Windows Revisted

Once I put the plane up on the gear and cleaned everything off to include the plastic on the transparencies I came to the conclusion I wasn't really happy with a couple things.  One was that the fiberglass lines around the windows were a bit sloppy. When I pulled the mess of tape off there were some area's that had chipped and others sections were some maybe the tape had covered it so it didn't fill correctly with micro. The other more important item of concern was that even though I felt I did my due diligence on keeping the windows protected there were still some scratches, paint or fiberglass resin left on the transparencies.

In regards to the window edging here is an example of what I'm talking about.  You can see some of the jaggedness of the tape and then where prime UV was applied directly to the transparency.  Maybe the painters correct this, maybe they don't.  Either way whats a few more hours spent on this over the grand scheme of things.

Over on VAF it was suggested that I retape the transparencies and thin epoxy with some acetone and work it around the areas to fill any gaps.  Then after sanding, remove the tape and end up with a new line.  I wasn't keen on thinning epoxy with Acetone because that in sense is diluting the epoxy and reducing the cured strength. I knew that heated epoxy is essentially thinner I decided to do some experimental aviation action with this.

My idea was to have some really hot water and work the cup in and out to get the consistency I wanted.  I used an electric kettle, metal bowl and some plastic cups and some duct tape to set it up.

Here's what I learned... boiling water is way too hot.  Even using an additional cup as a bit of an insulator as soon as I put the water in it started melting the cup.  So I ended up removing that, mixing some tap water in the bowl to cool it down.  Then in rapid succession dipping the cup in and out, stirring the epoxy and repeating if necessary.   It really didn't take long, maybe 5 - 10 seconds to have the epoxy to paint consistency. Word of caution is this speeds up the curing process so even with this slow cure hardener I had maybe 20 mins to get this on the window.  I did this work in two small batches.

Using just a foam brush I worked around the sides and used a spreader to move the epoxy outwards.  Took extra caution not to get any on the transparencies and wiped off any that made it onto them.  Used dye to make the epoxy black so it would stand out in area's I didn't want it.  All worked out well and after I got it all down I went back over everything with the spreader just to ensure all was good.

Now cure time..., you can see the scratches too.

After curing I used 220 and a small sander block and slowly worked my way around the edges. I made sure I didn't go off onto the windows or too far back onto the cabin top.  To help remove the tape easier I went around the perimeter with a heat gun.  Seemed to either not be needed or worked extremely well because everything came off in one piece. The end result was a more defined edge that the painter will have an easier time working with.

Now to tackle the scratches.  I read about two ways to do this type of activity.  One is to order a micro-mesh kit which seems to be a collection of sandpaper between 1500 to 6000 grit.  I watched a video of someone doing this and they worked a very small area for about 5 mins up to the 6000 grit and then polished it.  Easy enough but might be tiresome...

So I went with the Scratch Off Windshield Repair kit. This comes in two versions, the one I purchased, and then there's the deluxe version that has some additional components.  I went with the smaller of the two to help reduce the learning curve and it's has everything needed to attempt your scratch removal. Even comes with two buffer pads to attach to your drill to help the process. Through my research I found an article talking about the various methods. Here's a decade old article I read.

The process is easy enough, you work against your scratches in perpendicular movements starting with 600 grit.  You wet sand each area until you can't see the scratch anymore.  Now you see a bunch of little scratches though and a foggy appearance so in order to get clarity back you use the kit to restore it.  Now with my windows there were only 3 scratches that I had to remove with 600 grit.  The remaining paint, smudges and what not I used 1000 grit.

The kit has 4 bottles of stuff you use with one of the two pads to start buffing.  Each bottle is numbered and for the 600 sanded areas I started with bottle 1.  Cleaned it off and then did all the areas  with bottle 2.  You cycle through all of this washing the windows in between until you get to bottle 4 which is more like a wax polisher.  With this step I went over all the windows in their entirety not just the scratched areas. Quick note the instructions say you can over heat an area but it wasn't an issue to keep moving around.  I tried to hit each area about 6 times which worked well.  Take your time to ensure you're doing it correctly and it's easy enough.

Before

After

I'm very happy with the results.  Knowing that I can do this now gives me a bit less angst about the wear and tear these will incur during flying. I will most likely go through this at least once every year or so to ensure these windows stay in good shape.  For the rest of the time I taped everything up and won't remove it until the plane is out at the airport.