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Windows (Some good news at last)

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Category: Hints & Tips
Forum Name: 320
Forum Description: 320 Hints and Tips
Printed Date: 04 December 2023 at 18:58
Software Version: Web Wiz Forums 12.06 -

Topic: Windows (Some good news at last)
Posted By: White Lines
Subject: Windows (Some good news at last)
Date Posted: 26 July 2022 at 14:23
It is some years since I last posted on the forum, mostly two years of Covid. Hello old and new faces. After many pleas to this board and arguments with boatyards - a solution!

Like most 2008 models my windows fell off quite early. Hanse came and stuck them on again with sikaflex an dall was well for a few years, then the trouble began - water leaks.

My first boatyard replaced the window and portlights strictly as Hanse reccomended. This worked for a short period before the leaks came back. This resulted in a length court case, which I mostly lost and cost me thousands of £ in having to pay for the abortive work.

The second boatyard used the now new method of screwing in screws until sikaflex had set and then removing screws - windows were leaking inside six months. Boatyard refixed them but this time left the screws in. Unfortuantely the boat flexes in use and th emovement caused the windows to crack and then the sikaflex started to leak again from all around. Major fall out with the yard again.

Talking to a shipwright in the marina storage yard about tboat sin general and mentioned my problem. His comment was pure gold. Sikaflex as specified is fantastic at sticking to the acrylic and to the gelcoat, but when exposed to strong sunlight (the leaking window faces the sun) it can't move enough, becomes brittle, cracks and lets in water. His advice - go to builders merchants and buy a tube of CT1.

When queuing for the CT1 they showed a video of CT1 being applied underwater to a brick and then picking it up by sticking another brick on top of it, whilst still under water! Interesting I thought.

Anyway, bought CT1 and cut into defective sikaflex in the middle to give the CT1 a decent depth. As he said, the sikaflex was never going to come off the acrylic or gel coat, so I just opened out a "V", put masking tape on coachroof and window and applied CT1, smoothed it down with soapy finger and removed masking tape. Result - the window is now totally waterproof and can move with the boat as it flexes. Very, very impressed. Has been in for a good few months now and has witfstood some big wave sailing offshore and the baking heat of the summer heat wave.

The only bad thing? I spent about £4000.00 with two boatyards and repaired it myself for £12.99!

Can't reccomend the product more highly. Smile

Hanse 320 #154 GBR7888L

Posted By: SailCS33
Date Posted: 26 July 2022 at 15:02
This is very interesting to me as I also have 2008 model 320. I purchased my boat in 2019 and it came with stainless "frames". Acrylic windows was glued in with some black stuff and after that, stainless frames were holding the window tight with screws approximately every 6 inches all around. Three windows out of 4 were leaking. It was not a lot but still annoying. All leaking would stop if I tightened the all the screws. This usually lasts about 2 weeks. As the boat moves, the screws loosen about 1/8 - 1/4 of a turn and it was enough for the water to start coming in.

During this past winter, I removed all 4 windows. The black "stuff" was is interesting to remove. It dissolves very easily with Xylene. In the cold, it becomes very very stiff. With some heat, it turns into something VERY soft like a bubble gum on a hot sunny day.

After a lot of cleaning and scraping of the gelcoat, I bought a sheet of  3/8(10mm) tinted acrylic and cut out new windows using the old stainless frames as templates. I also used a 45deg router bit to chamfer all the inside edges so there is space for the calk to go in later on.

Window installation was done using 3M HVB 5962 Tape. I purchased 4 rolls (15 feet each). The 3M tape is meat to hold the window only not seal it from water.

After the windows were installed I applied DOW 795 sealant in the groove I made earlier with the router bit.

So far so good. No leaks :)

p.s. I used to have two opening lewmar windows which were inside the acrylic windows. I decided to not reinstall them for now but might do at a later time above the stove.

H320 "Curacao", Hull #085, 2008

Posted By: White Lines
Date Posted: 26 July 2022 at 15:17
That is interesting, as the second boatyard was about to put the aluminium frames as a fix for the second failed attempt. I most certainly wouldnt reccomend it. I think the boat flexes too much for a non-flexible solid attachment.

Hanse 320 #154 GBR7888L

Posted By: Mschesser
Date Posted: 27 July 2022 at 03:31
I own a 2007 370 that underwent two failed window replacements using the original Hanse procedure and materials before I did quite a bit of study to learn that the urethane sealants recommended by Hanse simply do not have sufficient UV stability which is why Hanse specifies a UV blocking tape (or SS frames) in an effort to provide UV protection for the glue joints.  Unfortunately this simply fails with time resulting in loss of adhesion and leaks.

My local yard also services a number of Sabre yachts which also use glued windows, so I replaced my windows a couple years ago using the Sabre procedure (see link below), except the referenced “Silpruf” silicone sealant was replaced with a newer GE SCS2000 silicone sealant now recommended by Sabre.  This material has excellent UV stability, adhesion, and flexibility.  ( This material is also routinely used in commercial construction for glued window installations).

Using the old windows as patterns I then made 3mm plywood patterns that were very carefully fitted for each window space to ensure each properly landed on the flat window flange with about a 3mm gap around each edge. (Manufacturing variability in the deck had resulted in slight differences in port/starboard and forward/aft windows that needed to be addressed to ensure the windows would have room to flex with thermal expansion.).  These patterns were then used to cut new 10mm plexiglass windows from a single 4 ft x 8 ft sheet of tinted plexiglass that I then routed to apply the bevel as shown in the procedure.  The remainder of the procedure was followed as documented." rel="nofollow -

I’m very pleased to say that I have not had any further failure and leakage having followed this process.  I strongly recommend abandoning the Hanse procedure and materials.  My local yard was “spot on” with their recommendation.

M Chesser, 370, “Red Sky”

Posted By: Merinalle
Date Posted: 12 October 2022 at 18:47
Many thanks for everyone, now I have good new ideas how to solve leaks next time! I hope any of you will share experiences, if it turns out that your solution is not long-lasting.

SailCS33, you mentioned that you didn’t install the small opening windows. I think it is a good decision, because those openings make the fragile windows even weaker. This year we never open them during the summer, and if we ever have to reinstall new windows, we will not make those openings any more. However, it is important to have ventilation above the stove. Here are some pictures of our solution:




The components used: “VETUS stainless steel deck ventilator UFO”, “VETUS electric ventilator, type FAN, 12 Volt”, some wire and a fuse holder, and a 3 euro 125 mm plastic collar from local builders merchants:" rel="nofollow -

The installation is quite easy, after you find out the correct place for it. The 12 volts can be easily taken from the ceiling light. However, if it is still the original halogen, take care not to break it. There was a Hanse320 topic “Ceiling lights in the bathroom” at 2011, read it first.


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