tag:blogger.com,1999:blog-266108914902271629.post8909762508171462031..comments2023-09-25T08:48:48.104-07:00Comments on John Vigor's Blog: Tension in the riggingJohn Vigorhttp://www.blogger.com/profile/02215080385571534292noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-266108914902271629.post-84311675833193948082012-03-21T16:16:47.812-07:002012-03-21T16:16:47.812-07:00Sun Burst, I can't find any specific reference...Sun Burst, I can't find any specific reference to fractional rig tuning in my home library. David Potter is not a fan of fractional masts and offers no advice about tuning forces. Brion Toss, the author and professional rigger, makes no mention of fractional rigs in The Rigger's Apprentice, second edition. And he apparently tunes the masthead rig by ear: "Start with the lowers. I like to get them so I can strum a low musical note on them . . ."<br />My gut feeling is that you should tune a fractional rig in the same way as a masthead rig, with the exception of the backstay, the tension of which is varied to induce mast bend. But I expect Mr. Google will help you out if you search for "tuning fractional rig."<br /><br />Cheers,<br /><br />John V.John Vigorhttps://www.blogger.com/profile/02215080385571534292noreply@blogger.comtag:blogger.com,1999:blog-266108914902271629.post-67724595619830468542012-03-21T13:11:27.935-07:002012-03-21T13:11:27.935-07:00Presumably these calculations (eg 10% of displacem...Presumably these calculations (eg 10% of displacement on backstay tension) are for a mast head rig? any suggestions for rule of thumb for a fractional rig?Sun Bursthttps://www.blogger.com/profile/11267683164519460851noreply@blogger.comtag:blogger.com,1999:blog-266108914902271629.post-49908390515986206622012-03-16T07:55:14.140-07:002012-03-16T07:55:14.140-07:00The forces involved in a Bermuda-type rig really a...The forces involved in a Bermuda-type rig really are quite dramatic.<br /><br />If you sketch it out, it becomes pretty clear that O.W. got his three failure modes right: Yes, the mast is trying to punch right through the bottom of the hull. Yes, the shrouds are trying their best to rip the chainplates out. And yes, the stays are trying to pull the bow and stern towards the masthead.<br /><br />This leads to a few headaches for the designer: The hull has to be stiff enough as a longitudinal girder to handle the stays, and it has to be able to handle enormous point loads at the step and chainplates. (And, of course, the keel root.) So you end up with a lot of complex, highly loaded (therefore expensive) structural components.<br /><br />If you trace all those forces back through the hull, and think about how much money goes into managing them, a free-standing rig (which is structurally much simpler) starts to look very appealing!Matt Marshhttp://www.marsh-design.comnoreply@blogger.com