Proper headstay tension with furling unit

[Brion Toss]

Hello,
First, since it's the backstay that tensions the jibstay, put a gauge on the backstay. Then compensate, through trig, for the angle difference. If the two wires are different diameters (they should be, in almost every instance), compensate for that, too.
Second, what you really care about here is luff sag, not too much, not too little. The gauge is just something to get you in the neighborhood.
Third, playing with the jibstay also means playing with the mast shape; both must be happy.
Fair leads,
Brion Toss

[seawolf]

Thanks for the advise.
In general, would it be safe to say, if the adjustment of the headstay and backstay are correct at its present state, this adjustment should be appropriate for after the installation of the furling unit.
At least a good starting point to adjust to while making observations.

[paramita]

Originally Posted by Brion Toss

...If the two wires are different diameters (they should be, in almost every instance), compensate for that, too...

A little off the topic of the original topic but I'm wondering why the two stays are normally different sizes? Is it necessarily bad practice to size them the same? I ask because I'm in the process of designing the re-rig of my Ericson 38, the original spec shows a 9/32" backstay and a 5/16" head stay. In the interest of minimizing the variety of part sizes I was thinking of increasing the backstay by 1/32" to match the headstay. Is there anything I should be thinking about here that I currently am not?

Thanks,

Matt.

[Brion Toss]

Hi there,
The backstay should be smaller because it has less load than the jibstay: the angle is greater, and some of the jibstay load is siphoned off by the weather upper. Making both wires the same size would gain you simplicity, but at the cost of weight, windage, and expense. tuning gets tricky as well. Oh, and you'd need to accommodate the larger pin size needed. Is it really worth it, just to limit spares? The boat has needs too, you know...
Fair leads,
Brion Toss