Chapter 7 -

March 7, 2005
Sept 5, 2005 - COMPLETE

Chapter 7 - Step 1 - Building the NACA Scoop

March 9th, 2005

The NACA scoop is the main air scoop underneath the plane that draws in air to cool the engine and other various things that need cooling in the engine compartment. The Cozy IV uses a convection cooling configuration. This means that the air is drawn in from underneath and flows upwards through the engine compartment and out exit ports on either side of the prop hub. So air flows naturally (cool air in the bottom is heated by the engine is allowed to rise as warm air does and exit out a higher location).This first part involves alot of fiddly bits as I like to call them. It also has quite a number of small cures of parts being bound together with either flox or micro that require you to wait. This along with work as of late has conspired to not see as much get done as I'd like to see done in a weekend. But there is news to tell and there has been progress, which is more than alot of builders so I guess I shouldn't complain :-) ---> Onward to the pictures and descriptions!!!The first thing I did is trace a full size"M-Drawing" and create a template for the floor of the NACA scoop. I then traced this on the underside of the fuselage. Then after cutting some 2" and 1" foam per plans I traced the template onto the foam and cut that out to the shape of the scoop. I then had the foam for the sides of the scoop and a location to place it on the fuselage. (see below)

Once I had all of that fitting nicely, I again got to put my weight set to use. I piled on the weight after applying micro to everything that I wanted to stick permanently.

March 13, 2005Not alot of progress this week. The fiddly bits got me down and I had my first real problem of this chapter. I cut out of plywood, these little cutouts that fit on the outside edge of the landing gear area and then this other set that fit between the aft landing gear bulkhead and the firewall. I painstakingly cut them out exactly per plans and they totally didn't fit. (see below to see what I mean) DISCLAIMER - Now the reason I had this problem was not because the plans are bad. It is fully my fault for letting a 1/4" overlong fuselage side go into place. I knew when I did it that this would find it's way to little parts in this area and so it has. Because I let the fuselage on this side be a 1/4" longer there is a slightly larger gap between these 2 bulkheads and well the part had to be adjusted to make up for my earlier mistake. What you are looking at below is a mock up to show where the problem bit me. The part I am holding is not the real part, just a piece of wood that I was holdling to illustrate the result of the mistake.

Well, a bit of measuring and a bit of cutting and a bit of sanding and I had it all fixed up and in place. This coming week I will put the other bits of wood in this area tomorrow after this all cures and then I can finish up roughing in the most aft part of the NACA scoop between the aft LG bulkhead and the firewall.

March 20, 2005
All in all it's been a pretty good weekend of work. This weekend started with finishing up all of the fiddly parts between the aft landing gear bulkhead and the firewall. There are a couple of reinforcing pieces of plywood that go back there that I finished up the cutting last week and this weekend I final fit it them, did the 2 ply BID that goes on the top and cut and fit the 2" white / cream foam that goes on the top of them. You can see this below being weighted down by a couple of taped up paver bricks. After that I also cut and fit the remainder of the NACA scoop foam out of blue 3/8" foam. I used a couple of small blocks hot-glued into place to hold them until the flox cures.

Getting that done was great because it allowed me to move on to the parts that I have really looking forward to. The shaping of the NACA scoop and the start of shaping the sides. I started by making a 22" sanding block out of a 2x4 per plans. I spiffed mine up a bit by adding a piece of 1" to the top as a handle. (I recommend this). This size block allows you to cut an 8.5" x 11" piece of sandpaper in half and get exactly 22" by using spray adhesive to stick them to the bottom. The the first bit of sanding foam begins. At this point I couldn't get Mr. Miagi out of my head. You know that guy from the Karate Kid movies! "Sand 'da flo, Danielson..."Sand 'da foam... Sand 'da foam... Sand... 'da foam...

Inevitably, as I was told that I would, I got one side done, went to the other side and then proceeded to gouge the foam on the finished side with the sanding block in my zeal. Try to avoid doing this but resolve yourself to failing. I'll micro that when it comes time...At this point I stopped working on this step because I thought it made sense to contour the bottom before making "the joggles". All of the extra foam is in the way of doing that and it gets carved off in the next step. Also part of the next step is glassing the scoop and I think that the extra foam needs to not be there for that either. I can sand it down because it is curing... so onward to step 2

April 24, 2005
I'm finally back to finish off this step. I have honestly been dreading this layup because of the difficulties that other builder have had and have been a bit happy for the spring diversions. But, this thing has got to get done and I can go no further without facing this layup... so here it goes. For starters I had to get the joggles cut in. I did this using a Roto-zip tool with router handle(see below) with a flat-bottomed plunge bit on it. You'll want to be carefull and work at a reasonable pace here so that the bit doesn't catch and throw the tool 1" further into that soft foam than you'd like causing a patch job. I managed it nicely and got good results. I did learn something new here. I had never used the sanding tool attachment of the Fein tool. I was wondering how to do the corners and short sides that I couldn't reach with the rotozip tool (with router handle) and it occured to me that this would do nicely. When I was done in pretty short order, I couldn't tell where I'd used the rotozip and where I'd used the Fein tool. This tool is sold at Coastal Tools just in cast that link doesn't take you to the right place. Search Google for it and you'll find it.

After finally getting the joggles cut in I had to install the hardpoints per plans. For this I cut the 16 aluminum hardpoints from the 1/4" aluminum stock ordered from Wicks Aircraft Supply. They were cut with my band-saw using a clamp to hold them during the process. I then routed out the foam in the areas of installation with a 1/4" drill bit, plopped in a bit of flox in each hole and inserted with a light hammer tap, making sure that they were level after installation. Voila! After getting the joggles cut in and the hardpoints installed I had several questions about rounding the foam that make up the joggles so that the 2 BID layup would lay down in them and around the corners. There doesn't seem to be enough height there to really round the corners enough for it to lay down. But with a bit of patience, an answer from the Cozy Mailing List, and a small peice of 50 grit sandpaper I got them rounded and ready for the upcoming layup.

BUILDERS TAKE NOTE HERE!!! This is something that you need to do that isn't made clear at this point in the plans: You need to round the edges of the bulkheads (a la above right) because you will be wrapping your BID layups around them in this layup. See Picture:Round in all these places: IMAGE HERE
Now... having done all of that. It's time to plan this "Joggles Layup". I started by planning how I was going to keep the BID in those joggles. I'd reccomend that you do the same. I measured and cut a bunch of wood pieces to fit in the joggles that I could put in them on top of the BID and then brace and weigh them down, keeping everything there in place. On the outside (in the LG hell hole) i planned to hot glue pieces to the bulkhead that overlap the layup to the edge to keep everything in place. The rest I left up to flox and skill. I precut all of my BID and did the whole waxpaper/cut to the outline thing per plans. Before I layed the BID in the joggles I "painted" some flox into them so that it could fill any small air holes that might want to form. I have heard that this works well for this purpose. (I'll update later how this whole bit works) I then layed everything in its place and started putting in the bracing. I really like the Irwin Clamps for this because you can turn the end around and brace outward as well as the normal inward (Squeezing). This allowed me to use very few clamps to hold stuff down and out. (Below - Top right)

Then I worked out a couple air bubbles and "The Inspector" came out survey the progress.