GRP/Fibreglass info needed

[irving2008]

Thanks all, but seems my idea is a non-starter. I need 750kN pull-out resistance and the best bigHead will manage only 1/20 of that.

The requirement is to tie down Solar PV panels to a GRP 'flat' roof without compromising water resistance or membrane integrity. Normally you ballast the panels down but that needs ~300kg ballast per panel and the roof simply wont take the load. and finding a way to fix through the membrane and insulation to the underlying joists hasn't, despite my best googling, come up with a solution. Ideas?

[Neale]

Will the GRP take the load anyway, assuming you could fix to it, or will you have to get a fixing to the underlying structure?
Maybe piece of angle screwed to side of joist and against bottom of GRP panel, hole drilled through both and then bolted together with external penny washer and appropriate sealant. Leaves protruding stud to take panel fixing bracket? My boat has plenty of examples of this kind of seal, underwater, and good for life of boat. I hope...

[irving2008]

If only it were that simple :(

This is a 'warm roof' so the GRP is bonded to the insulation, 120mm Kingspan polyurethane, which is itself pinned to 6mm marine ply over the joists. On the bottom of the insulation is a vapour barrier. any fixing to the joist would need to penetrate the ply and the vapour barrier and the insulation, and should have a thermal break in it to avoid cold spots/condensation forming...

Will the GRP take the load anyway, assuming you could fix to it, or will you have to get a fixing to the underlying structure?
Maybe piece of angle screwed to side of joist and against bottom of GRP panel, hole drilled through both and then bolted together with external penny washer and appropriate sealant. Leaves protruding stud to take panel fixing bracket? My boat has plenty of examples of this kind of seal, underwater, and good for life of boat. I hope...

[irving2008]

Panels are on a flat crown roof, no way to have guy lines there's too much else in the way. The issue is wind uplift, the panel, even at 10°, acts as an aerofoil; it's about 3kN per panel on the 1 in 100y wind. I could take a risk of course...

[charlieuk]

in that case just fill the gap between roof and pannel if the wind cant get under it wont create any lift.

[GEOFFREY]

in that case just fill the gap between roof and pannel if the wind cant get under it wont create any lift.

I don't think that is quite true. G.

[irving2008]

I don't think that is quite true. G.

Its not.... you still get suction... but it will reduce it...

[EddyCurrent]

Ask a reputable company to give you a quote, when they come round to take a look, pick their brains, it works most times for me.

[GEOFFREY]

Its not.... you still get suction... but it will reduce it...

Not even sure that is true Irving. Obviously it depends on wind direction and strength, but according to Bernouli, (can't remember spelling) wind blowing between the surfaces will cause a reduction of pressure on the underside, so in some instances will actually create negative lift (downforce). Anyway that is all academic - try to pass all responsibilty on to the installer!!! Good luck. G.