Fuse Side Skins

There are a few countersinks that still need to be made on the sides of the fuselage structure, particularly around the center section bulkheads where the wing attach bolts go. In order to gain access to these areas, the bolts holding the two center sections together must be removed, and this makes me a bit nervous to remove them all at the same time (I'm trying to minimize the number of times I tighten and loosen these bolts, since they are a close-fit tolerance and I don't want to wear anything out more than I have to). Looking ahead in this section (29-21 step 1), I see that we will soon be final-installing the landing gear mounts, and with that step there will be four spacers bolted between the center sections and holding them together. I had the idea to make these spacers now, and temporarily bolt them into place, which ought to hold everything in the proper orientation even with the main attach bolts removed.

Looking at the dimensions for these spacers, I realized this was going to be a bit time consuming and require quite a fair amount of precision. The plans call for AT6-058x5/16 aluminum tubing, which they provide approximately 9" of in the kit. From this tube, I'll need to make four spacers, each 1-11/16" long, with a tolerance of -0" and +1/64"... that's a VERY narrow acceptable range within about 15 thousandths of an inch, between 1.6875" - 1.7031"!

I carefully cut four slightly oversize pieces (1-3/4") using the bandsaw, and then sat down with the belt sander and dial caliper to gently sand away the excess until I had four very close-tolerance spacers:

Measuring the length of the F-1082 Spacers

All four spacers fabricated and labeled with length, all within 0.002"... not bad!

Once the spacers were made, I bolted them into place using the super-long AN3-41A bolts along with a nut and four washers to account for the missing landing gear mount.

Spacers temporarily installed between the center section bulkheads

Once this was done, I removed the nuts from the main wing attach bolts and was free to slide them from side to side in order to get in there with a countersink. Unfortunately, the microstop is too big to fit near the bulkheads here, so the inner-most rows need to be countersunk freehand. No huge deal there, but it's more time consuming and it's hard to get the same consistency we've come to expect using the microstop. In time though, all of the hard-to-reach countersinks were complete, and after a quick double-check session ensuring all the understructure was ready, we could start attaching the skins!

After clecoing the skins into place, the plans have you start at the double row in the middle, where the skins meet and work outward from there. I did this, as well as the rows on the forward and aft sides of the center section, allowing me to re-attach the wing bolts, hopefully for good now until much later on in the build.

Just a few rivets in this area!

Some of the rivets along the sides were quite difficult to get to with a bucking bar (I can't imagine how a person could do it at all without these nifty tungsten bars) but patience and contortionism prevailed. By this time, we had to run to a mid-day family event and didn't return until later, when my friend Roy stopped over with his father, sister and her husband for dinner and to see the project. His father (also named Roy) was quite the handyman back in the day, and when he visited last year I had shown him how to buck a rivet using scrap material. He did such a great job then, I thought this time, why not have him set a rivet on the plane itself?

Roy Jr. (father of Roy III) setting a rivet in the fuselage side skin... he did an excellent job!

He did the first one so well we had him set another!

It was really cool to see him step up to the physical challenge of holding both the gun and bucking bar straight and set the rivet properly. There are adults 1/4 his age who struggle with that kind of precision! Excellent job Roy... you're welcome back anytime!