Design features
Monohulls
Typical cruiser/racer
The typical cruiser/racer has a plumb bow, short overhangs fore and aft and a long waterline with a U-shaped or trapezoidal section forwards and a wide or flared stern. These boats are light for their length and therefore have only a small lateral surface and minimal wetted surface area. The rig is tall, the keel deep, the rudder fully balanced with two bearings and the propeller shaft mounted on external strut.
Advantages:
- good manoeuvrability under engine even going astern
- easy sideways motion in breaking seas
- only moderate force required for steering, so favourable energy consumption under autopilot
- relatively fast and may even plane, good mileage when the wind is blowing
- large sail area and stiff hull
Disadvantages:
- noisy sailing and less comfortable below decks
- tendency to be stable when inverted, especially if sails are set
- relatively little reserve buoyancy forward
- keel and rudder more susceptible to damage in collision or grounding (and remember all those thousands of shipping containers lost at sea every year!)
- exposed propeller shaft vulnerable to drifting fishing nets and other flotsam
- heaving to sometimes inadvisable
- keel usually bolted through the hull
- flat bilges, so even relatively small quantities of water can cause problems
- lower centre of gravity increases pressures on the rig
- often unsuitable for anchorages and moorings that dry out
- requires a hoist or Travelift to take out of the water
- strong cradle necessary for storage on land (potential for hurricane damage)
Examples:
Aerodyne
Baltic,
J-Yachts www.jboats.com
Sentijn, Netherlands
Winner www.winneryachts.com
X-Yachts www.x-yachts.com
Long keel and centreboard
Many more traditional yachts have a long keel with a deep V-shaped hull section and a centreboard. The centreboard provides for good performance on the wind while keeping the fixed draft relatively shallow.
Advantages:
- sets more gently into a rough sea
- more peaceful below decks
- less wetted surface area downwind
- gentler rolling motion thanks to higher centre of gravity
- good upwind performance
- greater reserve buoyancy in the bow and stern for bad weather
- keel and rudder better protected against collision/grounding damage
- keel forms a solid backbone for the boat
- no problem with fishing nets
- less leeway in heavy weather
- sits well when hove to
- deep, high volume bilges
- rights relatively easily after rolling
- ok with drying anchorages and moorings
- more stable and secure when stored on land (hurricane)
Disadvantages:
- speed is always a function of waterline length
- will not plane
- lifting keel mechanism has to be serviced
- higher centre of ballast usually means a heavier boat all-round
- narrower hull
Examples:
Hinckley www.hinckley.com
Hood, USA
Hutting www.hutting.nl
Koopmans, Netherlands
Shannon www.shannonyachts.com
Lifting keel
The ability to reduce the draft (raise or swing back the keel) as required makes lifting keels very popular in tidal waters. Most of the ballast is in the keel, which therefore has to be well attached to the hull (usually steel or aluminium) and raised using an electric or hydraulic system. Lifting keel boats often also have twin rudders, which together give the same effective steering area as a single rudder but draw significantly less.
Advantages:
- minimal draft when keel raised
- stiff boat with the keel lowered
- good on the wind
- easy to dry out and slip
Disadvantages:
- sets less gently due to U-shaped or trapezoidal section
- noisy boat in a sea
- design has to be able to absorb high loads
- keel raising (hydraulic) system requires maintenance
- twice as many rudders to service
- more complex construction (more expensive)
Examples:
Dübbel & Jesse
Rommel
Multihulls
Catamaran
- upright sailing with plenty of accommodation and deck space
- greater potential speeds
- high loads on hull and rig
- two engines simplify manoeuvres
- more comfortable at anchor (no rolling)
- less comfortable sailing upwind in waves
- greater leeway due to lower wetted surface area
- weight and loading always highly significant for speed
- ideal for drying out and very secure on land (hurricane)
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Typical cruising boat
- moderate underwater profile
- gentle V-shape section forwards
- moderate overhangs
- ballast usually in integral keel root
- small bilges
- partially balanced rudder (three bearings) mounted on a full or partial skeg
- high righting moment
- moderate weight
- stern with a bathing platform
- planing unlikely
- usually able to dry out
- stable on land (hurricane)
- usually OK for conventional slipping
Examples:
Internal ballast and centreboard
Boats of this design are very popular in France and for tidal water sailing generally. The ballast is carried in the bilges while a centreboard helps upwind performance. The trapezoidal or U-shaped section in the bow makes for a wide and dimensionally stable vessel.
Advantages:
- minimal and adjustable draft good for beaching in flat bays and
sailing in highly tidal waters
- wide hull with good dimensional stability characteristics
- sails in a more upright attitude
- smaller/adjustable wetted surface area, which may lead to better downwind speeds
- will plane
- dries out comfortably
- more stable and secure on land (hurricane)
Disadvantages:
- noisy sailing
- less comfortable below decks
- relatively poor pointing ability
- flat bilges
- high centre of ballast
- inversion can be a problem
- keel/centreboard and rudder mechanisms require maintenance
Example:
Long keelers
The traditional long keel yacht has large overhangs fore and aft, a deep V section in the bow, a larger lateral surface area and a shallower draft. The rudder is mounted at the trailing edge of the keel and the propeller shaft is within the hull. Long keelers tend to be relatively heavy and long for the size of accommodation provided.
Advantages:
- sets easily into waves, movement altogether more gentle and therefore
more peaceful below decks
- plentiful reserve buoyancy in bow and stern for heavy weather
- heels more in strong winds, which reduces wind pressure on the rig
- keel and rudder protected in the event of collision or grounding
- long keel gives the boat a solid backbone
- no problems with fishing nets and less leeway in bad weather
- behaves well when hove to
- large and deep bilges
- can dry out
- more stable and secure on land (hurricane)
Disadvantages:
- lower speed potential, cannot plane
- heels more due to higher centre of ballast
- can be difficult to manoeuvre under engine
- rudder is not balanced, so steering is harder work
- higher power consumption under autopilot
- usually relatively low freeboard, so can be wet to sail
Examples:
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