How to measure mast prebend?

Last Update: April 20, 2022

This is a question our experts keep getting from time to time. Now, we have got the complete detailed explanation and answer for everyone, who is interested!

Asked by: Miss Bette Emmerich
Score: 5/5 (59 votes)

This is measured by taking the main halyard all the way to the gooseneck (making sure the halyard is tight enough and the wind light so that it does not blow your halyard around and skew your measurement). You will find the deepest part is usually halfway up the mast; that is the pre-bend measurement.

How is mast rake measured?

Mast Rake: Attach a weight to the end of the main halyard and let it hang down just off the deck. Measure the distance it hangs behind the backside of the mast. E Measurement: Measure from the backside of the mast at the gooseneck, along the boom to the location of the clew.

What is prebend in a mast?

Mast prebend is the degree of bend placed in a sailboat mast when the shrouds are adjusted. The [ fore and aft angle ] of the mast spreaders, in relation to the mast, determines the desired angle of mast bend and corresponds with the profile of the sail luff.

How tight should shrouds be?

They should be tight enough that when you push or pull on them, they don't want to jiggle around too much. If they feel loose or floppy, you need to tighten them further. Once the cap shrouds are set, the rest of the shrouds simply follow in sequential order with none of them being tighter than the cap shrouds.

How is standing rigging tension measured?

Using a fiberglass or steel tape measure, measure the distance from pin-center to pin-center or bearing point to bearing point as applicable. It is important to use a tape measure under tension and that does not stretch.

Catamaran mast set up 1 - prebend, diamond wires and spreaders

31 related questions found

When should I tension my backstay?

It's usual to ease backstay downwind and put on backstay tension when going upwind. If one over tensions the backstay, it can have a significant effect on the boat, depowering the mainsail. This may well negate the need for a reef.

What are cap shrouds?

Cap Shrouds

These are the parts of a sailboat's rigging that hold the mast in place athwartship. They're attached at the masthead and via chainplates to the hull.

What do spreaders do on a mast?

A spreader is a spar on a sailboat used to deflect the shrouds to allow them to better support the mast. Often, there are multiples, called spreaders. The spreader or spreaders serve much the same purpose as the crosstrees and tops in a traditional sailing vessel.

How long does standing rigging last?

Most insurance companies reckon you should replace your standing rigging about every 10 years. Sometimes they let you go longer if you have the rig professionally inspected, particularly if you have an electronic check carried out on the terminals and other crucial fittings.

How much is a prebend?

Most tuning guides will recommend a certain amount of pre-bend. Pre-bend is measured on shore, with the rig in place. Usually this pre-bend is somewhere around half of the luff curve and is the straightest your sail is designed for. In our 3-inch luff curve example, the sailmaker may recommend 1.5 inches of pre-bend.

What does it mean to bend a sail?

Bend ~ (1) A type of knot such as a sheet bend for joining two lines together. (2) To secure a sail to a spar before hoisting. Bend On ~ To tie onto or fasten. Bermuda (or Bermudan) Rig ~ A two sail rig - mainsail and foresail, both triangular - more commonly known as sloop.

Why are masts raked?

Specifically, a raked mast lifts the end of the boom as it is eased out. This is good for offshore work, as it keeps the boom from dipping in the water and possibly breaking when the boat rolls deeply.

What is a mast jack?

The mast jack system consists of a hydraulic cylinder located inside the mast. The cylinder piston moves down vertically through the heel of the mast to a steel plate in the boat's T-base, thereby lifting the mast and increasing the tension.

How do I tighten my backstay?

Fixed backstays must be set up as tight as possible, as there is no way to tension them more while underway.
  1. Adjustable. ...
  2. When you have a split backstay, you simply set up a grommet set up over low friction rings with a line to raise the system (release tension) and a line to lower the system (tighten the system).

What is the difference between a shroud and a stay?

A stay is part of the standing rigging and is used to support the weight of a mast. ... The shrouds serve a similar function but extend on each side of the mast and provide support in the athwartships direction.

What holds a mast in place?

Standing rigging is cordage which is fixed in position. Standing rigging is almost always between a mast and the deck, using tension to hold the mast firmly in place. Due to its role, standing rigging is now most commonly made of steel cable.

How tall should a sailboat mast be?

As a general rule of thumb, the height of a boat's mast will be somewhere between 1.25 to 1.35 times the boat's length, for an average of about 1.3 times the length overall (LOA) of the boat.

What is a keel stepped mast?

A keel stepped mast is a sound conduit whether caused by an internal wire slap or loose running rigging or general wind through the rigging.

How often should standing rigging be replaced?

Normally, the replacement of standing rigging should be done every 10 years. Generally, insurance companies today require the standing rigging be replaced approximately every 7-10 years, depending on how often, or how far the yacht is sailed, they may require the rigging to be replaced earlier than 7 years.

What is a Triatic stay?

trīatik. A stay running from the foremast to a mast or stack nearer the rear of a ship. noun. (nautical) A stay connecting the mastheads of a multi-masted rig such as a schooner or ketch.

How are shrouds attached to the mast?

Shrouds are attached symmetrically on both the port and starboard sides. For those shrouds which attach high up the mast, a structure projecting from the mast must be used to increase the angle of the shroud at the attachment point, providing more support to the mast.

What are shrouds used for?

Shroud usually refers to an item, such as a cloth, that covers or protects some other object. The term is most often used in reference to burial sheets, mound shroud, grave clothes, winding-cloths or winding-sheets, such as the famous Shroud of Turin or Tachrichim (burial shrouds) that Jews are dressed in for burial.