Well founded yachts like a Seastream are almost entirely bomb proof from big seas and storms if handled correctly. However, raised pilots houses and coach roofs are a liability on any boat. A large smashed window, from either a wave during a knockdown or a flying object inside the cabin, can mean the total loss of a boat. There are a number of documented cases but here is one in-particular where I met the skipper and heard it from the horses mouth: https://www.theguardian.com/sport/2017/jun/11/mervyn-wheatley-73-queen-mary-2-liner-rescue-north-atlantic-storm
The first priority is to secure everything inside the cabin. Anything that could fly about in a knockdown and smash a window should be stowed and the floorboards fixed. Second to that is making windows that can’t smash! This is the project I undertook on Shadowfax to solve the issue.
1. Firstly I took a photo of the boat from the side and used that photo to draw a template of the window shape in Photoshop.
2. I sent these shape files to the polycarbonate manufacture www.par-group.co.uk. The cost was approx £40 per window for an 8mm thick pre cut piece of polycarbonate. The make pullet proof glass from this stuff so no wave is going to smash them.
3. My window frames did not have screws on the outside so I had to find some way of fixing them. Some Seastreams have windows with external bolts or screws which will make the job so much easier. I used aluminium closed ended Riv Nuts (threaded inserts) shown in the photos below which I drilled and riveted into the frames. It is important to bolts and inserts that are the same material as the window frame.
4. I then drilled holes in the boards where I’d installed the new Riv Nuts. There holes were larger than the M4 bolts I would use to allow the windows to flex in place taking some of the impact of a wave. M4 may not sound like a lot but the bolts are just to hold the windows in place really.
5. I then put 3mm compressed neoprene on the inside each storm board which would then sit on the top of the window frame. This made it easy to tighten down whilst it compressed, but also act like double glazing for the window, eliminating condensation!
The result killed three birds with one stone. Firstly and foremost they act as storm boards for off shore passages. Secondly they act as security windows as they cannot be kicked in. Lastly, they very effectively eliminate condensation from both the frame and window in cold weather and I do not doubt help retain the heat!