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Old Apr 18, 2009, 07:49 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,426 Posts
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Tiny Dancer micro F3P for AR6400 & MM Brushless

Clearly I'm into bipes these days. Here is another project on my workbench slated for the AR6400 6-channel brick when they arrive. This one is a micro F3P bipe, the Tiny Dancer. It's an amalgamation of many different non-micro F3P planes.

Construction is laser cut skeletonized foam skinned with 025 Durobatics. This accomplishes almost exactly the same result as milling foam to save weight. The wing shown here is 3mm Depron skinned with Durobatics. When my Gediplac arrives I'll make the skeleton for the lower wing from Gediplac and see if it saves any appreciable weight (probably not). The fuselage will be from Gediplac where the weight savings will be more substantial. I figured a micro F3P plane should look like a F3P plane, so came up with this paint scheme. The paint added just 0.35g, which seems worth it.

Span is 18-inches. Like my Der Jager project this plane will use the AR6400 brick, the Mighty Midget 1-cell hot wind motor, and LCD 3A BL controller. It will use two of the Parkzone 1.5g servos to allow flaperons. All equipment is from BSDmicroRC. Estimated weight is between 31g and 33g. Wing loading should be between 1.25 and 1.4 oz/sq.ft. My goal with this plane is to get as low a wing loading as possible so the plane will fly slowly enough that even I might be able to pull off some aerobatic maneuvers indoors. Because of my wing loading goal I went with more rectangular shaped wings rather than the swept leading and trailing edge wings that I see on many F3P biplanes.

Here are pictures of the top wing and a beta test elevator. A new Elevator will be made using Gediplac. Side stiffeners on the fuselage will be skeletonized to save weight. The rear portion of the vertical part of the fuselage will be skeletonized and skinned with Durobatics.

Gordon
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Last edited by Gordon Johnson; Sep 18, 2009 at 01:49 PM. Reason: changed equipment specs
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Old Apr 18, 2009, 09:41 PM
Team30 Micro EDF
NitroCharged's Avatar
Adelaide, Australia
Joined Apr 2004
11,181 Posts
That laser makes those cuts look fantastic Gordon!
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Old Apr 18, 2009, 09:47 PM
MAD MEN QCRC
RCBilly's Avatar
Joined Jun 2006
604 Posts
Nice Looking, Gordon! Did you use Inkaid and print the 0.025 Durobatics? Should be a good flyer!, Bill
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Old Apr 18, 2009, 10:31 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,426 Posts
Billy,
I just laser cut painting masks, sprayed the back with stencil magic, and then painted with short cuts paint. Clearly printing with inkaid would be the better way to go. But, I'm not set up to do that yet.

Dave,
The laser does allow for very thin skeleton ribs. It's pretty accurate. It takes some trial and error to settle on a good thickness.

Gordon
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Old Apr 18, 2009, 10:50 PM
Micro EDF addict
metroidrc's Avatar
Upstate NY
Joined Jun 2007
4,782 Posts
Gordon, nice design so far! Looking forward to the flights!
-Josh
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Old Apr 19, 2009, 03:45 AM
Old age is not for sissies
Azarr's Avatar
Dayton Intl, Ohio, United States
Joined Jan 2000
7,719 Posts
Very nice Gordon, you should post a link in the F3P forum, I know they'd be interested.

Azarr

Edit: Why do you feel you need a new elevator?

Azarr
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Last edited by Azarr; Apr 19, 2009 at 09:32 AM.
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Old Apr 19, 2009, 11:05 AM
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Tennessee/Mid-South US
Joined Mar 2002
1,534 Posts
Very nice Gordon! Should I have Lionel Richie or Elton John playing in my head as I watch the finished product fly? (can't remember)

What are you using to attach the framework to the durabatics?

I've been wanting to build a micro version of my Vantage design for my Falcon gear... guess I need to break down and do it.
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Old Apr 19, 2009, 11:12 AM
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indoor_fr's Avatar
Paris (France)
Joined Jan 2006
845 Posts
Hi Gordon,
very nice start.

Could you please translate Oz/sq ft to g/dm≤ ?

Also about the 7500KV motor:

Thrust is 44g (3.7V 2.1A 3020 prop)

4000KV motor :

Thrust is 43g (3,7V 1,6A 5030 prop)

If these data are correct, the 4000KV motor would require a smaller battery and you would save some weight.

Frank.
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Last edited by indoor_fr; Apr 19, 2009 at 11:25 AM.
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Old Apr 19, 2009, 11:30 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,426 Posts
Azarr,
I had a notch in the front of the elevator and had planned to have a matching notch in the fuselage and then slide them together. But, I've decided to not have a notch in the elevator, which allows the foam at the LE to continue through from one side to the other and make for more strength. I hadn't thought that through far enough when I did the elevator. Mostly what I was doing with the elevator was testing the concept of lasering a skeleton and skinning it with durobatics. I wanted to see if I could get something close to the 35% weight savings that people who mill/route Depron can save. The answer was that I can get a similar 35% weight savings this route. If you look closely you can see a hand written "v4" on the elevator. That means it was the fourth variation I tried.

Jeremy,
I attach the skin with 3M77. Seems to work -- so far.

Gordon
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Old Apr 19, 2009, 11:37 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,426 Posts
Frank,
You could be correct about the 4000Kv motor. I don't have one of those and haven't tested it yet. But, I have one coming and will test it. I generally don't trust mfg's data, and for these motors they seem to give only data for small diameter props. Regardless, I think I can use a FR 130mAh cell with even this hot wind motor as at 60% throttle it still puts out plenty of thrust and amp draw is a lot lower. I doubt I'll do any hovering so I think I can use this cell instead of a 200mAh cell. If the 4000Kv motor seems good enough once I test it then I'll use it instead.

I don't have a conversion ratio of oz/sq.ft to metric handy. I used to have one but don't know what I did with it.

Gordon
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Old Apr 19, 2009, 11:49 AM
is it flying time?
Jerry Combs's Avatar
Wyandotte Oklahoma
Joined Oct 2004
2,777 Posts
Gordon,

One of the advantages of the 4000Kv motor will be the larger prop. A larger prop will help keep the models speed constant when doing acrobatics.

Jerry
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Old Apr 19, 2009, 11:50 AM
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Paris (France)
Joined Jan 2006
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Quote:
Originally Posted by Gordon Johnson
Frank,
I generally don't trust mfg's data, and for these motors they seem to give only data for small diameter props. Gordon
Gordon,
These data come from others builders.
See this thread:
http://www.rcgroups.com/forums/showthread.php?t=1009761

Hope you'll publish your thrust measurement soon.
Frank.
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Old Apr 19, 2009, 01:10 PM
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glenn2626's Avatar
United States, CO, Colorado Springs
Joined Jan 2008
1,171 Posts
Quote:
Originally Posted by matchlessaero
Should I have Lionel Richie or Elton John playing in my head as I watch the finished product fly? (can't remember)
Aero, That would be Elton John - just saw him here live about a week ago, I'm not a huge fan but got roped into going with SWMBO - I'm glad I did now, it was excellent.

Gordon - excellent work as usual!

Having just finished one of Bill Lowe's Ghost Bipes, I appreciate how a super-low wingloading can make everything better, if not much more difficult to achieve.

Do you think your durobatics skin would be even lighter than the colored saran wrap that Bill uses?

Do you cut the outside frame with the laser again after attaching the depron framework to the durobatics? Must be very tough to get realigned perfectly with the laser table.

Glenn
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Old Apr 19, 2009, 04:21 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,426 Posts
Glen,
I've done a plane using Reynolds wrap, like Bill does.
http://www.rcgroups.com/forums/showthread.php?t=930298
For that one I cut the final perimeter after applying the plastic wrap. For the Durobatics skin I don't do that. I just cut the outside perimeter of the Durobatics with a hobby knife after it's been glued to the skeleton. Durobatics skinning is heavier than Reynolds wrap, but adds more stiffness.

Gordon
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Last edited by Gordon Johnson; Apr 19, 2009 at 04:44 PM.
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Old Apr 19, 2009, 04:28 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,426 Posts
Quote:
Originally Posted by indoor_fr
Gordon,
These data come from others builders.
See this thread:
http://www.rcgroups.com/forums/showthread.php?t=1009761

Hope you'll publish your thrust measurement soon.
Frank.
Yes, I saw those posts. For example the reason thrust is less and amp draw is higher for a 5x4.3 compared to a 5x3 is the 5x4.3 is stalled in static tests. Anyway, those posts came out after I ordered my 7500Kv motor from HK and it took a while for the motor to come. I also prefer to measure motor constants as well as static tests.

Jerry, I don't intend to run more than a 5-inch prop, so with either wind I'm ok in terms of prop diameter.

Gordon
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Last edited by Gordon Johnson; Apr 19, 2009 at 04:45 PM.
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