Parts of the Hull
A hull is a single piece made up of 'regions' and specific parts. The front of the hull is called the bow, and the rear is called the stern. The keel is the structural spine of the hull and runs along the bottom-center from the base of the bow to the base of the stern. The bilge is the lowermost section of the inner hull, where unwanted water tends to collect.
Types of Sailboat Hulls
What are the different types of sailboat hulls? Sailboat hull shapes and configurations vary widely. Some are ideal for offshore sailing, while others are designed for inland and coastal cruising.
Full-Keel Sailboat Hull
Full-keel sailboat hulls are a mainstay of rugged offshore cruising design. They feature a long and deep keel that runs along the bottom of the hull. The keel keeps the boat on course while sailing and also adds to stability. Full-keel sailboats are extremely rugged and often quite heavy.
These vessels range in size from 20 feet to well over 100 feet. At one time, full-keel sailboat hulls were quite common. Today, modern designs have largely supplanted traditional and labor-intensive full-keel boats. Nonetheless, full-keel hulls make tried and tested seaworthy vessels.
Deep 'V' Sailboat Hull
The deep V-bottom (or 'vee') hull is a relative of the full-keel sailboat and features distinctive 'V' shaped lines along the bottom of the hull.
Decades ago, boat designers realized that the deep V-bottom hull shape mimicked the benefits of the traditional full-keel shape while being significantly easier (and cheaper) to build. Deep V-bottom hulls are seaworthy and an excellent choice for materials such as plywood.
Flat-Bottom Sailboat Hull
Flat-bottom sailboat hulls are common on 'shoal draft' boats. This hull design is an excellent choice for inland and coastal cruising but not the best option for offshore sailing. Flat-bottom sailboats are easy to trailer, low-maintenance, and usable in shallow water.
Many flat-bottom boats are beachable too, which is great for river and weekend cruising. Flat-bottom hulls are easy to construct. These 'hard chine' designs have fewer complex curves than V-bottom and full-keel hulls, which reduces construction cost in virtually all materials.
Other Monohull Designs
Many modern monohulls (single-hull) cruising sailboats don't appear to have full-keel, deep V-bottom, or flat-bottom hulls. Newer designs (specifically in fiberglass) often use a shallow, rounded hull with a long fin keel. Thanks to modern engineering and material science, boat builders can utilize shallow hulls and long dagger-like keels to improve performance and reduce weight.
Multihull Sailboats
Multihull sailboats utilize two or more narrow hulls. These hulls are positioned side-by-side, similar to a pontoon boat. Multihull boats, while less common than traditional monohull boats, offer increased stability and deck space. The most common kinds of multihull sailboats are catamarans (two hulls) and trimarans (three hulls).
Sailboat Hull Materials
Sailboat hulls are constructed from numerous materials. Each common hull material has advantages and disadvantages, and maintenance requirements vary widely between them. Here are the most common sailboat hull materials.
Fiberglass
Fiberglass revolutionized sailboat construction in the 1960s and 1970s and brought affordable large cruising boats to the masses. Fiberglass boats can be constructed in huge numbers by factories, which reduces initial cost. Fiberglass boat hulls are made from shredded glass fibers combined with a hard resin.
After fiberglass and resin are molded into shape, it hardens and becomes completely watertight. Fiberglass sailboat hulls don't rust or decompose and require much less maintenance than steel or wood hulls. The vast majority of sailboats on the new and used market have fiberglass hulls.
Wood
Wood is the oldest sailboat hull material. Wood sailboat hull craftsmanship developed over thousands of years. Wood hulls are a perfectly viable choice to this day, though they require more maintenance than fiberglass or metal hulls.
The most common and finest traditional sailboat hull material is white oak, a dense hardwood that resists rot and swells when wet. Gaps between the planks of traditional oak hulls are caulked with strands of cotton and tar, onto which the oak swells when submerged, creating a watertight seal.
Modern wooden boats are often constructed with cedar and fiberglass, giving the appearance of wood while increasing strength. Plywood is also a common hull-building material, especially on hard-chine sailboats.
Aluminum
Aluminum is an excellent sailboat hull material, though less common and more costly than fiberglass and (sometimes) wood. Aluminum sailboat hulls are strong, lightweight, and never rust. Aluminum is ideal for large, custom-built sailboats that stay in the water for long periods of time.
And though aluminum sailboat hulls don't rust, they're extremely susceptible to galvanic corrosion. This phenomenon occurs when aluminum contacts steel or copper in a wet and salty environment.
Repairs to aluminum hulls must be done carefully, as using the wrong materials can cause rapid and extreme corrosion. A single steel bolt or copper thru-hull can ruin your day and burn a hole in the hull. Despite its limitations, a well-constructed aluminum sailboat hull is an excellent choice for premium offshore boats.
Steel
Steel is the most rugged sailboat hull material. Steel is cheap, easy to repair, and extremely strong. Many hardy offshore sailboats utilize steel hulls. Steel is an excellent choice for utility boats but often appears visually unattractive.
Steel rusts and requires frequent painting and maintenance to avoid degrading to an unacceptable level. Steel is an excellent choice for world-cruising sailboats, as virtually every country has skilled workers capable of repairing and maintaining steel.
Sailboat Hull Maintenance
Sailboat hull maintenance requirements vary based on material, size, and length. The hull should never be neglected, as it's the most important part of the boat. Here are the typical maintenance requirements for sailboat hulls.
Scraping
The oceans are alive, and owning a sailboat will ensure that you never forget it. In a matter of months, areas below the waterline on any sailboat can become their own marine ecosystem.
Barnacles, muscles, and other sea gunk can grow several inches thick on the bottom of a boat. Marine growth causes drag and hull deterioration. Boat owners should scrape their hulls several times per year, especially before long cruises.
Painting
Painting is essential on all sailboats, but the extent and location of paint vary. All sailboats require a thick layer of specialized bottom paint. Bottom paint contains chemicals to discourage gunk growth.
Steel and wood boats require paint above the waterline as well. Red and white lead paint are popular and quite effective, though traditional lead-based marine paint can be difficult to come by. Modern alternatives work fairly well and are often easier to find.
Gel Coat Maintenance
Fiberglass sailboat hulls have a 'gel coat' top layer, which preserves the finish of the hull and prevents decay. Therefore it's important to maintain the gel coat of your fiberglass boat hull. Gel coats also improve the appearance of fiberglass boats.
Sacrificial Anodes
Maritime engineers developed an unusual way to reduce corrosion on steel sailboat hulls. Blocks of zinc called 'sacrificial anodes' are placed around the hull. These anodes essentially 'attract' corrosion and draw it away from the hull itself.
Over time, sacrificial anodes corrode beyond recognition and disintegrate, requiring replacement. It's essential for steel sailboat owners to watch and replace. Zinc anodes are also used on aluminum boats and metal boat parts, such as propellers.
