Our model of Viking caravan came with four corner windows. This is the feature Lou loved so much. At the time of purchase, all four windows were present. However, they are made of thin acrylic sheet and at least one was cracked, and all the rubbers holding them in place were dried out. We were lucky though, as many of these have fallen out on other examples, and we have seen pictures on the internet of a number of bodged up repairs.
As luck would have it, a very kind couple named Robin and Jo had made their own replacement corner windows and were willing to lend their former to other restorers. On collecting the former from them, they also generously donated one of their old windows. This was when I realised these were probably hand cut at the factory as theirs was several millimetres smaller than ours; enough to ensure the rubber seal didn't have sufficient surface to grip on.
I bought eight sheets of 3mm acrylic. This should give me a couple to practise with, four for new windows and two for spare windows. Acrylic can be bent by heating it, and a mould or former is used to achieve the desired shape. After attempting to bend three sheets with a heat gun, I found I could not achieve an even temperature over the whole sheet, so the curves were decidedly angular. Furthermore, the sheets were too large to fit in our oven. I approached a local sign maker but their oven was too small as well. They directed me to another business who was able to help. However, he was unwilling to use my perspex and insisted on supplying his own, at 5mm thick, which he said would be easier to cut. Upon collecting these a couple of weeks later, we noticed imperfections like bubbles, ripples and stress cracks, so he had to remake them all. Several weeks later, we took delivery of six curved sheets ready for us to mark and cut.
Fast forward to autumn 2018, and we got the sheets out to mark the shapes of the window apertures before applying paint to the caravan, as we did not wish to risk scratching the paint at a later date. I held the curved sheet on the outside of the window aperture and manoeuvered it until the curvatures matched. Lou then drew round the window aperture from the inside, onto the perspex with a permanent marker. We purchased new rubber seals from COH Baines, who offer a range of different sizes. Ours (part no IRS 0634 W/S) has a 1mm slot on one side (for the aluminium) and 5mm on the other (for the window). The gap between the slots is advised as 7mm, so our new window has to be 7mm smaller than the aperture all the way round. A further line was drawn 7mm in from the outside of the original line.
I had to resort to cutting by hand, using a fret saw. This has a deep frame allowing me to cut half way along the long side before having to start cutting at the other end. Fret saw blades are extremely thin and break easily, so I bought 60! A test with a fine blade with 22 teeth per inch (tpi) made slow progress so I bought blades with 16 tpi; still finer than the jigsaw blades, so less likely to bind and cause a crack. I also used a coping saw with 14 tpi blades. The frame isn't as deep but the blades are more robust. My cut was several millimetres away from the line, and the excess material was sanded off with a drill mounted rotary sander.
 |
| One down, three to go |
 |
| All cut now. |
When it came to fitting, we had no way of checking if the perspex was the right size as the rubber seal blocks the view, so the first window was fitted four times, with small amounts of perspex removed each time.
In the first trial fit, the filler strip that locks the rubber seal would not even go in. In the second, although we got the filler in, the window fell out as there was little rubber holding it. The third trial got nearer, but we could still see it was not right as the outer part of the seal was much lower than the inner, still giving insufficient grip on the plastic. By this time, I had damaged the rubber with the implements I was using to install it. Finally, on the 4th attempt, with a new piece of rubber, the first corner window was in. This process took me a whole afternoon!
I would offer the following advice to anyone doing this installation;
1. Don't use metal tools like screwdrivers to fit the rubber weatherstrip, use a plastic spatula.
2. A professional windscreen fitter advised me to cut the rubber to length with a brand new razor blade. A new one for each cut. This will slice through the rubber in a straight line, thus giving a good seal where the two ends meet in the window aperture.
3. There is a special tool for fitting the insert strip. Baines sell one as a multi-tool for around £27. The same thing can be bought new on e-bay for less than half that price; usually listed as "classic mini windscreen tool". "Gunson 77136" also returns similar results.
4. When fitting the insert, use a washing-up liquid solution for lubrication (don't use neat washing-up liquid). Use plenty of it. If it's not pouring over your feet, you haven't used enough. My thanks to the author of http://www.landyrebuild.com/vehicle-window-installation.shtml#sthash.S3oMvjU6.dpbs for this one.
5. Get some help (or grow three extra hands) and make sure your assistant isn't upset by bad language, because there will be plenty of it.
The second corner window took almost as long as the first one. My problem with this window was the curve didn't match that of the caravan, and I cannot be certain it will stay in place when on the road. We will have to see. (Edit: by July 2021, we had taken the caravan out eight times, and the windows were all still firmly in place)
The third window surprised us both by fitting nicely, and in less than 2 hours!
The final corner window again only took a couple of hours but the curve, like the 2nd, isn't an exact match. I guess this may be down to using one former for all four corners, and perhaps left and right corners have different contours. We'll put this down to the hand-built nature of the Viking.
Edit: Since completing the caravan, I have found this video on YouTube giving a tutorial on making a curved window for a Viscount caravan. The curve on a Viscount window is less complex than on a Viking, but it gives a good overview of the process of bending acrylic. As mentioned above, I was not successful with a heat gun, but the video shows it can be done.