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Old Feb 06, 2010, 05:22 PM
Gordon Johnson is offline
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in persuit of low wing loading
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Airbender: 19g, 18 inch Aerobat


Here's my latest plane, the Airbender. Wing span is 18 inches, weight is 19g, and wing loading is 0.95 oz/sq.ft -- slightly less than a Vapor's 1.0 oz/sq.ft.

Equipment is the Leichty 900mhz servo receiver with Martin Newell's fantastic HipHop spread spectrum software code. Servos are three of the Leichty/Zigras 0.70g ultra light servos. Propulsion is a Gasparin G10 Micro 2.4g brushless motor and Micro Invent MBC-1 0.6g controller. Battery is Full River 90mAh. Since covering is clear, the color comes from a dusting of paint on the skeleton. The top side is red and the underside is yellow to aid in keeping track of the plane's orientation when in flight.

The name Airbender comes from a favorite show of my boys, "Avatar, the last Airbender".

The Airbender has not flown yet. First flight will be Feb 21. I'll try and get video and pics and post.

Gordon
Last edited by Gordon Johnson; Feb 07, 2010 at 02:28 PM.
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Old Feb 06, 2010, 05:23 PM
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Here are some close up detail pictures and some of the equipment. Soldering up the servos and RX connections, which are done with litz wire, is not for the soldering faint hearted.

Shown are two of the Leichty/Zigras servos next to the ubiquitous Parkzone linear servo. One of the Leichty/Zigras servos is upside down to show the mechanism. The action on the LZ servos is very smooth.

The motor mount is very minimal. Two slots are cut with the laser when cutting out the fuselage. Then, two 1/64 ply pieces with holes sized for the bearing tube on the BL motor are glued and slid in place. A hand reamer reams out the foam. Finally, the motor has some UhHu Por applied and it's slid into the ply motor mounts.
Last edited by Gordon Johnson; Feb 06, 2010 at 06:32 PM.
Old Feb 06, 2010, 05:23 PM
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Airframe is all laser cut foam. The fuselage is 6mm Depron, for stiffness. The wing and elevator are 3mm Gediplac. For each part, the openings are laser cut out. It is then painted (just a dusting). Then, the part is dusted with 3M77 adhesive and applied to a previously stretched and taped down sheet of film. The fuselage is covered on two sides and requires working fast.

After the part has the plastic film applied, it is put back in the laser (using temporary locating pins to position the part accurately) and the perimeter of the piece is cut out with the laser -- cutting through the foam and the covering in one step.

Covering is WES Technik micro indoor film, which has a weight about 1/5th that of Reynolds plastic wrap.
Last edited by Gordon Johnson; Feb 06, 2010 at 06:23 PM.
Old Feb 06, 2010, 05:24 PM
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The wing is undercambered, not a flat plate airfoil. The center section has a two piece rib that is glued on the wing on top and bottom. This is sized to insert into a matching opening in the fuselage. The center rib also holds the aileron servo and the bell crank. Bell crank is 1/64 light ply and a BSD wheel hub and keeper. One aileron is folded back on the top of the wing when inserting the wing through the opening, and it is then folded down into its normal position. The wing also has two undercamber ribs 2/3 of the way out toward the tips. This is where the CF struts attach.
Last edited by Gordon Johnson; Feb 06, 2010 at 06:21 PM.
Old Feb 06, 2010, 05:25 PM
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reserved 5
Old Feb 06, 2010, 05:28 PM
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Old Feb 06, 2010, 05:30 PM
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Air bender


Wow!!!! The level flight speed has to be super slow!!!! Thanks for showing how you kept the covering tight and smooth and I see how you keep the camber by the rib where the struts attach. Really neat!!! Ta ke off and landings will really be something else!! What kind of thrust do you expect. Also not having the bottom of the wing covered will help as air brakes.
Last edited by flybob1; Feb 06, 2010 at 06:24 PM.
Old Feb 06, 2010, 05:57 PM
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slow climbing turn to the left

Airbender


Amazing!
Old Feb 06, 2010, 06:58 PM
fmhans is offline
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Awsome job Gordon, nice and clean.

Fritz
Old Feb 07, 2010, 09:36 AM
Azarr is offline
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RIP Azarr - "Old age is not for sissies"
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Beautiful, can't wait until your flight reports.

Azarr
Old Feb 07, 2010, 10:14 AM
melkor is offline
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Inspiring advance of the state of the art! Thank you for sharing this.
Old Feb 07, 2010, 11:55 AM
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I have seen a Ghost bipe in person and thought it was the coolest thing. This is another level up,. Very cool.
Old Feb 07, 2010, 04:06 PM
356Jim is offline
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Quote:
Originally Posted by Gordon Johnson View Post
Soldering up the servos and RX connections, which are done with litz wire, is not for the soldering faint hearted.
Tell me about it!! I have a Leichty Cricket Rx and love it. Also, I have been bumble-thumbing actuator wires for years.

Each of my planes has secret epithets gingerly engraved into the foam by my self-wavering soldering iron!!

On another note, what is the torque spec for the LZ servos?
Old Feb 08, 2010, 06:52 PM
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Quote:
Originally Posted by Azarr View Post
Beautiful, can't wait until your flight reports.

Azarr
Azarr,
I'll do better. When KIEF comes around I'll let you fly it.

Gordon
Old Feb 09, 2010, 07:49 AM
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Glad you guys like it. My goal was to get a very low wing loading and thus very slow flying speed. I am really looking forward to flying it.

Quote:
Originally Posted by flybob1 View Post
What kind of thrust do you expect.
The Gasparin G10 Micro is listed as putting out about 24g of thrust with a 4x2.7 CF prop. So, while the thrust/weight ratio won't be tremendous, at 1.26 to 1 it should be sufficient for reasonable Aerobatics. It won't be a hovering machine, but that's not what I built it to do. I want it to fly on the wing not fly on the prop.

Quote:
Originally Posted by 356Jim View Post
On another note, what is the torque spec for the LZ servos?
Nick lists them as putting out up to 10 grams of force on his site
http://microflierradio.com/Actuators.html

Gordon


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