Helpful Hints for Fixing Cleats to Spars

Reprinted from The Firezone spring '95
When fixing a new cleat on a spar, or reinstalling an existing one, the potential for ending up with a mast or boom looking like a piece of Swiss cheese is high. Too many holes in a small area are guaranteed to weaken the spar, possibly enough to cause it to collapse as soon as a good gust of wind comes along. There is a theory that a row of holes along the length of a spar will not cause any greater weakness than one hole on its own, but always drill as few holes as possible. A sharp corner in a hole is an open invitation for a crack to develop.

The whole procedure should be quite straight forward if you follow a few simple rules. The most important is to mark the position of the holes accurately before you let rip with the electric drill. Drilling holes in the wrong place can be a "holey" embarrassing experience, as can be oversized holes. Don't forget to check that you are using the right size drill and fasteners.

The CL704, with its build-in becket facility, is ideal for rigging a quick and easy 2:1 purchase for a Cunningham line or an outhaul control. It has a full radius on the base especially for fitting to round spars and saves two screw holes as a separate becket is not required.

Most Clamcleat(R) rope cleats have a partially-radiused base so that they can be fixed firmly on a round spar as well as on flat surfaces. Cleats for halyards or spinnaker pole uphauls can usually be installed right over the exit hole in the mast which makes a neat and tidy installation.

Self-tapping screws

The most popular method of fixing Clamcleat (R) cleats to both masts and booms is with self-tapping screws. Cleats can be removed much more easily and quickly than if Pop rivets have been used, although Pop rivets are a useful remedy where the original screw holes are stripped or oversize.

The screws should be of the appropriate size for the cleat, usually No 8 or 10 as marked on the package. They should be the shortest length possible to prevent ropes rubbing against the point of the screw inside the mast. It is good practice to drill a small pilot hole first and then drill the hole of the correct size for the screw.

Self-tappers are available without a point, but if a pointed or over-length screw is used, first tap the screw into the hole but do not drive it right home. Then withdraw the screw and cut off the excess length. You can now screw it into the hole that you have just tapped and tighten it fully.

Pop rivets

When using Pop rivets the choice of rivet gun is important. The lazy tong type can be awkward to use and may hit the mast when the rivet mandrel breaks, possibly damaging the anodizing. It is better to use a type that is designed to rebound away from the job when the mandrel breaks. If possible use a proper extension nozzle on your rivet gun which fits right into the cleat. If you cannot get one, then place some small nuts on the rivet mandrel. This gives the standard nozzle something to pull against. Alternatively you may be able to use a short length of small diameter, thick-walled tubing in place of the nuts.

Whichever method of fixing you choose, you should always put plain silicone bath sealant, zinc chromate paste or a proprietary product such as LanoCote on all stainless steel fastenings. This is to prevent corrosion through the electrolytic re-action that occurs between stainless steel and aluminium when salt water is present.

The final result should be a neat and well-secured fitting of which you can be justly proud.