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The following are the measurements that I have on my fuselage currently. All measurements in inches

To the other builders that offered helpful suggestions, ideas, and encouragement... Thank you! This page reflects one of problems that I ran into during the construction of my airplane. I am sure that there will be many more problems in the futute that I will have to work out. I am please to report that I have moved on, corrected the problem, and continue building.

Since taking the bulkhead fuselage station measurements, I have decided to remove the landing gear bulkheads. Although this isn't the entire solution to my error, it needs to be done. The landing gear bulkheads were only attached with flox. thus far (no fiberglass layups over them yet), but they were impressively strong and well-attached. I made quick work of removing them using the Fein Multimaster with the HSS flush cut blade.

I have discovered that my fuselage sides are not the exact same length. They should be exactly 101.75 inches in length as measured parallel to the centerline (not measuring along the curvature). I seem to be a little bit short of this length, somewhere in the neighborhood of 101.2 inches to 101.5 inches. I knew that the LG bulkheads needed to be removed, and those are now gone. I need to figure out exactly what needs to be fixed and changed before moving forward. I don't want any small problem now to turn into a big one when I install the wing spar or the landing gear. The center section spar cutout area has already been removed, and if the fuselage length is off a little bit, then the stringers LWX and LWY will be off a little bit, and the firewall will be off a little bit... etc.

My most forward bulkhead, F22, also appears to have a bow in it. This bulkhead naturally has a bowed sort of dimension due to the thick buildups near the sides and the thin buildups of glass near the center. I currently have it clamped to a rigid straight edge to take the slight bow out of it.

Saturday, 03/24/2007 Now that the bulkheads are removed, sanded, and the area cleaned up, I have floxed and glassed the aft bulkhead into place. The forward LG bulkhead is next. This is the first time I tried the technique of laying up the glass (BID tape) over wet flox using the aluminum foil method, but it worked well.

Forward LG Bulkhead (aft face) to F22 (forward face) as measured along the landing gear mounting holes
Now removed
Pilot side = 88.65 inches
Passenger side = 88.25 inches

Forward LG bulkhead (aft face) to instrument panel (forward face)
Now removed
Pilot side = 69.5 inches
Passenger side = 69.2 inches

Forward LG bulkhead (aft face) to forward lip of the bottom side of seatback (measured while fuselage is upside down).
LG bulkhead now removed
Pilot Side = 46.45 inches
Passenger side 46.35 inches
Note, I intentionally placed my seatback about 2.0 inches aft

Space between landing gear bulkheads
LG bulkheads now removed
Pilot side: top = 8.10 inches, bottom = 8.0 inches
Center : top = 8.05 inches, bottom = 8.0 inches
Passenger side: top = 8.05 inches, bottom = 8.08 inches

Firewall front face to aft face of the aft langing gear bulkhead, or space between firewall and aft bulkhead.
LG bulkheads now removed
** note that these figures are after I pulled the firewall back to the point where it aligns. The firewall with these measurements is not flush against the tail end of the fuselage as trimmed in Chapter 5.
Pilot side = 5.0 inches
Passenger side = 5.0 inches
Gap between the firewall and the aft (foam and glass) portion of the fuselage = 0.5"

Total fuselage length (with firewall pulled back as described above)
Passenger side = 101.5" inches
Pilot Side = 101.75 inches
The plans specify 101.75 inches These figures include a substantial gap.

Total fuselage length along the exterior curvature (most forward foam to most aft foam, as cut in chatper 5)
passenger side = 102.3 inches (97.3 inches from the front of the spar cutout to the forward side of F22 + 5 inches for the spar cutout = 102.3 inches)
pilot side = 102.0 inches (97.0 inches from the front of the spar cutout to the forward side of F22 + 5 inches for the spar cutout = 102.0 inches)
Clearly, with these curved distance figures, I am short of the 101.75 inch ideal straight-line distance.

fuselage sides with forward and aft bulkheads removed, showing temporary firewall
Forward and aft landing gear bulkheads removed (the fuselage is upside down in this photo)


Below, I have a bunch of photos that I have shot of the problems.

Cozy fuselage, chapter 6
Fuselage is being assembled upside down. The red line is a laser, illuminating the centerline, fore to aft. The fuselage bulkheads, front to back, are well centered. The line on the back wall is also lined up with the fuselage centerline. The two tape measures don't look parallell in the photo, but they were during all measurements.


Cozy Mark IV, Fuselage Chapter 6

Cozy Mark IV, Landing gear bulkhead drilling jig

Cozy Mark IV, Fuselage Chapter 6

Fuselage general condition with laser showing alignment along center.



Fuselage, pilot side, showing spar cutout area. In this photo (above), the fuselage is upside down. Notice the aft LG bulkhead at the top of the photo. This meets the spar cutout area about an inch or so into the forward edge of the spar cutout.


Cozy Mark IV, Passenger side spar cutout
Fuselage, passenger side, showing spar cutout area. In this photo (above), the fuselage is upside down. Notice the aft LG bulkhead at the top of the photo. This meets the spar cutout area about an 1/4 inch or so into the forward edge of the spar cutout. The pilot side and passenger side of the aircraft came out different. This should have been my first clue that there was a problem developing before I continued on with my build. Fortunately, so far I have only floxed the landing gear bulkheads into place without adding the fiberglass layups.


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Cozy Mark IV, spar cutout from fuselage sides
Passenger side spar cutout area. In this photo, it is a little difficult to see, but the firewall is pulled back (towards the right in the photo) about 0.25 in. from the foam to the point where the firewall is aligned, parallell, and exactly the correct length from the aft LG bulkhead.


Cozy Mark IV, Spar cutout from fuselage sides
Pilot side spar cutout area. In this photo, the firewall is pulled back (towards the left in the photo) 0.5 or more in. from the foam to the point where the firewall is aligned, parallell, and exactly the correct length from the aft LG bulkhead. Somehow I made a big error in alignment of things. Pulling the firewall back to this point makes everything line up perfectly except for the stringers, LWX and LWY, and the spar cutouts. Clearly there is a problem that I need to correct.


Cozy Mark IV, firewall gap Chapter 6
Another view of the pilot side fuselage where I have pulled the firewall back to the point where things align properly. Here firewall to fuselage gap is clearly visible and quite large. The firewall position indicates how far back I would need to place it to make sure all of the spacing is correct.


Current solution being considered for next plane day:

At this point, I think that I will need to cut out the landing gear bulkheads, re-measure, square everything, and start over on the aft portion of the fuselage. I am looking forward to a free weekend when I can get past this and make some progress on the aircraft every weekend.

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Dan Dillon
Cozy Mark IV project
Chapter 6
March 2007

Copyright 2007, 2008 - Daniel Dillon - All rights reserved