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Old Aug 24, 2012, 05:49 AM
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prondel's Avatar
France
Joined Aug 2003
997 Posts
I think there is something wrong in my spreasheet regarding the variation of CoG
initially the formula I used was:

variation = factor / ballast weight

I was wondering if it should be instead: variation = factor / (ballast weight + plane weight)

comments are welcome ...

Cheers,

Pierre
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Old Aug 24, 2012, 06:33 AM
F3B
satinet's Avatar
Warwickshire, England
Joined Sep 2006
5,541 Posts
hi Pierre,

Yes I think you need to combine the weight of the plane plus ballast. I.e total weight of the airframe.
I'll try to have a think of the formula whilst eating lunch. Too much like friday.....

Tom
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Old Aug 24, 2012, 02:25 PM
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Alvaro Silgado's Avatar
Madrid, Spain
Joined Sep 2004
229 Posts
Nice training day! Lot of crossed wind (5-9 m/s), changing from -60º to 45º on its orientation. High temperature and very dense air, perfect for the Precision!

Entrenando con el Pike Precision (6 min 41 sec)


Regards,


Al.
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Old Aug 26, 2012, 12:22 PM
Ja9
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Norway, Rogaland, Tjelta
Joined Dec 2004
161 Posts
Finally got to maiden the Precision today. Wind was blowing around14m/s ( around 30mph) so the maiden flight was done with around 1,5kg of ballast.
Still it was very gentle to fly.
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Old Aug 26, 2012, 10:15 PM
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Old Aug 29, 2012, 07:27 AM
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prondel's Avatar
France
Joined Aug 2003
997 Posts
New and generic spreadsheet

I revisited the formula for the variation of the CoG based on the file ballast_cg_graffiti_xls and I produce a generic spreadsheet for F3X plane, including a fuselage compartiment.

It gives more consistent result now

The spreadsheet highlights in red when the wing load is above 75g/dm2

Cheers,

Pierre
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Old Aug 29, 2012, 08:06 AM
Registered User
The WALL
Joined Dec 2010
269 Posts
Help

Gday,
I flew my Precision today, full ballast in 23knots(not sure m's that is?)Had the plane working hard for 30minutes or so, untill the right aleron servo went dead on me mid flight!,my first throught was flat battery as this was not my first flight of the day.I battled to pick the wing up and get enough control to fly to the landing zone. Landed with no damage.I walk up and had a quick look and yes right side ron was dead. Took RX out, and wiggle with wiring, with no success still not working? 10mins later at the car I removed the wing then put wing back on and now it works ?

Do theses MKS servos over heat?
I have 5 cell battery.
This servo was "jumping" abit form new.
I have a clean wing, no servo holes.
This has rattled me for next comp in 2 weeks.
I came very close to loosing model.

Any thoughts ?
Chad M
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Old Aug 29, 2012, 08:26 AM
Ja9
Registered User
Norway, Rogaland, Tjelta
Joined Dec 2004
161 Posts
23knots = 11,8m/s

I dont think the MKS servos like a 5cell battery to without any type of regulator.
This is clearly stated on the MKS homepage:
please use 4S Nicd/NiMH or use UBEC @ 4.8V~5.5V
Not sure if this is the problem with your servo.
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Old Aug 29, 2012, 11:55 AM
MCS / NCSS / SVSS / LSC / SAM
David Olson's Avatar
United States, CA, Santa Rosa
Joined Jun 2010
1,960 Posts
Chad:

MKS is the only servo that can not handle an unregulated 5 cell pack. All others seem to be able to handle 6 volts just fine. I believe MKS's specs state nothing over 5.8 volts. What seems very misleading is they also publish torque ratings for 6 volts.

If you want to run a 5 cell pack you must run a regulator at least on the MKS servos.

I have been following this thread and is where I discovered this information:

http://www.rcgroups.com/forums/showthread.php?t=1554075

Nice job getting your plane back by the way.

Dave
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Old Aug 29, 2012, 12:40 PM
War is over (if you want it)
vespa's Avatar
Thousand Oaks, CA
Joined Mar 2004
2,665 Posts
I've seen people show up at the field for a maiden and have 6125 servos start failing before they can even get the plane airborne. They absolutely do not survive anything over 4sNi.

I'm surprised it was your aileron though since that servo gets the lowest voltage. Usually it's the fuselage servos that fail first, followed by flaps of course. I'd guess you have non-MKS servos on the tail and little/no flaperon coupling. Your aileron servos may be on borrowed time now -- I don't know of any thermal shutdown safety feature on these servos, I think they usually just work until they fail.
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Old Aug 29, 2012, 03:57 PM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
21,855 Posts
Knock on wood, I have had (2) 6125's [Flaps] and (2) 6125H's [fuse] in my 4.0 Xplorer since day one on 2S unregulated LiFe....
I think a lot has to do with the load on the linkages.
I have 2, maybe 3 seasons on the Xplorer, flown almost every weekend for about an hour per session.

R,
Target
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Old Aug 29, 2012, 04:45 PM
War is over (if you want it)
vespa's Avatar
Thousand Oaks, CA
Joined Mar 2004
2,665 Posts
Wow! Yes of course it's greatly dependent on the loads and friction but still, I hope you have a v-tail!
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Old Aug 29, 2012, 04:45 PM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
21,855 Posts
Nope.
Cross tail.
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Old Aug 30, 2012, 02:18 AM
4 wheels move a body; 2 a soul
Saratoga, Ca
Joined Feb 2004
1,462 Posts
Im not overly happy with one of my new MKS servos in my Precision, it too has "jumped" around from day one. Flap servo, 4.8v. I worry about these servos on the tail surfaces as well.
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Old Aug 31, 2012, 07:25 AM
Registered User
The WALL
Joined Dec 2010
269 Posts
Guys I will be replacing the 5cell down to 4 Plus checking the plugs again.


Heres my Precision at a F3Fcomp, cranking!
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