Plywood Shape question

When using plans with a top and side view like one in the picture, how are you supposed to know the actual shape the plywood should be for the side of the boat? I know its not the shape drawn in the plans.

 

You are building a Chapelle sharpie, which is designed for solid lumber planking. Specifically, it is file planked on the bottom and has dory style, side plank seams. On many hulls this alteration can't be made easily, because the plywood can only bend in one direction, without compound. Except for the stern and near the bottom of the stem, you should be able to substitute plywood on this hull shape. Of course, you'll have to generate your own scantlings for the structure, which will be different, depending on which plywood building method you intend to use.

Since expanding plywood panels escapes you, I would strongly recommend you select one of the many sharpie designs (there are hundreds) that have been converted to plywood construction techniques. This would provide you with a full set of plans, rather then the lines, construction profile and possibly offsets, which don't help the amateur builder much, unless he has considerable boat building experience under his belt. The full set of plans would include expanded panel layouts (what you're asking for in your post) which you can transfer to the stock, plus the dimensions of all the pieces to the boat. This will permit you to build a boat that isn't too heavy, one that is strong enough for the stresses involved and with reasonable assurance it will sail predictably.

Speaking of sailing predictably. Your Chapelle drawing is of an antique boat type. I sailed these as a lad and they aren't like a modern craft. They are witches with sails, fast, shoal, unstable and powerful beasts. In the right hands these things will fly, but don't screw up or your reward will be a very quick dunk in the drink, with hopefully no damage to you, the crew or the boat.

Most modern variations on the sharpie theme, have more bottom beam and topside flare, usually with decreased sail area and other refinements. This makes them more palatable to the sailors of our era and safer.

I have several sharpie plans available and they all include several sheets of drawings, offsets and expanded panel layouts where applicable. I wouldn't offer an incomplete set of plans. My goal is to have them built, not a head scratching builder, frustrated about how things go together.

I mean no disrespect, Justen. If you have good sailing skills, having skippered a few different types of "hot rod" sailboats (many times), then you may be able to handle these cranky wenches. I love them, but do understand what they're all about.

There are several places on line to get free or near so plans for modern sharpies. Many of these plans are also not complete, but more so then the limited information available in Chapelle's books. I also have designs that would suit your need for a sharpie, if you'd care to drop me an email (click on me name). My sharpie designs range from 15' to 34', some are wholesome shoal cruisers, others, just plan crazy fast, light dayboats.

Another option, to get your panel shapes would be to import the lines into software (some freeware is available) and develop the panels out, then print up the corrected offsets.

 

There is a list of freeware and some discussion of their various merits in the design/software subforum "Poll, best free of low cost marine design software" and several other related threads. You would need software that provides plank developments, the simplest and easiest I know of is Carenne, it is limited to constant plank angles (no plank twist) but your hull looks close to that. I have lost track of the source page but you could try a search.