7'-3" Dinghy

Design Number 176

Some years ago, I was approached by the shop teacher at the Friday Harbor High School about helping with a boatbuilding program at the school. They were looking at building a boat somewhat larger than this, and a lot more complicated. We discussed the pros and cons of the more complicated project. We came to the conclusion that something that could be quickly built would produce more sense of accomplishment in the students.

With this thought foremost in our minds, we created a design that could give the students something that would go together quickly, and not be beyond the skills that one might assume they'd picked up in the woodworking program.

This meant that complicated bevels and fits were to be avoided and simplicity was to be emphasized. The resulting design has a virtually constant bevel cut for the chine, so this can be run off on a table saw. Any minor variations from the bevel cut can be taken care of with the better quality gap-filling glues....

The specified materials were chosen to be readily available from a normal lumberyard's stock. Primarily they are a bit of clear fir and a couple of sheets of ¼" plywood. Alternatively, she could be built with the stitch and glue technique at the chines, and/or epoxy sealed and sheathed with a protective layer of cloth set in epoxy.

This sort of boat does best if kept light, so she is easily lifted aboard or onto a car-top for transporting. Thus, resist the temptation to increase the scantlings to "make her stronger" or to match the size of the materials on hand.

Keep the towing eye low, as shown. Be sure to fit the skeg shown for best results towing her. Otherwise, she'll wander or yaw from side to side on a towline.

If a sailing rig was wanted, something like that shown for the 8' Portland Yawlboat would work, using her rudder and daggerboard details too.

Length overall7'-3"2.21 m
Length datum waterline6'-93/16"2.06 m
Beam3'-9¼"1.15 m
Draft0'-4"0.10 m
Freeboard:Forward1'-41/8"0.41 m
Least0'-9¾"0.25 m
Aft1'-03/8"0.31 m
Estimated structural weight45 lbs.20 kg.
Displacement, to DWL205 lbs.114 kg.
Displacement-length ratio296 
Prismatic coefficient.63 
Pounds per inch immersion86 
Entrance half-angle35° 

Note: The displacement numbers are calculated to the arbitrarily chosen DWL.
The calculated ratios of displacement-length and sail area-displacement will vary widely depending on the loading of the vessel.

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