Hi Julien
Building from a plan is not easy and a little knowledge of how to read a set of lines is required, however once you've mastered this it all becomes quite logical. A good level building board is required and on this mark the frame (or shadow) spacing, this can be obtained from the drawing, if it's a full size plan just measure between the vertical lines on either the elevation or the plan view of the boat. Accuracy at this stage is imperative as the hull will not be "fair" if these measurements are inaccurate. Draw a centre line up the middle of the building board, again being extremely accurate. The next step can be done in several ways, from the body plan, i.e. the part of the drawing which shows the actual cross sections of the boat, you can either trace the hull shape from the lines, use carbon as Bob suggested, or by carefull measurement from the centreline of the drawing, (this is the method I perfer, being a boatbuilder to trade I find this the easiest way!!). Remember to take all measuements from the centreline of the bodyplan, transfer on to a piece of 3 - 4mm plywood onto which you will have already marked with the various waterlines and a centreline, it helps if you paint the plywood with flat white paint, (helps subtantially with the accuracy required!), join up the mearements using a thin batten id timber bent round the dots you've left or some french curves, I use a cheap plastic set bought from the local stationery shop. Cut out the frames and set them up on the building board, matching up the centreline on the frame or shadow with the centreline on the building board, making sure the frames ae "dead square" across the building board and are square vertically from the board. I can't emphasise enough the importance of accuracy at this early stage, if not accurate the hull will be full of lumps and hollows. Once you've got all the shadows set up test for fairness by running a batten around the outside edge of the frames, any bumps will show when you do this, you can either sand down the lumps or add bits to the shadow. If it's a painted boat you may get away with adding filler once the boat is planked, however it's always best to get the intial faitng as accurate as you can. If it's a varnished boat you'll have to divide up every second frame (shadow) into the number of planks you want, this will make sure every plank is of equal width.
I've attached a couple of photo's showing the early stage of a One metre build, this in fact was a wooden mould I was making for a fibreglass hull, so I was able to fair the hull up using car body filler!!
These early stages can be quite boring and time consuming, but accuracy at this stage is well worth it in the long run.
Best of luck
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