Five questions to your tree – Second installment

We continue our journey to discover the tree(part 1 here), to really understand how it works and be able to adjust it to the best of our ability!

What are the crosses for?
Their task is twofold: they transfer some of the shaft stresses to the shrouds and serve to move them away from the shaft so as to increase or decrease the angle of incidence of the cables on the shaft. The number and width depends very much on the sail plan. To better understand how guns are thought of, one must always consider that with the same mast and boat, if there are few spreaders they will be longer and the heaths are likely to be in the hawser; a situation that usually leads to a less adjustable mast and a sail plan with a low overlap or with a less closed genoa on the channel. On the other hand, if there are more spreaders, they will be short with a smaller shroud angle. The mainsails will be on deck, the genoa overlap greater, and most importantly the sail will be more closed.

So what is involved in having more or fewer crosses?
The number of spreaders depends on the length of the mast, the width of the hull, and a maximum length of the spreaders themselves. A racing boat will tend to have multiple orders of short spreaders, to favor jib adjustment and channel closure. A purely cruising one, on the other hand, should favor a simpler and more versatile rig, thus with fewer spreaders but longer lengths. This will allow the attachment of the shrouds to be found in the gunwale with a greater advantage for the use of space on board.

What are aquartierate crosses?
A mast must have four restraints to remain standing: two shrouds, forestay and backstay. To prevent the latter from being structural and to make sure that it only performs the function as a deflection adjuster, the spreaders are tilted aft, so the shrouds on deck are fixed aft of the mast. In this way they are able to provide not only lateral resistance but also longitudinal resistance to shaft stresses. On some boats, the neighborhood angle of the spreaders is such that a backstay is not provided. The disadvantage of these solutions, however, is the difficulty in fully opening the mainsail in carrying gaits.

What are diagonals?
The spreaders, as mentioned, are used to move the shrouds away from the mast and load the mast in compression. To limit this load, additional cables, known as diagonals, run from the base of the spreaders near the mast to the connection with the rigging. Their job is to decrease the compression on the mast by unloading the forces on deck.

Does the backstay and forestay affect the mast?
Certainly, and each of their adjustments affects one another and the shape of the sail. The backstay, like the forestay, is usually a steel cable. It starts from the masthead to the stern of the boat. The forestay, on the other hand, can start from multiple points on the mast and run all the way to the bow. The backstay is easier to adjust, and there are several ways to change its tension. Both therefore affect the tension of the mast and consequently the shape of the sails. A practical example with lots of wind: you cock the backstay so that you move the masthead toward the stern and flex the middle part toward the bow. This adjustment allows the mainsail to be flattened (thinned). If at the same time the forestay tension is increased, a backward displacement of the masthead is achieved, which allows the catenary effect to be eliminated and thus flattens the headsail in its entrance.