Building a Cozy MK IV Fuselage Assembly

Chapter 6

Fuselage Assembly


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On 9/1/09 I started this chapter by building a fixture according to the plans to assemble the fuselage on. I made it out of a 2"x 10"x 10' and four 2"x 4"x 8's. Next I laid the fixture on the floor and shimmed the fixture to level with a Stabila digital level. See picture below.

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Next I installed the temporary firewall to the fixture making sure that it is plumb and the slots for the upper longerons are at the proper waterline. I then trial fitted the bulkheads in place one last time, checking that their locations are correct and that they are plumb. I also rechecked the overall length again (which makes about the 15th time) being that it is so critical. I drilled small holes through the fuselage sides and installed small nails through the wall into the bulkheads and seat back to hold everything in place. I disassembled everything. Using slow cure epoxy to give me some time to work, I mixed up some thick flox. I then began assembly from the rear with the seat back first, floxing each bulkhead back in its place checking again that they are perfectly in their correct position and that they are perfectly plumb. I reinstalled the nails and I made sure that there were no gaps between the fuselage sides and the bulkheads or seat back. Everything fit amazingly well. I next used a ratchet strap (ratchet strap was overkill, I wouldn't suggest doing that) and budgie cords to hold everything tight together until the flox has time to cure. Below is a picture of the fuselage completed to this point. Well crap, the front bulkhead was installed backwards with the doubler on the wrong side. I carefully cut the bulkhead off, sanded everything down again and reinstalled it correctly. I re measured everything and rechecked everything for level and plumb. I next made flox corners on all of the bulkheads and the seat back to prepare them for the glass taping. Below is what it looks like to this point.

I ordered all of the materials needed for the next three chapters and enough epoxy to get me through the winter (like a Squirrel getting ready for winter). While waiting for the materials to get here, I finished fiberglass taping all the bulkheads and seat back. Next I laid out the heat duct parts on a piece of Clark's foam that I had left over from a previous chapter. These will get glassed still in sheet form, and then they will get cut out of the sheet. Picture below before glassing.

After fiberglassing and cutting the heating duct parts out of the sheet, I made a fixture to assemble the parts with. I started out by cutting blocks of 2"x4"'s to the proper lengths to support the top of the heating duct . The 1 1/2" thickness of the 2"x4"'s are already the correct size for the inside dimension of the duct except for the end with the flare, which is shown in the picture. I then screwed the block to my workbench, keeping them perfectly aligned. Next I covered the blocks with clear box tape to keep the heating duct from getting glued to the blocks.

Then I test fitted everything on the fixture and checked the heating ducts finish size to make sure it will be correct. I dissembled everything and floxed the mating edges and reassembled the heating duct and clamped it.

The next day I unclamped the heating duct and removed it from the fixture. This fixture worked great and took no time to throw together. I then removed the foam from the top of the heating duct for the seat belt hard point. I installed the aluminum tube used for the seat belt hard point. I then glassed over the hard point with 7 layer of UND fiberglass. I made a bracket to hold the fuel tank selector valve which will be located in the seat brace per plans. Not the John Denver location. I glassed the outside of the heating duct with BID fiberglass. After it cured I cut the excess fiberglass off and fitted it on the fuselage. I built the front seat back brace and floxed the fuel selector valve bracket in place. Sorry no pics of that. I glassed the seat back brace in place on top of the heat duct.

I Bondoed the saw horses to the garage floor and leveled the fuselage. I then Bondoed the fuselage to the saw horses to make sure nothing moves. I floxed the seat brace and heat duct in place and taped it per plans, making sure that everything stays square, plump and straight. Below is a picture of the seat brace and heat duct fiberglassed in place. The fuselage is still upside down on the saw horses.

I took the foam for the bottom of the fuselage and positioned it in place. I added weights to the top of it and climbed under the fuselage and marked the positions of the stringers, seat back, instrument panel and the heat duct.

I took it over to the work bench and marked the cutting line 3/4" out from the stringer lines. I cut the foam and used 5 minute epoxy to glue to ends of the sheets together. I placed it back on the fuselage and checked the lines again. While it was still on the fuselage, I ran 2 2"x 4" running length of the fuselage making sure they far enough out to clear the landing brake (it gets cut out next) and I took some 1" x 3"'s and ran them perpendicular to the fuselage and Bondoed them in place. This was done to maintain the curvature of the fuselage bottom when I move it to my work bench.


Next it all went back to my work bench turned over. I marked and cut the landing brake out of the foam with a jig saw set to a 45 degree angle.
I then began laying out the 3/4" Last-a-Foam and found out that there is not enough in the "kit" (you buy a chapters worth of materials and the supplier calls it a kit). The Last-a-Foam is to give depth to the bottom of the fuselage and it will also give a little more material to work with when I shape the outside of the fuselage. This chapter comes to a screeching halt until more Last-a-Foam gets here. While waiting on this to get here it looks like I can start on
Chapter 8.
The Last-a-Foam has arrived so back on chapter 6. I finished cutting and shaping the foam parts for the bottom of the fuselage and laid them in place. I marked the location of the Last-a-Foam on the bottom of the fuselage so that when the epoxy is mixed, I wont need to measure everything out. Below is a picture of the fuselage ready to have the Last-a-Foam microed to the fuselage bottom.

Next I microed (mixture of micro balloons and epoxy) the Last-a-Foam parts to the blue foam and inserted small nails to hold it in place until the epoxy set up. I then cut the fiberglass cloth to size in preparation for doing the layups on the fuselage floor. These layups will take a while to do so I will need to wait until the weekend to do that.
Below is a picture of the floor fiberglassed and floxed in place. Next I climbed under the fuselage and fiberglass taped all the corners whit two layers of fiberglass. What a pain. This ended a 12 hour day of fiberglassing only. The 12 hours didn't include all the prep work like cutting the fiberglass cloth, laying it out on the fuselage floor and cutting all the tapes.

The next day I removed the wood framing and checked out my work and didn't see anything needing repaired. Below is a picture of the fuselage with chapter 6 completed. The white area is the landing brake cut out of the fuselage.


Below is a picture of the inside of the floor trying to show the contours that the Last-a-Foam formed. It gives the floor some depth and keeps it from looking so flat.

This completes chapter 6. Ready to start chapter 7.

If you have any questions, comments or concerns, feel free to email me at