Finishing Kit

April 22, 2012

Canopy Installation - SikaFlex! page 2 - 7.0 hrs.

After the big day yesterday, I came out today to continue the follow-up work on the Sika job. The first order of business was to unclamp and pull the canopy off the plane. The Sika has firmly set up by this time, so Jamie helped me lift it off and set it on my workbench. Here it is, upside down laying on a soft sleeping bag, so I can examine the inside thoroughly and decide what to do next. Things looked good, so I went right to work riveting the side skirts in place. You can see I've pulled the clecos from about 2/3 of this side, one at a time as I went along riveting, and squeezed the flush rivets in place.

This was fun. Most of these are easily squeezed, and I couldn't wait to see my canopy without any clecos!

There are a few on the ends that can't be squeezed, so I rigged up the rivet gun and hammered those down. I also carefully pulled the black electrical masking tape off the exterior (interior was done yesterday, right away). Finally, after a couple hours, here's the finished result. No more clecos. No ugly hardware. Nice! This is precisely the smooth, no-hardware look I was hoping for.

Here's a shot of the left side.

Here's a closeup of the left side. You can see the lift handle installed on the right. I'm very pleased with how this turned out. Nice tight bond all along, no gaps or wide spots. The key to this was masking the plexi down very close to the side skirt, and completely masking the metal off on the side skirt itself (refer again to the photo above, where the canopy is laying the bench upside down, you'll see what I mean). Smoothing the small filet out with my finger while it was soft yesterday left it like this. All I did today, after riveting, was pull the tape. I used the same close taping method on the interior as well, and it looks this good in there, too.

Here's the right side closeup. Looks good here, too.

Now, around the front, I pulled the popsicle stick spacers out late last night once the Sika was firm enough to hold up. The next job is to fill in these gaps and add a more substantial bead of Sika all around the front of the canopy. Here's a shot of the right side, after the application and roughly smoothing it out.

Here's another closeup shot of the center area. Looks kinda messy at this point, but I'm going to sand this out as soon as it's good and hard. I hear that Sika sands quite nicely. We'll see. The gaps are all filled in and this is really going to bond the canopy securely across the front. Eventually, I'm going to do the standard fiberglass layups over the front and make a nice fairing.

And here's a shot of the left side. It's all filled in nicely. Nothing to do with this now but wait.

Okay, now to the interior. There was no way to get a look at the aft end of the canopy over the curved bow, as it sat on the fuselage yesterday curing, since the roll bar was in the way. So I was very anxious to see what happened here. Sorry this picture is a little blurry, but you can see how the Sika smooshed out along the curved frame, barely oozing out in a few places just to the edge of the metal. Just right! Had I used too much Sika, this could have smashed out in big globs and made a mess here that would be very difficult to trim down or clean up now that it's hard. This is why I say, use less Sika rather than more, for the first application.

Here's another closeup. The canopy is very firmly bonded to the frame. My job now is to finish this with another application of Sika. I'll go along and fill in all these gaps and make it look nice. The black electrical tape I used for masking is still in place, you can see it in these pictures. It starts about 1/4" in from the edge of the plexi and goes right up to the Sika bead. I will apply a new layer of primer right over the uneven Sika, wait 30 minutes, and then fill this all in with a generous bead of Sika, smooth it out to make a nice looking filet, and then pull the tape off.

I had a similar situation on the other side of the frame, on the inside. I had some paper masking pieces here, all along the curved canopy frame, but I pulled them off, leaving the black electrical tape that I had originally masked this off with. The paper stuff was overkill, not necessary at all. So what I did on both sides was to go along with my caulking gun and apply another bead of Sika, filling in all those gaps. Then with a gloved finger as seen here, just go along and smooth out a nice filet. This was easy to smooth out. This material is low viscosity, very easy to work with.

When you're done smoothing out a nice filet, immediately pull off all the masking tapes while the material is still soft. Here's what you're left with!

Not bad! I'm very pleased with this. I don't have a picture of it, but I did the same on the aft side of the frame. It came out just like this back there as well.

Here's a real closeup shot. It's not perfect, but I can definitely live with this.

At this point, the Sikaflex work on the tipup half of the canopy is essentially finished. I used less than one tube of the product for all of this work. I have maybe an inch to 1-1/2 inches of material left in the tube. Nothing to do now but let this cure completely. This next picture was actually taken a day or two later, after I got some help putting it back on the plane. It fits so tight over the roll bar, you can't find a gap anywhere along there. I couldn't wait to see it in place, no clecos or any clamps or hardware, and see how it works. It tips up and goes back down very nicely! But that's without the front skin clecoed on. The skin is on in this picture. I still have some fitting issues with the gap between the canopy frame skin and the front skin that I'll have to resolve later. Left as is, it will snag when you try to open the canopy.

My only disappointment with this whole thing is that I ended up with a gap on the right side. It's about 1/8", and it's along the right side all the way from front to back. It's hard to see in this picture. But it's there if you look close. The aft end of the side skirt sits above the fuselage skin behind it, when I had made them to be straight and aligned. I don't know how I ended up with it like this, after clamping the frame down before the Sika job, but that's how it ended up. I'm not sure what I'm going to be able to do about it. Probably just put a weather-stripping piece on the bottom of the frame and live with it. The left side actually fits very well.

The rear window will be a while. I have a lot of work to do before that goes in. I plan on doing all the wiring in the aft fuselage first, while I can still uncleco that skin and have easy access to the interior behind the baggage bulkhead. When all that is done, I can finally rivet that skin on. Then I can plan on putting in the rear window for good. I also have plans for the fiberglass fairing across the front of the canopy, but I'm going to give this a good week, at least, to make sure it's solidly cured before doing any work with epoxy resins and fiberglass layups.

April 29, 2012 - 2 Hours

Well, it's been a week now and I spent an evening working on sanding the Sika across the front of the canopy. I wanted to make sure the Sika was fully and completely cured before going ahead. I'm sure I didn't need to wait this long, but there's no harm. I thought I would put this addendum onto this page for the sake of continuity, rather than have another page later, mixed in with other tasks I've been doing in the meantime.

As it turns out, reports were accurate. Sika sands very well! I started first on a test strip that I prepared. I simply applied a bead of SikaFlex to a scrap piece of aluminum and let it cure for a week. I wanted to see how well the epoxy resin binds to the Sika, before I do the fiberglassing across the front of the canopy. Here's my test strip. Interestingly, I was also curious about one other thing. I wanted to see how well the Sika bonds to the aluminum. I lightly scuffed the aluminum, but I didn't use the special Sika Cleaner or the Sika Primer. This is just plain Sika on aluminum. And once again, this stuff is so tightly bonded to the aluminum that I can't get it to break loose, even with a sharp knife.

I sanded the Sika down, taking out all the bumps and irregularities. It leaves a micro-rough sort of textured surface. It's perfect for absorbing the epoxy. As seen above, I mixed up a small amount of epoxy and dribbled some of it directly on the Sika. I also applied a small scrap of fiberglass cloth. I'm happy to report that the epoxy bonds tenaciously to the Sika. After it cured, I used a sharp knife blade and tried to slip it under the hardened epoxy and see if it would lift up and separate from the Sika. NO WAY. You cannot separate the two, no matter how hard I tried. You end up cutting through some of the hard Sika but the material won't separate or come apart. I'm now fully confident that I can go ahead and sand across the front of the canopy and apply the standard fiberglass layups for a fairing.

My plan was to make a tape line, or boundary line, right where the fiberglass layups will come to on the plexi. This is about an inch above the canopy skin at this point. I can always go higher later if I decide to. I wanted to be on the conservative side at first. I used a hard rubber sanding block with a piece of 100-grit sandpaper, the sandpaper over the curved part of the block. The beauty of sanding Sika is that it doesn't clog up the sandpaper. At all. It just falls off. It's unlike anything I've ever sanded before in my life. After an hour or more of sanding, the sandpaper still looks brand new! Here's how it now looks on the right side.

Here's across the center:

And here's the left side. Notice the sort of "2 tone" appearance? Well, the lower blacker part is the Sika. The lighter part above is the sanded plexi. So I'm accomplishing 2 things here; sanding the Sika, and scuffing up the plexi for the fiberglass to come.

Here's a closeup, showing how it's turning out. I can't believe how easy it is to sand this material and clean everything up. Any Sika that had oozed over the front of the plexi has all been sanded away. But that's okay. It's contoured just the way I would like for the fiberglass layups, and the plexi is scuffed nicely, too. I think it's ready to go.

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