Mark, my vines are all about 30 years old and pretty thick. They are supported by 4x4 poles with 2x6 braces on either side of the poles, then with a simple ladder made of 1x2s on top of the braces. A hemlock took out one of the main support poles several years ago which we've never replaced. Other than some slight leaning, all remains pretty sturdy. To some degree, the grapes will form their own support system, and use the wood as more of a guide than an actual support. Here's a photo showing the under support and another in full on grapeness. As you can see from photo 2, that particular grape isn't even relying on the support pole to climb up (poor training on my part, but oh well).
