Chapter 18 - Section 10

Installing the Canopy

 

The directions for fitting the canopy onto the TB/fuselage is a bit vague in this section. Since you can't really afford to mess up (i.e. a new canopy each time) unless you have unlimited $$$, I took time to visit all the web sites and archives before diving into this section. Evidently, many builders were confused as well - that didn't make matters any better.   

 

Making the BL0 Template

I took measurements of M27 and drew the outline on a 1/4" wood board. The angle of tilt turned out to be 26o. I was a bit confused with the statement "increase the height of F28 to 4.0" per plan. After researching a bit, I realized that when we first made the F28, we had a choice of making it 3.3" or 4.0" tall. I chose the 3.3" for a flatter nose for better visibility. Therefore, to use this template correctly, I need to prop up the template by 0.7" (to make up the difference). I just cut a small board and clamped it onto F28, with 0.7" extending above F28 for the template.

 

[Hindsight] The positional dimension between my canopy to the aft face of F28 is way off per the template. Template dimension is ~7 5/8" and mine is ~3.25". If you look closely, you can see the pencil mark on the left end of the template. Its supposed to be at the forward face of the F28. Evidently, many builders had the same problem. I am guessing that the profile of my canopy (Todd Silver's) must be different than Nat's.

 

[Hindsight] After repeating Steps 1 & 2 (below), template BL0 worked out OK.  

 

Trial Test

There are plenty of warnings from the Cozy archives and the plans that there is no turning back if you screw up in cutting the canopy. I decided to do a trial test in cutting the canopy - though I have already gained some experience in cutting the window panes for the TB. When I received the canopy from Todd Silver, it came with a protective canopy (replica) which is shaped very close to the real one. So I butted the replica against the fore edge of the TB step through the entire trimming process. There were a few lessons learned and will be discussed below.

 

Trimming The Canopy

It was not clear to me (from the plans) the sequence of steps for trimming the canopy. After the trial test above, I followed a couple general steps. First, I notched out the aft base of the canopy such that the canopy rests flush on the TB. The second step is to notch out the canopy, where it rests on the instrument panel (left and right), until the dip at the canopy/TB interface disappears. In preparation for the trimming effort, I put down ~1" width of electrical tape along the aft end inside surface of the canopy just for scratch protection.

 

Step 1: Notching Out The Canopy Aft Base

First, I measured the arc of the TB (fore end) and the canopy (aft end). The canopy is 55.5" and the TB is 53 7/8". I took the difference of the two measurements and divided the result by 2. That's the approximate height of the notch I need to remove on each side of the canopy. That came to about ~7/8" .

 

The width of the cut is about 1". The reason for this wider width is because as you notch the canopy over the IP in Step 2, the entire canopy will tilt forward - especially the top aft edge, reducing the amount of overlap between the canopy and the TB.

 

I notched out the canopy base (with my air grinder & cutting wheel) a bit at a time and alternating left and right, until the top of the canopy sat nice and flush on the TB. The air grinder/cutter is an awesome tool for cutting the plastic. Watch out for the flying debris (plastic particles) that get kicked up during the cut. It stings when they hit your arm and they do not taste good either... Yikes!!! (Lesson learned - keep your mouth shut while using an air grinder...)

 

Note the extra gap I have between the end of the glass notch and the TB? I also put a set of alignment marks at each side (masking tape) and the front to make sure the canopy stayed in the appropriate position throughout the trimming process.

 

 

 

 

Step 2: Notching Out The Canopy Fore Base    

I marked the location of the front notches at its contact points on the Instrument Panel (IP). Then I lifted the canopy off the fuselage for trimming - just didn't want to have the tool slip (that would make my day...for sure). 

Again, I trimmed a bit at a time (normally about 1/4"). Once trimmed, I put the canopy back on the fuselage, re-aligned my marks (above) and observed the dip. I repeated this process until I was comfortable with the appearance of the interface. I had to remove the protective cover because it masked the real curvature of the canopy.  I just had to be real careful throughout the trimming process.

 

The key to this step (in my opinion) is the give and take process. The more I trimmed off from the front, the less the tip (at the interface) becomes. However, the more you take out, the less internal space you'll have - especially at the front and (maybe) a bit less streamline to the overall profile of the canopy and TB. I measured the space between the top of the IP and the canopy.  

 

 

Here's a picture of my canopy after trim. I think there's still a slight dip at the interface (if you stare at it for a while) - but its not obvious. I think I can cover it up with the subsequent glassing process. Again, this is one of those personal preferences / give and take situations. I wanted to maintain maximum internal space but no dip for better profile appearance.             

 

 

 

Here's my positional dimensions for comparison:

- Height between top of IP to canopy --> 3.75"

- Horizontal distance between fore face of F28 and canopy --> 3.25"

- Distance between inside edge of canopy (contact point w/ IP) to the rising point of IP (for breaker panel) --> 2" (both left and right)

- Remember that I raised the fore end of my TB by 1".

I replaced the protective cover back on the top of the canopy after trim.

 

Repeating Step 1 and Step 2

Though my canopy looks OK, it just bothered me a bit that my dimension was so far off when using the BL0 template. I decided to contact builders that used Todd's canopy and had raised their TB by 1". Surprisingly, they were tougher to find than one might expect. Finally I got a nice response from Jon Dembs who matched my same build criteria. His dimensions were 3.125", 6" and 1.25" respectively. After a couple of email exchanges, we concluded that my canopy is too far forward. In addition, I read forward a bit to Step 11, Fig. 45, I definitely need more space in front of the canopy for the skirt.

 

After fussing with the dimensions a couple hundred more times, I ended up trimming the aft end of the canopy by 1" at the top to 1 3/4" at the base (remember the canopy is tipped forward?). I also had to widen the slot over the IP by 1"+. My final dimension turned out to be:

- Height between top of IP to canopy --> 3.5"

- Distance between fore face of F28 and canopy (using BL0) --> 7"

- Distance between inside edge of canopy (contact point w/ IP) to the rising point of IP (for breaker panel) --> 1.25" (both left and right).

That's more like it and the canopy/TB interface flows much smoother. If you look real close (at the pictures) between the 1st pass vs. the 2nd pass, you can see the difference.  

 

[Hindsight] If you are using Todd's canopy, most likely, you need to trim ~1" excess at the aft end. BTW, so did Jon Dembs. 

 

 

Trimming The Canopy Edge

At this time, the plan calls for trimming the canopy edge to 1/4" above the longerons. Marking the trim line on the canopy can be tricky because it has a curvature that varies in distance from the longerons.

 

 

 

 

 

 

 

 

 

Here's what I did:

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Mount a 1" electrical tape all the way around the bottom of the canopy, so that I can draw a line on it with felt tip pen;

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Cut up 2 small pieces of wood (~ 1" x 2") and draw a fine straight line 1/4" above their bottom edges;

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Place the wood blocks on top of the longerons (span of the canopy);

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Cast a horizontal laser beam connecting the two lines on the blocks. The laser beam, in-turn, will cast a nice horizontal line, 1/4" above the longerons onto the white electrical tape along the bottom edge of the canopy;

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Trace out the lines with a fine marker...you have just established a precise cut line on the canopy per plan.   

 

Note the laser in the foreground (bottom left of the picture), the 2 blocks on the longerons, the white electrical tape on the canopy and the red laser line? One additional note, besides a side to side alignment of the blocks (with the laser), do a front to back alignment as well by putting one of the 2 blocks on the opposite longeron. As shown, I did not have much to trim. In other words, I am using most of the canopy --> that equates to maximum internal space.

 

BTW, don't forget to trim an additional 1/4" from the slot above the IP and add the 1/4" shim below it.

 

Marking the Tape Line

Instead of using the templates FS 70, 60, 50 & 41 to establish the tape line, I used my laser again as above. Firstly, from M27, I extracted the height dimensions of the tape line above the longerons (WL23) - they are 2 11/16", 2 5/8", 2 3/8" and 2 1/4" respectively. Then, I made 3 wood blocks 2.5" x 3" with horizontal lines drawn with the above height dimensions.

 

Using my long angle ruler, I marked the FS 41, 50, 60 & 70 locations on top of the longerons. Then I set the 3 blocks on the longerons and lined up the laser at each FS location respectively. Note the vertical laser line is in-line with the appropriate FS. Once set, I placed a small piece of vinyl tape on the inside of the canopy (right at the cross hair) as a back drop. The position can be marked with a felt tip pen. Make sure you line up the laser with the 3rd block (located on the opposite longeron). This assures that your laser is square, both vertically and horizontally.

 

 

See how close my BL0 template matches my canopy position per plan - after I re-trimmed the canopy the second time? The laser mark is at the same height as template FS 41 tape mark.

 

I connected the marks with a felt tip marker and a 1/16" thick x 1/2" wide x 6' long aluminum strip from McMaster-Carr. Then I applied vinyl tape along the line per plan.

 

 

[Hint] You can wipe off the felt tip pen markings with vinegar and a cotton swab with no adverse effect on the canopy plastic. I always wipe over the area with water to make sure I remove all vinegar residue. You can also remove the markings with a soft pencil eraser - just as effective.  

[Hint] I got my laser from Costco for $20 that has a tripod and a three prong adjustable level - very handy for this task.         

 

Nose Template

I held off working on the nose cover until the Canopy Skirt Section as recommended by many Cozy builders. That way, one can shape both at the same time - thus providing a better flow/profile. I don't think there is a better way to get a smooth flow from nose to canopy than using a nose template (as suggested in Wayne Hicks web site). Unfortunately, you have to make your own nose template because your canopy position plays an important part to the nose template profile and it'll be hard to find 2 Cozys having the exact canopy positions.

 

I cut out two strips of 1/8" masonite boards (the brown ones we used for shaping the fuselage in Chapter 5) about 85"x17". Then I drew a straight line about 4" below the top edge - that's my WL23. I did not trace out the nose profile directly from the drawings because the fuselage is curved from the fuselage sides to the nose, but the drawings are flat. Therefore, I first marked out the FS positions along the longerons (i.e.. 0, 5, 22, 28, IP, 41, 50, 60 & 70 respectively). Then I mounted the masonite boards (nose templates) onto the sides of the fuselage and transferred the FS positions from the longerons onto them. I extracted the profile positions (WL) at the above FS from the drawings and marked them onto the nose template, above WL23. I connected the dots with a 1/16" thick x 1" wide x 6' long aluminum strip - forming my nose profile. I bolted the 2 nose templates together with 3 bolts so that they will not shift while I trim them to shape. I made minor corrections to the nose templates to make sure the apex of the nose template lined up exactly with the foremost tip of the canopy. You can do that with a straight edge resting at the apex of the nose template and observe its position relative to the canopy.

 

 

Instead of bondo (I never had good luck with bondo) or screws, I mounted the nose templates by resting them on small blocks of wood hot glued to the fuselage sides, complemented with clamps. Notice the clamps at the nose and the TB? The top edge of the nose templates lined up quite well with the tapes. Now that I got the nose templates made, I wonder if I even needed to put tape (along the tape line) on the canopy in the first place.

 

 

 

 

 

 

 

One of the most important check points with the template is to make sure the apex of the template intersects the canopy at the exact height (shown left), otherwise you will end up with a miss-match.

 

 

 

 

 

 

 

 

 

Mounting the Foam Skirt Support

Mounting the supports for the foam skirt is pretty straight forward. However, there are many ways in doing so per various builder's web sites. The plan suggested using bondo to hold the support beam but I am just not good in using that stuff. I prefer to use clamps instead. The picture (left) shows how I used clamps to hold the support beams at the IP and F22. Note that I cut a slot in a couple of support blocks to make sure the support beam stays-put.
  

 

 

 

 

 

The beam at the shoulder support, on the other hand, was a bit more challenging. There's just no good way in clamping it in place. After contemplating the problem a while and I realized the solution is right in front of us. Here's what I did... 

I made two (2) L brackets (elbows) with a 1/4"x2" slot on both faces. I bolted one end of the elbow to the safety belt bolt and the other to the support beam with a screw. That way, I can adjust the level of the support beam as necessary - simple, no bondo and no clamps.

 

 

 

Here's a picture of the support boards in place for the foam skirt.

 

 

 

 

Floxing In The Canopy

I roughed up the aft edge of the canopy w/ 220 grit and the flange of the TB with 36 grit. Then I spread some flox on both mating surfaces and re-installed the canopy per plan. Instead of the Bondo boards, I used a couple of screws holding the canopy tightly in position (at the base). I did not use any weight on the top of the TB because they fit together very well.