New Portlights

As with most fiberglass boats the quality and age of mine, the portlights leaked like a sieve. After doing many hours of internet and book research, I settled on the technique described here:

http://www.thecoastalpassage.com/windows.html

This method uses no fasteners or frames and instead relies solely on the adhesive to hold the portlight on. The adhesive I used was Dow Corning 795 silicone building sealant, which was recommended on several boating forums. This stuff is water and UV resistant, has a high tensile strength, and has an elongation factor of 50% so it should easily stretch with the expansion and contraction of the acrylic in response to temperature. Evidently, this is what's used to hold windows into skyscrapers, with no fasteners, so that seems pretty strong. Here is the info on the sealant:


http://www.dowcorning.com/applications/search/default.aspx?R=264EN

The reasons I went with this method are:

1) Replacing the acrylic and reinstalling in the stock aluminum frames looked
a) time consuming since cleaning and bringing the frames back to good condition required removal of lots of old sealant and deck paint.
b) low strength due to weak attachment of frame to cabin

2) Cost effective since purchasing new retail boat windows was prohibitively expensive and would likely require fiberglassing in the old portlight holes then cutting new holes to accommodate the new windows. Alternatively, Corona Plastics in southern CA makes exact replacements of the Col 26 mk2 complete with nice vinyl frames, but this option was way out of my price range.

3) Easy and quick installation.

4) Strong with allowance for acrylic expansion/ contraction, as discussed above.

I didn't take many picture during this process so I will describe what I did as accurately as possible. First I removed the old portlights be unscrewing the inner frame piece then carefully pried and cut the window free with a metal paint scraper and razor blade. I then detached the outer frame from the acrylic pame and scraped all the old sealant from one of the panes.

I took the old pane to the local plastic store and ad them replicate two new panes from it, only with each 2 inches wider all the way around. I used 1/4 inch, dark tinted acrylic.

To install, I scraped and cleaned around the portlight holes thoroughly. I followed this by painting 3 coats of epoxy onto the exposed portlight cutout's plywood inner core all around the opening to seal the open plywood grain. Once the epoxy was dry, I held the new panes (left the backing paper that comes on the acrylic on) onto the outside of the cabin such that the window extended beyond the cutout 1.5 inches all the way around. A second person then traced the window in pencil around the outside of the pane onto the cabin, then traced the outline of the portlight cutout from the inside with a sharp razor blade. This allowed the removal of the backing paper around the perimeter of the inside of the pane.

I sanded this exposed perimeter with 400 grit sandpaper and then sprayed it with black all-purpose, high bond, Rustoleum primer. I removed the rest of the backing paper from the inside face of the acrylic before the paint dried. The purpose of the primer is mostly aesthetic to make sure you cant see the tape and sealant around the edge of the portlight, through the acrylic, when finished. The primer also adds UV protection to slow the degradation of the sealant.

When the primer had dried. I applied 3M VHB 4991 double-sided tape, leaving the backing paper on the tape, around the perimeter lined up right next to the inside primer border.

Using a scraper and razor, I stripped the old topside paint down to just past the pencil outline on the outside of the cabin, though I left a few spots of pencil in place so I could realign the window, retrace it onto the now exposed cabin gel-coat, the go back and remove the remaining paint at the realignment marks.

I cleaned the frame opening thoroughly with acetone. With assistance from another person, we removed the tape backing paper, held the new pane up to the hole, carefully aligned the tape edge to the cutout edge and the pane edge to the pencil trace, then pressed it into place on the cabin. This left a nice 1/8 high by 1/2 inch wide gap all around the pane edge due to the double-sided tape acting as a gasket. I then taped off the outside of the cabin around the acrylic outline leaving the tape edge 1/4 inch outside perimeter so that a nice bead of sealant would be left along the pane edge in the final product.

With the sealant tube in a caulking gun, I squirted this gap full of sealant all the way around, then pressed the excess into the gap with my finger and smoothed a nice edge all around. I removed all the tape immediately and then removed the acrylic backing paper from both sides and voila, it was finished!

The finished product looks pretty good I think. The larger portlight size gives the boat a much different look. Just need to finish the inside of the portlight cutout with some sort of frame or or trim t o dress it up in the cabin.