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May 13, 2005, 10:10 PM
Registered User
hardlock's Avatar
Idea

Carbon Eagle development


Due to the large demand for a larger Carbon Falcon for soaring and AP etc, I've gone a step further and now have a completely new design for a larger wing.

It combines the best features of both the CF and CK with double surface wing and internally tensioned structure. All aluminum ribs (24 of them!) that start at the root as a fattened S3021 transitioning out to a S5020 at the last rib.

First test flight was today and although it's got some tweaking and trimming to do, performance was better than expected. Wind was gusty however and the CG was too far back so quite a handful. One surprising thing was how fast and flat a glide it has.

The specs are:

Span = 62"
Area = 564 sq in.
AUW = 18 oz
Motor used = AXI 2212-34
Pack used = Polyquest 3S 1100 mAh
ESC = CC Phoenix 10
Prop = 10x6 APC folder

Based on motor charts, that prop acts about like a 9x4.7 as to current draw. About 6 amps on the meter at an RPM of 6600. Good 45 deg angle climbout but a better folder should get more from the motor.

How it works - following the porta-plane tradition, after removing the root "bra" (which BTW still needs some work) the two wing halve skins are disconnected by releasing rubber bands and then slide off the frame. The frame halves then slide off the root frame and fold flat. That's about it and you end with a 36 x 6 x 2 inch package. Control is still wing warping of course using CK technology with 1/4 chord sweep torque tube allowing the forward 1/4 chord to droop at the tips to aerodynamically balance the "control surface" for reduced load on the servos at high speeds.

Now the testing fun begins! Hopefully it will handle quite a payload and offer good soaring performance. Now if I can just figure out how to hold it for launch.

Any suggestions, comments, etc are always welcome. However, please don't ask how much or when available as this bird is so labor intensive it will be quite some time before I can reduce the construction time down to anything reasonable to price it for production.
Last edited by hardlock; May 13, 2005 at 10:30 PM.
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May 13, 2005, 11:34 PM
Registered User
LTChip's Avatar
That is really cool. I miss my Carbon Falcon. Can we see the underbelly and mechanics? Congrats on the new design!

I especially like the "price it for production" part. Soaring with the hawks and vultures with this would be a blast.
May 14, 2005, 12:34 AM
Registered User
hardlock's Avatar
Thanks! Here's some more pics showing details:
May 14, 2005, 12:47 AM
Duh
crashawk's Avatar
that's pretty neat, just like a full scale hang-glider. now how 'bout one with a trapeze, a scale pilot and weight-shift control?
I been thinking about a scale hang-glider for sloap soaring, this looks very close allready.

Jason
May 14, 2005, 01:19 AM
Registered User
hardlock's Avatar
Jason, I originally built a scale HG many years ago but found out the hard way that weight shift won't work for models. The mass scaling factor ruins it. Think of it this way. A real HG pilot weights 3-4 times the gliders weight. If you run the numbers for a scale model with 3/4 the mass needing to be moved under the plane for the proper leverage, you start to see the problem. It CAN be done but you'd need perfect landings on wheels or risk stripping servos. That's why the wing warping works so well. The wing has the effect of changing CG like weight shift from the increase or reduction of lift behind the CG.

Besides, for soaring, why add all those draggy parts out in the breeze.
May 14, 2005, 03:38 AM
Bertrand MICHELS
bmaaa's Avatar

beware the FRAGILE aluminium ribs !!


I owe a "standard" falcon, and I will love to have also it's big brother. I am just concern about those Aluminium ribs : they could loose their original shape easily during crashes or transportation ! could we use some more bending materials ?

I already has to make a new set of my wood ribs because, I found that my falcom was slowly loosing its good flyins maners until I found by chance that the ribs were not having anymore the recommended shape. Thereofre the airfoil has modified. This change in shape must have occured slowly during transportation, small crashes, handling....

Moulded kevlar will be perfect .....
May 14, 2005, 07:06 AM
Registered User
Nice looking plane !
May 14, 2005, 10:12 AM
Registered User
LTChip's Avatar
I agree on the ribs. The softer and more shapable the material the more maintenance there is with those. The CF uses bbq skewers as ribs and it was one of the things I did not like about the plane. They were senstive to humidity and I had to be careful to always store the plane hanging so the pressure would not bend the ribs out of shape. They eventually lose their shape from use and you have to heatgun and bend them back. I was going to try plastic Pick-up-Sticks (the kids game/toy) but sold my CF to fund another project before I gave that a go.

Using molded plastic or something like a composite may help but it also may increase the price. Maybe using carbon fiber ribs as a upgrade option would be a way to go. Seems making them would be possible as there are several upgrade parts makers doing incredible things with carbon fiber in the micro heli forums. That way only those willing to pay would get them. Al ribs could be the standard.
May 14, 2005, 12:31 PM
Crash Master
Gene Bond's Avatar
Looks great Ken. I know the Bra has made a significant difference in the glide on my CF, so I applaud any attempt to continue that direction!

I do see a bunch of labor... Going to be tough to keep the cost down, assuming you can pay yourself $2/hour for the labor

Keep the research going!
May 14, 2005, 04:20 PM
Registered User
LittleJon's Avatar
Aluminum ribs work really well on my Carbon Falcon, much, much better than the original bamboo ones in fact. The flying characteristics were greatly improved and now I can fly in strong winds without having the airfoil collapse.

I've had them in for over two months now and they've never bent out of shape.
May 14, 2005, 04:49 PM
Registered User
hardlock's Avatar
I like them in my CF also. Too bad they are so time consuming to create.

I found that if you first bend in a large bow, then finish the front airfoil shape and flatten out the rear section, you in effect work harden the AL the full length and it's much stiffer. When I just formed the front curve and left the rear area straight, they seem softer at the back and tend to want to bend there.

If I can ever get around to making a former, I'll first run it through creating a large radius curve to work harden the material and then once cut to length run the back halves backward through the former to re-bend them straight. Should make for some nice stiff ribs.
May 14, 2005, 05:28 PM
Registered User
LTChip's Avatar
On the Eagle the electronics and skeleton are all inside the dual surface sail correct?

It would be good to do the sail in contrasting colors top and bottom for orientation.

Al ribs should be better than the wood ones since they wont be affected by humidity, heat, or pressure warping as much. Laser cutting ribs from CF sheets would be cool too.
May 14, 2005, 06:22 PM
Registered User
hardlock's Avatar
Here's the bottom view. Yes, all the gear is internal. Color contrast it has except the red bottom shows through the yellow top and makes it sort of orange. Not a big deal but other color choices might be better.

Just got back from test flight #2. Since the CG was too far aft yesterday and the 3S 1100 pack was right at the nose, I went with a 3S 1500 pack today with an AUW of 19 oz. Got it flying pretty good but am afraid it will need some vertical area. If not careful and allowed to tip stall, the spin is really radical and almost non recoverable if not enough alt.

Got it high enough to power off and do a little thermal hunting. Flys fast, flat and has good L/D. Even managed a couple loops. To get down I dive tested it that's where it got interesting. It had a catastrophic structural failure of the wing spar joiner. I knew I should have lashed the ends of it!

It was doing well straight down when at the pull-out it went into convulsions like I've never seen before. Really weird with tumbling, flapping, totally warped every which way.

I had no idea what was up but the gyrations slowed it enough to recover sort of, but the LE tube had popped out of the nose piece as well as a clevis popped loose on one wing so I had no control on that side. The other wing spar joiner was split but the spar was out and poked through the wing fabric. Even so I almost managed to get it down gently but eventually lost what little control I had and spun it. I'm test flying over 3 ft grass so stall, spin, and dive-in crashes are a non-event.

All-in-all, not really much damage to fix from the break-up and I'll guarantee no other plane will continue flying after breaking a spar and losing half it's controls as well as the CE did.

Even dorking it into the street yesterday (narrowly missing my car and a cady parked next to it) didn't do any damage so I feel it's now totally crash tested with complete success!
Last edited by hardlock; May 14, 2005 at 08:08 PM.
May 15, 2005, 12:57 PM
Duh
crashawk's Avatar
Quote:
Originally Posted by hardlock
Jason, I originally built a scale HG many years ago but found out the hard way that weight shift won't work for models. The mass scaling factor ruins it. Think of it this way. A real HG pilot weights 3-4 times the gliders weight. If you run the numbers for a scale model with 3/4 the mass needing to be moved under the plane for the proper leverage, you start to see the problem. It CAN be done but you'd need perfect landings on wheels or risk stripping servos. That's why the wing warping works so well. The wing has the effect of changing CG like weight shift from the increase or reduction of lift behind the CG.

Besides, for soaring, why add all those draggy parts out in the breeze.

I never thought about landing with the sudden stop and what it would do to the servos, ouch. I guess it could be done with some of the bigger new servos on the market but I'm not sure I want to spend that kind of cash. I guess one of these with a static trapeze and lightweight pilot would be pretty realist even with the wing warp controls.

Jason
May 15, 2005, 01:52 PM
De-Brushed user
How well do you think it will fly if you add about 5 ounces? I am thinking this could make a great portable camera plane. Thanks,

Jonathan


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