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Old Jan 16, 2013, 08:25 PM
"Five Easy Pieces"
United States, IN, Terre Haute
Joined Sep 2011
1,417 Posts
Marvin Martian's X-IIB my second and slightly smaller attempt. She's 36" in diameter with a three-channel set-up and a SMJv2 motor spinning a 7x4 prop. She weighs in on the flight-line at 29 oz which is just 2 oz. heavier than my 5EZP F-18E Super Hornet.
She also has a new gizmo box design with a lower frontal area than her predecessor so other than her nacelles she's pretty flat.
Weather permitting I'll take her up in the morning.
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Old Jan 17, 2013, 12:14 AM
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Northwestern Illinois
Joined Jan 2003
189 Posts
As for the balance point of your disk, I have some known numbers to throw into the mix. Mine is some what different than yours, 39" diameter, glow powered, no airfoil. But I've found on my disk a CG of 10 inches from the leading edge fly's the best. Great flier, only bad habit is it sometimes nose dives when at higher speeds.
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Old Jan 17, 2013, 03:44 AM
DIY Mania from Taiwan
Taiwan
Joined Aug 2011
1,933 Posts
Bob,pretty sure your new saucer will doing good on it's maiden flight
love the saucer,well....here's one more made last year,just take a quick look
regards
Sam
PICT0670 (0 min 38 sec)

PICT0657
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Old Jan 17, 2013, 07:35 PM
"Five Easy Pieces"
United States, IN, Terre Haute
Joined Sep 2011
1,417 Posts
Third times the charm.
Once trimmed with a bit of up elevator the X-IIB flew just fine.
I think though that the foam in the prop wash is flexing and causing a thrust vectoring effect.
So I reinforced the fantail and then cut out a larger prop slot. I saved the piece in case it has no effect.

Return of Marvin Martian's X-II.mov (3 min 34 sec)
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Old Jan 17, 2013, 11:56 PM
skumgummi dave
Gresham, OR.
Joined Mar 2004
1,818 Posts
Pretty tough bird!
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Old Jan 18, 2013, 04:53 AM
"Five Easy Pieces"
United States, IN, Terre Haute
Joined Sep 2011
1,417 Posts
Quote:
Originally Posted by foamdave View Post
Pretty tough bird!
She balanced much better now and only pancaked this time.
The repeated nose....er, wing-ins of her predecessor caused much foam fracturing and damage.
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Old Jan 18, 2013, 04:54 AM
"Five Easy Pieces"
United States, IN, Terre Haute
Joined Sep 2011
1,417 Posts
Quote:
Originally Posted by n553302 View Post
As for the balance point of your disk, I have some known numbers to throw into the mix. Mine is some what different than yours, 39" diameter, glow powered, no airfoil. But I've found on my disk a CG of 10 inches from the leading edge fly's the best. Great flier, only bad habit is it sometimes nose dives when at higher speeds.
Is your motor on the front or mid-mount?
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Old Jan 18, 2013, 08:06 AM
gpw
“There’s no place like Foam”
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United States, LA, New Orleans
Joined Jul 2002
24,105 Posts
Front or mid motor mount , the wing CG stays the same ... usually ...
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Old Jan 18, 2013, 11:36 AM
"Five Easy Pieces"
United States, IN, Terre Haute
Joined Sep 2011
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Quote:
Originally Posted by gpw View Post
Front or mid motor mount , the wing CG stays the same ... usually ...
Absolutely.
I was just curious.
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Old Jan 18, 2013, 09:24 PM
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Northwestern Illinois
Joined Jan 2003
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Quote:
Originally Posted by bobdaeronort View Post
Is your motor on the front or mid-mount?
Front mount. 40 OS
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Old Jan 19, 2013, 12:46 PM
"Five Easy Pieces"
United States, IN, Terre Haute
Joined Sep 2011
1,417 Posts
OK so with my last set-up on this I have the SMJv2 motor mounted 12" back on the 36" disk and the 2250 Li-Po sits an inch back from the front edge (1/3). It balances about 10" back. The Glide is good.
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Old Jan 30, 2013, 08:46 PM
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Joined Jan 2005
48 Posts
We built a similar design, for the San Francisco Flugtag. Here is a video of test gliding the scale models

San Francisco Flugtag Model (0 min 15 sec)


Here are build instructions for the model

http://www.instructables.com/id/2012...ircraft-Model/

The model got/gets about a 12 to 1 glide ratio. I haven't tried adding power. As you can see, we didn't use a 'airfoil' per say, although a cross section would show and airfoil shape with the thickest point in the center.

Thanks
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Old Feb 05, 2013, 05:49 PM
"Five Easy Pieces"
United States, IN, Terre Haute
Joined Sep 2011
1,417 Posts
Marvin Martian's Ride (2 min 28 sec)
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Old Feb 05, 2013, 05:51 PM
"Five Easy Pieces"
United States, IN, Terre Haute
Joined Sep 2011
1,417 Posts
Quote:
Originally Posted by adamalbert View Post
We built a similar design, for the San Francisco Flugtag. The model got/gets about a 12 to 1 glide ratio. I haven't tried adding power. As you can see, we didn't use a 'airfoil' per say, although a cross section would show and airfoil shape with the thickest point in the center.

Thanks
That glides very well. It reminds me of the USAF saucer plane. It had a very tall single rudder.
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Old Feb 05, 2013, 09:44 PM
DIY Mania from Taiwan
Taiwan
Joined Aug 2011
1,933 Posts
Quote:
Originally Posted by bobdaeronort View Post
That glides very well. It reminds me of the USAF saucer plane. It had a very tall single rudder.
Got the pics
regards
Sam
USAF_disk
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