Polycarbonate Windows

[John Bonnett]

I'm thinking of weight saving and looking at the possibility of fitting Lexan windows to the driver and passenger doors and to the tailgate. Losing the glass and the winder mechanisms would make quite a difference.

I'd be interested to hear from anybody who has done this.

[nang]

Would it be road legal ?
Certainly not in New Zealand.
Tony.

[John Bonnett]

Quoted from nang

Would it be road legal ?
Certainly not in New Zealand.
Tony.

In the UK polycarbonate is fine for side and rear windows. Illegal for front screens.

John

[JohnD]

I've done it twice, on Silverback and then on SofS, when I put its saloon roof back on.
Cut hardboard (could be cardboard, but less durable for multiple fits) patterns, to fit inside the frames without rubbers.
Drill through the PolyC into the flanges that carry the rubber.
Apply draught sealant, closed cell foam in adhesive strip to the flange and bolt up with 3 mm (? can't recall for sure) bolts all around.

Doors - SofS already had PolyC door windows, but I had to replace them to fit the saloon roof.     Windows about half as tall again as needed, lower edges braced against the door's inner skin by adjustable bolts, to force the upper edge inwards, against the door jamb, else it flies out at speed.
On Sb used totally different method.    Hung the door windows on the A-posts via plastic rising hinges (Caterham catalogue).  Kept closed by A/ strip of angle plastic extrusion along top of door and B/ clips in the roof edge.
To use, first open door, then lift window.  It's easier than it sounds!
Added advantage, you can leave the windows behind, or stash then in the boot in case it rains!

John

[John Bonnett]

Thank you John. I've used Caterham hinges on the trials car so I know exactly what you mean.

On my set up I may have to keep the quarter lights because of the strap that goes across the gap on the door skin. This would add weight but would have the advantage of adjustment. The GT6 drop glass has a bit of curvature so that may need to be replicated. As you say the window would need to be longer in the vertical direction so that it can be fitted into the rear guide and some sort of  securing bracketry to fix it to the door skin. Plenty to think about.

[Clive]

Have a peek at the ADU le mans cars. I am pretty certain they are polycarb types.

On a spitfire, with the window fully up, there is precious little holding them vertical. You should be able to fabricate a bracket to go a couple of inches up the window and attach to the runner fixing points? If you keep the quarterlights they would add a great deal to the installation, and retain at least some ventilation.

[yorkshire_spam]

IIRC Mik Davies has "plastic" windows on his racing Spitfire John, might be worth pinging him about it?

[thescrapman]

Mike Helm has plastic windows on one of his TR6.

The passenger one (now modified so it opens as it was annoying at Time Controls) is sucked outwards at speed, so there is a short strap to keep it in place. This also prevents the passenger having a free shower when it rains.

May be less of a problem if you have quarterlights

XCheers

[JohnD]

Quoted from John Bonnett

T
On my set up I may have to keep the quarter lights because of the strap that goes across the gap on the door skin. This would add weight but would have the advantage of adjustment. The GT6 drop glass has a bit of curvature so that may need to be replicated. As you say the window would need to be longer in the vertical direction so that it can be fitted into the rear guide and some sort of  securing bracketry to fix it to the door skin. Plenty to think about.

Ah! Sb had GRP doors (5kgs with the hinges v.30 in all steel)  Top of door sealed, and window hinged as described.
SofS has metal doors, slotted right along the door top, no quarterlights.    The weight of the plastic is taken by an alloy strip rivetted to the door top and to the plastic.
On that fulcrum a pair of long bolts are fixed to the inner skin and through the bottom edge of the plastic.    Nuts either side of the plastic allow the leverage to be adjusted.
Never weighed the SofS doors,  steel with only the winder mechanism removed.    20Kgs?
John

[Mik]

Quoted from yorkshire_spam

IIRC Mik Davies has "plastic" windows on his racing Spitfire John, might be worth pinging him about it?

Yes, I do Polycarbonate (genuine Lexan in fact though that was just what turned up when I ordered them, no idea if there's any difference between brands of polycarbonate).

The question of how to fit the side windows depends largely on how much of the original door you want to keep. In the previous incarnation of my race car I just cut polycarbonate to the shape of the original glass, removed the winder mechanism (to save weight) and bolted a channel across between the original winder channels at the position the glass would have been supported with the window fully up. Then I just fitted the plastic windows as a direct replacement for the glass.

Apart from the usual issues with plastic being more flexible than glass and therefore being pushed out at speed (two or three inches at the top in fact) this system worked well. The flapping top edge was solved by attaching a small length of aluminium angle under the edge of the hard top. Just push the window under the "tab" when closing the door.

Having just finished rebuilding the car I've replaced the steel doors with fibreglass ones that have the inner skin cut away (mostly to clear the roll cage but I must have saved at least a couple of grams weight too ). That meant a new approach to the windows so I started again with a polycarbonate window that extends down inside the door and is supported with aluminium angle , long bolts and spacers very much like John was describing earlier. Despite using much thicker plastic I couldn't get enough tension to hold them in though so I've kept the tabs under the hard top as well.

Not sure if this link will work. If it doesn't I'll try and share this picture a different way.


https://goo.gl/photos/knBow2rV3VTaowi97

As for the rest of the windows, I've left the windscreen as standard laminated glass. I don't have quarterlights and all the others were polycarbonate anyway that came fitted to my fibreglass hardtop.

[BiTurbo228]

Not sure how well it'll work in this particular application but a mate of mine has recently availed himself of a Peugeot 106 GTi race car which has fibreglass doors (and similar problems of them pulling out at speed).

They fixed it by affixing little strips of stick-on Velcro to the door and the shell. Must have taken a bit of trial-and-error to get enough Velcro to hold it in place but not too much that it'll stress the door when you open it.

[John Bonnett]

Thank you all for your very helpful replies. As my car is not a dedicated racer and will be used on the road more than on hillclimbs, I'm  going to retain the quarter lights in the doors and this will give two advantages. One, ventilation and the second, positive location for the 5mm polycarbonate in the vertical channel. The guide at the far end of the door can be retained so all I have to do is to fit an adjustable stop to keep the window in the vertical position. I'm hoping the quarter light and rear guide adjustment will be sufficient to bring the window into contact with the seal.

There should be a significant weight saving in changing the tail gate glass to polycarbonate.

Can anyone see any problems?

[John Bonnett]

I'm going ahead with the polycarbonate windows and if anyone wants a GT6 tailgate window done there should be a cost saving if done at the same time as mine. I'm providing the patterns which will be leaving me tomorrow. And before you ask, I have no idea of the cost of the window on its own because I only have the price of the whole set. If you are interested speak to Mike at Templar Performance.

http://www.templarperformance.co.uk/