Finishing Kit

January 05, 2014

Installing the Rear Window - 5.0 hours

Today is the big day, for my rear window! With all the prep work finished, as best as I can figure it, it's time to dive in and get this window installed. Here's the first task, getting the window that has been scuffed, cleaned, and masked off, ready to install. As usual for Sikaflex, you first apply the Sika cleaner, wait 10 minutes. Then apply the Sika Primer, as seen here. Then wait 30 minutes. The primer is on the top surface for most of the window that goes under the fuselage skin, and on the bottom surface where it goes over the roll bar.

Next, the roll bar and the fuselage skin get the same treatment. Sika Cleaner, wait 10 minutes. Sika Primer, wait 30 minutes. If you recall from earlier when this skin was riveted to the fuselage, I left the forward rivets on the "arms" of the skin un-riveted to make it easier to pull them out and slip the window in place. Those clecos are now removed, as you can see below. I might comment on one more thing that I gave a lot of thought. For now, I have left the inside clear plastic on the plexiglass window, as it comes from Vans. I wondered, though, about being able to pull it off afterwards, with the canopy brace in place. I didn't want any chance that pieces of it might be stuck above the canopy brace and under the plexi. Highly visible, yet impossible to reach. There's hardly any clearance under there. So I ended up trimming the plastic off along the canopy brace, leaving the top portion that's directly above the brace clean with no plastic. Then I worried, what if some Sika gets smeared on that visible part of the plexi? That would look horrible. I figured some might be squeezed out from under the skin when pressure was applied. So I took an old plastic electronics bag (like computer motherboards come in, for example, this stuff is really tough), and cut it and wrapped it around the brace. You can see it here, with a piece of masking tape on it. I figure, this will keep the brace clean of any Sika, and it's tough enough to allow me to pull it out of there when the Sika has cured. So the window and the canopy brace are both masked off.

Here's the inside, the underneath surface of the fuselage skin. It too, has received the Sika cleaner and primer. Note: no holes drilled! We're ready for the SikaFlex!

When I got busy applying the Sikaflex, I didn't stop to take a lot of pictures until the window was installed. It's real straightforward. Apply the Sika and smooth it out on all the surfaces it's supposed to go on, then slide the window carefully in place. I pulled it forward against the tape spacers and wrapped the yellow strap around the whole thing.

Then I lifted the canopy up, so I had access. On the inside, I put the flexible pusher sticks in place, and you can see the masking for the canopy brace is taped in place. This all worked beautifully! The window pressed right up tight to the skin, just like I wanted. A tiny bit of Sika oozing out all around.

Here's another shot, showing the left side. It all looks good in here, so far! Before climbing back out, I reached in with a gloved finger and smoothed out the fillet on the Sika all around the window, now that it's in place. It was a bit difficult to reach around the roll bar, but I smoothed it out too, as best as I could. I didn't get a picture of that.

Back to the outside, it's well-known that there is a problem area with the forward parts of the skin. The skin wants to pull away from the plexi along this area, and it's a challenge to close the gap. If the window is installed with the traditional Vans drilled holes and hardware, no second thought is given to this area. The hardware pulls it together. How do you do that with Sika? Well, earlier I had taken some wood blocks and cut them with my bandsaw to closely approximate the shape of the area, thinking I could put them under the yellow straps and pull them down tight, pulling this area together and closing the gap between the skin and the plexi. When it came time for the real deal, it didn't give the results I had hoped for. There were still gaps I didn't like. Some quick thinking, and I started pushing some popsicle sticks under the block where needed.

Here's a closeup picture. The popsicle sticks pushed the skin in and closed the gap until it fit nice and tight along here, just like the rest of the skin. The sticks are doubled-up in a few spots. Not needed at all in others. I was very pleased how this worked!

Here's a couple shots of the left side. Same thing here. This method worked very nicely.

At this point, it was time to take a gloved finger and go around and smooth out the fillet all along the seam. This also gives you an opportunity to inspect every inch of the work. This is basically finished at this point, until it cures.

Now I closed the canopy and once again, looked very carefully to make sure the window was pulled forward to bump up against the tape spacers I put on the rear edge of the canopy. Lookin' good! I think the gap is perfect.

Nothing to do now but "wait for the cure". I was a bit nervous at this point. I kept staring at it and walking around. There's no turning back once this stuff cures, and I kept looking for anything I might have overlooked. Seeing it all looking good, I decided to pull some of the black electrical tape while everything was still soft. So I pulled off most of the blue vinyl and the black electrical tape around the window. Wow! Now I can't wait to get rid of the strap and finish this up.

Not being able to find anything else to do, I finally called it a night. Before going to bed, I slipped out here a few more times, just to make sure nothing had moved, slipped, or changed.

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