Building a Cozy MK IV Fuselage Assembly

Chapter 7

Fuselage Exterior


Click on the pictures for a larger image.

I started this chapter on November 8, 2009. This chapter starts with building the National Advisory Committee for Aeronautics scoop (NACA). The NACA was the precursor of NASA, yes the space people. Here is a link that explains the idea of the NACA scoop.
http://en.wikipedia.org/wiki/NACA_duct The Cozy MK IV uses the NACA scoop to move air into the engine compartment for engine cooling and air intake for the engine combustion.
I started by tracing the shape of the NACA scoop from the full sized drawings to make a template. Then I traced the shape from the template onto the fuselage bottom making sure that it is centered and straight with the fuselage. I laid out some 2 inch thick urethane foam on the bottom of the fuselage and transferred the shape of the NACA scoop onto the urethane foam. I used my jigsaw to cut the foam to the shape of the NACA scoop. I took a piece of 1 inch urethane foam for the leading portion of the NACA scoop. After I had the pieces all cut I test fitted them in place. Then a mixed up some slurry and glued the urethane to the fuselage.
I then made the bracing for the landing gear bulkheads and floxed them in place. The next step was to cut some PVC foam to close up the area between the bulkheads. Below is a picture of the NACA scoop finished to this point before shaping it. The picture was taken from the rear of the fuselage with the fuselage still upside down.










I took some quarter inch Birch plywood and made the bulkhead supports per plans and floxed them in place. This is what they look like.









I then made a long sanding block from a two by four with sand paper glued to it. I used this sanding block to sand the NACA scoop flat on what will be the bottom. I then vacuumed all the dust up and glassed the inside of the scoop with two ply's of BID fiberglass run at a 45 degree angle. After cure I trimmed the edges and this is what it looks like now.









I then marked a line 2 1/2" from the edge of the fuselage to use as a reference for cutting a 45 degree angle on the edge of the fuselage exposing a maximum of 1/4 inch of the wooden longeron. I used a belt sander to achieve the quarter inch consistently from the front of the fuselage (F22 bulkhead) to the mid area of the speed brake. I used my saws all with an 8" wood blade for this and it worked great. This is what it looks like now.


 







I then made templates to use for sanding the radiuses on the corner of the fuselage. Yes those fancy 45 degree angles don't stay there.
Tonight I sanded the radiuses on the bottom corners of the fuselage, starting with a belt sander with 36 grit paper. Then I used the sanding block that I made to sand in the NACA. It made for a nice looking radius. Wow what a foam mess. After sanding the radiuses, I cleaned up the mess and that finished the night.
I made a 1/16 th of a inch recess with a router behind the f22 bulkhead so when I join the nose to the fuselage, a bump wont be made from the overlapping fiberglass.









I then made a recess around the landing brake and filled it in with duct tape as the plans called for.








Next I cut a slot in the side of the fuselage and installed wood for a hard point. This will be used for installing a step later. This still needs to be sanded down to the contour of the fuselage.








The next step is to install the antennas. I will be installing several ferrite toroid- copper tape antennas that will be installed under the fiberglass. This is one of the many advantages of a composite aircraft. You don't have to stick the antennas on the outside of the airplane to make your airplane look like a pissed off Porcupine as they say. Most of the antennas will be installed in the belly and winglets of the airplane. The transponder antenna will be installed in the nose of the airplane. No antennas will be on the outside of the aircraft. I ordered an antenna kit from RST Engineering and the picture below shows what comes in the kit. Order the kit long before you need it (4 weeks +) because it take a while to get. The 17 pages of instructions seem to be easy to follow with no electronics background.







I then laid out the antennas on the bottom of the fuselage. I installed the navigation (VOR) and the Marker Beacon antennas on the bottom of the fuselage. The remainder of the antennas will be in the canard, the wings and the winglets. I used my router and a 1/4 in bit to make 3/8" deep channels for the cable to lie in. I then used a 1/2 inch bit in the router to make a pocket for the toroids to lie in and be potted. The cable then passes through the bottom of the fuselage behind the instrument panel.









Next I tested continuity from the end of the antennas to the end of the coax to make sure there are no breaks. I potted the solder joints to help support them through my wonderfully soft landings, ha ha. To do this I used Permatex clear RTV silicone, I squirted some under the connection and then filled the pocket, keeping the level of the silicone below the level of the foam. I then allowed 24 hours for it to cure before I closed it up with fiberglass. The lines on the bottom of the fuselage are the direction of fiber orientation in the fiberglass cloth.








While waiting for the silicone to cure, I cut the fiberglass cloth that I need to finish the bottom of the fuselage. I laid it out and test fitted it. I marked the cutout for the canard in preparation for the side being fiber glassed.

The following day I fiber glassed the bottom of the fuselage with the two layer of UNI fiberglass with the fiber orientation at thirty degrees, one in each direction. I then did the landing gear reinforcement layups and the fire wall reinforcements. This took me about 4 hours doing it by myself.

After allowing 24 hours to cure, I cut the fuselage loose from the saw horses and turned the fuselage over. The fuselage has been Bondoed to the saw horses since the beginning of chapter 6 to hold it twist free. Then I cut the opening for the canard in the fuselage in front of the f22 bulkhead.

 

The next step was to contour the top of the fuselage. Using the templates that I made from the plans, I sanded the top edges of the fuselage to match the templates. Then I once again, cleaned up all of the foam off of the garage floor. I then made some tripods to mount the fuselage to. I didn't worry about adding extra braces to the tripod legs being that the fuselage is so lite. Below is a picture of the fuselage in its first 45 degree bank turn, well ok on the tripods.










I then cut the fiberglass needed for the sides, test fitted them and rolled them up to be ready for another glassing session. I will wait for the weekend to do these large layups.

I fiber glassed one of the sides, including the extra reinforcement layups on the longerons and firewall. I peel plied the edges of the layups. The next day I cut the excess glass off and fiber glassed the second side. The outside of the fuselage is fiber glassed and this completes chapter 7 on 12/07/09.











If you have any questions, comments or concerns, email me @
Jfisher59@gci.net


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