The Return of the TigerKitten (12)

Get yer pants on! The TigerKitten as presented in the Premier Balsa kit uses wheel pants derived from the original molds I made over twenty years ago. For a time I was offering molded fiberglass pants for sale on line, but those are no longer available. The Premier short kit includes vacuum formed moded plastic wheel pant halves, which the builder…that’s you… gets to trim out, fit and assemble. There’s no process I’m aware of to make parts like this as a single component, and including pre-assembled pants in the kit would cost far more than you’d probably be willing to pay. So…here’s a quick course in doing molded plastic wheel pants. This technique should apply to any molded wheel pants you might encounter in other kits as well.

My pre-production kit included a sheet of plastic bearing all four half-pants in a single matrix. Here I have already rough-cut each half free, just a bit oversize. You get two left and two right halves...this is how they'll fit together.

These moldings are drawn really deep...there's nearly half an inch of plastic extending past where each molding must be cut to fit together into a wheel pant of the correct width. Compare the part in my hand in the previous photo to the one I'm trimming here. Mark a line in pencil or with tape so you know where the cut needs to be, then trim the excess plastic away. Here I'm using short, curved-blade snips (scissors) from the hobby shop that are ideal for jobs like this.

A big sanding block is the best way to square off the trimmed face of each part. Here I have taped a sheet of 80 grit production paper flat against my work surface to ensure cutting a true joining face onto each half of the wheel pant assembly.

This is how the trimmed halves of each wheel pant are supposed to fit together. You can see the smoothly rounded front in the previous photo; this is how the rear end should look...just rounded off, not a sharp point and not "wide and clunky" the way it would look if you hadn't trimmed and sanded away enough of the matrix.

When each wheel pant half is cut to the correct shape, we need to mark where the opening for the wheel is going to be cut. This has to happen next, as we can't get inside the assembly to join the halves without an access hole.

Those curved snippers are just right for roughing out the wheel opening. Don't cut too deep!

I used a coarse rotary cutting bit in my drill press to clean up the wheel opening. I prefer this to using a hand tool, such as a Dremel, because I can depend on the solidly mounted power tool to be exactly where I expect it to be while I use two hands to guide the workpiece. (Yeah, you noticed that the tool is turned off...I'm using my right hand to hold the camera just now!)

With the wheel cutouts made, I joined each pair of halves into a complete wheel pant using masking tape. At this point the left and right assemblies are identical.

There are a number of ways to join the halves. On this airplane I'm depending on a generous bead of SLO ZAP flowed into the inside of the assembly. I then rotated the part to let the heavy, wet bead flow along the entire length of the inside seam. When it had spread out evenly I gave it a shot of Zip Kicker. On a bigger, heavier model or one intended to be flown from rough fields I'd have included a narrow strip of fiberglass cloth along the seam, saturated with more ZAP. Since I have the luxury of flying from well tended grass fields I elected to leave that out to save a little weight. (Post-flight report...it works just fine this way.)

You can just see the cured SLO ZAP filling and bonding the inside seam. There is still some trimming left to fit the cutout neatly to the wheel.

When finishing cutouts like this one, at some point I like to go from the power tool to a hand-held sander in the interest of precision and caution. This is one of my favorite tools...a piece of production paper of the appropriate grit wrapped around a tube or dowel or bottle that happens to be the right size for the job at hand.

Sanding the outside of the seam is less intricate, but it's just as important. This is 80 grit autobody abrasive on a block. At this point you need to sand until the only sign left of the joint is the rough place where it used to be... then you switch to finer paper and sand that away. Joint seams on the outside of finished wheel pants are a sign that somebody forgot to learn about patience back in kindergarten.

I messed up and lost the image that I wanted to show you here, illustrating a piece you can now barely see as it was being assembled. There's a lamination, or backing plate, of 1/16" plywood about 1 1/4" square inside the face of the wheelpant where it's going to mount against the landing gear. With that in place I marked the opening that will allow the assembly to slip into place over the assembled wheel and went back to the drill press to cut it out.

This is the landing gear, with the axle and wheel in place, over which the cutout I just made is going to fit. The little rectangular aluminum mounting plate is made per the plans, drilled, and captured by the axle nut against the gear leg.

Just so I can say I showed it to you, here's the same wheel and axle assembly from the other side. On this little airplane the outer face of the wheel pant will float free over the axle end and wheel collar.

The assembled wheel pant is held in place with masking tape in exactly the position I want it to be mounted.

I used a soft pencil to mark through the holes in the mounting plate onto the face of the wheel pant to locate drill hole locations.

While you weren't looking I drilled the holes in each pant assembly to accept this 2-56 tap. Those short litle 2-56 cap head screws will go through the mounting plate and lock into the the threads I'm cutting now. This saves messing with separate 2-56 stop nuts inside the wheelpants, where they are hard to get to when the screws get loose. (In real life, once I'm satisfied that the pants and wheels won't have to come off for a while I'll put a drop of light LOCTITE on each screw.)