Wednesday, January 28, 2015

Oh, I've Been Working on the Windows...

...all the live-long day.  As I mentioned in my last post, my replacement acrylic windows arrived yesterday.  Also mentioned was the fact that the quality of the cutting done by Lee and Cates Glass was sub-par.  They apparently used a jig saw to cut the shape and the jig saw operator apparently wasn't the best at following the lines. The shop then took a belt sander to the edges to clean up the saw marks.  The sander used apparently had about a 40 or 60 grit paper on it, and the result of the sanding was a very rough finish with a random depth chamfer on the edges.  A really poor edge finish that would be OK if there was a trim piece to cover it, but not at all suitable for a Leopard (the windows are only held in by a bead of sealant).

What passes as a finished edge at Lee and Cates Glass

So, the first thing I had to do today was to clean up the mess left by the glass company.  If the windows had been cut a bit oversize, I could have used a router to trim down the edges and get a good result...but that wasn't the case.  So, I decided I would try sanding the edges to straighten them out.  After some sanding with 120 grit, I realized how un-straight the cuts were and decided I would do my best to give it the illusion of straight.  When I got the worst of the waviness out, I hand sanded the remaining chamfer to even it up.  I then switched to a 320 grit paper to try and clean up and slightly round the chamfer.  Four hours later the end result on the two windows, while not perfect, I think looked significantly better.  By rounding it is a little harder to see the lack of straightness in the edge.

After a lot of sanding, it looks a little better.

The next step is to black-out the edges of the window.  You see, the shape of the window is different than the window opening and in order to not see the mounting and fuselage underneath the window, these areas are coated with a black paint. In order to do that, I needed to transfer the shape of the internal window opening to the protective covering of the new glass so I could cut and remove it.  I created a pattern using construction paper by shining a light through the old window and tracing the outline. I then cut the pattern out, leaving tabs that went to the windows edge at several locations to aid in placement on the new window.

Lining up the pattern using tape reinforced positioning tabs.

Once the pattern was cut out, I laid it out on the new window and traced the outline with a marker. Using a sharp knife I then carefully cut the protective paper along the line and removed it.

Removing the protective paper for the blackout area.

In order to get the paint to stick, I hand sanded the exposed acrylic.  I re-taped about 3/4 of an inch of the edge of the window that I didn't want covered in blackout to help guarantee the sealant will hold the window this time.

Sanded with edges taped, ready for the blackout

Of course the black paint they originally used when installing the window I believe to be the main source of the seal failure (the whole reason I am doing this) so I tried a different option.  On the Leopard Catamaran owners group on Yahoo, someone said they had thinned down some Dow 795 sealant with mineral spirits and then used it to black out the window.  Since 795 is the currently recommended sealant and the one I will be using, and since it is supposed to stick well to itself, I decided to give this a try.  Using a partial tube of 795 that was graciously given to me by a fellow Leopard owner and blog reader, I created the thinner 795 and applied it to the window.

Blackout thinned 795 applied

As you may be able to tell from the shadows in the last picture, the day was ending as the blackout started to dry.  So, it took all day, but the edges of both windows are now better and the starboard window (if the sealant "paint" cures) should be ready to install tomorrow.


  1. It's a little late for this tip. With JUDICIOUS use of a small torch, the ratty edges of the cuts may have been blended into something smooth. If you have some leftover to experiment with, give it a try. It takes some practice to get the right flame size, distance away, and fanning technique but when done correctly, the acrylic will flow/melt a bit and dress up the edge nicely. Experiment first, Grasshopper.

    1. Hey Dave,

      I'm familiar with flame polishing and if I wanted a polished edge I probably would have given it a try after my sanding. Since my goal is to get the sealant to adhere as best it can, the sanded finish should be least in theory. I don't know that flame polishing would have taken care of the very rough shape the edges were left in though...and I know it wouldn't have lessened the wavy/unevenness of the edge.

      I do have some scraps so I might play around with flame polishing it sometime just to see what it does...if I can find someone with a MAP torch.