KR Progress Report

I'll try to keep this page up to date, but I don't make any promises. Here are some recent pictures of the progress I've made on the KR. If you notice I'm saying "we" a lot instead of "I", it's not because I have a rat in my pocket. There are two of us building our KR's in a shop at my father's farm at Cumby, Texas. Mine is original with retractable gear, his (Curtis Wright) is a fixed taildragger with Dan Diehl's main gear.

Here are my elevators just after I trimmed the extra fiberglass cloth off the edges. Notice the seam in the elvator to the right. I sanded the foam and tried to feather it out to a smooth taper as in the plans, but it just didn't seem to work out. Luckily this is the bottom of my elevator so maybe nobody will crawl under there and look too closely. It left a little bit of a seam that I'll have to fill before I can paint or finish out the elevators, but I don't think it will be a problem. I've since found a much better way to make a seam in the foam which you'll see in the wing root pictures. I don't want to see any of you guys at fly-ins looking under my elevators either!

The next series of pictures will be of my wing roots. We also had a novel way to make the wing ribs by using an aluminum template and a router with a bit which has a bearing on the end like you would use to cut a formica countertop, so I'll include a couple of those pictures also.

Here is a picture of how I blocked the foam in the wing root. In the trailing edge, the plans show to taper the two foam pieces and feather one to a point on top of the other piece. I found that this leaves a very delicate edge which is easily damaged and leaves a ridge when you apply the glass/epoxy. Here is how I got around this problem - I used butt joints in the foam as shown in these two pictures.

School of Hard Knocks hint - Use a hot-glue gun to glue in the foam. You can control where you put the glue so you never have to sand over it and it dries almost immediately.

Here is the side view of the wing root after the foam is sanded to shape on the bottom and around the nose. I used a piece of aluminum channel with sandpaper glued to the bottom to sand the foam down to the templates. Some of the larger pieces of foam were pretty flimsy and it was hard to get enough pressure on them to sand them properly, so I put the hot glue gun to work again. I cut little 1" squares of foam and stuck them up under the foam against the rib templates to support the foam. They pull right out when you're done.

Here's another view of the almost-completed wing root bottom. I did block in a little more foam to come out even with the end of the spars.

This picture shows the ribs being attached to the spars. Hint: You can never have enough clamps!

Here are the ribs after we finished cutting them out. Below are a few pictures of the process. Note the aluminum template. If you look closely, there is a piece of duct tape, er, 300 mph tape, on the nose of the rib on the template. We took off a little too much metal, so the duct tape gave the router bit bearing something on which to ride.

Here I am diligently cutting out the ribs as they are clamped to the rib template and the small table. I cut them two at a time.

This is a picture of the router bit I used just in case anybody wants to try it. It's the same kind of bit they use to trim the formica on a countertop. Note the bearing on the end of the bit, I set the router so that the bearing would run on the aluminum template and the bit would cut the two ribs clamped to the template.

Here is Curtis demonstrating how to use the glue-bottle sanding block. I looked all over the shop trying to find something just the right size and shape for the fillet between the bottom of the wing and the fuselage. I finally settled on a bottle of wood glue with sandpaper glued to the side. I used 36 grit self-adhesive sandpaper.
Here is a close-up of the fillet-sanding tool itself and the fillet on my plane (which is much prettier than the fillet on Curtis' plane!)

You may notice that some of my parts have a clear epoxy on them while a few have a dark brown color. The dark ones are made with some old left-over Safe-T-Poxy but the new parts are all made with Poly Epoxy. It is easy to work with and has almost no odor, even much less than the old Safe-T-Poxy. How's this for a shameless plug for a really good guy - we are buying most of our parts from a local supplier in Greenville, TX:

Alpha Aviation Supply Co.
PO Box 641 Greenville, TX 75401
Phone# 903-455-3593

For a couple of bucks the proprietor, Russ Chambers, will send you a catalog. He handles all kinds of KR parts plus hardware and everything you need to cover a fabric airplane. We are supporting him because he's local and he's a nice guy. Besides, the competition might keep the big guys honest.