Arbors 101

Picture from here.

I’ve spoken of the grapes we grow before. One of my two readers asked about the arbors that support them. The other one was uninterested.

So I’m going to talk about the various arbors I’ve built. Let’s be very clear. I’m belong to the Brut Forse Carpentry Skool of Construkshun. It doesn’t have to look nice. It just has to work.

We all have a pretty good idea of what arbors tend to look like. The picture up there is a fairly common style. Essentially, it’s a set of four or more posts with a set of cross beams. I’ve built a couple of these using 4x4 pressure treated wood and set into concrete. They last about ten years or so without some sort of maintenance—paint and the like. However, I don’t like to paint around things I eat. So I tend to replace them.

About fifteen years ago I decided that working with the lumber was 1) too much a pain in the butt and 2) too expensive. So I began experimenting using 2x2 lumber. The remaining example is shown to the left.

There are a few of things to note about this arbor. For one thing, there’s a lot of wood—more than when I built it. A tree fell on the arbor and I patched it together. The other is the half A-frame construction. Note that one side falls at a slant. It’s not a square shape.

I started doing this because I wanted a fairly broad surface area for the plant. But that meant that to harvest I had to reach over a long distance. The answer was to mount the arbor at the slant and harvest from the back of the arbor instead of the front. I’ve retained this for a couple of arbors.

Then a tree fell on one of them. (The one pictured.) And the others started to rot. Pressure treated is sort of a suggestion against rot rather than a preventative.

Picture from here. 

Meanwhile, I was working in Cambridge and when I walked around I saw some old grape trellises made of plumbing pipe. This turns to have been a thing for many first generation European immigrants. They ended up in these small houses with almost no space so they would build a trellis of pipe over the driveway or other similar space and grow grapes over it.

Most of these constructions used galvanized pipe and plumbing fittings. With any luck, these arbors might outlive me and I was tired replacing wooden structures. So, why not?

This was my first attempt. Again, note the slanted construction.

I was attempting to minimize cost. So I used relatively thin black pipe and plumbing fittings. Note that though the top rail is straight, the bottom rail is staggered. This is because I wanted the cross beam at the bottom and needed the staggering to fit it in with the cross posts. The black pipe turned out to be a problem in that it is more rust prone. I’ve been using Rustoleum’s rust converter to correct this. Wire is used as the material for the grapes to grow across.

This particular arbor is not currently in use. Originally, I just stuck them in the ground. But I’ve concluded this is a mistake. First, the arbor can rust—although there’s not much evidence of it here. Second, the arbor can sink asymmetrically. The thin pipe works in this arbor but that’s because of the inherent bracing of the shape.

Shortly after I built the black arbor I built this one using the same sort of pipe. This is a more square form. This is much less braced than the previous black arbor—I had different space considerations and couldn't do the slanted style. But without the  bracing this arbor isn’t stable. The plumbing joints tend to unscrew and the thinness allows a lot of creep. I’m hoping putting the legs in concrete blocks will allow me to correct the creep issue.

I also moved away from black pipe. It just rusted too easily. Instead I started using galvanized. This arbor is essentially the same as the angled black one but writ large with galvanized pipe. Here the creep problem is quite pronounced. Note the slope of the back. Sticking them straight into the ground was a mistake.

I measured the rise and fall of the ground over that winter and concluded the whole anchoring problem was an illusion. Grapes live on trees and trees creep much more than a stationary arbor. Instead, I put the base in hollow concrete bricks which I then fill with concrete. I’ll straighten this one and fit it into concrete overshoes next year.

Here’s a close up of the sort of plumbing joints I’ve used. The black is again the Rustoleum product.

Working with the plumbing joints in a complex structure turned out to be really, really tedious. Imagine trying to screw everything tight. I was going to weld them but then read about zinc poisoning when welding galvanized pipe. I looked around for an alternative and found KeeKlamps. These are galvanized fitted sleeves that can be tightened over a pipe with a hex wrench. They come in a variety of fittings and are very easy to use.

We used all kee klamps on this square arbor we built for kiwi. (The kiwi had been destroying the fence they were on.) As advertised, it was easy to build and put together. Me and Ben managed it in about ninety minutes. The problem with kee klamps is 1) They’re not cheap and range between $5 and $8 per klamp and 2) You have to use a lot of them to make the joints.

Here’s a close up of the corner joint. It takes three klamps to make the joint at $5/piece. And four corners. $60 was just too much. (BTW: Ben invented this joint. The problem was that when we put the joints together the way I thought they should, the joint slipped easily. Ben figured out how to interlock the joints so that rotation caused the joints to tighten and not loosen. Clever young man, him.)

This was also the first arbor we put into concrete blocks. Three years and no appreciable creep.

One of the old arbors had rotted out needed replacing and I wanted to try something different. It was a flat arbor and while I found it was pretty easy to harvest, the turkeys did, too, and I lost a lot of my harvest. I came up with a sort of house structure. 

But this time, I came up with a different way to mix the kee klamps with plumbing fittings. The KKs are the joints that preserve the angle: 3 triples on the top and three single fittings on the base pipes. But instead of a complex corner joint I just used 90 plumbing fittings. This is worked out really well.

All of these structures are pretty utilitarian. I can understand if someone found them ugly. But they do work.

That said, I’ve been looking at some images from a simple google image search of “DIY Metal Arbor” or “DIY metal trellis”. Some of these have been stunning. Some used simple copper pipe sweated together. Some have bent normal conduit pipe (much softer than plumbing pipe which is why I haven’t used it.) into magnificent shapes.

Gives me some ideas. Heck. Maybe next year I’ll break character and make something beautiful.