Sealing the forward window

Tammy Norie’s forward window had a slow leak from when I first sailed her in 2014. It wasn’t very significant, but in the winter of 2017 it managed to rot a couple of books, even though they were in plastic bags. I did two things:

  • Moved the books into waterproof bags
  • Dismantled and re-sealed the window

I’ve been somewhat afraid of dismantling Tammy Norie’s windows in case I couldn’t get them back together without unobtainable parts. As it happens I did have to make modifications. This post should help others with similar windows.

Firstly, I chose a dry day with many more dry days forecast. Then I cautiously loosened the screws around the window frame. At this point, I had no idea what kind of screws they were or what they were screwed in to.

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About half the screws didn’t really seem to be attached, and were probably held in by old sealant and dirt as much as anything. Worse, they were self-tapping screws, not bolts. What were they supposed to bite against?

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Once they were undone I carefully pried the window away from the cabin top using a scraper, breaking what remained of the outer seal.

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With the window removed I could see the old sealant tape, which was in quite poor condition.

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Grains of old salt or possibly aluminium compounds had built up behind the window seal.

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The dried-up sealant was easy and satisfying to remove with a scraper.

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The rubber seal around the window glass (actually a sheet of curved acrylic) was also easy to remove.  It was in good condition, in spite of its age, and only needed a bit of a clean with washing-up liquid.

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The next task was to figure out how to get the glass out of the window frame so that I could renew its seal. I could see that the window frame was in two halves, but didn’t know how it was joined together. At the ends of the window were some very coroded screws, which refused to turn without severe damage.

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In the end, I was only able to get one of these screws out without destroying it.

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Pulling apart the halves of the window frame revealed a metal block that holds the halves together, serving as a nut for the corroded screws. If absolutely necessary, the screws could be drilled out and this block replaced.

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Now the frame was being held together by another strip of sealant around the window glass. I was able to separate the glass from the frame using a soft plastic scraper.

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Then at last I was able to get the glass out of the frame.  In this picture you can see the old sealant tape on the inner side of the frame where the glass was attached.

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After cleaning out this dried-up sealant, I inserted two replacement beads of butyl tape in its place — one on each side of the glass.

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Then I was able to squeeze the window glass back into the frame. There’s plenty of time to do this, since butyl tape does not set. Any excess is easy to gather up for re-use.

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Now, on to the mystery of the self-tapping screws that were failing to hold the window to the boat. Fortunately, they weren’t screwed in to the fibreglass. Less fortunately, they were screwed into a thin layer of aluminium on the inner window frame! Very poor engineering. What’s more, the areas around the screw holes on the inner window frame were severely coroded. No wonder half of the screws weren’t doing anything.

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Still, I didn’t really want to modify the frames, so I attempted to repair the screw holes with Milliput epoxy putty. This was a bit of an experiment, since I hadn’t used Milliput before.

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When the putty had cured, I attempted to mount the frame, first laying a bead of butyl tape around the hole. I gradually tightened up the screws, giving the butyl tape a chance to spread.

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But the screws soon started rotating without biting properly. The putty wasn’t strong enough for this job. Back off with the window and on to plan B. Fortunately, butyl tape is forgiving, and you can gather it up and re-use it.

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Plan B was to replace the awful self-tapping screws with 4mm machine screws, passing right through the inner frame to proper nuts. This unfortunately meant drilling holes right through, and that nuts would be visible inside, but it allowed the frame to be tightened properly. It also means the window is properly attached to the boat!

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(I later bought stainless-steel dome nuts so that the ends of all these screws are covered up. This looks very nice, and also reduces the chance of any injury. I must take a picture of this and insert it here.)

An important detail that I learned by trial-and-error. Do not turn the machine screws in order to tighten them. This tends to make the screws pull away from the butyl sealant, making them leak. Instead, add an extra blob of butyl tape to both side of each hole, then slowly push the screws through. Then tighten up the nut. After this, none of the screws leaked.

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Here’s how the window looked after tightening up the screws, but before I’d cleaned up the excess butyl. A little more squeezed out over the next few months, but was easy to tidy up using a plastic scraper.

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Now, did you spot the “deliberate” mistake? At this point, my windows were still leaking slightly. I was rather frustrated. But by careful observation I was able to work out what I’d done wrong. I didn’t put extra butyl behind the joins in the outer window frame. This mean there was a path for the water from outside to get around the window glass. Here’s a close-up of one of the joins.

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Fortunately, I was able to fix this without dismantling anything. I simply pressed a generous amount of butyl tape slowly through the crack with my fingers.

I tested the window simply by pouring and throwing buckets of water around. But it had a much more thorough test through the winter of 2018/2019. I’m pleased to report that there is no evidence of any leaks.

I’m pleased with this work for three reasons:

  1. I stopped the leak.
  2. I now know how the windows are constructed and can service the others.
  3. The window is now firmly attached to the boat!

That last one is reason enough to service all the windows, so that’s going on the to-do list.

(You can also browse the photos in this album on Flickr.)

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8 Comments

Filed under Repairs and Modifications, windows

8 responses to “Sealing the forward window

  1. Antoine Maartens

    Nice one!

    We did all windows on Siskin save the front one. It’s very much cracked (must be some type of non-glass (acrylic or yoly-carbonate). A pointer to a replacement of the front window glass would be very welcome!

    No leaks in Sskin’s other windows resulting in a completely dry boat. Well worth the effort.

    • Although I say “glass” in the article, mine is also plastic. I have heard that polycarbonate is not good for boat windows as it is soft and goes dull when it is scoured by the sea. I suspect mine is also acrylic. I have not tried it, but you can bend acrylic if you heat it, as described here https://www.wikihow.com/Easily-Mold-Acrylic-Plastic-Sheets . So you could cut a new piece, warm it up, and bend it to fit.

  2. Good job – big fan of butyl tape for all the reasons you describe… the post also reminds me that I must get some dome nuts for some exposed bolts in Sparrow…

  3. Richard Dalglish

    Hi Richard. Yet another really useful post, thank you. It’s just added itself to the list of jobs I’ve got to do on my Coromandel when I finally start to get it back into useable order. It’s still in a barn, though a different one now, so that makes about 10 years since the previous owner laid it up that it’s been out of the water. Hull should be pretty dried out for epoxying then…
    I bought another boat in the meanwhile, an ex-motorsailer (IP25) which has had the rig removed for use as a canal boat. I was thinking of re-rigging it, but have decided to keep it for exploring the Brittany canals and use the Coromandel for actually sailing. With the extra twist that I want to convert the IP24 to electric drive to replace the old Volvo diesel. Silent travel along the canals…possibly powered by solar panels in addition to shoreside top-ups.

    • You might like to get in touch with Kurt Ulmer, who has been cruising England’s waterways in the Coromandel “Minim” (formerly Missy Moto), which he converted to electric drive with solar charging. He has a bunch of electric/solar experience. I’ll put you in touch via email.

    • I still have it very much in mind to sail to Saint Malo and throug the Dinan canal system to visit you and your Coromandel in Brittany. It’s a shame my health prevented it this spring. I won’t forget!

      • Richard Gavin Dalglish

        Maybe I could help you sail over when the time comes. I have done the crossing a couple of times. I brought back my previous boat from the Med through the canal du Midi, sailed to Arzal and through the canals to St Malo and then to Warsash via Jersey. We’re looking at moving to a smaller house nearer to the Vilaine estuary later this year.

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