split backstays

[osteoderm]

If this is one of those topics that has been over-discussed somewhere, i sure haven't read about it... yet.
My double-ended boat has a split backstay. The plate connecting the lower legs to the upper leg is about 8" above the deck. There are no adjusters other than the turnbuckles. My question is a general one: What is the optimum height above deck for the join, or better yet, what is the optimal angle off vertical of each lower leg? It's not applicable to my relatively narrow boat, but at what point of beaminess aft is it better to go with dual backstays rather than the split (assuming that a single central backstay is somehow otherwise undesireable, say, in a boat with a wide swim platform like Beneteau 42, etc.)?

Thanks,

Yuri

[Brian Duff]

I think that as long as the backstay components are strong enough in the application they are used in the angles could be whatever you choose for the split. The higher the split, the higher the weight of the delta plate with associated terminals, ( and sometimes turnbuckle) is above water. Probably better to keep the split as low as possible while still keeping backstay legs from obstructing flow of traffic.

I am not sure it is ever necessary to use split backstays. One led slightly off center works fine, that is of course assuming that the hull and rig are designed for or can handle the loads of single backstays ( in other words, careful switching designs).

I suppose split backstays are sometimes done to keep things looking symmetrical, or because the backstays were maybe an after thought to cockpit layout or whatever.

Splitting the backstay makes for some more pieces to buy and replace, or loose.. or break...I don't particularly like the practice. Takes longer to inspect, make and tune too...

Yuri, how about getting some pictures of that little cutter of yours up here, I regret not taking a closer look back in February.

[osteoderm]

The one instance i can think of where split backstays are required in in applications just like mine: a relatively narrow double-ended boat with a well-raked sternpost and outboard rudder/tiller.
To keep the horizontal compression loads between the two lower chainplates to a minimum, i would guess one ought to keep the athwartships angle of the lower legs as low as possible. Weight aloft does not particularly concern me, but having the plate close enough to readily access from deck while underway does.
As for the little gaffer... it's hard for me to take pictures of myself sailing! Great fun, b ut a handful indeed. Others keep taking pics of me, and several have promised to email me copies; so far, nothing in my inbox...

[Brion Toss]

Hello,
First I'd like to recommend that you read an old Fair Leads at this address: http://www.briontoss.com/education/a.../miscapr99.htm. It's titled "Why Twin Backstays are Evil," which should give you an idea of my opinion. A forked backstay, on the other hand, can be preferable to a single one for a number of reasons: it distributes load over more of the hull; it can allow for more aft cabin space on hulls where the backstay comes to deck well forward; it allows for "frapping" adjusters on small craft, and 2:1 purchases on larger ones; gets the stay off the back of the helmer's head; and so forth. But if the transom is up to the load, simply offsetting to one side of the middle, as someone suggested, gives you the simpler single option. And a convenient handhold to boot. On boats like Concordia's, the single backstay is just a tiny bit off-angle, to miss the mizzen, and lands just far enough forward that it doesn't interfere with the mizzen boom. But most yawls and ketches will split their backstays.
A forked backstay is also the best thing for a double-ender with outboard rudder. There, and on most other boats, try for an angle between the legs of 40? or less. 30? is optimal, if it doesn't put the link too far up. Or even if it does.
Fair leads,
Brion Toss

[osteoderm]

Instead of a "delta plate", does anyone make a fitting specifically for this application? i'm envisioning something cool like a Hayn insulated terminal, with the end being in the form of a slightly wider double-eye to accomodate the fork terminals atop the lower legs.
Is this pure fantasy, or does somebody already make one of these? i think i've seen similar double-eye fittings on runner/checkstay blocks...