I'm reposting this because s/how my photos got messed up.
Thx.
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Hi Guys,

I wanted some experienced advice on servo placement on a Four Star 120.

I will install a separate "rack" for the throttle servo, towards the nose of the plane. And I guess I need an extra servo for cut off on the engine?... ( Don't I?)
I think I'm okay there cause I need to be 12" back from the engine and I've got 13 or 14 inches to work with. (a BCMA 26cc gas).

I'm waiting to receive most of the hardware I'm going to need from Tower Hobbies in the mail, sorry I only had 1 spare servo for the pics.

I know s/one will ask me what servos I'm using so I may as well tell you now. I also ordered 4-40 size hardware, and heavy duty kwik links & hinges, control horns etc.
I'm kinda guessing at some of what I need, but I think I got it covered.

In the pics: I want to use the two outside servos for th elevator & the one in the center for Rudder.

I drilled holes to give myself a straight line already through the fuse, and carved out one of the Kit cutouts to feed the pushrod through the side.

Is it okay to mount my servo horn this low on the rudder? I could go a little higher w/ a little more work.

For the Elevators (& 2 more for the ailerons): 2 @ "Tower Hobbies TS-64 Servo High Torque Standard 2BB U" . These are 83 oz. Each @ 6V

Here's the link:

<http://www3.towerhobbies.com/cgi-bin...LXHHW0&P=K>

For the Rudder:
1 for the Rudder : Tower Hobbies TS-70MG Super-Torque 2BB Servo U. This one is 133.3 oz. @ 6V

Here's the link:
<http://www3.towerhobbies.com/cgi-bin...LXANT5&P=K>

I've seen other set ups w/ the servos in the tail. I much prefer to have the servos hidden inside the plane.

I'm also going to modify the size and shape of the elevator and rudder. (Looks more like a Super Sport when it's done!)

Tell me what you think.

Thanks,

Dan

It looks fine to me! Rudder horn that low, no problemo. Good luck!

dont mount them that way, your push rods are to long, way to long, mount your servos on the fuse to the back, wear the cut outs are fill them in and mount everything there

Why use dual elevator servos? Just curious since the design only calls for one.

Check it to make sure you have clearance for however the tail wheel is mounted. You don't want the horn's bolt(s) trying to pass through a piece of music wire or other hardware bedded in the rudder.

They don't look too long to me... I've never had a problem with long pushrods as long as the outer tube is glued to the formers and/or supported as much as possible down the length of the fuse so they don't flex under pressure. Pull-pull would be even better, easiest to do just the rudder as pull-pull though.

I agree about 2 elevator servos... Unless you think you'll need both of them, one with a split connection to two pushrods would work nicely. You can build your own (download the GP super skybolt manual, there's a technique laid out in there) or buy one: http://www3.towerhobbies.com/cgi-bin...?&I=LXBWL8&P=7

Thanks guys,

Yes I plan to support the tubes at each former w/ a small brace w/ holes drilled to feed it through & epoxied at each .

Second, I'm adding an extra servo to the elevator because I plan to increase the size and shape of the Rudder & Elevators. (Will look like the tail of a Super Sport)

I saw it on another thread here, I wish I could say I thought of it. But this is my first plane kit.

I wouldn't think long push rods would be a problem, ( as long as they're straight, supported etc.) why would they make them 48" long if they didn't work? No offense meant.

Thanks for the tip on the L/gear too. I may buy a leaf-spring tail wheel assembly. So the gear would be mounted into the fuse,....right ? with T-nuts I guess. Sound good?

Thanks for all the help guys, much much appreciated.

Dan

P.S. The link for that part from Tower Hobbies is DISCONTINUED.

I love digital cameras, what a great help to post photos!

They made the YUGO, that sort of worked too.

The dual servo idea is not a bad one but you really need to be anal about matching up those servos. They have to travel the same distance and at the same speed. The least difference and your going to have a plane that will be very difficult to control.
Even with the enlarged control surfaces a decent single servo will cost you no more than 2 less expensive servos and will handle the job just fine without the headaches of trying to match up dual servos and be much more reliable. My rule in KISS it. Keep it simple.

Thanks tstotts,

I'm def. reconsidering the dual servos . I was a little concerned about even pressure on the elevator too. Tower Hobbies shorted me on 2 servos on my order anyway. Maybe I'll cancel one. I have more odds and ends to buy anyway.

Like I said above, this is my first plane kit, (my second Kit if I can count pontoons) so I am very open to suggestions.

By the way here's a link to a You Tube video of my pontoon build if you guys want to see.

http://www.youtube.com/watch?v=3JpgePMLAI4

Thanks,

Dan

Your 120 is A big plane and designed for stunts. With two elevator servos you can match the travel using your radio and A degree meter, I make my own meters. With two back there you can keep your control rods short and close to the controls, that makes them stronger and easy to adjust. When you trim your plane you can adjust the throws with your radio so your plane will loop and not roop. If you kill A servo you still have an elevator working. The reasons for them can go on and on. Another thing to think about is you are installing A nice heavy gas engine. Right up front you know your plane is going to need some tail weight.
The aircraft set up is the most important part of the building next to building straight with correct incidence. Anyone can glue wood and sand.
I always build my plane and while it is in the bones I assemble it. Mount the tank over the CG and only install A servo if it has to be in A certain spot. Then I move all my gear around and hold everything in place with tape until I find the correct CG then hard mount close to those locations.
If you mount your gear now you will be adding lead to get your CG. I know someone has posted A thread on aircraft set up in A build thread someplace on RCU so you may want to do A search. It's the part of building that takes the time to learn. Take A look at some IMAC and 3-D planes or just some good weekend stunt flyers at some local fields and see how it's done. I can't remember the last time I built one of my own planes with less then 6 servos. I'm just finishing up A little SIG Kobra for A friend and customer for racing, as small as this plane is it still has five servos.
Set up makes your plane fly as well as it ever will!!

I appreciate your advice for sure on "pre-installment" of equipment and checking the CG.

Especially since I am also going to be adding a smoke system. So I guess I should fill both fuel tanks during the process of balancing. Never thought of that till just now.

Like I said this my first build.

I read s/where once how to check the CG, w/ a home-made set-up. How about a 2 x 4 with 2 dowels on the ends(rounded off), or w/ a rubber (s/thing) on the ends.? Sound good ? I'll do a search, I'm sure it's in here s/where.

Thanks once again,

Dan

Hi Dan. He said to temporarily install your tanks...but not the liquids! You should always install tanks on or ahead of the CG and always balance dry!

Please take Dan's advice..... ballance dry.... If you can place the smoke tank around the CG point that would be best... as you could end up with a VERY nose heavy model with a combination, gas engine, fuel and smoke all in the nose....

This is a pretty good way to build a CG machine. The "rubber things" my brother used are pencil erasers