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Hull and Keel

A sailboat’s hull and keel receive considerable attention from a sailboat designer since they determine the capacity of the vessel, how fast it will go, and the degree of safety and comfort.

The hull is the essence of all boats. It is carefully designed for water flow. Some hulls are designed to go fast across the top of the water. These are called planing hulls because the velocity of the water under the hull provides lift so as to lift the hull upward. This reduces the amount of hull in the water and thus less water needs to be moved out of the way. This reduces the drag and consequently, the boat can go even faster. Many smaller dinghy sailboats plane on top of the water.

Most larger sailboat’s hulls are called displacement hulls. This is because there is no appreciable lift provided to the hull from the boat’s velocity. Thus, the boat will always displace the same amount of weight of water as the boat’s weight. This is the essence of the ability to float.

Still, you can imagine there is considerable thought invested in designing a displacement hull to make it slippery. Reducing resistance from the water makes the boat go faster. Think of the resistance of a knife slicing through water versus the same knife turned sideways.

Keels are a sailboat’s stabilizer and provide the ability to sail in directions other than directly downwind. Their weight and design provide resistance against the heeling power of the wind and determine a sailboat’s ability to stay upright. On very rare occasions when keels have dropped or been ripped off—not a fun experience—the vessel will capsize and sailing is over for a while, sometimes forever. Additionally, as the keel slices through the water, the keel also provides resistance to the sailboat from being pushed completely sideways through the water from the wind.

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Mono & Multihulls

Historically we are used to thinking primarily about monohull sailboats. However, in the past 20 years, stronger materials have led to multihull (catamarans and trimarans) sailboats entering the sailing market. Each configuration has its own features.

Multihulls, usually catamarans (two hulls), are popular among charter companies because of their ease of use, stability, and creature comforts. Due to the catamaran’s width, slips are sometimes difficult to obtain and if so, are usually at twice the price. But for those who are willing to pay, the tradeoff can be worth it.

Hull protection

It is vital to protect your hull from the harshness of the water environment. Algae and barnacles are not your friends. For this reason, serious amounts of research have gone into various types of paints for the section of the hull that sits below the waterline. No matter what paint technology you use, serious blistering and damage can occur if you do not maintain and recoat the hull every three to five years, depending on the environment.

Some environmental considerations depending on the water include:

  • Barnacles
  • Temperature of the water; higher temperature water spawns faster growth of algae
  • Algae count
  • Salt: salt water is a harsher environment

The more often you brush the unwanted nasties off your hull, the longer you can extend your paint job. But that usually requires a swim or paying someone to do it for you. Keep several brushes and masks/snorkels on your boat; make your guests pay their rent by helping you brush the bottom when anchored in a nice cove in warm water times. Chuckle chuckle! Guests are often only too happy to help.

You can learn more in the Skipper Course....

Knowledge and theory for longer distances and overnight sailing in diverse conditions. The Skipper Course is a comprehensive sailing course for beginner to intermediate sailors wanting to learn how to sail larger sailboats 26ft to 56ft. Or upgrade to the Skipper Course Bundle to also master maneuvering under power and docking!

Source: Skipper
Topic: Sails and Sail Trim
Authors: Grant Headifen, NauticEd Global Director of Education
NauticEd is a fully recognized education and certification platform for sailing students combining online and on-the-water real instruction (and now VR). NauticEd offers +24 online courses, a free sailor's toolkit that includes 2 free courses, and six ranks of certification – all integrated into NauticEd’s proprietary platform. The USCG and NASBLA recognize NauticEd as having met the established American National Standards.