Using Polycarbonate sheet (or similar)

I posted back last year Q about using Acrylic sheet - advised that Polycarbonate would be better ... went off intending to do job with triple wall (or X-Lite) problem is you should fix this with ribs running vertical ... and in this instance due to width being ~80" Can't get pieces ~80" wide and only 24" long ... (unless with very expensive waste)
I'll describe job again ... anybody any thoughts ... would solid Polycarb sheet work ... if so how thick over this span ?
Need some ideas on how to achieve fitting an acrylic sheet. I have a large 'barn style' outbuilding, on 1 side it consists of 6 " square post & gallows brackets. The other side of this building is a fence, which comes up over 2/3 of the open bays. The bays are open to allow through draught of air, and air come through fence no problem, the issue is the top 1/3rd allows rain to blow in, and too much..
Hopefully this sketch will show what I mean: http://tinyurl.com/28q5u7g
I don't want to close off the bays as I need air flow (& light) ... thought about putting in a Polycarbonate sheet between the gallows brackets, just to prevent the blow in of rain. If I sloped this so that the lower edge was clear of upright posts, it should also provide a 'drip' to prevent much of the water ingress. i.e. as in sketch .. aprox 10degree http://tinyurl.com/24jt8r5 Space between each support posts is ~80"' ... and there 3 bays to do.
Assume I use something like 10mm thick sheet work ?... I can easily manufacture side & top edge supports out of wood .... some ½" x ½" either side of ends & top, would provide location slot. The issue is what to use for bottom support ... i.e. along bottom edge. 80"' is a long span ... what I need is something waterproof I can bond to sheet to provide a drip, and if it is longer than sheet would also provide a fixing point to outer face of posts.
I have thought about using 16mm triple wall (or X-Lite) in wrong direction ... i.e. ribs running left to right ... not sure if this is good idea or not. It would be a lot lighter than solid sheet.
Any suggestions.
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On Sun, 23 Jan 2011 17:20:52 -0000, Rick Hughes wrote:

I'm no expert in polycarbonate roofing (though I may well be, by next weekend - see an earlier post on the topic). ISTM the advice about running the sheets with the ribs lengthwise is to do with fitting them in glazing bars, to increase the width of the roofed area. The glazing bars are effectively a push-fit for the poly, so need an even height to make a waterproof seal. If you tried to do this with the sheets running width-wise, you'd end up with the glazing bars trying to make a tight seal to the uneven. slightly ribbed edge.
If you were in a position to make up some wooden, waterproof frames amd could seal the polycarbonate in (and somehow account for expansion gaps), without having any conventional joints, then it might work. It wouldn't look as nice/professional as glass or acrylic windows, but might do the job.
BTW, you can get 4mm twinwall for greenhouses, cut to size up to 2.1metres wide at quite reasonable prices.
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On Jan 23, 5:20 pm, "Rick Hughes"

Surely any sort of rigid bar along the bottom of the poly would do, metal or timber. I dont see it mattering which way round the poly ribs run in this case. I'm also not seeing why you'd pay the extra for twinwall polycarb for an open structure, solid acrylic would do fine. The main advantage of twin & triple wall is insulation.
NT
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