A 12' Pulling Boat Begins

[Charlie43]

Good weather --meaning, weather when it's comfortable and inviting to put on to the Willamette or Columbia for an hour or two of rowing--  isn't quite here. But it's not too far off, either, and some of the guys in the club are talking about rowing to Astoria this summer, which means suitable boats need to be gotten ready (or built) and some training done, so hands toughen up and arms, legs, and backs get used to working hard. Depending on how hard one wants to push, Astoria is three to five days from Portland, which is a trip that needs a boat big enough to haul camping gear. But something like a row to Sand Island, or a circumnavigation of Hayden Island, say 20-22 miles, depending on the launch point and route chosen, could be done in a morning in a smaller, lighter craft. So that's what I intend to build and use for my training.

As everyone knows, theoretical hull speed (in knots) for a displacement hull is estimated by the formula, 1.34 times the SQRT of the Waterline Length. Translated into English, if a dinky little 7'6” to 7'10” pram  can put 81” on the design waterline, and it isn't so overloaded its stern is dragging, then its theoretical hull speed is a very decent 4 MPH. But to get to  5 MPH requires 126” on the waterline, because length and speed aren't directly linear. Worse, as speed is increased, hull friction increases, so much so, that to double speed requires cubing the effort.

Them that worry hugely about rowing speed build long, narrow, and light, which makes for a very tiddly boat. That's fine for racing, when allotted time is mere minutes and the distance to be covered is two thousands yards. But a bunch of old guys aren't going to be racing to Astoria, or even around Hayden Island. They're willing to row steadily for a couple of hours. But then it's time to get off the water, and by then, the winds have come up away.

So the design problem was to build as narrow and light as possible as would be consistent with open water safety and reasonable comfort, but as short as possible to enable easy handling on to and off roof racks.

To my way of thinking, a boat long enough to do 5 MPH is a boat that's fast enough for recreational, fixed-seat rowing. So, something that's 10' 6” would be long enough, provided the stem were plumb and the stern moderately raked. But Mark happened to give me enough material to cut a pair of 12' planks. So that became my target length, which some fussing with lines and expansions dropped to 11' 8”. The gate on the ramp down to the docks that RW has access to has a 41” opening. So a 40” beam became a good target.   A heavily rockered boat is sea-kindly. A shallower rocker is faster. 3” on the bow. 3.5” on the stern were a good guess. As for hull shape, I much prefer building and using flat-bottomed, double-skegged boats to vee bottoms. As for side shape, a huge amount of framing can be omitted if sides are knuckled.  Three planks is conventional, but two is sufficient (and less work).

Bingo! The boat all but drew itself in my freeware marine CAD program, Greg Carlson's, Hulls.  I faired those lines to the nearest one-hundredth of an inch in a freeware graphing program. Now I'm lofting the portions of the boat I always loft: the fore and aft portions, sectionally and in profile, so I can pick up angles and bevels and plan crowns. My house-guest departs Tuesday. Tuesday, I set up my building station and mark and cut wood. But with lines drawn and faired, the build has begun. I'm guessing a weight of 70 pounds and a cost of $120 (ply, framing, epoxy, screws, and varnish). Due to  its narrow beam, I'll have to fabricate out-riggers, as well as a set of oars.  I'm thinking about hollow-loom spoons and maybe even a sliding seat. But that's later, later. First, I've got to get a hull the water to confirm I drew it correctly.

Charlie

[MarkR]

Charlie,

Photos.  We need photos!  Looking forward to seeing your latest project.

Mark