Lofting the Coot

Okay, so as I've continued to study lofting, I realized trying to tackle a full description of lofting might be a bit too much to bite off because a) it CAN get really complicated and b) I don't understand all of it.  So I've decided to just go into detail about the portion of lofting that will actually apply to my first project.

The Coot is a simple, 8-foot boat with few bells and whistles.  As discussed in my last post, the offset tables for the Coot describe how to build the frame of the hull (see below).  In strip-planking, the hull is not actually a part of the finished boat; it is simply the frame that the finished hull gets bent around.

 The offset charts give you a list of coordinates for each cross section of the hull (often referred to as forms).  Each form is graphed on large sheets of graph paper, cut out, glued to plywood, and then the plywood is cut to match the contour of the graph paper.  Then, each form is placed at set intervals from its neighboring forms along a straight backbone, and, once complete, you should have an accurate frame to wrap your wooden strips around.

 But first, you have to learn how to read the tables.  Reading an offset table is a lot like reading the x and y coordinates of a graph (if it's been a while since you took geometry, no worries!).  The only catch is that there are a few keywords that have to be explained first.

This is an example of a column from a typical offset table.  The 4 main keywords to focus on are half-width, elevation, keel line, and DWL.  Basically, the keel line is a vertical line that goes through the center of a form, and the DWL (design water line) is the theoretical water line of the boat, but most importantly, it is out main point of reference for measuring vertical displacement.  To really grasp how to read this thing, let's set up our graph.  Your horizontal axis is the DWL and the vertical axis is equal to the keel line.  The elevation is the distance of a point on the outline of a form from the DWL, and the half-width is the distance of a point from the keel line.  I have a rough illustration of this below.

  There are a couple important things to note on this graph.  1) Replace "Height" with "Elevation" (Oops!), and 2) the negative values for elevation will actually be charted ABOVE the DWL on the chart (the hull is built upside down, so what will actually be below the water line (negative elevation) is above the DWL while you are building it).  3) The offset will only make one-half of the cross-section.  The other half is simply a mirror image across the y-axis.

That is really all you need to know to get started with drafting, however let's take a look at the offset table again.  We have briefly discussed waterlines and buttocks lines in my last post, but I have not mentioned gunwales or feature lines yet.  A gunwale (pronounced "gun-null") is simply an area along the top of a boat hull that an extra strip of wood is added to prevent wear and tear on the hull (in the case of the Coot, most likely from oars).  The offset table simply tells you where to place the extra strip of wood.  The feature line is point on a form where the outline makes a hard angle, and from that point to the tip of the gunwale, the outline of the form continues as a straight line instead of curved (my graph above does not have a feature line on it).


And thaaaat's all folks!  Thanks for tuning in!



Term of the Day: To Freeze the Balls Off a Brass Monkey

Nowadays, we think of this term as a crass way of saying, "It's REALLY cold!" However, it's roots might surprise you.

Oddly enough, this term is a throwback to the times of cannons and sailing ship warfare.  The true saying actually went "to freeze the balls OF a brass monkey", and did not refer to any crass references our imaginations might conjure up.  Instead, it dealt with the science and freezing points of various metals!  A "brass monkey" was a small brass cannon on the deck of many ships.  When the temperature would get extremely cold, the brass of the cannon would shrink faster than the iron cannon balls inside it, and when this happened, the cannon was rendered inoperable because the cannon ball was stuck in the cannon.  On cold nights, sailors would exclaim to one another, "Tonight could freeze the balls of a brass monkey!"

...And sailors are always the ones accused of having dirty minds...

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!

The First Project: The Coot

As alluded to in my last post, I have chosen the boat I will build for my first project.  It is a small, 8-foot dinghy called the Coot.  This is (hopefully) what the finished project will look like.

It is broad and slow, but it can seat two people (a request of my "crew") and is a good beginner strip-planking project.  Also, if I am so inclined, it can be modified into a small sailboat; we'll see about that.  The cost of construction should be no more than $800.  Actually, a more reasonable estimate would be $600, but I'll tack on $200 since it's my first project. 

The Coot combines a strip-planked, open hull with a stitch-and-glue interior.  The sides of the hull are strip-planked and attached to a transom (flat side) on both the bow and stern.  The transoms are made out of a single piece of marine plywood, as are the seats in the boat. At the end, the whole boat is fiberglassed.  This is a simplified description of the procedure, but I'll go into details once the project is underway.

Term of the Day:  Length/Beam/Draft
There are three main measurements when looking a boat diagrams: the length(s) of the boat, the beam, and the draft.  There are several measures of length when talking about boats, but for now we will discuss the main two: the Length Overall (LOA) and the Length at the Waterline (LWL).  The LOA is fairly self-explanatory; it's just the length of the boat from tip-to-tip.  The LWL is the length of the boat at its waterline.  The waterline can be thought of as the hypothetical line at which the water reaches when the boat is launched.  Basically, the LWL is important for calculating the hull speed of a boat.  The longer the LWL, the faster the boat... more or less.  The Beam of a boat is a measure of the widest point of a boat.  Pretty simple. The wider the beam, the more stable it is (harder to capsize); however broader beams also affect speed. The Draft is the vertical distance from the waterline to the bottom of the boat.  The draft is important because it tells you what the minimum depth at which a boat can travel.

Financing the Armada and Other News

It's been a bit too long since the captain's log has had a new entry!  As well as school being particularly busy lately, I've been working on how to finance this little venture. 

First off, I've added a donate button on the site, so if you feel like donating out of the kindness of your heart, feel free!  Also, I plan on opening a new page on this blog that will feature pieces of "knotical" macrame art that I've made by hand.  I will try to have that new site up and running soon.  I'm also considering adding ads to the site, but I'm not sure about that yet.  At this point, I don't think my viewership is quite large enough to garner much from advertisements (however the few that I do have are quite loyal and greatly appreciated :-)  ).

Viewership runs hand in hand with money when you're trying to get a blog started, so if you have any friends you think might enjoy what I have to write about, please get them to become followers of the site.

Monetarily, I'm aiming to raise $800 for this first project.  I've settled on an 8 foot, strip-planked dinghy that I think would be a great, sturdy starting point for the armada.  More on all this in a later post!

Finally, I would like to welcome a new crew member aboard!  She may not be able to help with construction too much, but she is quite aerodynamic.  Her name is Tink, and she is a Southern Flying Squirrel.  My girlfriend Ivette and I just got her last week, and she's a very chipper little pecan pirate!

Term of the Day: Leeward/Windward
This is a very important concept to understand when sailing.  The windward side of a boat is the side the wind hits first.  The leeward (pronounced loo'erd) side of a boat is (surprise!) the other side of the boat.  For example, if you're sailing along and the wind is moving from left to right (port to starboard), then the port side of the boat is windward and the right side is leeward.  This can apply to anything on the water (ie. docks can have windward and leeward sides as well).  Although its fairly simple, this concept doesn't come naturally to most of us landlubbers and requires a bit of practice to develop the windward/leeward sixth sense.

Sailing 101

So I finally got to go sailing for the first time, and it was as awesome as I hoped it would be and then some!  I'm hooked.  I sailed out on Travis Lake (TX) with the UT Sailing Club.  It was a beautiful day with a moderate amount of wind... a perfect day to learn how to sail!

The first boat I sailed on was a small sailing dinghy called a Sunfish. It is a small, 1-2 person boat that utilizes a single lateen sail.  A lateen sail is a triangular sail that has 2 yards (poles attached to the sail.) and is not directly connected to a mast.  Anyway, I crammed onto it with 2 other guys.  I was manning the main sheet (the cord that controls how far out the sail is let out) while my new friend Jacob (pronounced "Yacob") manned the helm (steered).  Although it is ideal that one person does both things at once, there were more people than expected that showed up, so we had to make do.  The third guy (can't remember his name) just clung to the mast for dear life... I kinda felt bad for him.  The Sunfish is a very light boat that maneuvers fairly well for its size although it tends to give way to the leeward force of the wind a bit; you don't sail exactly in the direction you are pointed.

After spending more than a few hours sailing around the lake in the Sunfish (time FLIES when you're sailing), we came back for lunch.  After grabbing a quick bite to eat, I met another new friend Neto (sp?), who has been with the team for a while.  Since he has climbed the ranks a bit, he is allowed to sail the next ship the team has above the Sunfish: the Laser.  The Laser is a fun boat!  It is a larger boat with a very large fore-and-aft mainsail.  It can fly compared to the Sunfish, however it is also easier to capsize.  Jetto showed me the ropes, and was eager to let me man the helm solo.  He said I did a good job as I never capsized her, which is apparently very common among beginners.  That made me feel somewhat accomplished.

After sailing the Laser for a bit, we pulled all the boats out of the water, and Paul (the unofficial leader of the club) showed us how to pack everything correctly.  And so ended my first sailing adventure.

Although it was completely amazing, there were several things that surprised me about sailing. A) Being able to keep track of the direction of the wind is not as easy as you would think.  Because the apparent wind (the wind you feel while sailing.  It is different than the true wind, but the apparent wind is what really matters) changes depending on both the fluctuating speed and direction of the true wind as well as the speed and direction of your boat.  I think practice is the only way to really get a feel for that.

B) I also found docking to be a challenge.  You have to do a lot of juggling and the technique of it varies depending on the direction of the wind relative to where the dock is. I think just explaining how to dock would take a whole post in itself, and since I don't have that great a grasp of it just yet, I'll save that for another time.

I was so intrigued by how well a sailboat harnesses the earth's natural energy.  Even when there was hardly a wind at all, it was possible to sail at a fairly decent speed.  Although a person can go on and on about the physics of sailing (which is quite interesting), the truth is that the best sailors just learn how to attune themselves to nature.  It's kinda like dancing with Mother Earth; you just have to practice.  And on that note, I intend to!

Term of the Day: To Know the Ropes
This one is actually fairly self-explanatory.  On a typical ship there are literally miles of rope that are used to rig the ship.  As would be expected, it took quite a bit of time for a sailor to learn all the ropes on a large ship, and an experienced sailor was referred to as someone who "knew the ropes".