What can we sailors do to feel more comfortable about the security of our keel? Matthew Sheahan has some advice

Following Matthew Sheahan’s feature on the shocking facts of keel failure, he looks at what you can do to make sure your boat is safe.

It might sound corny, but understanding your boat is much the same as understanding your body. Unless you are a medical expert, few have the technical knowledge to carry out a personal diagnosis on keel safety, but we usually know when things don’t feel right. A boat is no different and, while industry experts would caution against owners attempting to be surveyors, they do reinforce the idea that owners are best placed to notice any changes.

raise floorboards

At the very least you should start by raising the floorboards regularly and taking a look at the keel bolts and the surrounding structure. Any water in the bilge should be taken seriously and dried out. If the water keeps seeping back, professional investigation is required.


Inner liners have become commonplace in production boatbuilding and, while technically such systems are not fundamentally flawed, their structural integrity can be difficult to assess.

“The incorrect or damaged bonding of an inner liner is surprisingly common in modern production boats,” says surveyor Julian Smith. “These liners are bonded into the hull at specific places, but because they are hidden we don’t always know where the bonding is supposed to be. However, there are areas that give us a good indication of whether there is an issue. Cracks that radiate out from keel bolt are an obvious indicator, but there can also be cracks around other areas of the liner where we can see the filler.”

A common method of testing if the bonds are in good order is to tap along the lines of contact with the hull. A hollow sound can indicate an area with no bond.

“Tapping around the points at which the inner liner should be bonded to the hull can be one way of identifying hollow areas,” points out Mike Taylor of non-destructive testing experts Minton Composites. “The trouble is that tap testing doesn’t give a conclusive result. But there are other ways of assessing these structures, including ultrasound, shearography and bond testing. The problem is that at £1,500-2,000 per day, these techniques can prove costly.”


Rust around the keel mounting area or a discrepancy in the appearance of your keel bolts can be issues too.

“A rusty nut on its own may not mean that there is a problem,” says surveyor John Freeman. “Cleaning it and coating it with petroleum jelly and then keeping an eye on whether rust develops will give an indication of whether there is a problem. But a rusty washer could suggest a more serious issue underneath and would need to be investigated further.”



Fractures in longitudinal and transverse members in way of the keel should be looked for, along with signs of stress cracks in surface coatings. The shiny internal mouldings aboard modern production boats show up such flaws well and these could indicate that all might not be well under the skin. Cracks in joiner work, especially where it is attached to the hull can also give an indication of potential problems.


Another is dust in the bilge. “White powder or dust should be treated very seriously indeed,” explains Freeman. “On no account can this be ignored as it can provide evidence of a structural failure.”

Loose keel bolts

Loose keel bolts should ring alarm bells. If you can tighten them easily, the yacht’s structure may have altered.


One technique recommended by J-Boats for an initial assessment involves checking whether there is any deflection between the keel and the hull:

‘With your boat suspended from travel lift straps (OK) or braced in a cradle (best) or trailer (good), grab the keel at the bottom and attempt to forcefully rock it back and forth. This test on a deep keelboat should create a small amount of flex over the keel span and sump (if solid glassfibre like most Js), but there should otherwise be minimal movement from side to side. When you release the keel it should immediately return to position.

‘It is also important to have someone below decks to check for movement in the keel floor or bilge area, or any evidence that the sump is moving independently of the keel floors. Any excess movement should trigger further investigation.’

This method is one commonly used among surveyors and assessors. “For half a day’s labour we can usually tell people whether their keel structure needs further work or whether it is sound,” says Hugo Morgan-Harris, a South Coast-based surveyor. “I believe this kind of check is essential for those looking to take a semi-light displacement boat across an ocean.”


A visual assessment is also crucial and, although owners are not advised to make the final judgment themselves, there are several key signs to look out for.

Firstly, any sign of corrosion or staining either at the hull to keel join, or at any other point on the fin and its attachment to the bulb should be investigated. First establish where the staining is coming from. If it’s from the surface of the ballast, it is most likely to be a cosmetic issue. Alarm bells should ring if it appears to come from the keel bolts or the surrounding area.


Discoloration from a cast iron keel is less likely to indicate a serious problem, although the issue should be investigated. Similar streaking on a fabricated keel should be treated seriously as this could indicate bigger problems with corrosion or even early signs of structural damage.


Big gaps between the keel and the hull, or evidence of repair work and/or rectification should also be investigated.

Stress cracks or semi-circular cracks around the ends of the keel can indicate movement. Damage to the forward end of the keel at its tip where the boat has been grounded should steer your attention to the top of the keel. Look for a crack around the leading edge of the keel at the top and compression at the trailing edge.

Grounding can cause more damage after the initial strike as the boat is pulled or rocked off the bottom.


Groundings can impose fore and aft loads on the keel

And finally, regular inspections are particularly important. While there are no legal obligations to keep records, let alone a timeframe to work to, many surveyors point to the aviation and motor vehicle markets as examples of why such inspections and logging are important.

“It is worrying that anybody can come along and grind out an area to an unknown depth before filling it with glass and gelcoat,” says Hugo Morgan-Harris. “It is possible that no one would be any the wiser about whether the structure has been reduced as a result.”

He, like the other surveyors we spoke to, believes that logs and a regular survey would represent improvements as well as help to maintain the value of boats, just as it does with a well-documented car. He also believes that a regular survey would be a step forward.

“There will be variations in what is necessary, but assuming there’s been no other incident, I think five years would be a good interval.”


See also an insurance insider’s advice for anyone worried about keel safety.



This is an extract from a feature in Yachting World September 2014 issue