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Rear Window Overhang of Roll-bar F-01431D Shim?

Bungalow Al

Member
OK, doing a "Take Deux" of the rear window after a gut wrenching and
expensive crack. Don't ask......:mad:

Now, trying to figure out what distance should the aft window overhang the Roll-bar Shims - F-01431D, before I drill again. I don't have a plane to look at, and I am not sure how far the fwd canopy overlaps aft.

Right now I have it where the channel created by the shim is not covered, and it is even all along the bar.

Anyone want to send me a pix or tell me what works?

TIA!
 

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I recommend you move it fwd. slightly so that it extends fwd, just beyond the edge of the aft ribs. This will give you a little more edge distance on the holes.

Then when you fit the fwd. canopy, shoot for a finished gap of about 1/16". This is to allow for the large amount of expansion that can occur in very hot temperatures.
 
So it is better to have the rear window hang slightly forward of the aft Rollbar F-01431 Shim?

Just want to be sure that leaves me wiggle room with mounting the forward canopy when it comes.

I understand and like the idea of some edge distance from the screws and definitely want the expansion room!

Thanks for getting back to me Scott!
 
Yes, you want the rear window slightly ahead of the shim. Mine was roughly 1/32"+ forward of the shim when I started mating to the canopy.

If the rear window is exactly even with the shim, you're going to have a hard time getting the finished edge to look nice as you'll be completely reliant on the shim itself for your edge. I'm sure there's a number of different ways to do it, but to mate the forward canopy with the rear window, I used a piece of 120 grit sand paper stuck to a 1/64 piece of ply with 3M 77 and worked my way around the gap. This will mate the rear window to the canopy and they will fit perfectly.

Once that small gap is set, you can decide how large of a gap you want by varying the size (thickness) of the wood holding/stuck to the sandpaper and working your way around the gap again. Since the gap will be perfect, stick the sandpaper to only one side of the ply and take the material from the canopy. You'll put the side with no sandpaper against the rear window. Time consuming? Yes. Perfect...yes! I decided on a a .040 gap but may increase.

If the rear window is flush with the shim, you won't be able to take any material off of it to mate with the canopy and you'll be stick with whatever edge/fit you had when the rear window was installed.

Hope that makes sense.
 
Thanks Reflex.

Playing around with it now. At the lower parts of the Rollbar I get quite a bit of overlap when all the rest of the bar is even.

Is the Side skin supposed to be trimmed even at the ends?

I also noticed that the last hole on each side is about 1/3 way into the second side hole at the end of the Rollbar. (Pix) I'm thinking that it will need to also be shave to avoid any cracking.

The work continues.........
 

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Don't underestimate the amount of expansion that the canopy has in hot temperatures, both at the rear on the canopy and the front lip. Heed what Scott says above or you will get interference between the canopy and the window edge and/or the dreaded snap in the front when it hangs up and bends the lip.
 
Is the Side skin supposed to be trimmed even at the ends?

Do you mean trimming the sides of the aft window (not side skin)? If so, then yes - the sides of my aft window were trimmed to be fairly even with the forward edge of the aluminum skin.

I did the final trimming after drilling all the holes in the aft window, since prior to drilling you won't know precisely how much to trim the forward edge of the aft window.

_Alex
 
Al,

A couple of thoughts:

  • Yes, the rear window will need to be trimmed at the bottom. This is to clear the F-01474A stiffener angles. This isn't mentioned in the manual. FYI - I don't recall the window running down into the second hole, but that doesn't mean it didn't.

  • Regarding the front on the rear window (the edge that mates with the canopy), yes, if you let the window come past the shim it will extend a bit past the rear skin as it does in your picture. I think you'll find that the front edge of the rear window is relatively straight and when you mate the to the canopy with the procedure above it will come out very nicely.
One of the things that I found important was to put pressure on the front edge of the rear window to insure that it was contacting the skin in the rear portion. This will move that vertical edge in you picture back just a little. However it will still overhang the front shim slightly if done properly. It helps to have a third hand while drilling.

I can't take credit for the photo below, I borrowed it from Steve's web site, but I did the exact same thing.

IMG-4179.jpg
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Chris, Alex, Reflex, and Scott,

Perfect, you answered all my questions. And the pix was worth a thousand words - thank you.

This website is great!

Now, to get my nerve back up to drill and trim after the first disaster..........
 
Chris, Alex, Reflex, and Scott,

Perfect, you answered all my questions. And the pix was worth a thousand words - thank you.

This website is great!

Now, to get my nerve back up to drill and trim after the first disaster..........

Use a tapered reamer to drill the holes. I used #36 & #27s. Worked like a champ. I just finished mine and had no issues.
 
Thanks to everyone for these posts, they're a must-read in my book.

One difficulty with the rear window install is that the KAI, at least as I read it, calls for the window to have zero overhang with respect to the F-01431D shim, and only a 1/32 inch gap between the window and the canopy. Page 38-03, steps 6 and 10, state rather clearly that the rear window should be trimmed flush with the forward edge of F-01431D, not overhanging. Page 38-21, steps 5-8, call for trimming the canopy to terminate 1/32 inch ahead of F-01431D.

Noting: (1) there is only 1/8 inch gap between the front and back roll bar frames to work with; (2) the rear window should slightly overhang the F-01431D shim; and (3) when completed, there should be a 1/16-inch gap between the canopy and the rear window for thermal expansion, it looks like:

(1) the rear window should overhang the shim by 1/32-1/16 inch, and (2) the canopy should be trimmed as necessary for a 1/16 inch gap. This places the rear of the canopy either flush with the forward canopy frame, or overhanging it by 1/32.

I think this accurately restates the above posts, will someone please confirm or correct this before I make an expensive mistake? Thanks to all!
 
Avatty,

I wouldn't say the manual is incorrect, but I can tell you what I did and I'm very happy (you might say proud) of the way my canopy turned out.

Yes, I left a 1/32 overhang on the rear window with respect to the shim on the roll-bar. As you've probably figured out, by the time the shim is deburred, countersunk, and riveted there can be some very tiny deviations from it being perfectly straight/aligned with the roll bar gap. On the other hand, it's relatively easy to get the rear window perfectly aligned with the canopy itself. Leaving a 1/32 overhang hides these deviations and allows an easier time "setting the gap" between the rear window and the canopy.

Page 38-21 calls for a 1/32 gap in Figure 3 while Scott in post #2 recommends a 1/16 gap. I began "working" the gap toward 1/16" and decided that a .050 gap looks about right for my taste. If it needs more gap, I can easily take a couple of hours and increase the gap while the canopy is on the plane.

For me, the bigger challenge was that once complete, the rear widow and the canopy weren't perfectly flush. There were a few places where the rear window or the canopy was .001 - .004 high/low. This doesn't sound like much, but when I saw the profile on a glossy surface, I thought it needed some attention.

When at Oshkosh, I looked at this on a number of RV's and found that many (most) of the pop-up canopies tend not to fit perfectly flush to the rear window. I estimated some to be as much as .020 high/low. I made a number of shims (washers) out of "feeler gauges" and placed them at 6 places between the canopy or rear window and the frame/roll-bar. The canopy is now perfectly flush with the rear window.

While you have to look pretty hard to see this on many planes...it's there. My fear was wind noise, drag, potential damage....and loss of pride. So I felt the need to make fit and finish better.
 
Thank you, Reflex, for your very thorough posts. I called the builder's hotline, and was also advised to overhang the window slightly. Your advice on a final round of shimming is much appreciated, otherwise I probably would have final-installed the window too soon.

Not meaning to be critical, I think the KAI is totally awesome. On this one particular subject, though, perhaps it could be revised to conform with builder experience and the hotline guidance. As always, this website is invaluable!
 
Avatty,

I wouldn't say the manual is incorrect, but I can tell you what I did and I'm very happy (you might say proud) of the way my canopy turned out.

Yes, I left a 1/32 overhang on the rear window with respect to the shim on the roll-bar. As you've probably figured out, by the time the shim is deburred, countersunk, and riveted there can be some very tiny deviations from it being perfectly straight/aligned with the roll bar gap. On the other hand, it's relatively easy to get the rear window perfectly aligned with the canopy itself. Leaving a 1/32 overhang hides these deviations and allows an easier time "setting the gap" between the rear window and the canopy.

Page 38-21 calls for a 1/32 gap in Figure 3 while Scott in post #2 recommends a 1/16 gap. I began "working" the gap toward 1/16" and decided that a .050 gap looks about right for my taste. If it needs more gap, I can easily take a couple of hours and increase the gap while the canopy is on the plane.

For me, the bigger challenge was that once complete, the rear widow and the canopy weren't perfectly flush. There were a few places where the rear window or the canopy was .001 - .004 high/low. This doesn't sound like much, but when I saw the profile on a glossy surface, I thought it needed some attention.

When at Oshkosh, I looked at this on a number of RV's and found that many (most) of the pop-up canopies tend not to fit perfectly flush to the rear window. I estimated some to be as much as .020 high/low. I made a number of shims (washers) out of "feeler gauges" and placed them at 6 places between the canopy or rear window and the frame/roll-bar. The canopy is now perfectly flush with the rear window.

While you have to look pretty hard to see this on many planes...it's there. My fear was wind noise, drag, potential damage....and loss of pride. So I felt the need to make fit and finish better.

Do you have pictures of your install that you would being willing to post?
On my first build my rear window was 1/16" thicker than stock and therefore left out the shim. Although I am pretty happy with the way it turned out there is room for improvement on the next build and I'll be using the shim.
 
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