Assembling the ribs

Assembling the ribs

The first load of steel was all flat bar. We would use 2 x 0.25 inch flats for longitudinals, 4 x 0.25 inch for our rib flanges.


The boats shape is mostly defined by its ribs. To achieve as nice of a shape as possible and to facilitate the work was modeled, faired and lofted with CAD software (see design section). From the computer model I had all the rib’s numerically cut.

A pile of flat bar and the giant jigsaw puzzle there’s our boat frame.


It only took me three weeks to assemble the ribs. Mark was away for work so I just went at it non-stop. Like for the rest of the building, having the boat detailed in CAD was a big advantage, I could double check the dimensions of my frames with multiple diagonals picked out of the computer model. To assemble the ribs, I had previously built four heavy steel tables with adjustable feet. A couple rollers on tripod also helped support longer spanned pieces. Each ring is different so I moved the tables around to support all the parts in a single plane. The more accurately the ribs are built the easiest the rest of the boat assemble will be.  I ran the laser level and adjusted the feet each time I moved the tables around (for each rib). Having a perfectly flat floor would have taken all the fun out of the process….

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Each rib was divided in two sides, a top (some split in two) and a floor piece; the ribs were pieced to optimize the nesting of the parts for NC cutting and minimize steel (and money) wastage. Knowing myself and how talented I am for mixing up order of things I had not only well identified and numbered all the parts but also “cut” the rib parts so the angles of the mating sides would allow only the proper parts to be assembled with each other. It was somewhat a fool proof puzzle.


Step two of ring assembly was: welding on a flange. All the centered ribs I made up in T sections, the bow ribs were L sections with the flange on the aft side of the rib and the opposite for the stern; I did so to get a better access under the flanges for blasting, painting and maintenance once the boat is fully assembled. We are hopping a bit of forward planning will make our life easier later. I made up many clamping jigs to position the flanges and help pulling the flat bar strait onto the ring.


Non of this was difficult just long and laborious after the first few ribs and a relief when I got to the fifteenth one. The trickiest part of the job was getting the bigger ribs out of the shop after assembling them. I was on my own to handle those giant rings.


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