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  1. #1
    Join Date
    Mar 2010
    Posts
    1

    21 ft 2 man, flat bottom rowing dory/pulling boat

    I just completed a 21 ft 2 man, flat bottom rowing boat. Plywood construction, with 1x4 ribs, 3/8 plywood, soaked in Timbor, then epoxied, pre-drilled and countersunk, stainless steel screws, attached to the ribs. The ends are rather like a canoe, somewhat rounded, not pointed. I drilled about an inch in from the ends and used wire the bring the two front sides together, then created triangular wedge shaped blocks from 2x4 pieces and predrilled from the outside into the wedges and epoxied the blocks in and the fronts together and then snipped and pulled the wire out. It has wood outrigger outside the top coping for the oars to rest upon and rotate against. So this is like a rowing dory, wherry, but with a sliding seat system ( made the rails from cut down 2x4's with a groove big enough for roller blade wheels and then a padded seat that has those roller blade wheels to run up and down the grooved rails)

    The problem is that with all the epoxy and 3/8 inch plywood, it tops the scale at around 300lbs, which is fine for farting around, but I don't think I could row 20 miles. But, do you guys think I could use something like nida core or something like that in place of the plywood? Not on this boat, but on my second build ( the second time around is sure to be better- I know so much more now) I still would think I would use the 1x4 ribs and screw the nida core to the ribs and then fiberglass over the screw holes (just a thought) Then, maybe, I could get the weight down to maybe 100 lbs.

    Right now, I can stand on the bottom, but I try to stand on the rails or the ribs. When rowing, my weight is evenly spread over the ribs, as the rail is on top of the ribs and my butt is in the seat sliding back and forth along the rail. Ready to start my next boat, especially if you guys think some light weight composite/foam thingy will work.


    Thanks


    The proble

  2. #2
    Join Date
    Mar 2001
    Posts
    399
    You should be able to get a light weight composite/foam thingy in at 100 lbs or less providing you want to fiddle a bit. One advantage of foam/glass is it is fairly easy to add ribs or extra glass if it is too flexi. Try something like 3/8 Corecell sides and bottom with 10 oz cloth or 12 oz knitted inside and out. If you are not mounting oarlocks on the gunwales cut 3 strips of foam, glue to the sheer and round off so you can glass over to add stiffness. If you are using oarlocks on the gunwales it would be better to use wood. Put some wood hard spots in the bottom for mounting your seat/outriggers. You can add foam ribs if stiffening is needed.
    A second option would be 6 mm Okoume plywood glued lapstrake, again this could be done without ribs and add later if necessary. This is more complicated, but we have had customers build some very nice boats with this method. In either case if you can add curves to the panels it will make the structure more rigid without any increase in weight.
    One caution about using wood preservatives, most are Varsol based, and epoxy will not bond well to wood coated with anything oil based. Glue on bare wood, then add the Timbor.


 

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