Thursday, January 29, 2015

I Almost Have A New Window

Yep, another window post. This is taking a lot longer than I thought it would.  I know others that have said they have rebed windows in just a day or two.  I don't know if new windows make much of a difference, but I'm guessing it is because I'm going slow.  Guess I really want to get this right because I certainly don't want to do it over.

After breakfast this morning, I go to check out my blackout paint work from yesterday.  What I found was that the paint was a little thin in spots. Guess I'm not the best at painting with thinned sealant.  So, I thin a little more of the Dow 795 sealant and apply another coat in hope that it will dry quickly so I can install the window in the afternoon.  After it skins over a bit, I removed the tape that was protecting the mounting edges of the window.

While the window dries, I start preparing the opening.  I removed the plastic that had been protecting the opening during the recent cold and wet weather and applied masking tape and paper around the opening.  Then I vacuumed up the last bits of the old sealant that had somehow been hiding in the opening since I originally cleaned it.  Following that, I clean the mounting surfaces with some denatured alcohol.

The next step was to apply the foam tape that acts as a spacer and creates a dam for the sealant.  When I was reading about this process, most seemed to indicate that the old foam could be left in place and reused.  Unfortunately, it seems they assembled the windows on my boat differently than others as they had applied the foam to the window and not the opening.  When I tried to remove the foam from the window, it pulled apart.  Apparently I finally found one glue on the boat that held well...the backing tape for that foam.

Window masked and foam strips installed.

I had purchased 3 - 10 foot rolls of 3/8" by 1/2" closed cell foam insulation tape at the local big-box hardware store to replace the original foam.  I applied one ring of the foam around the inside window opening and that took one of the rolls.  I then applied another ring to act as the sealant dam that was roughly between 5/8" and 3/4" from the outside edge of the window (I measured the distance from the inside edge of the blackout to the edge of the window to determine spacing).  In the forward corner there is a large space between the inner and outer rings of foam so I added some additional foam strips, similar to what was originally there.  Unfortunately the tape on this foam wasn't as good as the original and I had to use some contact cement to re-glue a couple of the corners down.  In the end it took about 25 foot of the tape for the one window opening.

I spent as much time as I could to allow the blackout to dry, but it was time to dry fit the window.  I needed to check window spacing in the opening and drill small holes that will be used to clamp the window in place while the sealant cures.  I had purchased a small 3/8" thick pine trim board and cut it into a few blocks to use as spacers and wrapped them in plastic (actually cellophane tape) so hopefully the sealant won't stick.  Using the blocks, I set the window in place and adjust the window position and blocks to get a uniform gap around the windows.  Marking the position of the block on the masking tape around the opening and on the protective paper on the window was done to aid in reassembly.  I noticed that the window will be a little recessed and I like the effect.  If I had wanted the window to be flush with the mounting surface, I would need foam that is thicker than 3/8".

Since the new acrylic is flat and the opening has a slight curve, it will need to be clamped in place.  To do this, I used some large fender washers and 1.5" drywall screws.  I held the window in place at the center and probed for points where I would need to clamp to get the window to conform to the curve. I pushed on the window in with one finger  and when I located a good spot, I drilled a pilot hole for the screw.  After marking the location of the hole on the masking tape, a fender washer and screw were used to gently clamp down the window.  I repeated this process until I was happy with the fit and look of the window.  Then I disassembled it all in preparation for applying the sealant.

I have to admit I wasn't looking forward to applying all this sealant with a manual caulk gun, but I don't really have another option here at the marina.  At least I did buy a good quality caulk gun for the job.  Since it was not a particularly warm day but the sun was shining, I had put one case of the sealant in my dark car to warm it up in hope it would help it flow better and maybe prevent my hand from cramping up.

After retrieving the somewhat warmer case of caulk from the car, I take a tube and cut the tip to allow for the largest bead possible.  Going around the outside of the outer band of foam, I apply a large bead of the 795 sealant making sure it stands above the height of the foam.  It took two tubes to run the bead around the foam.  I place the spacer blocks back in the marked locations and then line up the window with the blocks and press it into the sealant.  Using the marks I made for the screw locations, I install the clamping screws until the window pressed against the foam but was not compressing best I could tell.

I expected more sealant to squeeze out of the joint than actually happened, so I got a bit suspicious.  I carefully peeled back a little of the protective paper from the outside of the window and my suspicion was confirmed.  While there was a pretty decent seal, there were some bubbles and voids so I ended up pumping more sealant into the joint and worked it under the window with a putty knife. This took almost another full tube of sealant, but everything appears to be full of sealant now.  Next time I think I'll run two thick beads of sealant around the window to avoid this messy step.

Window installed and clamped with the curing sealant.

So, now I need to wait several days (I'm thinking 4 or 5) to allow the sealant to cure enough to hold the window in place without the clamps.  Once the clamps are removed, I can apply more sealant and created the finished edge bead of the window.  In the meantime, I have another window to work on as well as finishing up the anchor roller mount repair.


  1. Holy cow and I thought the ports on Kintala were difficult???

    S/V Kintala

    1. Yeah, it is quite a process. I can't believe how hard it was to get the sealant off the boat...especially how bad the portlights were leaking.