The flying monkeys got me...

Helis and fixed wing

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Saturday, April 12, 2014

Skyline/Goldwing Sbach 342 60" Build Day #2

One long build day today! Got the Honey-Do list done this morning, and set to it!

 

Elevator installed. This is a single servo-U Bar system. The elevator servo is attached to the right elevator which it moves directly. The U-bar transfers the movement to the other elevator to which it's attached. One end of the U is in the right elevator, the other in the left elevator. If the elevators are not equally deflected, a roll force occurs as if they were ailerons. The hard steel I think they intended for the U-bar snapped when I shaped it, too brittle, and the softer steel rod (I think intended for throttle control rod not needed on an electric) torqued too much at full deflection. I ended up adding the left over hard steel rod (see below) as an anti-torque bar and it worked it great!

 

 

Clean install, you can see the silver U-Bar.

 


Elevator servo without extension. The aluminum control arm is standard length, shorter than the supplied fiberglass one. Inadequate throws, I mean, good, but not complete. The geometry is off with the servo end below the elevator carol horn.

 

So I modified the setup by laying the fiberglass arm over the aluminum arm.Perfect geometry.

 

 
Side view. Trimmed the screw ends for a cleaner look. Now get full throw range of motion.

 

 
Zaphod, sleeping on the job... Just can't get good help these days.

 

The aircraft, like many, benefits from an underside tail vent opening to improve ventilation across the motor, ESC and battery. I made that opening, and then created a louvre system to direct the air. I had seen this mod on RC Universe on this model and liked the way it looked. I had no idea how to make it but McGyvered a fairly decent set. First made a box that fit in the opening and created a jig for the louvers, cutting guide slits.

 

I added a scoop for the inside tail end to further direct air out the hole.

 

Super glued in construction then coated with alochol thinned epoxy for strength and sealing. I painted it matte black.

 

The vent opening. When I install the louvers I'll post a pic. I used the needle nose pliers to hold the bar in the grooves.

 

The anti-torque bar. I routered out a slot and dropped the bar in there, superglued it, and later coated it epoxy.

 

The other side.

 

In place before the cote covering. It lies parallel to and just aft of the U-bar, so gluing them together increases the support against torque.

 

After I put white cote over it, and voila, can't see nothin'.

 

Rudder and tail wheel assembly. Rudder control horns are fiberglass one piece. I am not fond of tail wheels that put the stress on the rudder and it's hinges. This design mitigates the stress with a sturdy stabilizing platform with three screws and the collar resting on the plate. I had to find an extra collar, there wasn't one in the kit. Went together nicely. I added a piece of nylon hinge material used for connecting the control surfaces across the bar as it goes up into the rudder to provide more support.

 

Sturdy. You can see the hinge material across the landing gear rod on the rudder.

 

 
I went to a lot of trouble to put the wheel pants on the correct sides. Fail.

 

Fixed. That's better.

 

First time resting in all three landing gear.

 

Takes up the whole breakfast table.

 

Rudder servo with the control arm and wire attachments installed. I haven't used aluminum control horns before, worried about fit. I got Hitec C1 21T spline, and they all had to be tapped (lightly hammered actually) to fit. This one went on by hand, snugly. All of the centered nicely without sub trim.

 

I mark the couplings with red Sharpie to show when I reach 50% of the length so I don't weaken the coupling.

 

 
When setting up the rudder pull-pull system it's important to center everything. I locked the rudder.

 

 
Rudder system is complete.

 

 
Looking aft through the fuselage at the pull-pull system. The wires cross to ensure they exit the fuselage aft in line with the rudder control horns. Snug tension, not stressed. I later secured the elevator servo wire to keep it off the wires.

 

The distance from the motor box to the end of the cowl was 113mm. The motor tfrom base plate to the prop rotor base was 60mm. I had to come up with 53mm. I was annoyed, there is nothing in the instructions on this. I remembered there was a bag with a lot of wood frames in it for the gas tank in a fuel model. I opened it to see if there was some wood I could use, and there was a motor box extension of 50mm! I modified it slightly to make it stronger. I was able to put it together and sort out how I wanted to install it.

 

Measure twice,epoxy once. I measured and centered it (the holes for the center were not centered, glad I ignored them). Epoxied into place and added a M4 bolt and self anchoring nut to ensure it never comes off.

 

Perfect fit! I love it when the engineering math works out!

 

Motor installed. Again, perfect fit! Math, baby! The HobbyWing FunFly 80A HV ESC in place. Plenty of ventilation!

 

I was worried that the deck the reciever was on was kinda thin, and it cracked when I pressed the reciever Velcro into place, so I added a piece of thin plywood as a deck, both repairing the crack and adding strength. Spektrum AR600 DSMX receiver. I like to use short extensions for the aileron servos so I don't mess with the reciever.

 

All the electronics in place. Forward the battery leads are lengthened with segments I salvaged from old batteries. The tap for the BEC is up front and the Exceed RC 6V BEC is Velcroed to the bulkhead (it can be seen in the lower right hand corner, forward in the fuse). The ESC has a spark eliminator circuit built into the wiring harness, but it's too far forward so I can't use it

 

I always take the motor stickers off since the heat will make it fall off anyway, and tape it to the firewall.

 

Long but fruitful build day!

 

UPDATE: Installed the louvers. Look better in real life.

 

 

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