How to Calculate a set up for F5J and FXJ (heihgt limited) - RC Groups
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Mar 15, 2010, 08:35 AM
the answer 42 is
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How to Calculate a set up for F5J and FXJ (heihgt limited)


Hello Everybody

I hope this is the right forum for this question. I had been flying electrics for quiet a while and I had been looking for a category that fit my interest (and budget). I was very ineterested on F5B but the costs are a limiting factor for me, at the moment I just cannot afford it. Just by coincidence I came across with the F5J (http://f5j.eu/rules.php) and FXJ (http://www.rivamodels.sk/FXJthread/FXJ09_5.html) categories and they inmediately caugth me.

I was cheking the rules and the outrunner category proposes:
Outrunner
◦ outrunner with 28x26mm outside dimensions, 22x9mm stator dimensions, direct drive,
unmodified (must conform to factory spec) (http://www.hobbycity.com/hobbyking/s...idProduct=5655)
◦ power source 2x LiPO
◦ smallest propeller diameter is 250mm (10")
◦ minimum model weight 500g

As you can see the motors and set up are in general afforbale, but I would like to know how to calculate the best setup for this category, In general it is requiered to have the plane as high as possible in max 60sec or 30sec in FXJ.

And I wanted to know if there is a way to calculate if a certain setup will take the plane to the optimal height?? in roder to check different possibilities. and how to calculate this setups in general,

thanks in advance for your help and input.

EZ
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Mar 15, 2010, 09:04 AM
Registered User
Hi EZ,

The best publicly known setup seems to be Axi2208/20 (18w is being tested), at least 30A ESC, RFM 10x6, 2S1000+ Lipos of latest generation and also pre-heated before start. However, the season will start soon and I am sure there will be surprises again

Jan
Mar 15, 2010, 10:17 AM
the answer 42 is
Ok so this little motor on 2s Lipo and a 10x6 prop can put in competitive height which plane?? 2 meter?? 3 meter?? Balsa build up or Full Composite?? how heavy the plane can be??

Thanks a lot for helping this courisious and everasking newby

EZ
Mar 15, 2010, 10:35 AM
Registered User
EZ,

1.5-2.3 m, 500-650 grams, rate of climb 8-12 m/s, maybe more. You may see http://lmk.polanka.cz/image-gallerie...dely-rcek-2009 for last year's models, also see http://f5jfun.com/e107/news.php (perhaps use the googletranslate button in top right corner) for pictures from the events.

Please note that F5J Euro is a variable motor run variety, so it is up to the pilot to decide when to switch off. The motor (single) run time is then deducted from the flight time.

Hope this helps.

Jan
Mar 15, 2010, 04:08 PM
the answer 42 is
Dear Jan

thanks for the input, I am new on this category so I am trying to learn and understand what it is all about, it is fun everyday I found something interesting. I never thought that such small motors running on 2s bateries could bring up a big 2m plane.

I will start soon building my BOLERO, was shipped today and I can barley wait to have it .

EZ hooked up with F5J and FXJ
Mar 16, 2010, 10:12 AM
the answer 42 is
Ok I found the solution, well partially, using motocalc I can get a pretty good prediction of the performance of the set-up. But still I woudl like to find a way to calcualte if a given set up will bring the plane to the desire altitude (e.g 200meters) on the time provided (30 secs). Any ideas???

EZ
Mar 16, 2010, 01:20 PM
Registered User
EZ,

Congratulations on the BOLERO, it is a great model.

Doesn't Motocalc return also the estimated climb rate?

For estimating a climb rate I use a following "thumb rule" formula:
climb rate [m/s] = input power [W] / model weight [kg] / 10 * efficiency

This efficiency is usually around 0.35, for heavily overloaded motors could drop to 25%, for geared motors could reach 50%. For the SOR drives defined above you may take 0.28 as a reasonable first estimate.

Jan
Mar 16, 2010, 03:01 PM
Registered User
Neil Stainton's Avatar
EZ, this thread should help:
https://www.rcgroups.com/forums/show....php?t=1150155

Neil.

Quote:
Originally Posted by Edwinzea
Ok I found the solution, well partially, using motocalc I can get a pretty good prediction of the performance of the set-up. But still I woudl like to find a way to calcualte if a given set up will bring the plane to the desire altitude (e.g 200meters) on the time provided (30 secs). Any ideas???

EZ
Mar 17, 2010, 04:46 AM
the answer 42 is
Thanks Neil, very handy I cannot get the Rate of climb column on my report?? Maybe is because I jsut have the demoa version??

EZ
Mar 17, 2010, 06:10 AM
Registered User
Neil Stainton's Avatar
You have to select that column in the Options dialog.

Neil.

Quote:
Originally Posted by Edwinzea
Thanks Neil, very handy I cannot get the Rate of climb column on my report?? Maybe is because I jsut have the demoa version??

EZ
Mar 17, 2010, 06:59 AM
the answer 42 is
I did that already and does not work :P
Mar 17, 2010, 07:37 AM
Registered User
Neil Stainton's Avatar
What exactly goes wrong? Can you post a screen dump of your Static Analysis form?

Quote:
Originally Posted by Edwinzea
I did that already and does not work :P
Mar 17, 2010, 07:59 AM
mostly gliders
liukku's Avatar
Hello
I belive Edwinzea just have one prop size and not a wide range as you Neil suggested, then he will get only "in-flight analysis"

/Ville
Last edited by liukku; Mar 17, 2010 at 08:06 AM.
Mar 17, 2010, 08:55 AM
the answer 42 is
I got it now :P the results are not so promising though :P

thanks for the input
EZ
Mar 17, 2010, 09:00 AM
mostly gliders
liukku's Avatar
Hej EZ
Tell us about the result. Always good to know what the opponent will fly.

/Ville


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