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Old Nov 13, 2012, 11:51 PM
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Manudepron's Avatar
Belgium, Walloon Region, Namur
Joined Apr 2010
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Build Log
Sphinx Micro Jamara with AR 6400

Hi,
I came across this kit in my hobby shop. It's intended for 3 2.5gr servo's and a 2 S brushless motor. It's annouced at around 50 gr. My target with all a 4-site equipment is around 30 grams. I begun building as always for me for this kind of structures upside down on a table to ensure a flat structure. It's a fast build but using UHU POR I need to lay it dry step by step. No CA with EPP for me, too brittle See pictures
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Last edited by Manudepron; Nov 14, 2012 at 12:50 AM.
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Old Nov 18, 2012, 04:37 AM
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Manudepron's Avatar
Belgium, Walloon Region, Namur
Joined Apr 2010
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Finished and maidened

Hi,
Yesterday was an indoor session and I maidened it. Weight was 25 gr with a 1S 160mah Nanotec. Flies very well but i have in order to "fine tune" it:
- To reinstall forward the landing gear (goes always on the nose on take off if I put too much power)
- Replace the orginal 4 site popeler by a GWS (planned but not done on time by lack of time)
- Strengthen the control surfaces by small carbon rods

Otherise it's very promising!

Next time I will ask someone to make a video!
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Old Nov 18, 2012, 08:33 AM
Gravity is a harsh mistress.
Tim Wolff's Avatar
United States, MI, Temperance
Joined Sep 2002
6,533 Posts
The nosing over on take-off may be due to the wheels rubbing on the landing gear struts. The wheels look like the one I got with a Techone Yak. I replaced then with a pair of much lighter GWS wheels. You could also change the axles 180 degrees so they point outwards rather than in. Much easier to get the wheels to spin freely in that configuration.
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Old Nov 26, 2012, 12:03 PM
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Manudepron's Avatar
Belgium, Walloon Region, Namur
Joined Apr 2010
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You are right wheels were rubbing! Thanks. Nevertheless I decided to replace the whole undercariage: 1 mm diam carbon pointing more forward and reinforced by a kevlar thread. I made also a light prop saver with a "servo x wheel" token from a HK 1.7 gr servo. A silicon piece of tubing and this fit the 5 x 4.3 gws prop. And I replaced the ailerons horns by long 0.8 mm wood in order to reduce ailerons flexing as seen during the first flights. Plane batt inclusive remains under 25 gr ready to fly and it flies very well but without being able to hang it by the prop.
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Old Nov 26, 2012, 12:10 PM
Gravity is a harsh mistress.
Tim Wolff's Avatar
United States, MI, Temperance
Joined Sep 2002
6,533 Posts
The power setup shouldn't have any problem hovering the plane at the weight you posted. What battery are you using?
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Old Nov 26, 2012, 04:27 PM
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I R Irv's Avatar
United States, IL, Washington
Joined Nov 2008
1,940 Posts
25grams RTF sounds extremely light, are you sure about that weight? I'm not trying to call you a liar it just sounds too light.
TODD
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Old Nov 27, 2012, 12:44 AM
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Belgium, Walloon Region, Namur
Joined Apr 2010
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Nanotech 160 mah, as you I am surprised it can't hover but maybe this motor isn't anymore 100%. As for the weight I am surprised also by the figures and I will check with an other balance. What i can say is I am a weight killer I used to build actuator planes of around 10 gr with JMP combo's for those remembering. I check and I tell you. But the kit elements were very light too!
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Old Nov 27, 2012, 06:13 AM
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I R Irv's Avatar
United States, IL, Washington
Joined Nov 2008
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Well then that's a great weight and once you figure out the power issue you should have a great plane. Some things to look at regarding your power problem.
Tight or dry gearbox
Motor on it's way out
Prop out of balance (a real thrust killer)
Prop adapter throwing prop out of balance
If your batteries will last a hole flight without hitting LVC then there probably not an issue.
TODD
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Old Nov 28, 2012, 01:25 PM
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Belgium, Walloon Region, Namur
Joined Apr 2010
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My appologises: My electronic balance is out!
Se attached pictures of this balance weighting a well known 9 gr servo at 6.5 gr!

I found in the house an old trusty mechanical postal balance weighting the plane at 40 gr batt inclusive! Thank you for your "at distance" analyse!
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Old Nov 30, 2012, 12:49 PM
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derk's Avatar
USA, ID, Coeur D'Alene
Joined Dec 2003
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Try weighing something you know is accurate like a calibration weight. Most pocket scales can be recalibrated with one. Should be in the instructions how to do it.
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Old Dec 01, 2012, 04:11 AM
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Belgium, Walloon Region, Namur
Joined Apr 2010
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I found the problem: I changed the batteries and my balalnce went back on track weighting things I know the weight correctly! I would prefer the balance to tell me "low batt" because the display with the worn out batt's remained bright!
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Old Dec 02, 2012, 04:33 AM
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Belgium, Walloon Region, Namur
Joined Apr 2010
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I I flown yesterday after replacing the prop saver with an eflite alu and a proper balanced prop and the power gain was obvious! Not yet able to prop hang but far better! I will try to post a video next week! Thanks
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