Rib Assembly – Some Modifications Required


Rib Assembly Table

Above is the temporary 40’x16′ table Will and Ben built for assembling the ribs of our greenhouse. There are 25 ribs each made of five sections of 2.375″ diameter heavy gauge galvanized pipe that slip together with swag fittings to make 50′ long ribs that we then lift into place onto the feet on the cedar wood foundation we built earlier.



Assembling the ribs for the greenhouse has been, er, challenging. We finally figured out the problems. That’s plural.

  1. The swag’s, the crimped areas at the end of the pipes were irregular and oval rather than round;
  2. The swag’s varied in size pipe to pipe;
  3. The top pipe had a very slight 1/64th of an inch difference in inside diameter (I.D.) than the other pipes; (Top pipe end shown above)
  4. The top pipe had a thick welding bead that took up some of the remaining space;(11 o’clock position in above photo)
  5. The top pipe had been cut but not deburred so the edges of the interiors were further reduced in diameter; (2 o’clock, 3 o’clock and 4 o’clock positions in the photo above) and
  6. It’s feakin’ cold out!

The cold might be a small factor in that it would cause the pipe to contract a little but that is minor compared with the other issues. A bit of time with calipers to check a variety of pipes revealed the other problems.


Fixing Pipe

Once we figured out all of the problems the solution was quite simple, we used a grinding stone to remove 10 cm of the excessive welding bead, debur the pipe end and bevel the last couple of millimeters. Heating the pipe wasn’t necessary although this probably all would be easier in July. But where’s the challenge in building during the easy season?!?


Fixed Pipe

Once the pipe was fixed the swaged section of the next portion of the pipe fit in, tightly, into the top section. Hallelujah!

It had taken us three days to get the first couple of ribs done. It took 12 minutes each after that. A vast improvement in construction speed. There was much rejoicing and dancing.

Outdoors: 33°F/29°F 2″ Snow
Tiny Cottage: 65°F/61°F

Daily Spark: Does a program fault if there is an error but nobody reads it?

About Walter Jeffries

Tinker, Tailor...
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10 Responses to Rib Assembly – Some Modifications Required

  1. bruce king says:

    as you mentioned, the cold is probably making things more difficult. When I put up my hoop barn there were the same sorts of variations, but I didn’t have to machine any of the ends – just used a bit more force to press them in. The oval and extrusion bead (that’s extruded pipe, not welded) made for a tighter fit.

    I used a manlift to attach the purlons, but I had a concrete slab we were working on. Going to use scaffolding?

    • We’ll use a siege tower for high access and for lifting. Similar to the manlift but mounts on the tractor for rough mountain terrain.

      Interesting question as to weld or extrusion bead – the company said weld. In any case, it was a bump in the road to progress but we removed it. :) The mid and lower sections of pipe have that too but because of their larger inside diameter the bump and burs don’t cause a problem. Soon it will be up. At that point I’ll appreciate the extra tightness.

  2. BruceF says:

    Looks good. Did you bend the pipe yourself, and if so, how? Same question applies to the swaged ends. I’ve had good results bending 12 gauge 1.5″ square tubing around a jig, never anything larger (by hand).

    I’ve followed your progress all the way along. Simply amazing!

  3. eggyknap says:

    It’s pretty rare when time and gumption coincide such that I can tackle one of the many projects I have in mind around here, and even more rare that I consider documenting the process in a way suitable for, say, blogging later on. But on occasion it does happen, such as for the steer we finished butchering last weekend. When that happens, though, I generally find I’ve lost the camera, or run out of time, or something. How do you approach documenting your projects, for the blog? Is carrying a camera (or a camera-capable NSA snooping devicephone, or something), and stopping to take photos of stuff just second nature to you now? Are there many projects you choose not to blog about?

    • There are a great many projects and such that never get blogged. The blog is but a small window into our lives and the farm. Writing is a relaxation for me, something I often do in the evening or late at night.

      I do usually have a small Casio EX-V8 camera in my pocket which takes remarkably good photos, in part because it allows for full manual control of all the settings which is why I bought it. The other reason I got that model is it has a fixed lens instead of the retractable which accumulate dust.

      I don’t have a cellphone camera or such as we simply don’t have cellular service out here in the mountains. The terrain is too rugged and blocks the signals.

  4. karl says:

    how are you attaching the ribs to the cedar?

  5. Ryan says:

    How does this greenhouse relate to the one you started with cement post with slots for dividing boards?

    • That became the south field shed which has partial glazing. The pigs have been enjoying it for years. That is where most of the winter litters have been born in the past although some have also been born in the old garden, Underhill and other winter paddocks. The south field shed is about a third the size of the new greenhouse and not as bright. The money that we had saved up to make the south field shed into a full cover glazed greenhouse ended up getting redirected to get going on the butcher shop when our butcher announced he was retiring. As our daughter Hope says, “Life is full if wiggly-squigglies.”

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