Sliding seat & rigger builds

  • Does it really matter if a few pounds of excess weight creep into your build? 

    Rowed Trip, Colin and Julie Angus's account of their voyage from Scotland to Syria in his-and-her Expedition rowboats, sometimes towed by the mountain bikes they were able to pack aboard, made me a weight-loss fanatic.

    Then I discovered you can't chop weight until you know the limits.

    I built my Expedition and rowing unit from kits during the pandemic lockdown. I used carbon fibre wherever I thought I could cut weight, but it was a hassle to find components that didn't come with the kit. I ended up repurposing discarded curling brooms for the carbon tubes I used as crosspieces in the cockpit box. The sides were 4" meranti ply with single laminations of unidirectional carbon inside and out. 

    After two seasons of regular use, the aluminum seat rails were showing uneven wear; I discovered the box was flexing in heavy conditions. My second attempt uses Alaskan yellow cedar for the 1" square tops and bottoms. I used eighth-inch oak ply for the sides with a single layer of unidirectional on the insides, fibreglass on the outsides.  

    Box #1 weighs just over seven pounds — 13 pounds with the seat, rails and stretcher. Box#2 came in at eight pounds, 14 with seat, rails and stretcher. 

    I'm curious as whether others think weight is a concern and how they address it.

  • Hello Jim.

    I'm keen to get a better understanding of the problem.

    Can you share photos of rhe uneven ware.

    Can you share photos or drawings of the 'flexing'.

    What is regular use?

    What is heavy conditions?



  • Hello Jim,
    The sliding seat and the oar pins are the only moving parts on the Expedition model. Hence, they’ll most likely to need close attention and maintenance.
    I’m very keen to learn from your experience. Please post photos of the wear on the seat rails. There is good learning to be had here. Include photos of the oar pins and gate too please. Even if it is not excessive, its all good learning.

    Meanwhile, I have guessed at the possible causes of the flexing. See diagram below.

    I-beams must be joined flange-to-flange to maintain their structural integrity. The web-to-web join shown in your photo may allow the flexing you have seen. At the end of the Sliding Seat Assembly consider these;

    1. A solid piece of timber similar to the original Angus Rowboat plans, but tailored to the I-beams
    2. Continue your experiment with the discarded curling brooms, but arrange them in an ‘X’ shape, upper flange on left joined to lower flange on right, and vice versa. That way they will maintain the I-beams at the correct distance apart, and prevent them distorting into a parallelogram.

    Happy building,


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