Split back stay adjuster

[C22BC]

I've just ordered the pieces for a split backstay adjuster , went off the owners manual diagram . As I mentioned in a previous post I can't get a rake in my mast when tuning rigging, basically level is about the best I can do with backstay turnbuckle adjusted alll the way in . Logistically I'm trying to sail the summer before ordering new rigging . It appears to be in good condition .
So for tuning the rigging with the backstay tensioner, I was reading a article where it seemed to say you have your fore and aft stays backed right off like 6" of sag , the aft lowers backed off , With the uppers set at about 30 on the loos gauge , with no mention of the lower fore stays , when the wind picks up you tension backstay . Could this be acccurate ? You sail light winds with some of your rigging slack ?

 

[dlochner]

Yes. Lighter winds, lower tensions. Higher winds, higher tensions.

Think about the forces on the rig. In light air there is very little pressure on the sail or rigging. Sails are designed to have a little sag in the forestay or bend in the mast. With little wind force, the tension needs to be lower to induce the shape. In higher winds, the tension needs to be higher to resist bending too much.

Another factor is shock loading. If the rigging is too loose the shock loads from a gybe or wave action going to weather can over load the rigging. When rigging is tighter, the shock loads are smaller because the movement of the mast is limited.

This is all really important if you are a competitive sailor in a competitive fleet. The guys at the top of the fleet are always adjusting the rig for the conditions before leaving the dock and even on the way to the race course. There is also a rule against changing rig tuning after the start of the race, but that doesn't include a backstay adjuster.

For the non-racer, tuning to the middle of the range is good enough. Going to weather in about 10-12 knots the leeward shrouds should be soft but not floppy. The soft but not floppy is also what the racer wants, but he wants it across all wind spectrums, so they change the tension on the shrouds.

 

[Joe]

You don't sound like you understand what the backstay adjuster really does.... do you have a sail trim guide? A good investment is Don Guillette's guide sold on this site... sweet and simple.

Mast Rake and Mast Bend are two different things and they have completely different functions. Rake is like "leaning" the stick off vertical and simply moves the center of effort forward or aft on your sail plan... which in turn affects the amount of weather helm you have on the tiller. Mast bend changes the DRAFT DEPTH on you mainsail...the more bend the flatter the sail.

On a masthead rig, where the backstay and forestay oppose each other, the backstay has very little effect on mast bend.... it's main purpose is to control the forestay tension... which will give you a fuller or flatter headsail.
On a fractional rig, the forestay attaches somewhat below the top where the backstay is pinned... they don't oppose each other, thus there is leverage created ... the backstay pulling the top back while the forestay acts like a fulcrum... causing the middle of the spar to bend like a bow.....

Most sailors will set their mast rake for conditions of the day.... sometimes... like me... they just leave it the same... Again... you don't use the loos gauge to set rake. A ruler and a weighted halyard to act as a plumb bob are the tools for that setting.

 

[C22BC]

You don't sound like you understand what the backstay adjuster really does.... do you have a sail trim guide? A good investment is Don Guillette's guide sold on this site... sweet and simple.

Mast Rake and Mast Bend are two different things and they have completely different functions. Rake is like "leaning" the stick off vertical and simply moves the center of effort forward or aft on your sail plan... which in turn affects the amount of weather helm you have on the tiller. Mast bend changes the DRAFT DEPTH on you mainsail...the more bend the flatter the sail.

On a masthead rig, where the backstay and forestay oppose each other, the backstay has very little effect on mast bend.... it's main purpose is to control the forestay tension... which will give you a fuller or flatter headsail.
On a fractional rig, the forestay attaches somewhat below the top where the backstay is pinned... they don't oppose each other, thus there is leverage created ... the backstay pulling the top back while the forestay acts like a fulcrum... causing the middle of the spar to bend like a bow.....

Most sailors will set their mast rake for conditions of the day.... sometimes... like me... they just leave it the same... Again... you don't use the loos gauge to set rake. A ruler and a weighted halyard to act as a plumb bob are the tools for that setting.

You are correct , if I fully understood , I would not have asked . Will look into guide

 

[dlochner]

We should also point out that mast rake is difficult to set with a deck stepped mast. Rake is usually set with a keel stepped mast by moving the base of the mast forward or aft. Racing boats will have a mechanical or hydraulic ram to move the base, other boats use blocks of wood.

The lower shrouds help to set prebend or putting a bow in the mast. The forward lowers pull the middle of the mast forward, the lowers keep it from pumping back and forth.

 

[Richard19068]

How much is the mast of a Catalina 25 designed to bend? Just curious.

 

[Joe]

We should also point out that mast rake is difficult to set with a deck stepped mast. Rake is usually set with a keel stepped mast by moving the base of the mast forward or aft. Racing boats will have a mechanical or hydraulic ram to move the base, other boats use blocks of wood.

The lower shrouds help to set prebend or putting a bow in the mast. The forward lowers pull the middle of the mast forward, the lowers keep it from pumping back and forth.

Not trying to be a pill, but I disagree on that point. It is very easy to set rake on a deck stepped mast by making forestay adjustment then resetting shrouds. On many small boats the forestay is fixed to stem with a multi pin hole adjuster. The forestay can be effectively lengthened or shortened..... when rigging the boat, not when sailing of course. This device allows you to set rake quickly... they will also have shroud adjusters that allow for easy settings, many have quick release levers that enable the crew to relieve tension and pull mast forward for downwind work.

In most equipped boats the hydraulic or mechanical ram is used to quickly depower the mainsail by bending the mast. In this case the deck will be the fulcrum for the ram.... similar to a fractional rigs backstay using the forestay as its fulcrum.