Why aren't my boat fenders protecting the hull, and how should I position them?

Fenders usually fail because they miss the contact point, ride out of the gap or squash flat under load. Position them where the hull will touch the berth, concentrate protection around the boat's widest part and check their height once the boat has settled alongside.

Find the hull's contact points

Look along the gap between hull and berth before buying more fenders. A pontoon edge, projecting bolt, rubbing strake or neighbouring boat's gunwale can pass above, below or between fenders that appear well placed.

With the boat securely moored, gently pull it towards the berth using a mooring line. Watch which fender takes the load first. Keep hands and feet out of the gap between boat and berth.

• Fenders swing clear: they are outside the contact area, often too far towards the narrow bow or stern.
• Fenders climb onto the pontoon: they may be too high, too small or catching underneath its edge.
• Fenders flatten completely: they may be undersized, underinflated or overloaded by tight mooring lines.
• Dull patches without impact damage: dirt and repeated rubbing may be responsible rather than a lack of cushioning.

Set the height and spacing

Against a floating pontoon, hang cylindrical fenders vertically with their cushioning body spanning the pontoon's rubbing edge. The edge should bear against the substantial body, not the tapered shoulder or rope eye. Keep the lower end clear of the water where practical, but cover the contact point first.

Start with one fender at maximum beam. Place others forward and aft where the hull remains close to the berth. Adjust the spacing to cover projections and allow for the bow or stern swinging in. Equal spacing along the guardwire is rarely the best arrangement.

Against a high wall, protect the topsides at the wall's contact height. Against piles or widely spaced uprights, a properly secured fender board outside two fenders can bridge the gaps and stop an upright slipping between them. A horizontal fender secured at both ends can suit a low pontoon, provided it cannot roll or escape from the contact point.

A floating pontoon usually rises with the boat. A fixed quay does not. Check protection throughout the expected tidal range and use a suitable board or another berth if the fenders cannot remain effective.

Choose diameter and inflation

Diameter provides the cushioning distance. Extra length mainly helps maintain coverage as the boat moves. As a starting point, many cruising boats measuring 9 to 11 metres use cylindrical fenders about 20 to 25 cm in diameter and 60 to 75 cm long. Heavier boats, exposed berths and persistent wash often call for larger fenders.