I once built a similar trellis using 1/2" conduit for the upper cross pieces. My tomato plants got so heavy, the pipe sagged. I hope your wood will be stronger. The following year, in the spirit of overkill, I used plumbing pipe for the vertical and cross pieces. I even planted the two vertical pieces in concrete. No sagging. However, those white strings like you're using snapped under the weight of the fruits on the vine. Further, the little white clippy things every tomato grower on YT recommends, became so brittle under our NM sun that they shattered and scattered. But, my biggest problem was that, perhaps due to a longer growing season than you have there (?), my vines ran out of places to grow. I think next year I'm going to try a cow panel arched trellis. That'll give my vines lots of support and 16 ft to grow on.
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I once built a similar trellis using 1/2" conduit for the upper cross pieces. My tomato plants got so heavy, the pipe sagged. I hope your wood will be stronger. The following year, in the spirit of overkill, I used plumbing pipe for the vertical and cross pieces. I even planted the two vertical pieces in concrete. No sagging. However, those white strings like you're using snapped under the weight of the fruits on the vine. Further, the little white clippy things every tomato grower on YT recommends, became so brittle under our NM sun that they shattered and scattered. But, my biggest problem was that, perhaps due to a longer growing season than you have there (?), my vines ran out of places to grow. I think next year I'm going to try a cow panel arched trellis. That'll give my vines lots of support and 16 ft to grow on.