Using the motor is main reason to build this boat. If not using the motor, it'd make more sense to build a Northeaster Dory. The accommodations motoring add a lot of cost and build complication.

I respectfully beg to differ, John. Yes, accommodating a motor is important to many folks, but the benches, the larger size, the resistance to swamping, the increased stability, the ability to carry more sail and payload (without the motor well) are attractive features even to the non-motorized crowd. Since the motor well is modular and can be skipped, the extra complications can be only the ones that a non-motor builder actually wants.

As far as the original question goes, the only concern I'd have with lockers is having a place to put my feet when sitting on a bench and facing in. If the proposed lockers only take up the same amount of room as the foam they replace, that won't be a problem.

I don't think that any of the foam volume needs to be made up for, as long as the lockers are loaded carefully. A good dense structural closed cell foam is 2 lbs/cubic foot. Water is 64 lbs, so each cubic foot of foam provides 62 lbs of buoyancy. When the lockers are empty, they can actually provide more buoyancy than foam since air is lighter than foam. As long as the lockers are carefully constructed. empty they should be fine.

Keep in mind that most of that buoyancy is there for regulatory compliance when there's a motor in the boat. Without that dense chunk of metal, a lot of that floatation can be safely done without. Wood floats, people wear PFDs. As long as the boat isn't loaded with something denser than water, it'll be unsinkable. You will have to pay attention to loading so that it will be balanced for sailing and rowing and that it will float high enough to bail when swamped in choppy water. But watertight lockers are a viable alternative to foam

Laszlo

Thanks for asking this question as this has been on my mind too.  I really like the SW Dory design, but side seats solely being used for floatation seems a waste of good storage space.

I was thinking more along the lines of creating a hinged panel on the top or sides.  Could even put inflatable bladders in there if not needing the area for storage. 

storage lockers are useful and covenient.

i would only offer that as you think about the hatches to the locker that you ensure you they are plenty large and that you have space to look into them and inspect/ensure the locker remains dry....and when storing the boat, keep the locker hatches open so it can breath.

any enclosed space also becomes a location for water accumulation and resultant damage/rot if stored uninitentionally wet for long periods of time.  Barry M's suggestion for hinged panels on top or sides is a great suggestion for how to handle.

h

If I were bulding a SW Dory, I'd definately add hatches to the side seats so that the area could be used for storage and to facilitate inspection per hspira's comments.

I did just that with the stern and bow compartments of my GIS using the CLC Flush Hatch Kit.  I only store light bulky items like sleeping bag, tent and extra PFDs etc in dry bags of course.  On the GIS, thge hatches are mostly above the water during a capsize and I get just a few onces of water.  Making sure the hatches on the SW Dory are water tight would be very important because the down side would surely be under water. 

Here is the fwd hatch in front of the mast: