Enciclopedia de yates
Spreader
Six degrees of rise on a Seldén spreader is not thirty degrees of sweep. The same maker's B&R rig is a different angle, not a second name for six here.
In Seldén memo 595-540-E the final vertical angle of the spreader is always 6 degrees. During the install the shrouds are tensioned along the mast, and the plug sits in line with the bracket. Spreader length moves the place, not the angle. This is rise upward, not sweep aft. The same maker's B&R rig, Bergström and Ridder, has no backstay: the spreaders are swept 30 degrees, and that is much more than an ordinary rig. Runners and a backstay are usually absent there. The thirty degrees of that scheme are not put onto the six.
What it is
A spreader is a strut on the mast that leads the shrouds out and supports the mast against a side load. The number of tiers does not by itself measure strength: the design and the condition matter. A distant photo from the pier does not prove that the tips are intact.
In the Sparcraft installation note the dihedral is 5 degrees. The spreaders are set with the upper side up. On the page for through-bars the standard is printed as sweep of 0 degrees and dihedral of 5. The same hardware allows sweep from 0 to 30 degrees, catamaran dihedral of 0, and on a monohull up to 10 degrees upward. Five and six are not averaged. In the same note, if the sweep is less than 15 degrees, runner tension has to be high. If it is more than 15, the spreaders already hold the mast fore and aft, and the runner need not be pulled so hard. The limit there is the mast inverting forward. Fifteen is not a third name for six.
A Seldén tip is not allowed to slide on the shroud. After the mast is stepped it should be possible to stand on the spreader, and the end must not travel. That is a check after stepping, not a snapshot from the pier. Covers on the tips are not cosmetic: they cut chafe from the genoa. A slightly bent tip is not guessed from the pier: a rigger is asked. On a rig with several tiers the lower end either clamps the intermediate shroud, which is the linked scheme, or the shroud continues downward, which is the continuous scheme. The plugs differ. This page does not take one angle for every mast. Nearby on the site: standing rigging, mast step, forestay and survey checklist are other pages, not this angle.