what considerations

[imull]

do you need to take into account if adding a backstay to a boat that has up to now no had one.

Obviously there are alterations to the mainsail shape and top of the mast/cast alloy insert.

I am really interested in the geometry of the shrouds etc...

 

[chippie]

What setup does the boat have at present?, are you doing away with running backstays? I think that you must have adequate anchoring for its lower end and some means of readily changing the tension. The roach of the sail must not exceed the line formed by the backstay. A chat with a friendly rigger is probably your best bet.

 

[vyv_cox]

Sorry, I don't think it is possible to answer this question given the information you have provided. What is the current rig? Why do you want to add a backstay?

 

[Twister_Ken]

Generally a backstayless rig is triangulated by using sweptback spreaders to bring the two cap shrouds down to a point well aft of the mast. If you want to add a (properly engineered) backstay, you could resite the cap shroud chain plates further forward , and reduce/eliminate the spreader rake to allow the main to be squared off more on the run.

OTOH, if you just want a backstay for belt and braces reasons, you needn't touch the rest of the rigging.

I've seen a backstay added to a fractionally rigged boat, where the owner wanted the option of setting a masthead spinny in light airs. In his case he added two 'chain plates' by glassing s/steel plates to the inside of the transom, and bolting outside plates onto them. He needed two because the boat was tiller steered and a central chainplate wasn't an option. He then brought a single backstay down, to a point about 10 feet above the cockpit which terminated in a single block. A wire stay was taken from one chainplate over the block and terminated with a double block. A double block with a jammer was mounted on a short wire strop above the other chainplate and a rope four part tackle completed the setup. The backstay was never hardened up unless the masthead kite was set. I think (but am not certain of the details), that he had a plate welded across the top of the mast which took a block for an external spinny halyard on the foreside and the backstay tang on the aft side. This projected aft sufficiently that the backstay didn't foul the leech of the main.