How to make/buy/obtain curved aluminium or PVC T-section?

[Chris Green]

This is also for my boat windows, for a different set of windows from the ones where I was having to remove steel grub screws from aluminium wedges.

I can't really afford to replace the windows or even have them professionally (by the people like the ones put steel grub screws in aluminium wedges!) refurbished. There's eight windows involved and anything 'professional' costs £1000 or more per window.

So I'm thinking about DIY methods to remount the windows such that they can be fairly easily removed to enable maintenance of the surrounding metal superstructure etc.

These windows are currently mounted using 'claytonrite' rubbers which sort of clip onto the glass and the surround and have a wedging strip to make them tight. I hate these for a number of reasons: they look horrible, they're **very** difficult to insert, you nearly always have to destroy them to remove them and they don't work very well (i.e. they don't make a perfect waterproof seal).

So I'm considering a completely different approach which would require mounting a strip of T-section material round the windows which would them be mounted with the 'leg of the T' through the gap between the glass and the metal superstructure. One then has some sort of clip that pulls on the leg of the T to hold the window into the hole. The T is stuck to the window with double-sided acrylic tape and has closed-cell foam strip between it and the metal superstructure to make it waterproof.

The fundamental problem with this idea (and many others that I have had) is that the windows have curved curners so would need T-section material with curves. Can anyone suggest a way of either making curves in straight T-section or in obtaining it somehow? Are there any fabricators who have equipment to do this sort of thing?

I think the T-Section probably needs to be about 1"/2.5cm wide with a

3/4"/2Cm 'leg of T' flange. I doesn't need to be incredibly strong so, say, 1.5 or 2mm aluminium, 3mm PVC would do I think.

The corner radius on most of the windows is about (very about) 6cm, there's two with larger 12cm radius corners. None of them is exactly square, they are tapered, or trapezoidal and one pair are actually five sided.

The only ideas I have come up with so far are:-

1 - Making up the corners with sectors of (PVC) T-section and gluing, very laborious I fear for almost 40 corners and difficult to end up with the smooth face needed for a good waterproof seal.

2 - Buy a metal 'shrinker/stretcher' tool and bend some aluminium myself. I don't think one can bend T-section with one of these but I could bend ordinary angle and join two pieces together to make a T.

Does anyone have any other ideas? Also has anyone here used one of the shrinker/stretcher tools on aluminium? Does it work well, what sort of radius is possible, etc.

I'm happy to spend a few hundred pounds on this but, as the boat only cost 19000 Euros to start with (back in 2010) I don't really want to spend several thousand pounds on just the windows.

Thanks in advance for any/all help. The thread on removing the grub screws was very useful.

[John Rumm]

Not tried it, but I would expect a shrinker could bend tee section since it will work on angle.

I have seen people bend fairly tight radii with a shrinker - not sure if you will get 6cm though.

You could probably do it with kerf bending - basically slit or cut vee notches in the projection, bend the profile to close up the vee's or slits, and then weld[1] up the result, and grind flat.

[1] If it is Ali, then you would probably need a spool gun on a MIG setup or AC TIG

[Roger Mills]

If you used hollow aluminium T section for the straight parts, could you get the curved corners 3-D printed - with spigots on the ends to fit inside the T sections?

[Chris Green]

That sounds a rather high-tech solution! :-) The main difficulty would be the 3-D printing I think because just about all the corners are 'not quite square' so telling the printer what to do isn't easy I suspect.

Having thought a lot about this T-section solution I'm beginning to think my previous idea is probably slightly more practical:-

Make two flat PVC surrounds for the window, sized to overlap window and metal surround by about 1cm each. These will comprise simple lengths of straight PVC extrusion with rounded corner sections cut out from larger pieces of PVC. The corners and straights can be glued together and joins smoothed down.

One of the two PVC surrounds is stuck to the window with strong double-sided acrylic tape. Then matching holes are drilled through both pieces of PVC close to the edge of the glass (probably 4mm or 5mm diameter, 10cm intervals), single-sided sealing tape is put on the PVC surrounds and the whole thing is fixed in place with screws through the holes.

It will probably be a two person job to actually install the windows but apart from that I think it's all fairly straightforward. The most time consuming bit will be making the curved corners but the material is cheap so failures can just be part of the learning process! :-)

A major advantage is that it can be done fairly easily on the boat, no need for any special tools, no need to bring windows home (from France) to do any necessary work.

Any better, cleverer, ideas are still welcome. In particular can anyone think of a simple way of producing flat, curved pieces of PVC?

[Theo]

If you have access to a plastic 3D printer you could make templates to fit. It might need a few goes to get right, but 'not quite square' isn't a problem with a bit of trial and error. You could also make a cast (eg if you aren't on the boat for long) and then try to reproduce something to fit the cast once back at home.

Rather than 3D printing it might be better to use a CNC machining service:

about $25 per part (maybe a couple of inches cubed) according to this video: So you could perfect it with plastic and then send off the file for CNC.

If you're able to do this in plastic rather than metal it makes it easier, but will that do the job weatherproofing wise?

Heat gun to stretch it?

Theo

[Thomas Prufer]

The machine that would do what you want is called a "profile bender": Three rollers, slots and grooves to fit the T (or more complicated profile), rollers turn slowly and with force while they move closer... . It rolls the profile fore and back. Large, expensive, tricky machines to use... but maybe a manufacturer can bend for you.

Other than that: is it possible to change from rounded to square corners? Possibly placing a square window over a rounded hole? Then it's cut at 45° and weld or join.

Use slotted ali profiles and find a corner connector that works?

Thomas Prufer