I have been studying this aircraft for almost 5 years now. I have collected a huge amount of data, including factory assembly drawings.

I have placed a video of this plane in the Video section. Be aware that the instrument panel and cockpit used in this video is actually the cockpit of the Ki-17 trainer. I guess the video editor screwed up, or thought noone would notice.

I bought a really expensive 3-view from a company in Japan that I wanted to use for the lofting of the fuselage formers. However, it turned out that the location of the stringers on the drawings were totally off and the formers were totally out of shape.

Next I went to the museum to get some photos of the Ki-55. This is what the fuselage looks like inside, looking back from the student’s/gunner’s seat.

Using my paint program, I first traced the outline of the former. You can see that the picture was not taken completely centered.

Then I made two assumptions:

• The airplane is at it’s widest at the thrust-line/center-line. 
• Engineers are lazy. They won’t use any weird curves. They will stick to circles, ellipses and hyperbolas, unless there is a compelling reason not to. Besides, that’s what would have been available on their sets of french curves.

I then took out my super-expensive 3-view imported from Japan, and measured the distance from the thrust-line to the top, bottom and side of the fuselage, and got:

Top: 119.2 mm
Bottom: 69.6 mm
Side: 75.5 mm

Finally, based on those measurements and my assumptions, I drew some ellipses and placed my “assumed shape” on top of the drawing traced from the photo.

It’s an almost perfect match.

I now know how to draw the remaining formers. It’s two semi-ellipses centered at the thrust-line.