Hitchhiking and I are just about to order some 3/4oz spinnaker fabric for winter tarps, but I read a slightly worrying passage from a DIY site:
"A lighter 'silicone' spinnaker fabric at 34 gsm can be obtained from several sources (typically yachting suppliers) but the samples I have tested and used are not as waterproof (~30kPa) and even this rating is not guaranteed. It was designed as an unwettable but light spinnaker fabric, not as a tent fabric.
It is rather stiff and crinkly and makes a lot of noise in the wind. I suspect that the proofing is actually a combination of a silicone polymer and polycarbonate (PC). The PC gives the fabric considerable dimensional stability: just what you want in a spinnaker. Creasing of the polycarbonate can present a long-term problem of worse leaks. This fabric is available from several sources here in Australia and overseas, but you should hesitate if you want something for the long term."
Is this right? I understood that the waterproofness (if it's a word) of Spin was better than silny?