Futaba S. Bus (S. Bus 2) Setup question.

[econpatric]

Alright, so these questions may have been covered in other forums or websites, or may also be elementary in nature, but what I'm looking for is a sort of Futaba S.Bus setup discussion that can be a reference for not only me, but others in regards to setting up multiple servos per surface/airplane on a Futaba system. I have watched this video through, but am looking for real experiences to help me wrap my head around this kind of setup.

Over the course of the last year, I have been drooling over the 104" AJ Slick. Sooner or later (hopefully sooner) I will be pulling the trigger on this plane and a DA-120. As I started to sift through the various photos spread over the net I found one of Joe Smith's 104" rocking a whopping 3 servos per aileron. (Joe or Jim: I was just watching the 104" at Joe Nall video and it seems there are only two servos per aileron. Where you guys running 3?) I know there are other airframes, but I would like to zero in on this plane for these questions.

Lets assume I have the Futaba BLS-172SV servos, the R6208SB and all of the necessary cordage required for the rx to servo setup.

I also have begun to add up the costs involved in putting this kind of airframe in the air and I am looking for an economical but powerful solution. I don't want to skimp, but I also don't want to go overboard to make this plane functional and powerful. In addition to the S.Bus equipment, can someone give me a list of necessary equipment required to put a plane of this size in the air? Would I be better off to stick with a conventional setup?

So the big questions are:

• Do I really need three servos per wing?
• If I'm using the S. Bus system do I really need a Smart Fly setup or expander type setup?
• Can I program the servos in a way, through my 8FG Super, that will allow for 3 servos in tandem on an aileron?
• What kind of power is needed to run these servos on the S. Bus system, and how many leads need to be plugged in for this to run efficiently?
• Financially would I be better off to stick with a conventional servo setup?

 

[teookie]

I put sbus in a 100cc Sbach last year. Unfortunately I lost the plane after just a couple flights due to servo failure, but for what it's worth, here is my rcgroups blog post about how I did it: http://www.rcgroups.com/forums/showthread.php?t=1622890

 

[teookie]

In response to your bulleted questions:

Do I really need three servos per wing?
Some people using 7955's have gone to 3 per wing. Supposedly you won't notice a difference between 2 per wing or 3 per wing unless you do lots of full throttle rifle rollers and such. If you use BLS152's or equivilant you are good to go with 2 per wing. Also if your more of an average pilot you'll be just fine with 2 per wing (If I was building a new 100cc plane I would have no reservations putting just 2 7955's per wing.)
If I'm using the S. Bus system do I really need a Smart Fly setup or expander type setup?
The power distribution and battery share features of the smartfly board would still be useful on a sbus system. You would not necessarily need/want to use the feature that lets you drive multiple servo's from one reciever channel, however.
Can I program the servos in a way, through my 8FG Super, that will allow for 3 servos in tandem on an aileron?
Yes. Using Sbus allows you to use all 14 channels in your radio so that every servo gets it's very own channel. Makes programming ganged servo's a piece of cake since you do it all with end points inside your radio (no external programmers).
What kind of power is needed to run these servos on the S. Bus system, and how many leads need to be plugged in for this to run efficiently?
Plan on 4 amps to each servo. This is where the current crop of sbus connectors falls short IMHO. I wound up using a DIY approach to wiring on my plane.
Financially would I be better off to stick with a conventional servo setup?
Most likely, yes.

 

[djmoose]

Remember, you can use SBUS servos like regular servos. I love them for their programming features...especially programming them directly with the 14SG.

I have them in two planes and I'm not using the SBUS system (with hubs and such) (But I have programmed them all)

 

[econpatric]

I put sbus in a 100cc Sbach last year. Unfortunately I lost the plane after just a couple flights due to servo failure

Thanks so much for all of your input. So if I understand correctly the three servos per wing is over kill for typical 3D, but necessary for extreme maneuvers?

I will read through that blog. I'm sure you state why the plane was lost, but I am wondering, did you find out what caused the servo failure?

 

[econpatric]

Remember, you can use SBUS servos like regular servos. I love them for their programming features...especially programming them directly with the 14SG.

I have them in two planes and I'm not using the SBUS system (with hubs and such) (But I have programmed them all)

Thanks for chiming in here Moose! Just curious with the S.Bus servos in hand why you haven't hooked them up the S.Bus route?

 

[teookie]

I will read through that blog. I'm sure you state why the plane was lost, but I am wondering, did you find out what caused the servo failure?

It seems that I just was unlucky. I shared all my set up info with futaba support to see if they could spot any problems but they said it all looked good. I even sent them my custom wire harness and my RX so they could look it over and they said there was no problem with it. Once they got the failed servo they determined that the amp board was bad and sent me a new one. So the servo I was using was just bad out of the box. If only I had exercised it enough on the ground before flying it I might have found the problem sooner and not lost my plane. Oh well.

 

[djmoose]

Thanks for chiming in here Moose! Just curious with the S.Bus servos in hand why you haven't hooked them up the S.Bus route?

The main reason is that I want each servo to have it's own power line from the power bus. (whether it's a distro board or a custom harness)

Second of all, I think 8-9 servos is the boarderline where SBUS gives you an advantage...any less, it's not worth it (IMHO) and any more...it probably IS worth it.

Lastly, I think the big advantage (no pun intended) is when you have huge models...especially large turbine jets....or even scale planes with a lot of extra stuff like nosegear steering, dual ailerons and flaps, airbrakes, thrust vectoring, etc etc. Or something like Mac's huge B-29....having a hub in each wing and one or two in the tail...that can make things a lot easier,neater, and probably save some weight.

 

[SnowDog]

Guys this is a really great discussion on S-Bus, thanks!