being myself '' infected' by having worked many years in the helicopter industry, a single engine located in the fuselage with two 90 degrees very small gearboxes with miniature propeller pods protruding from the leading edge of the wing. I think friction losses can be kept to a minimum and two 40 mm driveshafts could do the job. You gave me a very interesting clue to think about and I will do some research on practical possible solution, at least on the paper.

The dream to take off on very reliable low power engine,climb at altitude, turn the engine off and enjoy what the experts call micro ilfts is getting close also for a low budget aviator, and when you are happy enough to stay aloft and is time to land, few electric horses drive you back to your place without off field retrieval such as for pure gliders.

Too good to be true!!

We stay in touch.

Compliments for your Carbon Dragon

Cesare

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Carbon Dragon with electric engine 01 Jul 2014 17:52 #824

Hi Cesare

I am keen to see what you come up with. I have been thinking about the possibility of an electric self launch glider and you seem to have looked at the same things for inspiration (Swift, Archeopterix)

Chat soon

Roger

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Carbon Dragon with electric engine 02 Jul 2014 19:47 #825

Ciao Roger,ciao Phil and all
as of today I am pretty sure that by keeping the max take off weight in the neighborhood of 400 lbs equivalent to about 180 kg the amount of power needed on board is 13,5 Kw ,about 18 hp,and the engine available is the german Flytec HPD 10 rated to 13,5 and turning 1950/2100 rpm.The complete powered kit ( engine,prop,batteries and electronic control) should remain in the 30 kg figure,little bit more than it is today on the Archeopterix.

Swift Lite and Archeopterix swing a 1.4 mt prop which is excellent for take off. Silent Electro swing a 1.0 mt prop turning 4500 rpm on a 22 Kw engine.

Point is the ground clearance of the prop on the CD, but if we see videos of the Silent, it reaches acceptable ground prop clearance by keeping a constant nose up attitude of the aircraft in taxiing as well in take off and landing. In other words it looks like the glider never keeps a level attitude while on the ground. If this is correct we can get some prop clearance clearance on the CD by operating the same way as the Silent and ,as Phil was suggesting, we can add few inches on the pod length so moving the pilot forward and balancing it with the engine placed in the back of the pod turning a long sized drive shaft connecting the prop on the nose. Prop should fold as the Silent and recessed nicely along the fuselage sides when engine is off. Silent Company is not far from where I live and I am planning to see them and ask for some advice.

Another modification guess is the size of the landing wheel because by enlarging it we gain on the distance from the ground and therefore the prop clearance. I think that even if large part of the bigger wheel will be protruding from the bottom of the fuselage,because of its small width it can be properly cowled and aerodynamically streamlined.

The above is just food for thought and comments or suggestions are always welcome.Next step should be to translate into drawings and see what is coming out.

In any case all the efforts spent to make this dream coming true are worthwhile!!

My best

Cesare

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Carbon Dragon with electric engine - Jim Maupin's Gliders

Carbon Dragon with electric engine 06 Jul 2014 19:22 #826

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