3D Hobby Shop 85" Katana - Assembly Thread

[sukhoi26mx]

Thanks Don! The credit for all of the hard work goes to Ben - I just get to have most of the fun. Seems like a good trade off to me! (just kidding Ben)

With the iron still hot, I prefer to go ahead and relieve all of the remaining covering holes required to mount the servos, wing tubes, stab tubes, etc...

Scott

[sukhoi26mx]

To ease the work surface a little, I prefer to get the model up on its gear as soon as is reasonable, so on to the landing gear. We used an aluminum landing gear on the Katana, so I'm sure there is a carbon gear that would fit and save even more weight. We include the axles, wheels, and collars in the kit. Be sure to space the axle off the hub enough to allow clearance to slide the pant on from the top.

Scott

[sukhoi26mx]

More landing gear. Unlike some ARF kits, we decided to tie the landing gear plate into the surrounding structure with aluminum angle stock. One side is preattached, and the other atttaches with washers and self-locking nuts through the aluminum landing gear plate and gear block. Access is through the pipe tunnel. This allows for an easy install that is also very strong and durable.

Scott

[sukhoi26mx]

... and from the inside with everything tightened up. This is probably best done with two people, but can be done with just one once your fingers adapt to the task.

Scott

[sukhoi26mx]

The stock axles are slightly too long to fit cleanly in the wheel pant, so they need trimmed. I used the cutting wheel on my Dremel tool. Be sure to use Loctite on the wheel collars. I also take the time to grind a flat spot on each axle for the collar set screw to ride on.

Scott

[sukhoi26mx]

The wheel pants are next.

Our pants are a very simple but light fiberglass pant with a preinstalled ply mounting plate and blind nut. I prefer to have my pants removable, so we'll need to router out a slot for them to drop over the axle hub. At some point, we hope to have this step completed at the factory, but the first run of models doesn't have this completed.

First, I marked an approximate slot based on the predrilled center point. Then, I used the Dremel cutting wheel to cut along the marked lines.

Scott

[sukhoi26mx]

In a perfect world, we'll use both friction from a tight fit of the pant over the axle flange in addition to the wheel pant set screw to hold the wheel pant both tight and in the correct position. Be sure to align the wheel pant hex flange vertically. Then, taking your time, slowly router out the slot with the small Dremel sanding disc until the wheel pant is a tight friction fit on the wheel axle flange. Secure the wheel pant to the landing gear leg with the included hardware, using Loctite to ensure it stays put.

Scott

[sukhoi26mx]

Back to the tailwheel - we use a carbon fiber tailwheel assembly that screws onto the bottom of the fuselage with included hardware. We had the factory preinstall blind nuts along the bottom of the fuse, so locate them first, and melt the covering from the holes with a hot soldering iron.

The tailwheel assembly uses a direct steering wire instead of springs, which I prefer. You'll need to drill and install a pull/pull connector into the bottom of the rudder to act as a housing for the steering wire. I used a 1/16" bit, then threaded the hole by hand. Finally, remove the connector and wick thin CA into the hole. Rethread the connector adding medium CA to help secure the connector in the hole.

Slide the tailwheel steer wire into the connector, and fasten the carbon tailwheel assembly with the included hardware. Remember to use Loctite on the machine screws.

Notice that the pivot point for the tailwheel is aft of the hinge line for the rudder. While some may prefer the two hinge points to line up, having the tailwheel pivot aft of the rudder hinge dramatically increases the tailwheel deflection for a given amount of rudder deflection. You won't run out of steering effectiveness with this setup!

Scott

[sukhoi26mx]

Let's set the fuse aside and focus on the wings for a bit.

I generally start by securing all of my extensions. You'll need 18" for each wing servo. I prefer safety wire, and simply wrap the two extensions, snip, and fold the excess away.

Scott

[sukhoi26mx]

I chose the Hitec 5955TG for all surfaces (great servo!), but we recommmend at least 150 oz./in. metal geared servos. We also include pull strings in each wing panel for easy routing.

Scott

[sukhoi26mx]

Secure the servos in each pocket and center the servo electronically. To avoid having to power the receiver, I use the Hitec programmer.

All of the ball links and hardware are included and individually packaged.

Scott

[sukhoi26mx]

With the servo centered, secure the ball link to the control horn and servo, adjusting the ball links evenly on both ends to center the control surface. The correct sequence for the hardware is screw, washer, phenolic, ball link, phenolic, washer, and self-locking nut. Be careful to fully but not overtighten the hardware.

Once fully assembled and centered, secure the servo arm with the servo screw. Rather than use Loctite on these screws, I prefer to use silicone on the screw head. The silicone will prevent any vibration related loosening without adding a chemical based locking compound into an electronic component.

Scott

[sukhoi26mx]

Next in line is the rudder rigging. I prefer to do the rudder pull/pull before attaching the stab/elevator halves as I have more room for my unruly hands.

Same sequence for the ball links on the rudder control arms.

Scott

[sukhoi26mx]

While back at the tail, I attached the pull/pull lines. There are a lot of diffferent opinions on the correct sequence for this step, so I'll add that this is just my technique. I prefer to use two crimps per surface attachment at both the servo and rudder. I've always had a time trying to get the line tight and also run through the initial link a second time. Instead, I tighten and crimp the initial crimp, then run the second crimp doubled. This is especially helpful when rigging the final two crimps while setting tension.

Scott

[sukhoi26mx]

Back in the fuselage, I installed the rudder servo and attached the large stock Hitec dual arm on the servo with the proper ball link and pull/pull hardware attached.

Scott