INVESTIGATOR 563

Not really directly a 563 subject but I was wondering if some one could tell me why some masthead rigs have single inline shrouds with a baby stay and some have forward and aft lowers. These two combinations are often seen on exactly the same type of yacht. Which would be stronger?, allot of the more modern boats have single inline shrouds, are the double lowers just old fashion?

Steve

It relates to mast bend used to change the shape of a mainsail. With a masthead rig, the baby stay can pull the lower part of the mast forward to get the bend. You can get a similar effect with forward lower shrouds, but more complicated. Multiple lowers also adds to the overall mast stability if you are not interested in mast bend.

On a T/s like the Investigator 563, with a solid, non-tapered mast, mast bend aint going to happen to a significant degree.

Thanks Ian,understood!
Would you be able to tell me if a single inline lower shroud would provide more support to a mast athwartships than a fore and aft set of lower shrouds? Ultimately if a yacht was to lose one lower shroud in either of these configurations, would there be an equal chance for both yachts to lose their rig.
Steve

I think I would go for anything that offered redundancy. Having lost a mast (only on the mooring,not doing Bass Strait ) if not terribly expensive, it has high nuisance value . I thought about baby stays on the 563 . The extra forestay I have fitted makes me feel safer . Probably in the mind but feels safer all the same

With a masthead rig backstay or forestay load, whether intensionally applied or not, puts the mast into compression (provided the boat isn't wrapping itself up around the mast). Under compression the centre of the mast wants to move either forward or aft or sideways therefore intermediate staying has to control this and can be used to "induce" a mast bend in the direction required - but not backwards (inversion) as that's when it breaks very quickly. Compression failure is a very common the reason for mast breaks. Double lowers are generally used with aft one with less tension to allow the mast to kick forward in the centre - when it does this the cap(inline) shrouds are no longer inline and their point to point distance is lessened allowing the top of the mast to lay off and free the leech of the main to depower it. As Yara said the size and rigidity of the mast section plays a big part. Also dependent on rig design is the sail cut - mainsail for a bendy mast is cut differently to one cut for a telegraph pole where cunningham and foot control changes sail shape.