Catana Headstay Issues

[Mike Meer]

Recently we replaced the upper shrouds on a Catana 582 with Dynex Dux. Initially we used dead eyes to tension the stays but found that we could not get enough tension to properly tune the headstays. We then went with a dead eye/turnbuckle arrangement with a fine and coarse tune ability. Needless to say we can now get massive tension on the uppers.

This rig is a tough case because it has no diamonds and no spreaders. It is a carbon fiber spar supported by uppers and lowers with a solent and forestay. Even with the turnbuckles on the caps, we are still unable to get adequate tension on the forestays. Being a big cat the headstays are way farther forward than the uppers are aft so the amount of relative tension is skewed. General consensus so far is that the boat needs running backstays. Picture is a good side view to show the difference in shroud angles....
Thanks in advance for any thoughts.

Mike, Southbound Cruising Services LLC

[CAM]

The simple observation is you have two headstays going to the same (+/-) point on the mast, so each can only receive half of the tension of a single headstay rig. Can one be struck or eased while the other is in use? (Don't ease one while there is a hoisted jib/tensioned halyard on the other...pop).

[Mike Meer]

Interesting point. Two headstays coupled with poor upper angle could enhance the problem. Seems Catana would have thought of that, right?? What's the solution. Install a soft-luff furler on the genoa with a 2:1 halyard?

[Brion Toss]

Hi Mike,
Yeah, it looks like a geometry problem, and yeah, you'd think Catana would have seen that. And they might have. At the very least, the tune doesn't need to be the same on both stays; the lighter-air one should be much slacker. Ideally, the shrouds will only be opposing one (loaded) stay at a time, at least when the loads are highest, on the wind in serious air.
Next, runners could be helpful; you could tune the heavy-load stay for light-to-medium, and crank on the runners when driving hard. This would also have the virtue of lowering the standing load on the Dynex shrouds, dialling down the creep.
Finally, assuming that the Dynex is typically massive, in terms of break strength, you just don't tune it like wire. My long-aborning "Fair Leads" on Dynex will cover this in detail, but the short form is that, since tuning is about anticipating stretch, and since low relative load means very, very little stretch, then you tune Dynex nearly slack, and still get net 1x19 performance.
Fair leads,
Brion Toss