The Super Awsome Leg-O-Mutton Sail Rig
This is my favorite sail, the Leg-o-Mutton Sprit (aka: mutton, aka: LOM), and this is the most popular type of sail to use on puddle ducks for many reasons.
Simple to construct
You can use the original edge of a polytarp, that already has the grommets in them. All you need to do is add one dart, and then cut the foot and leech.
Boom is very high
So as you tack, it is unlikely to konk your head. So many of the other sail rigs have "deck sweeper" booms so if you aren't careful when tacking, you will get clubbed right in the head. When you have kids aboard, this is a much bigger issue.
This also gives great visibility, it is easier to see around this sail than one with a horizontal foot.
Do you see how part of the sail forms a triangle below the boom? That prevents the boom from lifting in the air, which in turn perserves the airfoil shape the sail needs to generate lift - which is one of the reasons the sail performs so well to windward. On a marconi sail (right triangle), to keep the boom from lifting, sailors often add a "vang" which is a block and line to pull the boom down.
Most sail rigs have some kind of mechanical piece, typically a gooseneck, to attach the boom to the mast. The LOM uses a thing called a "snotter" which is shown in this diagram as a link of chain. Instead of the link of chain, you can use all sorts of other stubstitutes, even just a loop of line.
Just think of how this helps your bragging rights. You can tell your friends "Not only did I build my own boat, but it has a snotter".
The great boat designer Phil Bolger recognized how great the Leg O Mutton sprit sail is, and specifies a mutton on many of his boat designs.
In particular, he uses one size very often which we all know as the "Bolger 59", because it has 59 sqft.
The dimensions are:
To make the draft in the sail using the dart method, then a 3" fold works good. That is, the depth of the V is 3", so the total of the edges is 6" at the widest part.
To make the draft in the sail using the curved luff and foot method, having 3" of curve 30% up and back seems to work good.
Easy to furl
The mutton is very easy to furl and deploy. All you do is unhook the snotter line, and then roll up the boom and main sheet inside the sail.
Here is why that is a great feature -- next time you visit a boat ramp with lots of sailboats, look around at how people launch their boat. Often they will setup their mast and then set their sail, while the boat is still on the trailer. The reason they do this is because most sail rigs are a bit of a pain to deploy. Here is the problem: one good gust of wind and their boat is going to get knocked over.
To deploy a mutton, all you do is unwrap the boom from the sail, pull the line through the snotter and cleat it. Thats it, so do it at the dock - untie your mooring line, push off and go sailing.
Easy to Store
For storage, I just leave the sail on the mast, furled like described above, then place the whole thing on a couple of hooks above the back door of my house. I have a porch back there, so the entire rig is kept protected from the sun & weather.
Easy to transport
Because the mast is 16 feet long, it is super easy to transport. If you have a roof rack, you can simply strap it to the to the rack. Most cars are 16 feet long, so it won't even stick out. If on a trailer, the mast is easily long enough to stretch between the winch post and the stern of the boat.
And as you can see when it is furled up, everything is neatly tucked inside the sail, so you don't have loose line flopping around or other problems.
Easy to Reef
At some point in time, you are going to be out sailing and mother nature is going to rear her ugly head and start blowing like she just doesn't care (and she doesn't). It is important to be able to reef down your sail so you can make your way to a sheltered location and wait out the bad weather.
This is one easy way to reef a sprit sail - you simply wrap some of the sail around the mast and tie it at the base to hold it there. You can tie on the boom, or leave it off and sail without it.
Great Windward Performance
Being a 3 sided sail, the mutton is very good at preserving it's airfoil shape and has some of the best performance sailing to windward of all sail types. This has been proven repeatedly in every world championship race we have ever run, the 3 sided sails are able to make it to the windward mark faster than the 4 sided ones. For more information about 3 sided VS 4 sided sails, see: Make Your Puddle Duck Go Fast
Fastest Ducker Ever
This is Kenny Giles sailing his brother Bill's puddle duck. On a very windy day in 2008 at the Lake Rend Messabout in Illinois, he was able to get this duck up to 9.0 miles per hour under wind power alone using the sprit sail in the picture, and holds the record for world's fastest puddle duck.
The "Bad" Tack
Because the boom crosses the middle of the sail, it is said to have a "good tack" and a "bad tack". The bad one being, where the sail presses against the boom. Sometimes a big deal is made about this bad tack, but I can tell you from experience, it really isn't that bad, and sometimes on poorly cut sails or stretched out ones, it ends up being the good side. One solution to the bad tack is to make a wishbone type boom. Look at any windsurfer for an example of what a wishbone boom looks like.
Is there anything a mutton can't do !?!?!?
While a mutton can easily beat any 4 sided sail to the windward mark, as soon as you turn and reach across the wind or run, those 4 sided sails will start to pull away. To compensate for this, you can deploy a spinnaker which if large enough, and shaped properly, will blow away the lug sails. The spinnaker shown in the picture is about half the size of what you will need, if you want to win.