I'm sure using Sketchup to develop planks would be at least as difficult as paper and pencil, but the original post was about lofting and not all designs are plywood. The issues when using any 2D computer drawing aid would be 1) does it accept absolute dimensions and 2) have you a printer large enough for the output. If the answer to both is "yes" then you should be OK.

There are free programs specific to hull design such as FreeShip. Creating a new design or starting from scratch to recreate an existing one is a bear with FreeShip, it is too flexible. However, it isn't difficult to create a text file with the offsets you want, just a question of arranging the numbers in a table that suits FreeShip and then importing them, and the job is done in a flash. You will need to know in advance whether the hull is plywood with chines and developable planks or strpped with rounded stations as there are two ways to import.

The big question is, what do you want to do next? FreeShip will develop the planks for you or generate station dimensions for forms to make a mold, but it won't generate the construction data for you. If that's what you plan it's a lot simpler to buy a plan.