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Jan 16, 2013, 09:25 PM
"Five Easy Pieces"
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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Jan 17, 2013, 01:14 AM
Registered User
n553302's Avatar
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.
Jan 17, 2013, 04:44 AM
DIY Mania from Taiwan
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
Jan 17, 2013, 08:35 PM
"Five Easy Pieces"
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)
Jan 18, 2013, 12:56 AM
skumgummi dave
Pretty tough bird!
Jan 18, 2013, 05:53 AM
"Five Easy Pieces"
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.
Jan 18, 2013, 05:54 AM
"Five Easy Pieces"
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?
Jan 18, 2013, 09:06 AM
gpw
gpw
“There’s no place like Foam”
gpw's Avatar
Front or mid motor mount , the wing CG stays the same ... usually ...
Jan 18, 2013, 12:36 PM
"Five Easy Pieces"
Quote:
Originally Posted by gpw View Post
Front or mid motor mount , the wing CG stays the same ... usually ...
Absolutely.
I was just curious.
Jan 18, 2013, 10:24 PM
Registered User
n553302's Avatar
Quote:
Originally Posted by bobdaeronort View Post
Is your motor on the front or mid-mount?
Front mount. 40 OS
Jan 19, 2013, 01:46 PM
"Five Easy Pieces"
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.
Jan 30, 2013, 09:46 PM
Registered User
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
Feb 05, 2013, 06:49 PM
"Five Easy Pieces"
Marvin Martian's Ride (2 min 28 sec)
Feb 05, 2013, 06:51 PM
"Five Easy Pieces"
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.
Feb 05, 2013, 10:44 PM
DIY Mania from Taiwan
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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