Most cruising sailboats have what type of hull?

Most cruising sailoboats have a mono-hull.

Cruising sail boat owners try not to spend their entire lives at the helm so a good autopilot or self-steering mechanism are often used. To keep the sail boat heading steady, a deep and long (or full) keel is desirable. The keel is the bottom of the hull.

However, lots of cruising sailors want to get in close to shore so a deep keel will be a hindrance. By making the keel less deep, the sail boat will tend to drift down wind more. One way to have a shallow AND a deep keel is to use a drop board or a swing keel. This is where the shallow (not so deep) keel has a board that either pulls straight up (to get in close to shore) or it swings on a hinge up inside the keel.

That's for the keel. Another consideration for a type of hull is the beam. If the sail boat is too wide, it will be very stable... both right side up AND upside down. Cruising sail boats on the wide open ocean would not want a very wide hull. But, so too, people living on a cruising sail boat don't want too narrow of a beam, either.

The final consideration for a hull type on a cruiser is what it is made of. Most modern sail boats are constructed of fiberglass. They are easy to build and can last for many years... IF taken care of properly. But fiberglass is fragile, so bumping into something (like whales, maybe...) isn't recommended. Old cruising sail boats are often made of hard woods like mahogany. Some home-made boats are made of plywood covered in fiberglass. Some sailboats (believe it or not) are made of steel wire covered in concrete. They are very easy to home-build but are so very fragile. The sail boat I had was built completely of steel and so strong that a bump was not very much of a worry.

There are two common calculations that sailboat designers use to "suggest" a hull design. One is called the SA/D which relates sail area to a sail boat's displacement (weight in the water). The other is the D/L which relates the hulls displacement to how long on the waterline it sits (LWL). I don't think I can print the formulas here, but often, in sail boat advertisements, you will see the SA/D and the D/L listed along with the sail area, LOA, LWL, LOD, Beam, ballast, and displacement.

Sail boat D/L ratiOS

Light Multi-Hulls 40 - 50

Ultra - Light Racers 100 - 150

Light Racers 150 - 200

Light Cruisers & Offshore Racers 200 - 275

Medium Weight Cruisers 275 - 325

Heavy Cruisers 325 - 400

More than 400, and the hull begins to develop undesirable characteristics.