Ch. 5 - Fuselage sides - Part 3

Shaping the fuselage sides (9.8 hrs)

With the second fuselage-side-panel completed, I took some time to sand them together, ensuring they are identical, then I moved on to marking the location of all the bulkheads on the sidewalls.

Two fuselage-side-panels stacked for sanding

This was pretty simple to do, as all the dimensions are clearly stated on the drawings. As far as the complex geometry of the landing gear support structure, located behind the rear seat, I had to resort to copying the drawing, and locating important intersections with my paperclip method.

Transcribing landing gear mount structure details

Gear mount structure outline

Here’s a look ahead to how it will all fit together, hopefully.

Test fitting

The space between the wood pieces will be filled in with foam, then the whole support structure will be glassed over. Enough plies will be laid, to strengthen the attaching point for the gear mount.

Another item on the agenda for today was digging out a circular depression next to where the joystick will go.

The purpose of this is to provide some room for the pilot’s knuckles as he hand-flies the plane, especially during full right stick deflection (I plan on lots of those). This is not a big concern in my case, because I have an extra inch of width right there, nevertheless I think it looks cool, and might remove a gram or two of foam.

I decided to go high-tech with my foam removal approach, reasoning that sanding blue foam looked a lot like hard work. Besides, it gave me some excuse to try out some router accessories that I bought a while back, but never used.

I decided to proceed in small increments, trying real hard not to make a mess of things. First I cut a circular groove 1/2” deep, to make sure this circle making attachment actually worked.

I can't believe this thing actually works!

Encouraged by the results, I switched to a 45˚ edge cutter, minus the bottom roller bearing. I raised the cutter to make sure the bottom of the tool would not dig deeper than the 1/2” groove I just cut.

Shaping the sloping sides

It wasn’t the perfect tool for the job, but it was the closest to it, and left a little edge that I could cut smooth with a razor blade later.

So far so good.

Finally I used a cylindrical(ish) cutting tool to remove all of the inner circle foam. Unfortunately for me, I forgot to lower the tool stop back to the 1/2” mark, and so I took this beautiful, as well as too shallow and useless cut next.

Basically, I ended up with 1/4” of foam left to cut by hand, which turned out to be as painful as I had imagined. The real shame is that it could have really been an awesome looking depression. Oh well!

Moving on!

The last thing I did before packing it up for the night, was floxing the stiffeners to the longerons. 

Stiffeners floxed to the longerons

That would normally be a pretty easy thing to do, but this time I had to disassemble the hardener side of my pump and clean it up with Acetone, as I couldn’t get much out of it anymore. 

Somehow the hardener had turned into some sort of sludge, and the ratio between hardener and resin had dropped from 44 to 100, to 4 to 100.

Not good at all!

This should emphasize the need to do a ratio test before each job, especially if the pump has not been used in some time.

Opening up a brand new can of hardener revealed a similar situation, and its content couldn’t even be poured out. When I called Aircraft Spruce, Tracy told me to heat it up to 120℉, and it should become like new again.

I remember reading about this somewhere, but I guess I’ll find out whether it works or not when I get back, because I’ve got to get on the road tomorrow.

I’ll try to take some photographs of the gelatin-like epoxy, and post an update on the results of the heating technique.