Bob stay and dolphin striker wire angle

[tiger37373]

I am currently questioning the angle that my dolphin striker approaches the bob stay. The rig is set up with a fitting at the end of the striker and 2 separate pieces of wire making up the bob stay. We have a lower fitting near the water line, a length of wire from there to the fitting on the end of the striker then another piece of wire from there to the end of the bowsprit. Currently the striker doesn't seem to bisect the bobstay. The angle between the forward section of wire and the striker is very close to being 90 degrees, with the aft section being a smaller angle. It has always been this way. And from pictures of other clippers that I found online it seems that they are similar, but I can't be sure. It seems to me that the angle on both sides of the striker should be pretty close to being the same. Am I wrong? I am obviously not a yacht designer (my boat was designed by Bill Luders), but I would like to get some confirmation, as to wether or not the present geometry is correct. The line drawing doesn't quite look like what is on the boat. I have your riggers apprentice book, but it doesn't discuss bobstay geometry in much detail. I would appreciate an opinion the matter, as well as, any good readin g material on the subject.thanks,JamieS/V Flying Cloudhttp://www.flying-cloud.org

 

[Brion Toss]

Ah, vectors

Hi there,You are right, the martingale (dolphin striker) should ideally bisect the angle that the stay forms about it. This way the martingale is in approximately pure compression, so it will be strongest for its size. On continuous bobstays it also means that the martingale will be less likely to slip in the direction of the more open angle, vector-propelled.In your case, if the difference is slight it probably won't affect things appreciably (you could draw it out to determine the imbalance precisely, if you want), and might even have been done on purpose, to keep the martingale from being too close to the water, while still obtaining a satisfactory angle at the cranse, which is the whole point.A more serious problem, often seen, is if the upper end of the martingale can't articulate, or, if it does, can only articulate fore-and-aft. This articulation makes for easier installs, but of course any impact is more likely to force the martingale sideways, and it needs to do this without snapping off.As for texts, try some of Harold Underhill's "The Clipper Ship and Ocean Carrier."Fair Leads,Brion Toss

 

[tiger37373]

Ah, vectors/bobstay geometry

Brion,Thanks for the helpful information. I believe that the reason for it's present positioning is due to the location of the upper fitting on the martingale that attaches to the hull. The problem being that our hull has the typical clipper shape to the stem. So that IF the fitting is to be perpendicular to the martingale then it needs to be at it's current (odd) angle. It really cannot be moved any further forward on the hull curve, and moving the martingale angle further aft would put the upper fitting under some amount of shear, rather than compression. I am sure that these sorts of things drive designers mad... Anyway, I couldn't stand it, so I shortened the lower stay by about 3/4" which wasn't a huge change obviously, but it made me feel better.Jamie