Chapter 7 is where we make the fuselage actually begin to look like part of an airplane rather than just a square canoe that is ready to sink. It feels great to finally be out of chapter 6. Hopefully this chapter will go a little bit faster. Either that or I am going to never finish. Below are a few pictures and comments taken as I go along. This is a big chapter so I have added some intermediate links to the major sections.

Adding plywood braces
NACA Scoop
Rounding the corners
Glassing fuselage bottom
Contouring the fuselage sides by the upper longerons
Glassing the sides

Adding plywood braces

The vertical plywood supports, A, B and C have been added. Not very challenging work. The picture is a little dark. The horizontal supports D have not yet been glued in place at this point and are not even parallel. That gets fixed later.

Here there is a major difference from the manual. (at least it seems major to me) In the manual parts C and D fit together well rather than crossing as shown here. If they fit edge to edge, part D would have to be at an angle matching that of the lower longeron and thus be less effective at reinforcing the firewall than when positioned perpendicular to the firewall as I chose. To make these pieces fit edge to edge and D be perpendicular to the firewall, I would have had to reshape C. In M7, they show D and C with a line contact rather than a face contact and thus very little ability to transfer load. As such, I am not worried about my deviation from the plans since the intent of the plans has been respected.

NACA Scoop

Putting in the 2 inch blocks of urethane. I decided to put these in, let them cure in place and then put in the 1 inch blocks so as to avoid having to put on to much weight during the curing process. The goals was to avoid putting in big depressions into the fuselage bottom. I also ended up putting a piece of wood beneath to prop up and support the bottom during the curing process. This may end up biting me in the a## because I forgot to take it out when sanding the NACA scoop to shape. I hope that the bottom doesn't end up "moving" a lot when I remove the post.
Holding everything down
Putting in the 1 inch blocks
Sanded to near final shape. It is almost impossible to believe how much dust there is. I used a combination of the tool that I made (long sanding block) and a belt sander. This foam is so easy to remove that it creates problems. Sometimes you find yourself in a single stroke removing more material than you wanted. You really need to manage your stroking effort.
Since the urethane foam is so fragile, which has been noted on most other Cozy sites, I decided to follow the Jerry Schneider advice of covering the NACA scoop with carboard to protect it whenever possible. I was worried that the cardboard itself might have a protrusion that would dent the foam so I first covered the foam with plastic to distribute the load from anyi protrustions in the cardboard. (I have also been tempted to wear suspenders and a belt at times)
Putting on a little card board and showing off my sanding tool.

Rounding the corners

A litle to vigorous with the sanding. Easy to take material off; harder to put it back on.
Here I am trying to fix the previous mistake. Unfortunately, the longeron was a little oversanded as well. What to do? Marc Zeitlin suggested just trying to make a good shape and not lay some foam over the longeron as well as this would reduce the bond strength of the fiberglass in this area since it would be a fiberglass to foam rather than fiberglass to wood. In the end, I put on two pieces of foam, one on each side of the longeron; sanded to a nice shape. The longeron was still about 1mm low so I filled in the gap with flox rather than foam or dry micro.
In the end the results are not so bad. Still there is a small flat to fix near the bottom of the front seat. This photo also shows my antenna placement. Basically following the advice of Jean-Pierre ALAGNOUX and previous practice of Marc Zeitlin and others. Pieces of duct tape are there to make sure nothing gets ripped out while I am waiting to put the RG58U wire and baluns.


I am becoming a little obsessive about practicing before doing it for real on the airplane. Here is my practice antenna. The antenna on the right was to develop proper soldering techniques. The holes on the left are from my second attempt. Here I removed the antenna to determine the condition of the foam underneath after I had soldered the leads onto the copper foil. To my surprise, there was very little localized foam melting and the leads held onto the copper foil tenaciously. In fact, when I tried to pull them off the copper foil failed before the solder joint! You can also see the step reinforcement in wood. There is an excellent link for soldering the RG58U at:
I was actually quite pleased by how things turned out here. My milled channel with my newly purchased plunge router looks great. Of course 100€ for just this one channel would be a bit much. I expect to use the router all over the place including making the 1/16" joggles and making 3/16" radii on bulkheads. The three baluns have been put in place and a shallow angle was put in the foam near the end of the foil so that the leads would not protrude.
The antenna after being potted with dry micro.
Another view of the step reinforcement, filed flush with the foam.
Here is the NACA scoop after being covered with 2 layers of BI. The edges were not yet trimmed when this photo was taken.

Glassing fuselage bottom

Lots of work today. (16-1-07) Covered the bottom of the fuselage with two layers of  UNI at ±30°. Doesn't sound like much; the manual says it will take three hours; Maureen and I took six hours to finish this step! Here are the results after peelply has been applied. Had lots of problems during this step including:
  • hardner (MGS 287) that had precipitated (crystallized)
  • exotherms
  • too cold
  • ...

In the end, solutions were found for each but it took so long that we lacked the courage to put on the UNI reinforcement strips for the front landing gear bulkhead. We also did not do any work on the area between the rear landing gear bulkhead and the firewall.
Here is what happens when you try to heat your epoxy by placing it on top of a radiator on a cold day. Exotherm city. I'll have to avoid this one in the future. Next to the exothermed expoxy is a great tool for alignment, a laser with 90° beams. Don't try to build one of these airplanes without something like this. (as well as the smartmeasure which you can just see in the background behind the thompson radio)
The final NAV antenna configuration. Not the optimal 30° called out for in the RST manual but I will add a second NAV to the canard which will respect the optimal 15-30°. This one turned out surprisingly well although the performance has not yet been analyzed. Strange how it looks almost exactly like what was called out for in the manual despite many iterations  on my part. In the end, I decided to abandon the beacon antenna because it isn't used so much here in France and probably won't be so useful in the US in the near future. (just speculation on my part for the US comments)
Finally tried to use the cling wrap solution for keeping the cloth sitting down in a joggle and avoiding the entrapped air bubbles. We'll see how it works out. Here is a shot of the cling-wrap in the F-22 joggle.
Clingwrap on the speed brake. Getting the tape to the right height was a real challenge. The first layer of UNI I was real "smart" and tried to cut out the outline of the speedbrake in order to allow the UNI to sit down in the trough (you remember the 1/16" trough that you have to sand out). Didn't work. Just made a mess. Repeat at least three times: "try to follow the manual as much as possible unless you have a real good reason not to."
After six hours, and a trip to Sweden planned for the following day with two presentations to make, I just didn't have the courage to finish by putting on more layers of UNI for the landing gear bulkhead reinforcement. I know it says to put them on while the resin is still wet but with peelply and a little sanding, I think it will be good enough.
This is really a moment where you can get a little stresses! "What if I am cutting the canard cutout in the wrong place" HELP! Definitely a place for measure twide (or in my case five times) and cut once. Happy to report that the cutout was done correctly.

Contouring the fuselage sides by the upper longerons

Another scary cutting moment. It is hard to believe that cutting a 200mph plane apart with a handsaw is the right way to make it but ...
My strategy for shaping was to:
  •  rough sand from F28 to the back of the front seat using template CC
  • finalize the shape from F28 to the back of the front seat using template CC
  • rough and finalize shape from back of front seat (CC) to front of  wing spar (DD)
  • rough and finalize shape from F28 to 3 inches ahead of instrument panel
The roughing was done with a large sanding block and wood rasps. The final shaping was done with a small sanding block. This was all done by hand to avoid the tendancy of power tools to quickly destroy months of work.
Intermediate step, here the side has been shaped using template CC.
Final shape. Not so bad if I do say so myself.
Another view of the final shape.


The fuselage has finally been put up on the rotisserie for applying fiberglass to the sides.
Another picture of the fuselage up on the rotisserie.
Here is the A-Frame that I made to make up the rotisserie. I haven't seen to many pictures of this on other web sites so I decided to include it in my own. I am a little proud of my wood working for the feet where I dug out a channel with the wood chisel.
Just a closeup to show the simple design that I chose.
I decided to end up holding the back end up by claming onto the firewall instead of using the group of 8 bolts. Why risk loosening them with transverse loading when they will never see that in flight?

Glassing the sides

Here I am putting on the 1st layer of UNI onto the pilot's side. Once again, I had forgotten how optimistic Nat is in the plans. Getting all the three layers on took me approximately 7 hours. I didn't manage to even get the reinforcements along the upper longeron or onto the firewall in place during these 7 hours. I am not a particularly slow worker but this is taking a depressingly long amount of time. At least the quality is good.
Here is the passenger side prepped and ready for UNI application. I was sure to put in some plastic covering to take care of any eventual drips. All the little white spots are from where I filled in the divots that were torn out in chapter 5 when I used 5 minute epoxy to hold the foam onto the masonite. In retrospect, I really wish that I had held them in place with two sided tape. All the extra work could have been avoided. I also wish that I had been smart and ordered materials locally instead of having smaller sheets of foam sent from the US (actually the same size as anyone who orders from Wicks or Spruce). Other builders here in France have bought correctly sized foam sheets and saved themselves a bundle of time by avoiding the joining steps.
1st layer of UNI on the passenger side.
All finished with the passenger side. I have not gotten any faster as this side also took about 7 hours to complete. You can see my mania for covering the plane up with plastic to avoid drips.
Nearly finished with chapter 7. Just have to add the final reinforcements.