In terms of the level of resistance it offers, the thickness of the grape stake remains crucial, together with the width – even more so than the section. With Cor-ten steel vineyard trellising, the weight of the material does not affect the galvanising process; indeed, increased levels of thickness have been successfully utilised, even up to 1.9/2.0mm, thus enhancing the resistance of the profiles to a considerable extent.
THE RESISTANCE OF THE VINEPOSTS
Normally, a steel trellis post has a resistance of just 1/3 with respect to that of wood, and 1/2 that of concrete. For this reason, over and above the fact that the structures used in the past were probably oversized from this perspective, with the introduction of metal stakes the distance between the poles along the row has decreased, with around 25% more vineposts being installed, improving the linearity and tensioning of the main wire in the process. The trellis is further strengthened by placing the stakes closer together on the outer rows, which are most exposed to the wind. In practice, this involves substituting, on the external rows, a brace with an additional stake that is identical to the others, thus not affecting mechanical harvesting in any way (the same cannot be said for concrete). If the rows are very long, one effective strengthening solution can be to insert additional stakes at regular intervals, transversally aligned vis-à-vis the vineyard (i.e. perpendicular to the direction of the row), substituting as before a brace with a vinepost. It should be stressed, though, that over the course of recent years we have also witnessed a notable increase in the sections and thicknesses of sika profiled vineposts, both Cor-ten and galvanised, rising from thicknesses of 1.5mm to a minimum of 1.8mm.