Double curvature windows

[chrisb1309]

Hi All

We have an elderly Westerly on which the original windows 6mm thick ,are located in an 'H' section rubber.
This rubber deteriorates and leaks over time.
The coachroof has a bit of tumblehome and also some curvature fore and aft.

I am wondering if anyone has tried replacing windows of this sort by enlarging the plastic to create an overlap so it may be through bolted, using interscrews. I have received conflicting opinions as to whether the polycarbonate /acrylic would accomodate this double curvature.

The old girl is elderly and am reluctant to spend huge amounts to have some frames made up.
Window sizes

420x235mm ovals And 500x195 reducing to 145 teardrop shaped

Any ideas?

Thanks
Chris

 

[maxi77]

I have seen this done on other boats nd the results look petty amateurish even when done well. The H rubbers are easy to get and not too difficult to replace and if replacing the headlining do it whilst the windows are out. When doing te rubbers make sure you get the right tools, it makes things a lot easier.

 

[VicS]

Hi All

We have an elderly Westerly on which the original windows 6mm thick ,are located in an 'H' section rubber.
This rubber deteriorates and leaks over time.
The coachroof has a bit of tumblehome and also some curvature fore and aft.

I am wondering if anyone has tried replacing windows of this sort by enlarging the plastic to create an overlap so it may be through bolted, using interscrews. I have received conflicting opinions as to whether the polycarbonate /acrylic would accomodate this double curvature.

The old girl is elderly and am reluctant to spend huge amounts to have some frames made up.
Window sizes

420x235mm ovals And 500x195 reducing to 145 teardrop shaped

Any ideas?

Thanks
Chris

it can be done.

With much of a curvature its best to get the new windows "drape moulded" using the old ones as formers .... I had to do that with my forward windows in order to fit them in rubbers. Might have pulled them to shape if bolting on.

Mine look as though they have a double curvature, at least a curvature and a twist but in reality its a single curvature with an axis diagonally across the window.

You'd need a bit more than simple drape moulding to get a double curvature I think ... male and female moulds probably and that makes them expensive

 

[DownWest]

To add to Vic's comments: Perspex will bend nicely at 120 deg C. Polycarb is a different animal and more difficult. I built an oven from steel sheet and a domestic oven 1500watt element to form 10mm perspex at around 800 x 30mm. All quite easy, just takes time. Mould was faced in formica and must be absolutly clean, small paricles of dust dimple the surface and effect the optical qualities. This was not double curve, but helical on around 2mtr radius. Amateur aviation types form canopies, but again, lots of time on the mould. A single one works with a frame to pull the edge down around a male mould.
DW

 

[JumbleDuck]

You'd need a bit more than simple drape moulding to get a double curvature I think ... male and female moulds probably and that makes them expensive

It may be possible to blow mould it: make a pattern for the edges, drape mould over that and seal, heat again and inflate, but sounds a bit complicated. I'm with maxi77 - overlapping plastc windows always look terrible, and replacing the rubbers is easy.

 

[LittleSister]

If the windows (and frames) are OK in themselves, the issue is not making new windows but producing a reliable seal.

It may be that the H section you have is the wrong dimensions (lots of different sizes available), or it may be that the radius of the curves in the frame is too much for the stiff rubber to cope with without swtress and distortion. We have the latter problem on our 'project boat', and the answer to this, I have been told by a very knowledgeable and experienced source, is as follows. (We have yet to do the job ourselves.)

Take a piece of the relevant H section rubber and chop into short lengths (5 - 10mm, perhaps?), position these at intervals around the frame and insert the glass. These will hold the glass centrally in the frame in both planes. Fix the two the two parts of the frame together. Run masking tape around the window both sides leaving a gap of 3 - 4mm adjacent to the frame. Now apply a suitable sealant to one side of the window/frame join and force it (using old credit cards or similar) between the two and round to the other face of the glass, adding more until you have filled the entire frame/glass gap side to side (the H rubber spacers will now be buried). Continue all the way round the frame. Clean off excess and smooth off (using water, meths or whatever according to the sealant type), and remove masking tape. Once the sealant is cured you should have a solid, unstressed seal between the frame and glass and adhered to both of them.

Suitable sealant and more varieties and sizes of rubber seal than you ever knew existed available from Hadlow Marine (no connection other than as a satisfied customer).

 

[chrisb1309]

Thanks for the suggestions.
The original windows are fitted into the GRP topsides by way of the the rubber section, no frames,and are flat sheets of plastic.
I am wondering if the replacements would take on this double curvature if I throughbolted onto the grp. I had thought to use butyl sealnt strip under the window overlap and make up an opaque ring to take the fixings and trap the headlining internally.
Anyone tried this?

 

[VicS]

Thanks for the suggestions.
The original windows are fitted into the GRP topsides by way of the the rubber section, no frames,and are flat sheets of plastic.
I am wondering if the replacements would take on this double curvature if I throughbolted onto the grp. I had thought to use butyl sealnt strip under the window overlap and make up an opaque ring to take the fixings and trap the headlining internally.
Anyone tried this?

IMO there is no way a flat sheet of 6mm Perspex is going to take on a double curvature without being heated and moulded to the required shape.

You mentioned earlier that the boat is a Westerly. Which model?

 

[LittleSister]

Thanks for the suggestions.
The original windows are fitted into the GRP topsides by way of the the rubber section, no frames,and are flat sheets of plastic.

There are quite a few boats with that arrangement, including those with curved coachroofs and flat windows. I'm not aware there's a particular problem with that. Yes, the rubber needs replacing from time to time, but if it's the correct section shouldn't generally leak.

 

[chrisb1309]

It's a w windrush

 

[VicS]

It's a w windrush

Oh one of these;

I agree with the suggestions to stick with the rubbers. Make sure you get the size which matches both glazing and GRP thickness and suitable for the tightest radius at the ends.

Also look for advice on how much overlong to cut the rubbers or you will end up with gaps. A proper fitting tool for the infill stip worth getting, although I made a simple one with a file handle and a bit of wire coat hanger.