If you have ever witnessed a boat colliding with a rock or other submerged obstacle you will know that there is an almighty thump and the whole boat shakes and judders. While such hard groundings seldom result in catastrophic keel failure, something has to give and even the sturdiest keels can easily be damaged by such an impact.

Following a hard grounding it is always recommended to contact your insurance company as you may be covered for this and they will advise you how to proceed. Either way, the boat should be hauled out and a surveyor needs to inspect the keel and hull for damage.

Fin-keelers – A hard grounding can cause the keel-to-hull joint of a fin keeled yacht to split open as the keel is forced away from the keel stub by the impact. Aside from any damage to the joint and keel bolts the impact can cause cracks in the gelcoat which need to be repaired. More seriously, it can also force the aft end of the keel upwards, damaging the hull laminate in the process. This is repaired as follows:

• The areas of damage around the hull-to-keel join area are identified and marked.
• Splits in the laminate tend to be on the outside of the hull forward of the keel and inside the hull aft of the keel.
• The damaged areas are ground back and repaired with layers of glass fibre and epoxy resin, before being faired, primed and painted.

Encapsulated keels – Although encapsulated keels are generally thought to be more robust than exposed keels, damage can still occur after a hard grounding. A gash in the GRP keel coating needs to be treated as it can lead to bigger problems if water reaches the iron ballast, which will begin to rust and expand as a result, eventually splitting the encapsulated laminate. This should be dealt with as follows:

• For superficial damage to the keel coating, wash and clean the damaged area. Then roughen the edges of the gouge with coarse 40 grit sandpaper.
• Wipe clean with acetone and dry the area thoroughly.
• Apply a clear coat of epoxy resin, followed by a second coat of epoxy resin mixed with micro-balloons.
• Cover the patch with some waxed paper taped to the keel in order to hold the epoxy in place until it hardens.
• Sand the patch when dry. Fill any voids with more epoxy if necessary and then sand smooth.
• Apply a two part epoxy primer to the patch, building up several layers of primer to create a waterproof barrier coat. Lightly sand when fully cured.
• The repair is now ready for priming and painting.

Bilge keels

A problem with bilge keel boats kept on drying moorings is that the keel bolts and hull-to-keel joints sometimes fail due to the constant flexing load caused by the continuous grounding that occurs at every tide.

This problem can be solved by strengthening the hull on the inside with epoxy resin and glass cloth. This is in addition to replacing the worn keel bolts and resealing the keels, see above: Keel bolt and hull-to-keel seal replacement.

Lifting and swing keel inspections

There are two main types of lifting keels fitted to sailing yachts, those that lift up vertically like dagger boards and those that pivot at an angle. Both forms have lifting tackle which needs to be inspected and maintained on a regular basis according to advice given in owner manuals. Manufacturers usually advise owners which maintenance work they can do themselves and the work that should be carried out by suitably experienced boatyards.

Most swing keel lifting mechanisms have four basic parts – a winch, a cable, a pivot bearing attached to the keel and turning blocks. On larger boats, keels are often lifted by electric motors and hydraulic systems.

Lifting keel maintenance

Most lifting keel maintenance needs to be done ashore with the keel lowered, in order to get access to the keel housing, but some systems can be checked and maintained with the keel raised. Annual checks and maintenance should be done in accordance with owner manuals and are likely to include:

• Winch mechanism inspected for corrosion and smoothness of operation. Lubrication of winch mechanism.
• Centre-board pivots to be inspected for wear.
• If applicable, lifting tackle rope checked for chafe.
• If applicable, wire cabling checked for condition. If any wires are broken the cable should be replaced. Inspect the condition of the eye bolt where the winch cable attaches to the keel.
• Turning blocks to be inspected for wear and lubricated with marine grease. Worn blocks to be replaced.

For a complete refurbishment of a swing keel, all the equipment will need to be disconnected and removed, the keel shot-blasted for rust removal and then repainted. Bearings, seals and cables will also be replaced.