All boats come with cleats installed, right? And the manufacturer installed them, so they must be right for the job and mounted correctly, right? The answer to both questions is a firm maybe. Some boats hew more to a design ideal than operating conditions, putting form and styling above function. Cleats can be undersized, improperly mounted or just plain missing.

Thankfully, installing cleats is something most boaters with average do-it-yourself skills can learn to do. Follow along and we'll go through Cleats 101, which includes how to select them, mount them, back them, bed them and minimize the mess along the way. As a bonus, most of the techniques discussed here also apply to installing other deck fittings.

Cleats generally come with the deck structure itself, fasteners and a backing plate. All are important to a successful installation, meaning the cleat stays with the boat and holds in the most severe conditions the boat endures. A look through any boating catalog or marine store will turn up a bewildering variety of styles. Some types are for other than deck use, such as galvanized dock cleats, cam cleats and jam cleats used by sailors. For our purposes here, we'll stick with those mounted on the deck and generally used for dock lines.Glen Justice

Most cleats have two horns connected to some sort of base. That base can be open or closed, and the cleat can use two fasteners or four. The cleat itself can be made from stainless steel, bronze or aluminum, but stay away from plastic cleats for dock lines. Some home boat builders have even made their own cleats from teak or similar hard woods.

I prefer the classic Herreshoff cleat for bow installations, and stern installations where there is enough room. The Herreshoff cleat is a four-bolt, open base style. I like the open base so I can pass the eye splice of a dock line through the base and over the horns. At my home dock, I have the bitter ends of my dock lines tied off to the dock cleats and the eye splices for use on the boat. With the dock lines remaining properly adjusted at the dock, it is a simple matter to pick up the eye splice and attach it. Tying off at the dock is quickly done and everything is perfectly adjusted.

Whatever your habit, learn how to properly tie off a dock line around a cleat. Nothing looks worse than walking down the dock and seeing some of the weird knots people use. More turns isn't better, and piling turn after turn doesn't really help.

SIZING YOUR CLEAT

Selecting the right cleat is more than just finding what strikes your fancy. The cleat must be big enough for the line or lines you intend to use. Most boating catalogs will list a maximum size line the cleat will handle. I would suggest going to the next size larger cleat for any given line size. For example, if you use ½-inch dock line, select a cleat designed for 5/8-inch line. This is especially true when using a single bow cleat to secure two bow lines.

Graphic by Paul Esterle Ah, but what size dock line should you use? The folks at West Marine recommend 1/8-inch of line diameter for every 9 feet of boat. A look around any marina will reveal that many people seem to tie up using whatever they have, and that the most common sin is undersized dock lines. The second most common sin is using cheap yellow polypropelene line.

But bigger isn't always better. Bigger lines are stronger and easier on the hands but they stretch less. That stretch helps alleviate the shock loads from passing wakes and surges. So the moral of the story is that you should select the dock line first, and then select the proper size cleat.

Selecting the proper size cleat is only half the battle. For the cleat to serve its purpose, it must be installed correctly. Any discussion about mounting anything on the deck of a boat needs to start with the way most decks are made. Almost every deck built today uses some type of "cored construction," a technique whereby two layers of fiberglass are separated by a layer of core (see illustration).

That core material can by plywood squares, end-grain balsa, plastic foam or a type of honeycomb material. The top and bottom fiberglass skins must be tightly bonded to the core material. The resulting structure is lighter and far stiffer than the fiberglass alone would be.

Core construction is not without its problems, though. Anything that disrupts the bond between the fiberglass skins and the core will result in a weak and "spongy" deck, which gives under your weight. While a bond failure can result from a shock load breaking the bonds between the skins and the core, a far more common cause is water in the core. In extreme examples, wooden cores can soften and rot. The resulting damage lowers the value of the boat, can pose significant safety issues and can be very expensive to repair.

Why all this emphasis on core problems? Because most of those problems are the result of improperly installed deck hardware. Mounting holes are often drilled through the cored deck and sealed only with some type of sealant. That works until the sealant fails and water starts leaking into the core. Often those leaks only show up below after core damage has occurred. Do not assume no leaks below means no problems with the deck.

PROPER LOCATION

Graphic by Paul Esterle The first step in installing a cleat is to find a location. Use some double-sided tape and mount the cleat temporarily. Try leading your dock lines to the cleat. Is there a wide range of angles for the line to access the cleat? Does the line contact any area of the hull that will chafe either the line or the hull? In some cases, you may need to install a chock to guide the dock line past obstructions and prevent chafing. Finally, you will need sufficient access to the underside of the mounting area in order to mount the cleat properly.

That last one is a biggy. A proper cleat installation, one that will stand up to both the stresses from the dock lines or a towing situation, must be mounted with a backing plate underneath. That plate distributes the forces applied to the cleat over a larger area. Cleats with no backing plates or only washers can pull right through the deck.

Once the proper location is found, it's time to drill the mounting holes. Do not even think about using self tapping screws or wood screws. Properly installed cleats must be through bolted. After you drill the fastener holes, it will be time to deal with that cored deck.

Deck crush is another potential problem. Tightening a fastener can crush the core under the fastener. To prevent both the leak and crush problems, we remove the core from around the fastener hole and replace it with epoxy mixed with high-density filler. In my case, I use W.E.S.T. Systems 105 resin, 206 Slow Hardener and 404 High Density Filler, but you should research what is best for your boat and your application.

Graphic by Paul Esterle Graphic by Paul Esterle There are several ways of removing the core from around the hole. You can make a tool from an Allen key by sharpening the end and chucking it in a drill (see illustration). You then insert the Allen key in the fastener hole and drill away, periodically vacuuming out the debris from the hole (see illustration). This technique works fine with a honeycomb or foam core, and adequately with a balsa core.

For plywood-cored decks, I use another trick. Select a hole saw slightly smaller than the base of the piece of hardware being mounted. Then use that hole saw to drill a hole through the top skin and the plywood core, but leave the bottom skin intact (see illustration). The center pops out with the twist of a screwdriver and you can clean out any remaining wood core from the bottom of the hole.

Once the core is gone it's time for epoxy. First, though, tape off the bottom of the hole completely. Failure to do this simple step properly will result in epoxy icicles hanging down from the underside of the deck. Paint the inside of the cavity with epoxy. This epoxy will prime the dry wood inside the cavity and prevent the wood from sucking the epoxy out of the epoxy/filler mixture. Once the inside is primed, mix high density filler and some colloidal silica like W.E.S.T. 406, which acts as a thickening agent, with the epoxy and fill the cavity (see illustration). Do it slowly to ensure no air bubbles get trapped in the epoxy.

After the epoxy has cured, the fastener holes are re-drilled. This time, however, you are drilling through a solid epoxy plug. Even if the sealant fails and the fastener starts to leak, that water won't end up in the core damaging it. The solid epoxy plug will also prevent you from crushing the core from over-tightening a fastener.

BACKING PLATE

If you haven't already done so, now is the time to make that backing plate. Backing plates are most often made from marine plywood, aluminum or stainless steel. Wood is the easiest to make, usually from ¾-inch marine plywood. The plywood must be completely sealed with several coats of epoxy before installing it, in order to prevent water from weakening the wood.

Graphic by Paul Esterle Aluminum is also used often for backing plates. In quarter-inch thicknesses, it can easily be cut and drilled. The downside is potential corrosion between the stainless steel through bolts and the aluminum. This can be mitigated by placing a hard nylon washer under the stainless steel washer and the nut on the bottom.

Stainless steel sheet can also be used for backing plates, usually in eighth-inch thicknesses. It is much harder to cut and drill but eliminates any possibility of corrosion between dissimilar metals.

Washers – even large fender washers – are not considered appropriate backing plates, especially for high stress applications like mooring cleats.

SEAL IT UP

With all components created and trial fitted, it is time to select a sealant and begin final assembly. There are three basic types of sealants commonly available: silicones, polyurethanes and polysulfides. Silicone sealants, in my opinion, shouldn't be used for installing hardware. It isn't a very good adhesive and doesn't bond to anything very well. It also "poisons" fiberglass, making future painting of that area difficult.

Polyurethanes, such as the 3M's popular 5200, are tenacious adhesives and good sealants. That adhesion characteristic is the problem. Deck fittings should be rebedded every five to seven years. Use 5200 and it will pull up the gel coat before coming loose. A better solution is a polysulfide, such as 3M's 101. It is still a good adhesive and a good sealant, but it is much easier to remove fittings for re-bedding.

Anyone who has used these modern sealants can attest how messy they can be. However, proper preparation can make for a mess-free installation. The first step is to apply masking tape where the cleat will be mounted. Tape several inches back from the actual location (how far back depends on how messy you are).

Graphic by Paul Esterle Put the cleat in its place and trace around it. Remove the tape from under where the cleat will be mounted (see illustration). Place the fasteners in the cleat, and then tape over the top side to keep them in place. Place either a rubber washer or an o-ring on the fastener below the cleat.

Apply a layer or sealant where the cleat will go. Don't scrimp, use plenty. This is the last place you want a sealant failure because you used too little. Place the cleat in place and push it down. Sealant will squeeze out from under the cleat, but that's okay. Apply sealant on the backing plate and push it in place. Add the washers and nuts, and then tighten.

Do not over-tighten! The worst thing you can do is squeeze out all that expensive sealant, leaving a very thin layer in place. That thin layer will soon rupture and leak from the differential expansion of the fiberglass and metal. The washer or o-ring is there to keep you from tightening too much. Clean up the sealant that squeezed out and remove the tape.

Let the sealant cure for the recommended time. You can now go back and tighten up the fasteners slightly. That will further compress the sealant layer, making for an even better seal.

But only tighten the nuts below. Do not allow the head of the fastener to turn, because that will break the sealant bond around that fastener and form a ready path for leaks.

There you have it, Cleats 101. Evaluate the cleats on your boat, and every other piece of deck hardware. If they are undersized or not properly installed, you know what to do.

Paul Esterle is Technical Editor for Small Craft Advisor Magazine, and his freelance work has appeared in Sail, BoatWorks, Voyaging and Good Old Boat magazines. He has produced a series of boating videos and lectures widely. He also works at West Marine and has written product reviews for the company.