New model - Pike Precision F3B / F3F - Page 51 - RC Groups
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Aug 24, 2012, 05:49 AM
Registered User
prondel's Avatar
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 ...


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Aug 24, 2012, 06:33 AM
satinet's Avatar
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.....

Last edited by satinet; Aug 24, 2012 at 07:14 AM.
Aug 24, 2012, 02:25 PM
Registered User
Alvaro Silgado's Avatar
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)


Last edited by Alvaro Silgado; Aug 24, 2012 at 05:17 PM.
Aug 26, 2012, 12:22 PM
Registered User
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.
Aug 26, 2012, 10:15 PM
closed due to popular demand
Last edited by ibuild; Oct 19, 2013 at 05:03 PM.
Aug 29, 2012, 07:27 AM
Registered User
prondel's Avatar

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


Last edited by prondel; Aug 31, 2012 at 08:08 AM.
Aug 29, 2012, 08:06 AM
Registered User


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
Aug 29, 2012, 08:26 AM
Registered User
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.
Aug 29, 2012, 11:55 AM
David Olson's Avatar

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:

Nice job getting your plane back by the way.

Aug 29, 2012, 12:40 PM
vespa's Avatar
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.
Aug 29, 2012, 03:57 PM
Detail Freak
target's Avatar
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.

Aug 29, 2012, 04:45 PM
vespa's Avatar
Wow! Yes of course it's greatly dependent on the loads and friction but still, I hope you have a v-tail!
Aug 29, 2012, 04:45 PM
Detail Freak
target's Avatar
Cross tail.
Aug 30, 2012, 02:18 AM
4 wheels move a body; 2 a soul
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.
Aug 31, 2012, 07:25 AM
Registered User
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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