When you are installing the rig, you will need rig setting tools: a square and a caliper. These are two simple devices that are immeasurably helpful when setting up the rig, and they are things you can easily make yourself.
The Basic Square
The square is used to plumb the mast fore and aft by simply placing it on the deck in front of the mast and sliding it back against the mast. It will be parallel with the mast when the mast’s position is correct. The triangle enables you to see if the mast is leaning forward or aft. You can adjust your mast accordingly by adjusting the backstay and the jib stay and jib halyard.
The square is made from a piece of ¼-inch medium density fiberboard (MDF) or underlayment. Make a right triangle using the dimensions shown in the illustration. Cut out your triangle and lightly sand and round the edges. You may want to cut notches in strategic locations to straddle certain deck fittings, like the mast step and the forward deck fairlead (see the illustration).
A Simple Caliper
The caliper is used to check the position of the mast from side to side. This is done using deck fittings like the shroud racks or by establishing identical locations on each side of the deck. The mast should align with the pivot point of the caliper when its position is correct.
The caliper is made from two pieces of 1/8- by ½-in wood of the length you desire and secured at the pivot end with a ¼-in screw post. An 18-inch caliper is a good length. It can be longer or shorter based on the size of your model yacht. Drill a hole the diameter of the shaft of the screw post in the ends that are to be the pivot of the caliper. Shape the ends away from the pivot with a point similar to the illustration. When assembled they should oppose each other.
The pointed ends can be snugged in against a static location on either side of the deck. For example, slide each end of the caliper in front of and tight against where the forward turnbuckle attaches to the shroud rack. When the mast is square side-to-side the top of the caliper will align with the mast itself. It is important to square the mast with the boat because that ensures that the rig aligns with the hull correctly. Using a level for this step is not a good idea because the boat may not be sitting in its stand correctly.
