Planking can make a fine looking boat that obviously worked for many years in plank-on-frame boat building. You could build Clinker or Lapstrake, or Tack-and-Tape which is a frame boat method using fiberglass tape to seal joints. CLICK HERE FOR INFO ON TACK AND TAPE
The strength that comes from cold molding (layers of planking going in opposite directions) is the next progression in P-O-F building but a small row boat or drift boat can't take the two layers of planking. When you start to layer very thin planks you are making your own plywood.
So, 1/4 marine plywood with it's five layers of wood each going in an opposite direction is a pre-manufactured cold molded panel that is flexible. Five layers of wood and four layers of glue will have more strength, less movement with humidity changes and a LOT less time to build that a boat if that boat is designed to have a flat panel side like many drift boats or row boats.
Many Clinker and Lapstrake boat builders that loft odd shaped planks to create curved bottoms are now using plywood planks because of the strength and stability of the material and how friendly epoxy is to make a strong long lasting joint. CLICK HERE FOR INFO ON PLYWOOD CLINKER
In my opinion, the reason to plank without plywood would be either to copy a historical method or because that is the wood that you have on hand. There is still something pure about building a boat with local materials that are available; however, for ease of build, longevity, and strength in the 1/4 in width, I believe any high quality marine grade panel that is properly protected from rot will out perform planking.
If this wasn't true you would see a LOT more planked boats.
Mike, you can make a cedar strip drift boat if you want. With inside and outside fiberglass cloth they can be strong enough.
The folks at Wood Watercraft have been doing it for some time. Check them out ON THIS LINK.
My first boat was a cedar strip/fiberglass take-off of the 14' Eastside glass boat, used on the Madison and the Snake, primarily. That was a very pretty boat, very light and easy to row. That Eastside is a good shape for two fishermen and a rower on windy rivers.
I 'selected' my 2X cedar stock from my carpentry jobs, finding excellent clear planks amongst house lumber and replacing them. I simply ripped 1/4" X 1 1/2" strips from long boards till I had my 'pile'. I used temporary frames, stapled the strips in place with edge glue and then glassed the outside before taking it off the building jig. I used just 10oz glass cloth and polyester resin. On the bottom, I added kevlar cloth, which was the main 'saving' factor...The bottom never holed, but the inside glass cloth finally failed, along the lengthwise strip lines, after repeated flexing as the boat slid over Madison River shallow riffles.
A hull similar to that would be better built using a more substantial glassing. Mine lasted for 4 or 5 summers of fishing and floating fun...a better ]'schedule' of glass would have made it endure much longer. It was pretty.
I haven't considered strip planking and frames (belt and suspenders?)....Though I have done some other style boats with some bulkheads in a strip planked hull. There are really too many variables in your method to advise you on scantlings (the relative size and strength of the various components in a boat hull)..If you go thicker with your cedar planking...and leave in frames as with a traditional boat...you are essentially building a regular planked hull.. So your external glassing would only need be there for protecting the cedar planking...the frames and the planks (strips?) would be the structure...
The cedar strip method of hull building...it was devised to eliminate the frames left in the hull...that is the reason for it. The cedar...it acts as a core, mostly, to separate two skins of whatever fabric/matrix you use..
I suppose you could construct a boat as you are envisioning, and it would work pretty well..but there are more efficient ways to get that same look, if that is what you are after.
Your specific questions: I used 1 1/2 cedar because most of the houses we were building had 2X6 cedar decks and 2X cedar in other places...I had no thickness planer at the time, so I simply ripped my strips with a 48 tooth blade on my table saw, from construction site lumber.
There is no reason to route the edges in the dory hull shape...the sides and bottom are flat in one plane...a 90 degree butt joint on the edges is fine...again, this is with a traditional strip planked hull where the edge joints of the individual strips is unimportant, once the skins are on...On a curved hull like a canoe, there can be angles where the strips join...hence the hollow/roundover joint that some use..
Strip vs plywood? If you want to build a boat with the look of strip wood....yet framed like a plywood boat, maybe buy some ornamental veneered plywood, for ease of building?... Or staple some strips on the outside of a plywood hull with an epoxy glue and glass over it all...I dunno,
The strip plank and frame boats I have seen, they are larger sailing hulls, and most of those, the planks are nailed, one on top of the next as the hull is planked, in between the frames. That was a fashionable construction method at the end of the wooden boat era when quality full size planking became rarer. They used strips sawed from more crummy boards rather than a wide plank, and they could also utilize unskilled labor to nail that up, rather than find a skilled shipwright who could actually spile a plank properly..
I don't think I would build another cedar strip dory...No reason to do that (other than the look of the cedar strips) The other available core materials are lighter and stronger than cedar strips, easier to do also....Clear cedar is expensive.
If I did a plywood boat, it would likely be built with Brunzeel or Occume ply in a frameless way...or maybe a few frames and bulkheads in key spots to perform a specific function...like holding the rower up or keeping your gear dry..
Here's a WAG..(Wild A** Guess) for your method described...I'd estimate...maybe 3/8" cedar for the sides. I'd use a couple of layers of 13oz glass in epoxy...overlapped and maybe doubled again at the chines. You could probably leave the inside unglassed and just coat everything with plenty of epoxy...cedar is rot resistant...but if water were to soak in, it would cause the outer skin to come loose eventually.
I would use a disposable 1/4 ply rock shoe on the bottom, again liberally coated with epoxy, graphite additive in the final coats and well bedded where it is screwed into the frames through the skins.
Have fun, keep us posted as you go.