Skywalker 168cm FPV plane - Page 1057 - RC Groups
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Oct 09, 2012, 08:02 AM
Crash=start of next project
CN I Dawg's Avatar
Quote:
Originally Posted by Cathay Stray
I'm slowly moving along assembling my SW

Never had a need to use BEC before but it seems like a commonly accepted thing that a bird as fat as a SW should be equipped with a BEC...

Now, I am going to use 4S setup with a 60A ESC (or 80A if 60A gets alarmingly hot during tests) and a bigger motor that together with a 10*6 prop will draw about 40A at 80 %.
ESC has a built-in switching 3A BEC.
4 digital servos + currently 1, later 2 analog servos for camera control.
Camera and video Tx are going to be fed from a separate 3S battery.

Do I really (really-really) need a 5A BEC for the servos only?

I do have it already, so it is not a question of money. I just see no point in adding an extra piece of equipment. People usually say, we might need BEC in case the ESC fries, but in my setup ESC will have more than enough power (and if I go for an 80A one it might only get slightly warm at all).
I'm a fan of less is better and use an ICE 50A with its internal 5A BEC on a 3S setup. That said, to be sure, you should measure your current in a worst case scenario. Some digital servos consume a moderate amount of current and 3A may be on the edge or create a "brown out" situation.
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Oct 09, 2012, 08:13 AM
Crash=start of next project
CN I Dawg's Avatar
Quote:
Originally Posted by tom3holer
Hi,
Dumb question sorry. Just putting my SW together. I guess its a version 3 from what I can tell.
Bought it about a year and a half ago.
I have 6000Mah 4s I am planning on using along with a 2200 ish 3s. Just for rough planning purposes where will I be placing the batteries to achieve proper cg?

Thanks,

Tom
Tom, not being a wise guy but in the front. It's the only real place with room for the 6,000 mAh 4S. Just a note, your AUW is going to be really high. >800g for batteries alone. Be sure to re-enforce the wings and use an appropriate propulsion system.
Oct 09, 2012, 08:24 AM
An Aussie in Chicago
Quote:
Originally Posted by ffinybryn
Further to earlier posts, I also made the mistake of not fixing the motor well enough. With disastrous results!! I was able to glide to land with the prop embedded in the rear.

Repaired with expanding foam. Motor fixed to ply with 50mm bolts extending into fuselage (and plenty of epoxy). Good as new...
Nice paint job. What type of expanding foam did you use if you don't mind me asking.?.
Oct 09, 2012, 12:12 PM
I tell her RC is cheap !
carguy1994ca's Avatar
Quote:
Originally Posted by hendrnk
Nice paint job. What type of expanding foam did you use if you don't mind me asking.?.
+1 ! Awsome looking SW
Oct 09, 2012, 12:24 PM
Mini Obsessed
Shadrack's Avatar
Group answer on a few posts.
Use a BEC.
You are putting a lot of amps through your esc. If that goes, then a good chance that SBEC whether it is 3 or 5 amps goes.
I can deal with no motor, but I can't deal with no servos, or in some cases, no autopilot (FY31).
I use a CC BEC that is 10A and it is almost nothing weight wise.

As for the extra battery. As Sander has said numerous times, go with a single battery solution, especially since you will have a 6000 mA battery, you have a lot.

Great paint job on that SW BTW.

Hey, CG, when I fly around my flat lands, at least I know that those flat lands still want to belong to Canada.
Oct 09, 2012, 12:48 PM
I tell her RC is cheap !
carguy1994ca's Avatar
Quote:
Hey, CG, when I fly around my flat lands, at least I know that those flat lands still want to belong to Canada.
And you said it flat out to me
Oct 09, 2012, 12:54 PM
Mini Obsessed
Shadrack's Avatar
I did. there wasn't any separation.
Oct 09, 2012, 04:12 PM
Cape Cod
tom3holer's Avatar
Thanks guys, Another dumd question. I have the need for 5V for the OSD and servos and also 12v for the Vtx. Do the BEC's come available with dual voltages?

Tom
Oct 09, 2012, 04:23 PM
Mini Obsessed
Shadrack's Avatar
I have not seen that. You can just take the feed off your battery and step it down to 12V for your camera using a step down, and use your BEC for the 5V needed.
Alternatively, a 5V camera to keep everything at 5V. (This is how I did it)
Thirdly, you could step up the 5V to 12V for the camera but that isn't a suggested way.
Oct 09, 2012, 04:33 PM
Registered User
muduck's Avatar
Quote:
Originally Posted by tom3holer
Thanks guys, Another dumd question. I have the need for 5V for the OSD and servos and also 12v for the Vtx. Do the BEC's come available with dual voltages?

Tom
Twin leads from battery..one to BEC, & the other straight to the VTx
Oct 09, 2012, 04:36 PM
Capital Knockers!
subsonic's Avatar
Quote:
Originally Posted by tom3holer
Thanks guys, Another dumd question. I have the need for 5V for the OSD and servos and also 12v for the Vtx. Do the BEC's come available with dual voltages?

Tom
They sure do! 12V on one side, and 5V on the other!
Oct 09, 2012, 04:45 PM
Capital Knockers!
subsonic's Avatar
Quote:
Originally Posted by Cathay Stray
I'm slowly moving along assembling my SW

Never had a need to use BEC before but it seems like a commonly accepted thing that a bird as fat as a SW should be equipped with a BEC...

Now, I am going to use 4S setup with a 60A ESC (or 80A if 60A gets alarmingly hot during tests) and a bigger motor that together with a 10*6 prop will draw about 40A at 80 %.
ESC has a built-in switching 3A BEC.
4 digital servos + currently 1, later 2 analog servos for camera control.
Camera and video Tx are going to be fed from a separate 3S battery.

Do I really (really-really) need a 5A BEC for the servos only?

I do have it already, so it is not a question of money. I just see no point in adding an extra piece of equipment. People usually say, we might need BEC in case the ESC fries, but in my setup ESC will have more than enough power (and if I go for an 80A one it might only get slightly warm at all).
In my experience, I've been able to have 4 digital servos bring in internal BEC voltage down to brownout levels a few times in flight. Granted, it was in 3D planes, but from then on, I've always used a BEC as soon as I run 4 digital servos or more on one system.

I'd say there is no "really-really need" level, but in your system, given that you run 4S, (higher input voltage and more load on the BEC), have 4 digitals + others for pan / tilt etc, If it were mine I would definitely add one to allow you some system headroom.

Also, with the decision to go with a 60A or 80A ESC should have almost nothing to do with the outside temperature of the ESC. You should go by the current draw first and foremost. Do you have a meter? Stay within 80% of the ESC's rated capacity and you're golden.
Oct 09, 2012, 04:48 PM
Cape Cod
tom3holer's Avatar
Ok, If I am going to use one battery, a 4S as mentioned earlier, then I need to step it down to 12V for the Vtx and camera and the 5 v I can get from a seperate BEC. The question is how do I get a reliable 12v in that type of setup?
Oct 09, 2012, 05:02 PM
Kostas
kstmark's Avatar
Quote:
Originally Posted by tom3holer
Ok, If I am going to use one battery, a 4S as mentioned earlier, then I need to step it down to 12V for the Vtx and camera and the 5 v I can get from a seperate BEC. The question is how do I get a reliable 12v in that type of setup?
Use a separate 12v battery for the vtx. There is always noise from servos and motor and you want yours vtx supply to be clear. SW can easily handle the weight of a 3s 800mah battery for the vtx
Oct 09, 2012, 05:37 PM
Mini Obsessed
Shadrack's Avatar
got to disagree kstmark.
even the guys that build the stuff say one battery.
extra weight, and if you build a small lcfilter, you can clean up the power perfectly. I have no noise at all and run a one battery system.
To me, I would just get a good 5v camera, I use a 600 line rmrc wdr and it is great.
Cost me 100 bucks, but love that my system runs very efficient, I see my amp usage as a total of servos, camera, motor, and osd/receiver.
My current sensor feeds 12V to my vTx, which gives 5V to my camera. I have an LC filter on the power from the current sensor to the vTx.
Have no noise at all.
I plug in one battery.
I can hold altitude at about 40 kph and 4 amps into a slight wind. That is 4 amps total including my osd, autopilot, limited servo use, 600mW vTx, and uhf diversity receiver. Plus the camera, and 2 servos for pan and tilt.
Still have rssi values in the high 60's and low 70's at 3km away.
Love this setup.


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