You state the word "backstays". Then you say "for the top bottom and back stay.
Not sure what you mean. I know some Cats have two backstays
, p/s. But top and bottom? Are you talking about running backstays
or shrouds or what? There are certain torque spec's for each wire size.
According to Loos Corp, manufacturers of rigging
wire, guages, swaging machines, and tools, tension should be 1/10 of the breaking strength of the wire, for starters. For 1/4" wire that would be 820 lbs. for #302/304 stainless, and 640 pounds for #316 stainless. Strength for 302/304 wire is as follows:
Strengths for type 316 wire are proportionally lower. Once tensioned, adjustments can be made for mast
rake, etc as desired. Tighten lower shrouds first so as not to twist the mast
. Most rigging problems, according to Loos, come from rigs that are too loose and allow the mast to "pump". Hope this is of help to one and all!
However, it is best to get your rigging tension specifications from the yacht manufacturer and to use a tension gauge to ensure they are correct. However if this is not possible you may like to proceed as follows.
The rigging tension has an important influence on both the durability and performance of the system. Contrary to popular thought a slack rig is more punishing to the cables
, fittings, and hull
than a properly adjusted tight rig, since it can subject the entire system to excessive movement and can cause misalignment, wear, shock loading, and fatigue. Similarly, the sailing performance is affected since the rigging tension determines the shape and deflection of the mast and the sag of the forestay. The expert skipper
will benefit by maintaining consistent rigging tension while developing the optimum sail shape and sailing tactics.
This topic is divided into lateral bend, side lean, fore and aft bend and rake.
Masthead Rig - Lateral Bend
are designed to work with a mast that doesn't bend sideways it is obvious that any sideways bend needs to be eliminated. Sideways bend on a masthead rig is often caused by too loose or stretchy upper shrouds. This is not always easy to spot._ Check the_ angle of the upper windward shroud
against the upper 6th of the mast and see if it has altered to a narrower gap as in the diagram below.
As the bend increases the angle between the upper shroud
and the mast narrows, increasing its leverage over the shroud. once the angle decreases to less than 11 degrees, the danger
of ripping the shroud out of the mast or crumpling the spreader is acute. As well as this, side bend allows the head
stay to sag excessively in a breeze, when it is most undesirable.