Window Installation Steps

I completed the installation of the two smaller forward, smaller windows at the beginning of the week.  Here are a few photos showing the procedure, as several people have emailed to ask about it since my last two posts.  This is my first installation like this, having learned the technique from David Halladay.  After asking him all my questions over the phone, I proceeded with it and it turned out great and was easier than it sounded.

First, here's a view of the prepared inner flange, as it might not have been clear from my last post how this was built.  The flange itself is made of 6mm ply, and is 1 1/4" wide all the way around the inside perimeter of the opening.  You can see from the shadow that it is set back from the inside of the opening.  This is because of the 6mm plywood spacer sandwiched between the flange and the opening.  This spacer allows a generous bed of the DOW 795 sealant to fit between the acrylic window and the flange.  The space is necessary to allow movement of the acrylic, which expands and contracts at different rates than the wood/epoxy around it.  

The painted area around the window opening is then masked with clean-release tape that won't damage the opening:

The acrylic window, which has been pre-cut and fitted, is now prepared for installation by Super-gluing several flat blocks of plywood to the paper backing that comes on it.  These blocks around the perimeter will hold the window panel flush with the outside of the cabin surface. 

On the inside surface it's best to remove the paper backing and tape it with masking tape so it can be pulled off easily after caulking.  The masking tape is cut back to the edge of the inner flange.  The glue surface of the acrylic and the inner flange is sanded and cleaned prior to application of sealant. 

 This photo shows how the window is held into the exact position in the opening by the glued-on blocks of plywood.  Paper masking tape is applied over the clean-release tape, as it glues better than the blue tape.  Then blocks of wood are Super-glued to the boat on the paper tape to hold the window in the center of the opening. There is a 3/16" gap all the way around the perimeter of the opening, and these blocks will maintain that position while the sealant cures overnight.

The forward window on the starboard side was done at the same time.  After getting the blocks set up, the sealant was applied to the flange and the windows set in place.  At this point the inside edge can be finished from inside the boat and the blue tape on the inside surface pulled away.

The next day, after the sealant has cured enough to bond the window in place, the blocks and the brown paper backing are removed.  Then the painted surfaces and the edges of the windows are re-masked with blue tape.  

The last step is to thoroughly fill the outer perimeter of the window, forcing the caulk into any voids left in the first application.  The excess caulk squeeze-out is then removed, and the perimeter is tooled with a small filleting tool for a nice, slightly-coved seam. 

At this point, the tape is pulled and the installation is done:

No screw holes to crack the acrylic or eventually leak, and no outer frames to trap water that could lead to rot.

Just a clean, flush surface that blends right in to the rest of the cabin sides.  With the huge amount of DOW 795 that it takes to fill between the flanges and the acrylic, there's little chance windows installed this way will ever leak or give any other kind of problems.