Cozy Mark IV Chapter 4, The Fuselage Sides


This photo shows the fuselage sides under construction. There are two types of foam mounted in curved jigs prior to fiberglass layup.

Cozy Mark IV Fuselage Sides

This photo (below) shows the two fuselage sides after the glass has been laid up. The round depressions are cutouts to give more knuckle room for the pilot and copilot holding the flight control stick at the front of the plane.  In the back of the plane, the brown areas are cutouts for windows to view into the fuel tanks. (The brown is actually some box-sealing tape that has been fiberglassed over and will later be removed from the exterior areas of the fuselage sides.)

There is no fuel gage that one could install that is as reliable having a window to view into the fuel tanks. That is exactly the type of fuel tank employed here.

Running vertically along the center of this photograph is the upper section of the aircraft. The top and bottom of the plane have long curved wooden structures called longerons. In this photo, only the top longerons are installed. You cannot buy these curved wooden pieces... the builder must fabricate them from straight wood. The curvature of the fuselage sides is not very evident from the angle of this photo.


When it came time to install the lower longerons, I didn't want to drill and add nails. Instead, I used a lot of clamps (even more than shown here) and cut out some jigs made out of scrap wood. I left the triangular wood pieces clamped in place for a week or so before I had a chance to work on the plane. The photo below shows the triangular blocking test-clamped, before it was notched and before any flox was applied.

This helped the triangular blocking accept the curvature more readily when it came time to flox them into place. The plans call out for notching the wood so that it will curve, but I don't even think that it is necessary. I didn't second guess the plans- I notched the wood exactly per plans. I tried several notches with one of those Japanese-style pull-saws unitl I tried using my Fein tool. After one test cut, I knew the right way to do this. I took the tape measure, marked off the intervals I wanted the cuts with a felt tip marker, and zip, zip, zip with the Fein tool and my cuts were done in about ten seconds.


This photo (below) shows the front of one of the fuselage sides after the fiberglass has been laid down. At this point, the front is cut to length. If I were doing this again, I think I would have waited to do this cut until I was ready to install F22 (a forward bulkhead) during chapter 6 fuselage assembly.

Only a very small amount needs to be cut from the front. I used the Fein Multimaster to make this cut, and it made the cut very easy. I was not comfortable at all with how the plans specified this cut and what I was able to read in the archives of the various Cozy Mark IV builder's discussion groups. For that reason, I wanted to cut the frontal excess off in one very clean piece just in case I needed to reinstall it. (I still have the scrap, but fortunately I didn't need it.)

Consider the location of the F28 bulkhead when deciding where to trim (front or back) and how it will line up with the frontal doubler in the upper longeron (the thicker portion of the upper longeron in the lower left of this photo). Be sure to read the Chapter 6 FAQ regarding he location of the F28 doubler and how it relates to the installation of the canard in later chapters.


When this chapter is finished, it really feels good to be able to pop the fuselage sides free of the jigs that were installed on the worktable and get the surface of the table back again. The table is a mess of epoxy, micro, flox, and other stuff by the time the fuselage sides are done. Many of those lost tools and misplaced items will be found under the jigs. After a little work with the belt-sander on ultra-coarse grit, the table is clean, smooth, and ready for Chapter 6, Fuselage Assembly!

These photos can give an idea how much curvature is in the fuselage. The sides are to the right of the table, and the bulkheads are stacked up to the right of them. After this chapter, I removed the legs of the table and replaced them with very short legs prior to assembling the fuselage. This is a feature that I designed into the table from the beginning when I worked on Chapter 3 and builder preparation.

I used the inverted fuselage assembly technique often called the Wayne Hicks method by other builders. His Chapter 6 web page was printed and in my shop for reference when that time came.

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Copyright (C) 2008, 2009 - Daniel Dillon - All rights reserved.