the Carpentry Way: Tower of Power                                                          

Tower of Power

    
My wife and I decided we wanted to grow peas and beans on a trellis. I figured I could come up with something that could mount on one of the locust beds I completed recently. After considering a few different designs, and wanting to make something fairly 'quick' and 'simple'  - those terms being, of course, relative - I settled on a pyramidal design. This meant making posts which were non-square in section, so that when on a compound slope they present surfaces which conform to the prism.

So, the trellis, made of Teak and Spanish Cedar scraps, took a few hours to construct in my shop, and fit nicely upon the planter box when installed. I nearly considered mortising stretchers in at one point, however decided to content myself with stainless screws to mount the battens to the legs, thereby forming the climbing surface:


You can see I've got a couple of pole beans started in two of the corners.

Backing the legs into the correct shape means that the battens lie flat on the leg faces - otherwise, with an un-backed leg, the shape would require the battens to bow outward to conform to the legs, or you'd have to bevel the inside face of the batten where it met the leg. The techniques of changing the legs shapes and finding the correct compound bevel angles with a framing square are standard apprentice-level projects in Japanese carpentry. One of the things I like about Japanese carpentry relative to what is practiced in other places, is how sophisticated techniques can be used to create structures which look simple in appearance. Simple lines, clean assemblies, elegance - a winning formula I would say. Not saying I achieve that, but I like the design sense and underlying methodology and strive to emulate it in what I make. That requires study and practice of course.

I was glad to revisit the geometry of the compound splayed leg arrangement with this quickie project, as I try to make something in that form every year. By now I can solve all the geometry involved without recourse to looking in books or having to scratch my head too much, which feels empowering. 'Use it or lose it' seems to hold true.

I chose the pyramidal form as it is inherently self-stable. The garden is a windy site. Before the battens were installed I was able to hang with my full body weight from the upper framework, with the feet secured from any lateral slippage, so I think it should support climbing plants well enough. The battens have their ends trimmed to be in plane with the pyramid.

The upper frame is made of teak, and uses Ipé pins. I painted the end grain to retard moisture loss:


I'm interested to see how these various materials in the garden, Black Locust, Teak, Spanish Cedar and Ipé, stand up over time and relative to one another. All of these woods are highly rot resistant and durable outdoors.

Another look:


A glimpse of the top - first time I have pinned post tenons on compound-sloped legs. I left the pins proud as trimming them was unnecessary labor in this case:


I have a couple of planter beds prepared, this one will be the 'hot' one, and has some eggplant and tomatoes now in place:


The bed with the agribon fabric cover has the leafy greens in it.

I'm in a lull between projects right now, which I'm enjoying, and now that the garden stuff is mostly done (well, I do have another smaller trellis to build yet) I'm looking forward to putting some time into developing a better website, constructing a large wood rack in my shop, moving a Carpentry Study Group project along, playing some disc golf, and maybe getting out on my bike once in a while. While 'work makes free' in this culture, a break is to be savored.

Thanks for dropping by the Carpentry Way.

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