To Loft or Not to Loft?

Before a boat can be built, it has to be lofted.  Lofting is the process of taking a bunch of numbers in an offset table and converting them into full-size diagrams that will be used to construct the actual boat.  For a simple boat like the Coot, this wouldn't seem like too tough a task, especially if compared to something like a cabin cruiser.  Comparatively, that is a correct assessment, but in actuality even lofting the Coot can be quite a task for a beginner like me.  Just looking at lofting diagrams is a bit disorienting.

This is a diagram of the three typical views of a hull's lines.

This second picture is an example of a boat hull's offset tables.  Pretty intimidating right?  Although it does take a while to learn all the jargon, the basic idea is not too difficult.  Let's start with the different types of lines associated with lofting.

One set of lines that are pretty easy to visualize are the waterlines.  Imagine a boat in the water.  Now imagine the line the surface of the water makes on the boat hull.  That, more or less, is a the waterline.  The rest of the waterlines run parallel to this line at set vertical intervals from the waterline.  They are a set of horizontal, fore-and-aft cross sections of the boat.

The next set of lines are the buttocks lines.  I ave no idea why they are called the buttocks lines, but they are.  The center buttocks line is the keel line, and it runs vertically fore-and-aft.  The way I remember it is that the keel line (the main buttocks line) follows the butt crack of the ship... not sure if that helps...  In summary, the buttocks lines create vertical, fore-and-aft cross sections of the hull.

The last set of lines I am going to talk about tonight are the section lines.  These are simply vertical, cross sections that run perpendicular to the keel line.  If you were gonna slice a hull like you would a piece of bread, you would be slicing it into section lines.

So anyway, that is a good starting point, and I will talk more in depth about reading offset charts for these lines and actually doing the lofting in another post, but for now, I am faced with the question of whether or not I want to deal with lofting for my first project or if its worth just buying all the diagrams pre-made in a set of plans.  Lofting IS time-consuming, but I can save a good $100 if I do it myself...

Ok, so that's not much of a dilemma; I'll do the lofting myself. Problem solved.

Term of the Day: Tack/Jibe

Tacking and jibing refer to turning the boat through the end, and in some ways, you can think of jibing as tacking's evil twin.

A boat can sail roughly 45 degrees into the apparent wind, which means there is a 90 degree no-fly zone for sailboats called the irons.  When you tack a boat, the object is to turn the boat through the irons as quickly and smoothly as possible.  On smaller boats, the tricky part is making sure to handle the boom correctly (the beam attached to the bottom of the mainsail that rotates about the mast) so it doesn't hit anyone while transitioning your weight so you don't capsize.  All in all though, tacking is pretty tame.

Jibing is like tacking, but when you are traveling with the wind.  Again, to turn through the direction of the wind, you must flip the boom to the other side of the boat.  Jibing is much more dangerous than tacking because when traveling with the wind, the mainsail is let out so that the boom is sometimes as far as perpendicular with the boat.  If an accidental jibe occurs, the boom will swing around almost 180 degrees and bludgeon anything in its path (and it can also do a lot of damage to the boat).

Sweet dreams everybody!