Protecting a Docked Boat: Mooring Whips, Bumpers, Fender Boards and Chafe Gear

Before buying anything, spend some time at the slip watching how the boat moves with wakes, wind from different directions and (in tidal water) through high and low tide. Practical Sailor recommends this before leaving a boat for a long time or before storm season. Note where the hull touches, where lines rub and where they go too tight.

At a typical slip, use a bow line, a stern line and two spring lines (one running aft from the bow area, one running forward from the stern area). Springs stop the boat surging forward and back and let you use longer bow and stern lines. Lines must be long enough for the full tide range, and must never snag on anything as the boat rises and falls. Don't lead too many lines to one dock cleat; BoatUS says two lines per cleat is usually the maximum.

In tidal water, longer lines led at an angle (crossing lines between pilings, for example) handle tide better than short, tight ones. Check the boat at both low and high tide after any change. A line that is right at mid-tide can hang the boat at low tide or pull it over at high tide.

Any line running through a chock, over a rub rail, around a piling or across a concrete edge needs protection. BoatUS notes that chafe can wear through even a new line in hours. Use proper chafe guards, and better still remove the sharp point: Practical Sailor describes fixing a knife-sharp rub rail edge that was cutting a bow line. Avoid crossed lines rubbing on each other.

Position fenders where the hull actually meets the dock, with fender covers to protect the gelcoat (and any wrap). Recheck height after loading the boat. On a floating dock, fenders compress directly between hull and dock and work well.

At a fixed dock with pilings, round fenders roll off the piling as the boat moves. Practical Sailor's simple design: a 3- to 4-foot board (about a 2x4 for a 20-foot boat, 2x6 for 30 feet, 2x8 for 40 feet), edges rounded, a hole at each end for a line, hung outside two fenders so the board rests against the piling. BoatUS's catastrophe team found fender boards worked against dock rash only when the boards were heavy and backed by several large fenders; two small fenders at the ends of a long board bounced out or let the board break.

Fit dock bumpers or edging along the edges and corners where the hull or bow could hit, and post bumpers on pipes or pilings. Choose marine-grade, non-marking material. Old car tires are a poor substitute: they leave black marks on gelcoat.

Whips suit a boat at a single-sided private dock exposed to wakes or crosswinds. They are less useful in a marina slip with pilings on both sides. Pick a whip size rated for your boat's length and weight; BoatUS warns that undersized whips can't hold the boat off and break early. Whip makers such as Dock Edge state that the boat's weight matters more than its length when choosing a size, so weigh in fuel, gear, a T-top and anything else aboard, and when you're between sizes go up, not down. The same maker also notes that some spots are simply too rough for any tie-up system; if your dock takes heavy open-water waves, a lift or a protected slip may be the better answer.

Whips put a strong, constant pull on their bases. BoatUS warns that whips bolted only to thin wooden deck boards will pull out or break them. Through-bolt the bases with a large aluminum plate or thick plywood under the deck boards to spread the load, following the whip maker's instructions for spacing and angle.

A standard whip setup uses the two whip lines plus a bow line, a stern line and two spring lines. The placement and tension of these lines keep the boat lined up and stop the whips from bending sideways, which they are not built for. To board, pull the boat in with a whip line or disconnect the whip lines first.

Look over lines for fuzzy, stiff or worn spots and replace them as needed (whip lines often need replacing every few years). Rinse salt and grit out of dock lines with mild soap and water at the end of the season. Wax fiberglass whips and their bases to slow sun chalking, and if you can, store whips indoors in the off-season. Replace cracked bumpers and flat fenders.

Whips, bumpers and fender boards won't save a boat in a hurricane unless it is also held by anchors or extra shore lines, and BoatUS's advice is to get the boat out of the water and inland if you can. See our hurricane prep guide for doubling lines, chafe gear and removing windage.