Chapter 18 – Canopy
In this chapter we finally start to make the boat look like a plane…..or at least something other than a boat………
The first step is to mount the hinges for the canopy on to the fuselage. The picture below shows this step. I used a level to make sure the hinges were aligned properly with each other so there won’t be any binding when the canopy is opened.
The plans give detailed steps on building a jig and constructing the turtle back but I purchased the turtle back from Featherlite. I figured this piece is a highly visible part of the plane and any flaws are easily detected. Featherlite also uses Kevlar honeycomb between the glass layers. It is stronger, lighter in weight, and they vacuum bag the whole thing so the surface is very true. It will require very little fill before paint. It also saves about a month in labor for me. Here is a shot of the turtle back in place on the fuselage.
When I sat in Nat’s plane, I found my head was pretty close to the canopy. Nat is considerably shorter and doesn’t have this problem. He has given me recommendations on how to increase the headroom. It is very easy and all you have to do is raise the front of the TB by about an inch. This will give me about 2” more head room where the canopy is in relation to my noggin. In the picture below you can see the sliver of foam under the TB.
The TB is actually cut in two once the canopy is add so the rear most window and portion of the TB are permanently mounted to the fuselage. The TB gets cut between the two side windows and the front window and canopy are designed to open to the side. Again an ingenious way of marking out this cut line is shown in the plans. You simply measure back a certain distance from the front and mark on the bottom of the TB, next a second measurement is placed further back on the top. A straight board is placed between the two points and a ruler is placed on the board and points are marked along the tangent of the board. It worked very well. The pictures below shows this.
Next, comes the installation of the side windows. See the FAQ’s in the archives for an easy way of doing this. I did have to do a little math and subtract the height difference created by the foam insert so the windows wouldn’t look like they were sloping down hill. I ordered my canopy and side windows from Todd Silver at Todd’s Canopies. It came very well boxed and the quality seems first rate. The side windows come oversized so the builder can opt for larger windows if they wish. The front windows are large enough and I don’t plan on too many people in the back for any long flights so I opted for the plans size. The windows are installed by inserting them between the fiberglass layers. First you cut the hole in the TB and I used my dremel with a small grinding stone to clear out the honeycomb ¾” all the way around the perimeter of the window. Next, a slice of glass is removed from the inside layer of the TB and the window is slid in and bonded with flox. The picture on the left shows one window taped and the outside edges sanded and ready for install. The picture on the right shows them held in place during cure.
For some reason while I was working with the windows, all I could think of was working on the plastic Revell models when I was a kid. No matter how careful I tried to be, I still always managed to get the glue on the plastic windows. This invariably ruined the whole project. I can report that all 4 windows are in place and no “glue” is on them. Now all I have to do is protect them from “glue” and scratches for the next two years of additional building……..Oh boy!
Here’s the completed window install…..
Some builders that have completed their projects have said that the fresh air vents are ineffective in allowing enough air into the cockpit. It’s because the composite construction is a much tighter fit than aluminum with its joints and seams. The air simply has no place to exit the plane. I added an exhaust vent that another builder suggested. It is incredibly simple yet effective. I installed it in the back portion of the TB where it will be out of sight. The install involves cutting a small vent on the outside of the TB and the inside uses an adjustable vent just like on your Kraft parmesan cheese dispenser. I used some urethane foam as a spacer because you can’t mount a flat piece of aluminum to the rounded side of the TB. Here are the pictures of the outside and inside portions of the vent.
Next, onto permanently attaching the TB to the fuselage and building the canopy frame.
Now that the turtleback and side windows are complete, it is time to tackle the canopy and frame.
I started with placing the canopy on the fuselage. Since the canopy comes “oversized” for builders like me who have opted to raise the turtleback for more headroom, it still needs to be trimmed to the proper size. It’s best to cut a small amount of the bottom so you don’t cut too much off and ruin a perfectly good canopy. The plans have you mark the canopy cut line ¼” above the top longerons on the fuselage. I just used a piece of 1/4” wood for the proper clearance and made the first cut. Once this is accomplished, scrap pieces of wood are bondoed in place under the canopy that will later support the foam for the canopy frame. The canopy is then floxed in place to the turtle back. The picture below shows these steps. The milk jugs of water are just holding the canopy in place on the turtleback while the flox cures. You can see the wood “jigs” underneath the canopy and the notch in the canopy for clearance over the instrument panel in the fore ground.
The picture on the right shows the “eyebrow” that is required to be glassed over because the turtleback flattens out at the top and the canopy is blown in a semicircle and has to be flattened out to match the turtleback. The flat spot will be filled in with micro during the finishing portion of the canopy.
The next step involved cutting a bunch of 2” urethane foam blocks to fit around the canopy to eventually form the canopy frame. This took quite a while because each one had to be custom cut and sanded to fit properly in its place. The picture doesn’t show it but I numbered each block because you are constantly taking them off and putting them back in place for trial fitting. After the 20th one, they start looking the same, but they surely are not interchangeable.
Once the foam is cut, templates are cut from the plans. (right side picture above) These are used at various points moving front to back down the side of the fuselage to give the proper shape to the foam for the canopy frame. Once the foam is properly shaped 4 layers of glass are applied and this makes up the outside portion of the canopy.
Next, a jig is fabricated on top of the canopy frame so it can be lifted off the fuselage and have the interior glassed. Be sure to include the cross piece that mounts just in front of the canopy glass, otherwise when you flip it over the center portion of the canopy frame will sag and the canopy won’t fit properly when reinstalled. The picture below shows the canopy frame after the foam was shaped and glassed with the jig installed.
Before lifting the canopy frame off the fuselage, it has to be cut from the rear most portion of the turtle back. This is why we used the ingenious measuring device to draw the cut line earlier in the chapter. The plans had you drill a series of 1/8” holes along the cut line so you could see where the turtleback needed to be cut. Even at an inch or so apart, it was difficult to get a smooth flowing cut line. I solved this problem by taking some 1/8” vinyl pinstriping I had laying around and just loosely connected the dots. Worked great! You can see this in the picture below.
Once the canopy is flipped over, the foam is shaped and glassed just like we did on the top side. Next comes the fabrication of the front rain gutter. This is important because this is all that stands between the rain and that “megabuck” instrument panel that will be installed later. To build the gutter, some 1/8” balsa wood is placed along the forward cut line and covered with duct tape for a release agent. The picture below shows the inside canopy frame shaped, glassed, and rain gutter glassed in place.
Provisions for accessing the back of the instrument panel have to be considered as well. The plans call for the forward deck to be cut from the leading portion of the canopy frame. The front deck piece is made removable by placing piano hinges on both upper longerons. To make sure they were perfectly level (allowing the hinge pins to slide in and out easily) I used two pieces of angle front and back for both hinges as shown below. The picture on the right shows the forward deck piece installed. As you can see, if this part was not removable, it would be very difficult to get at everything behind the panel.
While waiting for some supplies to show up for the canopy, I jumped ahead and fabricated the NACA ducts that will provide fresh air to the front seats. The plans were excellent and were simple to make. I did both sides in one evening. I was very pleased with the results. I just copied the plans layout for the back side of the duct and traced the template on the side of the fuselage. You just cut out the shape of the duct, make sure you don’t cut the leading edge and fold it into the back portion of the duct that you glassed. The picture on the left shows the male foam plugs I made to lay up the inside portion of the duct. The two pictures below that show the inside and outside portions of the duct.
Next, I have to order the canopy latching hardware and start installing all of that. That’s all for now…….Have a Happy Thanksgiving!!!!!!
The final step to finishing the canopy is attaching the hardware that will latch the canopy in place. Since this plane is capable of 220 mph, a rather beefy latch system needed to be used. It is comprised of three latches that are connected by aluminum rods. These rods move everything in unison when the front lever is moved. Some builders have had difficulty in getting everything to work at the same time, but I fortunately didn’t have any problems.
I fabricated the upper hardpoint for the canopy support gas shock out of ¼” aluminum and glassed it into the cross bar portion of TB1. I later drilled and tapped it for the mounting ball for the strut. You can see it in the picture on the right. The picture on the left shows the gas strut installed.
While waiting for things to warm up to start more fiberglass work. I bought a polishing wheel attachment from Harbor Freight and had some fun polishing the canopy hinges and hardware. Here you can see the difference in the same hinge after spending some time polishing it.
This ends chapter 18. A total of 232.5 hours and I didn’t even get any modeling glue on the plastic windshield!