Because I have been involved in Carpentry for the best part of 35 years I thought that building a boat would be pretty simple. The reality is that it's a whole new ball game, for a start it's mostly all curves and twists.  Nothing is straight and level like building houses or cabinets!

Still the hand and power tool familiarity is the same, I just had to remind myself that any curve needs to be a nice flowing or also known as a 'fair curve'. This notion of a curve being 'fair' is mostly in the eye of the beholder but can be judged with the use of a good batten. A straight grained length of Oregon or Douglas fir of around 1x1 inch is handy for small curves of a reasonable length. For tight bends maybe a piece of cedar 1/2 x 1/2 inch would work well. I have even used a length of PVC tubing to loft some curves on ply sheets, use whatever you can find that will have  a little stiffness to it but will still bend in a graceful way, not in peaks and flats so to speak.

Lofting,  what is it and why do I advise you do it?  Even though most plans are pretty accurate, many are only drawn to scale and the full size measurements are noted on the scale drawings.  Any small error in measuring the scale drawings then converting to full size can often have variations from 5mm up to 40mm or more. This is more often the case with new designs where no prototypes have been built to verify plan accuracy.

To avoid nasty surprises it is a good idea to loft the full size dimensions on the shop floor, if you are lucky to have concrete or timber floors then do it. You have the room to build the boat in the work shop right? So before you put your building frame in the way loft the boat out first. To do this you need a chalk line or a long straight edge to mark a reference line along the floor a bit longer than the overall boat length.  This line will be your Centre Line (C/L) as shown on the drawings, most dimensions are referenced to one side of the C/L. Your plans will have a detail page for the grid spacings and bulkhead positions along the C/L from the stem to transom, so first off mark the overall length of the boat as shown, then mark the position of all the bulkheads along the C/L, make sure they are correct "double check" all measurements! and also make sure the lines are dead square from the C/L. It's best to make these lines longer than need as you will soon find out.  Now start at either the transom or stem (doesn't matter) and mark out the widths from the C/L for each reference point on the bulkhead details, these are usually the chine positions, number them from 1 at the first chine, 2 the second chine and so on up the bulkhead.  You only need to mark these on one side of the C/L to check them.

Now comes the use for the batten I mentioned at the top of this page, if your floor is concrete then you might need a helper to stand on one end of the batten or use some heavy weights if on your own. If the floor is timber then just use some nails to hold it in place. Fix the batten on one of your chine marks (number 1 would be logical) and spring the batten over all the other number 1's and see how they fair up in relation to the curve in the batten, you might find they are all pretty close or that some might need to be adjusted slightly, if any adjustments are need to get a fair curve then mark the new position on the floor, measure it and note it down on the relevant plan straight away.

Continue to do the same for all the rest of the chine points and note any adjustments required at the relevant position on the plans until all your widths are done. What you have just done is determined that all horizontal positions from the C/L are now going to create a nice fair curve, and that the designer has either got it spot on, or he needs to do the same thing that you just did to correct any small errors! :-)

Now you can do the same thing on the other side of your C/L on the floor to fair up all the elevation positions, the only difference this time is that the C/L now becomes the Water Line (W/L) and you will find that all the elevation measurements are referenced from this W/L up from it and down from it. Follow the same method above and mark all heights above and below the W/L for each point on the bulkheads numbering the same as before to avoid confusion, fair them up with the batten and note any adjustments you need to make.

When it comes time to mark the bulkheads you now know with confidence that the new measurements you have added will create nice fair curves in both the vertical and horizontal surfaces of the boat.