Beyond the lines

The Drawings

The lines drawing that we have just completed is just the start of the process. To make a complete set of drawings several more are required. The list can vary depending upon the design. The following are the basics for small boats.

Lines drawing

Table of offsets

Construction plan

General arrangement plan

Out board and inboard profile

Deck plan

Machinery

We'll move on to the construction plan and come back later to the table of offsets.

Before starting the construction plan a few things need to be decided. First off, are the lines drawn to the inside or outside of the planking? What material will you recommend for construction? And what construction method?

Inside or Outside

This question is not very important in a small boat but in a larger vessel it makes a great deal of difference in the displacement. If the lines are drawn to the inside then the actual hull will be wider and longer increasing the displacement. If the lines are to the outside then care must be taken in drawing the frames because where the planking has a bend in it so that it meets the frame at an angle the width of the planking is different,

it has the same thickness but the width is at an angle. This makes very little difference on a boat that is planked with 3/8 ply but a lot on a vessel where the planking runs to two layers of 2”. I draw all my lines to the inside.

Material

Will the planking be plywood or structural lumber? In a boat such as this one, which will  be utilitarian, I would use plywood and epoxy cloth over the outside, we're designing a work boat not building a piano.

Construction

Plank on frame, plywood on frame, stitch and glue, these are the choices for a hull of this size. Plank on frame is traditional but may require skills not possessed by your client, in this case you. Stitch and glue uses modern methods and materials but it requires you, the designer, to lay out the panels, not always easy to do. There is a program, Hulls, which will do it for you but it doesn't work well with Windows 7 for some reason. So for this project we will select ply on frame.

The last thing you need to decide before doing the drawing is scantlings, the sizes of the materials you have designed the boat to be built from.

There are many scantling rules to choose from. Since I did the Westlawn course I use their rules. I do like Goerge Buehlers rules which are very simple, build it big, build it strong.

So we'll end here and next time start the drawing.