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Section 3, Boat Design and Hull Types

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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.

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Figure 3–1 Entry Angle

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Figure 3–3 Full Keel with Cut-away Forefoot

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Figure 3–4 Fin Keel with Skeg Rudder

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Figure 3–5 Fin Keel with Spade Rudder

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Figure 3–6 Bulb Keel

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Underbody Shapes

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Figure 3-7 Winged Keel

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Figure 3–8 Winglets on Keel

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Figure 3–9 Canted Keel

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Figure 3–10 Water Ballast

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Figure 3–11 Small Centerboard

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Figure 3–12 Daggerboard Hull

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Figure 3–13 Centerboard Keel

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Note centerboard and pendant

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Figure 3-14leeboards

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Figure 3-15 Bilge Keels

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Figure 3–17 Catamaran

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Figure 3–18 Trimaran

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A cruising trimaran

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Figure 3–20 Transom Hung Rudder and Tiller

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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.

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Section 3, Supplemental Illustrations

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Design Parameters- Intended use

- Size

- Aesthetics

- Cost

- Hull shape

-- Minimum water resistance

-- Maximum leeway resistance

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Functions of Keel

• Reduce Leeway

• Lower Center of Gravity– Increase Stability

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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

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Full Keel

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Fin Keel, Spade Rudder

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Winged keels come in different shapes

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Bulb Keels

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Bulb Keel on model of America’s Cup boat

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Dutch Sailboat with LeeBoards

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What kind is this one?

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Lots of room on a catamaran

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Sailboat with HydroFoil Wings for lift

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Trimaran – what is hung from the center hull?

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A large trailerable trimaram.

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End of Section 3 Slides