Thu Sep 24 2020

Forward fuselage and canopy structure

First things first...

HAPPY BIRTHDAY, SNICKERS!!!

Snickers turned 13 today. He's such a good boy!

While checking out the canopy frame weldment, I noticed that it appeared to be sagging a bit in the middle. Not surprising since I haven't installed this joint plate at the center where the frame is split. Up until now, I've just been using a piece of 1/8" thick bar clamped to the lower flange.

Before preliminarily fitting the joint plate, I decided to square up the flanges of the canopy frame in the relatively flat zone between the hinge goosenecks. Because of how thick this material is (.063), my seaming pliers weren't up to the task, so I made this little tool to tweak the flange in one small section at a time. This is very reminiscient of what was necessary on the wing spar flange back on Sat Apr 28 2007 where I used a larger, but similar tool shown on Tue May 1 2007.

Nice and square.

Laid out and drilled the splice plate as shown here, except that I only drilled up to #40 for now.

I thought it was strange that the flange of the splice plate wasn't riveted to the lower flange of the canopy frame. I was thinking of adding rivets (holes) through those flanges, but checked to see if the canopy stiffening kit ended up being riveted there. Sure enough, it does (pop rivets).

So, clamped the splice plate to the canopy frame...

...and put the frame in place. I can immediately see that the frame is about 1/8" higher at the center. Also, the frame is now narrower where it sits on the longerons...no longer wider than the fuselage. Actually, it looks like I'm going to need to space the two halves of the canopy frame apart by, perhaps, 1/8".

As I mentioned before, I adjusted the flange angle of the canopy frame in the center, flat region. However, outboard of the goosenecks, the flanges won't be adjusted to 90 degrees. The angle will be a bit more open than that, owing to how the fuselage narrows towards the firewall. So how to figure out what angle? I could just lay a straightedge across the firewall and canopy frame, but because the curved profile of the forward fuselage gets narrower toward the firewall (as I mentioned), and also angles downward. These changes lead to uncertainty...what point on the curve of the firewall correlates to what point on the curve of the canopy frame?

I ran over to Target to pick up a piece of posterboard to use as a simulated skin. Taped it in place.

So, with the "skin" in place, I was able to orient a straightedge in various positions to find the straight loft lines of this "skin". Here, you can see that the straightedge has a cap at the ends, so this orinetation of the straightedge is not following a loft line.

Several loft lines drawn on the "skin".

I transferred these loft lines to the flanges on the firewall and canopy frame and numbered them. Shown here, I'm using the straightedge to follow loft line #4.

...and now, I can see how much the flange of the canopy frame needs adjusted at this location. I'll work on adjusting the curved section of the canopy frame flanges tomorrow.