7½' Dinghy

Design Number 122

This boat was designed while friends were in the business of building the Benford 30's in fiberglass. It looked to be a good size to carry on her aft deck, and I liked her shape.

They built a plug out of plywood, and did comment that the narrow double chine panel at the bow was a bit difficult to twist in place, but that otherwise she went together easily.

Then, they laid up a mold on the plug. However, they either forgot about the necessity for using some mold release agent or didn't get it uniformly over the boat....

About this time, I think that they began to realize that they were putting in a lot more time doing the very nice detail work on the B30's than they had put in their estimates when they signed the contracts. So, this dinghy project was set aside while they concentrated on turning out several nicely done B30's. Unfortunately, they never got back to it, so I can only speculate that I think she'd be a good and well mannered little tender.

I'd suggest building her of ¼" (6mm) plywood, or 3/16" (4mm) if a really light version was wanted. Scantlings like the 7'-3" dinghy would work. This is a good candidate for using the stitch and glue techniques that are well described in Sam Devlin's book, Devlin's Boatbuilding. Sam is a master of the technique and turns out great examples of it from his Olympia, Washington boatshop.

If a sailing rig was wanted, I'd use the one on the 8' Portland Yawlboat, using her rudder and daggerboard details too.

Length overall7'-6"2.29 m
Length datum waterline7'-0"2.13 m
Beam3'-9"1.14 m
Draft0'-5"0.13 m
Freeboard:Forward1'-4¼"0.41 m
Least0'-9 5/8"0.24 m
Aft1'-0¾”0.32 m
Estimated structural weight45 lbs.20 kg.
Displacement, to DWL365 lbs.166 kg.
Displacement-length ratio190 
Prismatic coefficient.62 
Pounds per inch immersion125 
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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