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Old Sep 16, 2007, 01:00 AM
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MustangAce17's Avatar
Ocala,Florida
Joined Sep 2005
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found a great deal on a rtf Voyager 55"

my friend showed up at the Ocala Summer's End with this bird today and I had to have it ,with a Axi 2820,apc 10X7e prop,Jeti 40,all servos(two futaba 3108's and a mpi)and a 3ch Neon trans at $125 it was a incredible deal even thought the aiframe is a bit raggy looking. I did the maiden on it and after a hairy take-off i managed to get some altitude,re-trim and fly her around trying to get used to my new plane.I found it does fly well at half power and anything below it flys like a glider.After about 20 mins of mixed throttle flying I brought her in for a very nice final approach and greased the landing rolling off into the grass since mine is non steerable.I now see why Nitro is sold out of these birds and I will now set it up on my good radio with dual rates and the Axi is great power overall,propped to 400 watts I was told.
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Old Sep 16, 2007, 04:18 AM
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Sydney, Australia
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Hi Ace, Thats a great deal. The motor and ESC alone are worth that. I like AXI's very much. A 2820 isn't particularly large for a 40 size model, depending on weight of the model. Are you limited in prop diameter due to ground clearance?
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Old Sep 16, 2007, 04:26 AM
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Ocala,Florida
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John,this Long Ez variant doesn't need this much power,it's more like .25 size and the same one Charles has and enjoys flying.
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Old Sep 16, 2007, 05:22 AM
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Ah yeh.. the electric version is more like it, using the 2820. Should go very well. Cool!
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Old Sep 16, 2007, 03:46 PM
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Ocala,Florida
Joined Sep 2005
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another additon to the canard family tree. Forgot to mention the Quickie EP was there and after a trade for a plane I wasn't flying it's in my hangar also
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Old Sep 16, 2007, 09:02 PM
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Fun Weekend

Just got back from a 495 mile trip to Cookeville Tn. with these models except the Voyager. The electric fly in at Cookeville was with 10 plus mph winds and my models remained in the trunk all the way. The scenery from Chattanooga up Hwy 111 was unbelievable and the weather was clear. When we got home,I just added the Voyager to the fleet and went to our field. There were five cars there and they said it had been windy all day and were packing out. I had the field to myself as the wind dropped to a gentle breeze down the runway at 4PM. I flew all four models for well over an hour. All did well and I had a good time. John235, it was great to hear of your success. That model just looks like a flyer and I know you must be proud of it after all that work. While flying my canards today, I noticed how well they penetrate the air with the stability of the rear wing and the positive way the canard wing holds the attack. A conventional plane dragging the elevator around just can't compare.I know the Wright Brothers must have had more confidence with the elevator control up front. Charles
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Old Sep 16, 2007, 10:14 PM
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Charles, Thanks for all the design info you provided. The more I read the thread, the more I realise how much detailed info you have posted here. I love to try my own ideas, but without studying your models and reading your experiences, I would have been at a disadvange. It was pleasing that with the correct canard proportions and cg location my model could fly with hardly any adjustment. My model is significantly shorter than the hobby lobby Shinden, but the pitch control seems very positive, and once it got up to speed the glide was very flat. I can't wait to try it under powered flight.
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Old Sep 17, 2007, 08:51 AM
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John, Thank you for the warm words. This thread could not exist without you and many others who have submitted pictures and experiences and I wish to thank each of you. You got me started on the idea of a ducted fan glider and it will not go away. It would have a monster fuselage about 3 inches wide and 4 tall and at least 4 feet long. The wing would be 6 feet with a canard about half as long. Do you think it would be worth doing with the pusher fan and rudder only control? The fan would have 21 oz. thrust and the model would weigh under two pounds. I am curious about how a two wing glider would float on the air. Comments anyone?
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Old Sep 17, 2007, 10:19 AM
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Charles and company!
I'm a bit curious how you plan on getting all that equipment into 31.99 OZ.!
Anyway, let me save you guys some work! C'mon and take a look!
http://www.rcgroups.com/forums/showthread.php?t=693727
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Old Sep 18, 2007, 02:01 AM
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I am not really sure about the merits of EDF in a glider. It seems to me like too much frontal area for efficient glide performance. If I make an electric glider it will use conventional folding props. I thought about using a single geared motor and a twin boom arrangement, but I don't like the layout from a structural point of view. For mine, I'd rather go for twin motors in a FW-42 style layout. I have been drawing up a new design for a 2m (78.5") glider. I am looking at twin 170W outrunner motors and 10" folding props to end up with competition style vertical climb and very brief motor runs. I still have doubts about the thermalling performance, but I think there may be some advantages in the canard layout. I might give it a go to satisfy my curious nature. Electric gliders are very popular at one of the clubs that I fly at, so its a logical direction for me to go.
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Old Sep 18, 2007, 08:15 AM
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John!
That's why I sat on it for a couple of months, but to get 90 some inches of span into the air, would cost to many lacerations! I was totally impressed with a pair of 6" props with brushed 300's, though- at 41 OZ.! I'm planning a "flap" which would 'close' the intake foe soaring mode, which is why some of the designing is a bit of a bearcat!
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Old Sep 18, 2007, 08:47 AM
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Captain, Too many lacerations.. Do you mean you are worried about getting hit by the props? I would use twin tractor props, so I think it should be possible to launch without getting lacerated. Please let me know if you think otherwise, because propeller cuts don't really appeal to me.

I am wondering.. Have you had a chance to do any more testing with streamers to visualise the canard wake flow? I have a copy of a journal paper that reports the effect of canard wake on the lift/drag of the main wing for low reynolds number airfoils. The layout of your canard models with the canard dihedral seems very convenient, but I may want to investigate if its possible to get any improvement in efficiency possibly by mounting the canard on a pylon and varying the amount of dihedral.
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Old Sep 18, 2007, 11:06 AM
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Quote:
Originally Posted by Captain Canardly
John!
That's why I sat on it for a couple of months, but to get 90 some inches of span into the air, would cost to many lacerations!...
EDF's would be a major step backwards, and pusher props would not be much better. Both result in significant losses of propulsive efficiency (major in the case of EDF's) in the realms where we are working. A folding tractor will give you less drag than an EDF when shut down, not much different from a folding pusher, and certainly less than a windmilling pusher. Propulsive efficiency will be better, so you will need smaller motors and batteries to accomplish the same or better climb rate.

EDF's are good for low speed thrust in comparison to a prop of the same diameter, if the ducting is designed properly, and if the blade tips are sealed against the duct wall well enough to minimize leakage. The duct reduces tip losses. At higher speeds the tip losses for a conventional unshrouded prop decrease, while the parasite drag of the duct itself increases. At some point there is inevitably a "crossover velocity" (just like the case with winglets) where the drag of the device itself exceeds the losses it is supposed to recover. At all speeds above that, the duct is a losing proposition.

The key phrase in the paragraph above is "of the same diameter". In the vast majority of the cases we are likely to see, we can use a much larger diameter conventional prop than the diameter of an EDF for the same application. Because of this, the EDF will almost certainly be less efficient (usually a lot less efficient) than the conventional prop. If you can somehow get away with an EDF of the same diameter, then your nacelle drag (even with a shutoff of some sort to fair over the inlet and outlet) will be higher than the much smaller aerodynamic signature of a folded conventional prop and motor.

Besides the safety issues, a pusher gets into efficiency problems as well. The typical rationale for a pusher is that supposedly it reduces airframe drag by not inflicting the airframe with the increased velocity of the propwash. However, in actual practice, only a small portion of the airframe is in that propwash, and the latest research suggests that even in that region the drag increase is not as much as folks formerly assumed. In particular, there is still a large percentage of laminar flow in the slipstream, unlike the turbulent flow everyone assumed was the rule in that area.

So, the effect on arcraft drag is minimal. However, ALL of your thrust comes from the prop, and the effect of inflicting airframe-wake-induced distortions on the airflow into the prop typically causes major reductions in the prop efficiency (very possibly as much as 15-20% or more), even without including the restrictions in prop diameter that are often inherent in pusher layouts, which further restrict prop efficiency.

The propeller company I used to work for had probably more experience with pusher installations than anyone else in the business. Our first reaction when someone approached us with another pusher application was usually to try to talk them out of it.

Any way you cut it, the EDF isn't likely to be your best bet, and a pusher usually isn't optimum either. I think John is on the right track, a folding tractor is likely to be your best bet.

There are a number of articles in the "Ask Joe and Don" section of our website www.djaerotech.com that discuss these issues.
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Old Sep 18, 2007, 11:09 AM
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Are you two talking competition or sport flying? If it is for a contest, it must be as light as possible which calls for single high power motor. I figure you are just after an exciting set up just like I am. The EDF might take a while to get to a thermal but it would be different. It would not have to carry an extra power system. Charles
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Old Sep 18, 2007, 11:14 AM
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Quote:
Originally Posted by canard addict
Are you two talking competition or sport flying? If it is for a contest, it must be as light as possible which calls for single high power motor. I figure you are just after an exciting set up just like I am. The EDF might take a while to get to a thermal but it would be different. It would not have to carry an extra power system. Charles
Both. If you have an anemic, inefficient, overweight power system that results in an obese airplane with lackluster performance, it is not likely to be
"exciting".

There is rarely an advantage to "different" just for the sake of being different. In the long term, the only "different" that amounts to an advantage is one that makes the plane perform its mission better. That is true for any model, including a sport model.
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