Section 3, Boat Design and Hull Types

Identify various hull configurations such as: a. Full keel. Boat Design and Hull Types: Identify various hull configurations such as: a. Full keel. b. Full keel with cut away fore foot. c. Fin keel with balanced rudder. d. Fin keel with skeg rudder. e. Centerboard hull. f. Daggerboard. g. Leeboard.

Figure 3–1 Entry Angle Hull Materials: Wood and fiberglass reinforced plastic (FRP). Aluminum, steel, and ferrocement boats are usually larger vessels. Designs vary according to the intended purpose of the boat. List the handling characteristics of each keel type. Discuss advantages and disadvantages of various materials used in construction. Identify FRP lay-up process (gel coat, cloth, roving, and mat.) Figure 3–1 Entry Angle

Full keel provides directional stability, but is slow to tack. Full keel, full keel with cut away forefoot. Full keel provides directional stability, but is slow to tack. Midships section design is cross section at longitudinal middle. Overhangs increase effective waterline length when a boat is heeled and are related to the boat’s speed. Freeboard and sheer as concepts of boat design. List the advantages of high freeboard on modern boats. Compare the characteristics of daysailers and larger cruisers. Identify types of ballast used today and historically. Figure 3–3 Full Keel with Cut-away Forefoot

Figure 3–4 Fin Keel with Skeg Rudder Daysailer sizes and characteristics. Cruising sailboat sizes and characteristics. Understand functional limitation and positive features of the various designs. Figure 3–4 Fin Keel with Skeg Rudder

Figure 3–5 Fin Keel with Spade Rudder Deep Narrow Fin Keel Effective in sailing to windward Quick to tack Harder to keep on track Limit to depth Figure 3–5 Fin Keel with Spade Rudder

Displacement. The weight of the amount of water displaced. Ballast, usually lead or cast iron or other heavy material. Ballast/displacement ratio. Figure 3–6 Bulb Keel

Underbody Shapes

Figure 3-7 Winged Keel

Figure 3–8 Winglets on Keel

Figure 3–9 Canted Keel

Figure 3–10 Water Ballast

Figure 3–11 Small Centerboard Centerboard boats. Function of centerboard. Figure 3–11 Small Centerboard

Figure 3–12 Daggerboard Hull Daggerboard boats.

Figure 3–13 Centerboard Keel

Note centerboard and pendant

Use of leeboards to reduce lateral motion (resist leeway). Figure 3-14 leeboards

Figure 3-15 Bilge Keels

Figure 3–17 Catamaran Catamarans compared to monohulls: higher initial stability.

Trimarans are similar to catamarans in tacking ability. Figure 3–18 Trimaran

A cruising trimaran

Figure 3–20 Transom Hung Rudder and Tiller Rudders with pintles and gudgeons found on smaller boats, but seldom on larger vessels. Rudder and tiller operation. Wheel steering on larger vessels. Identify: rudder, tiller, gudgeons and pintles from illustration. Figure 3–20 Transom Hung Rudder and Tiller

Vocabulary Ballast. Weight carried low in boat to improve trim or stability. Board Boat. Small (car top) centerboard sailing dinghy with very low topsides and virtually no cockpit. Centerboard. Pivoted board that can be lowered through a slot in the keel to reduce leeway. Daggerboard. Sliding board that can be lowered through the keel to reduce leeway. Displacement. The weight of water displaced by a floating vessel; hence, the weight of the vessel itself. Gudgeon and Pintle. A metal eye and matching pin used to mount a rudder on the sternpost or the transom of a boat. Leeway. Sideways movement of a boat through the water, caused by wind or current. Also, the angular difference between the true course steered and the true course over ground. Stringer. A fore-and-aft structural member of a hull. Tiller. A lever attached to the upper end of a rudder stock, used by the helmsman to turn the rudder. Wetted surface. The portion of a vessel’s exterior which is in contact with the water.

Section 3, Supplemental Illustrations

Design Parameters Size Aesthetics Cost Hull shape Intended use Size Aesthetics Cost Hull shape -- Minimum water resistance -- Maximum leeway resistance

Functions of Keel Reduce Leeway Lower Center of Gravity Increase Stability

Boat Design Summary Fiberglass most common hull material Keels evolved from Full to Bulb or Wing Prevents leeway Waterline length determines max speed Wetted surface determines water friction

Full Keel

Fin Keel, Spade Rudder

Winged keels come in different shapes

Bulb Keels

Bulb Keel on model of America’s Cup boat

Dutch Sailboat with LeeBoards

What kind is this one?

Lots of room on a catamaran

Sailboat with HydroFoil Wings for lift

Trimaran – what is hung from the center hull?

A large trailerable trimaram.

End of Section 3 Slides