I occasionally get requests for more details of Herbie's DiY secondary double glazing the latest request being from VallyP who of course I cannot refuse, so here goes . .
I claim no credit at all for this valuable and ingenious addition to our windows, it was all done by Herbie's previous owner Roy who was a dab hand at such things.
Basically what we have is a made to measure set of simple wooden frames over each of which is stretched flexible transparent PVC of the type use for tent windows. Roy managed to stretch it very tightly so there are no wrinkles or ripples. The material itself is very strong and durable.
I found a few old photos to show how they fit. First this one of the galley window where you can see the frame in situ.
As you can see the frame has a central vertical spar for strength. The whole thing is a tight push fit into the outside of the boats window frame, leaving an air gap of perhaps an inch and a half. lets look more closely.
Here's a corner showing that the frame is really simple being mitred and stapled at the corners. I can tell you is is pretty rigid though and has stood up to more than ten years of use without bother. You can also see the swivel tab which holds the frame in at the corners. Couldn't be simpler could it?
The secret of course is the precision with which Roy made the frames. They really are a close push fit with the slightly compressible pvc I suppose being squashed tight between the double glazing frame and the boat's normal window frame. I doubt very much they are completely airtight, but they work well enough to virtually eliminate condensation between the frames as long as you take care to have it all very dry when you install them. and of course the pvc facing the inside of the cabin doesn't get condensation either.
Here you see a third picture showing the top centre of the frame. The fit is tighter than it looks. each frame is marked with which window it fits and which way is up e.g Starboard No2 TOP
The little ribbon tag is needed to pull the frames out when we remove them after the winter. That pvc needs a clean doesn't it? We just wash it with soapy water now and again. The stuff is pretty clear over all and as you can see from the top picture, the view out of the window is only very slightly compromised.
So there it is. It really works even though there is no fancy carpentry. There are frames for each of Herbie's seven windows. During the summer, we take them out and store them at home.