Wooden jon boat question.

I have just completed the outside hull of a 14' jon boat with a 56" beam. I built this out of 3/8" AC pine plywood. I noticed that the structure so far seems rather weak. I was wondering if everything will strenthen up after adding the bottom runners, rub rails, and encapsulating with 6# cloth and MAS epoxy. It was constucted as a stitch and glue, but it will have two bench seats and a front platform when completed.

 

On a boat like yours all the parts work together. The glass will add strength to the seams and some stiffness. The rub rails will stiffen the top sides, the runners stiffen the bottom. The benches stiffen both top sides and bottom. They are all part of the structure and should be treated as such.

Welcome to the forum and we want pictures,
Gary

 

Bulkhead stiffening

Would be good to have a bulkhead to make the bottom more ridgid how about below bench seat.
Yours James

 

This is normally done in the form of tanks for seats. They serve two purposes, one as transverse stiffeners and two as flotation chambers because they are normally stuffed with foam. Note that the bottom corners are usually not sealed so there is a bit of air flow and drainage. Knees in the rear corners and a small deck up front or additional knees are used to stiffen the corners and give some resistance to twisting. The transom also normally has a knee from the center floor to the center transom to help support the thrust of the motor. Often with large open areas of flat plywood you will have what is called oil canning. This is the popping flex of the panel in open unsupported areas. Aluminum boats get around this by creasing the panels to give them ridgidity. For ply you will need some intermediate framing and longitudinals to provide the same rigidity...or accept a bit of flexing.

Steve