How keel type affects performance

The performance and handling of a yacht depends on many things, but perhaps the most important single feature is the shape of the hull and the profile of the keel. Over the years hulls have become shallower and keels narrower, but for many types of sailing this progression is not necessarily progress. Of the various shapes that have evolved, each has its own advantages in different circumstances. Here is a run-down of how they may fit your sort of sailing.

 

FIN KEEL WITH SPADE RUDDER

The most common modern option, usually combined with light but beamy hulls with high freeboard.

GENERAL AND TO WINDWARD

Pros

• Low wetted surface and good aerofoil shape means good speed, high pointing and quick tacking
• Light steering
• Best designs can slice through heavy seas in reasonable comfort

Cons

• High volume, light-weight designs can be lively and tiring in heavy weather
• Flat sections can cause slamming
• Less steady on the helm, requiring more work and concentration
• Strong tendency to round-up when hard pressed
• Generally require earlier reefing
• Can be unstable when hove to

DOWNWIND

Pros

• Fast
• Quick to surf and may even plane

Cons

• Can broach easily and suddenly
• Can be directionally unstable and hard to control in heavy conditions

UNDER POWER

Pros

• Handling is precise and turns tight and quick
• Some handle almost as well astern as ahead

Cons

• Limited lateral area so susceptible to beam winds at low speeds
• An unattended helm can slam over suddenly

 

FIN KEEL WITH SKEG RUDDER

Similar to above but with some key differences.

Pros

• Skeg provides better support for the rudder
• Tracking under sail or power is improved
• There is less chance of damage

Cons

• More wetted surface so potentially slower
• Objects can get stuck between rudder and skeg
• Limited balancing can make helm heavier

 

LONG KEEL

The traditional option, usually found on pre-1970s designs.

GENERAL AND TO WINDWARD

Pros

• Good tracking
• Slow, soft, comfortable motion
• Drive powerfully through short seas but can be wet
• Carry way through tacks
• Resist rounding-up
• Heave-to well

Cons

• High wetted surface area and a poor aerofoil shape, so speed reduced, tacking slow, leeway increased and pointing ability reduced
• Long ends can cause hobby-horsing
• An unbalanced hull or rig can cause heavy helm

 

DOWNWIND

Pros

• Track well and very resistant to broaching
• Very stable in heavy conditions

Cons

• Slower
• Reluctant to surf (a mixed blessing)

UNDER POWER

Pros

• Carry way well
• Track straight
• Heavy construction can reduce vibration and noise

Cons

• Large turning circle ahead
• Unpredictable and hard to control astern

 

LIFTING OR SWING KEEL

The ultimate shallow-draught option.

GENERAL AND TO WINDWARD

Pros

• A fully retracting keel offers shallowest draught
• A well-designed lifting keel can be very efficient and fast

Cons

• Grounding on anything other than soft mud or sand can damage an unprotected hull
• Stub keels offer better protection but are less efficient and prevent level drying out, except in soft mud
• Stones and dried mud can jam the lifting plate
• Internal keel boxes reduce accommodation space
• Directional stability is poor

DOWNWIND

Pros

• Early surfing and planing

Cons

• Control can easily be lost in strong winds

UNDER POWER

Pros

• Good performance and handling with keel down

Cons

• Directional control increasingly poor as the keel is raised

 

TWIN OR BILGE KEEL

A popular shoal-draught option in Britain, less so abroad.

GENERAL AND TO WINDWARD

Pros

• Shallower draught
• Dry out upright on a flat bottom
• Good protection when grounding
• Good designs are better to windward than long keels, almost as good as fins

Cons

• Pointing and speed to windward is reduced, considerably so in older designs
• When well heeled, waves can slap under the windward keel
• Can topple over if one keel finds a hole or soft ground

 

WING KEEL

Once popular, now largely replaced with various types of bulb.

Pros

• Reduced draught
• Low CoG means good righting moment
• Modified water flow over keel foot means greater efficiency and gives the motion of a longer, heavier boat

Cons

• More likely to pick up lobster pots, etc
• Risky drying out
• Weed and barnacle growth under wings difficult to remove

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