Plywood dinghy frame placement

I'm working on the design of a beamy 7.5 ft sailing and rowing dinghy. The construction will be 1/4" plywood, stitch and glue or possibly something similar to the "Instant Boats Tack and Tape" method.

My question is about placement of the frames (see attached image). I'd like to put the frames as shown. Or even move Frame #2 further forward and Frame #3 further aft (to improve the interior space). My concern is that I do not have a frame at the location of max beam. I'm wondering if this will cause problems during construction? I'm unsure if hull will take an unpredictable shape due to the lack of a frame at the location of max beam. Or during use? Should I expect more damage from crashing into the dock, etc than if I had a frame at max beam? Any thoughts would be appreciated. Thanks

 

Shouldn't be a problem at all. There is no absolute reason you have to have a frame at the maximum beam.

 

Using the methods you've described you haven't any need for frames at all, particularly on such a small and lightly loaded hull. It would be wise to use conventional wisdom in the area of the dagger case to contain athwart movements, but other wise you don't need plank on frame methodology in a taped seam build. If you are unaware of these engineering considerations, if I might ask, how did you align the appendages to the sail plan, size the appendages, size the sail, etc.?

 

Dinghys of this small size do not usually need any transverse frames at all. They will just clutter up the interior. Some proper design must be done to give the boat enough stiffness but that is easily done.