Rigging tension adjustment.

[joss]

Fractional double spreader rig, discontinuous cap shrouds i.e. shroud is two lengths, each fixed to end of lower spreader rather than passing over it in one continuous length. I think that I need more tension on in the cap shrouds, but the spreader tip is flexing downwards slightly already, so I don't want to tighten anymore. Looking at it, I think the upper section of the cap shroud (i.e.end of lower spreader, past upper spreader to top of mast) should be shorter, but there is no way to adjust it other than forit to be cut and reswaged. Does this make sense? Any advice or random views appreciated.

Jo

 

[jeremyshaw]

Makes sense to me, but is there not an issue of relative lengths? What I'm thinking is that if the lower part of the two-section shroud is say 3 quarters of the whole, then tensioning it up would only deflect the spreader a little, which might be within tolerance. Many spreader designs seem able to cope with quite a bit of flex (they pretty much have to in gusts), so it might be worth a closer inspection of the fitting and observation of the design to judge whether you really need to remake the upper shroud.

 

[savageseadog]

First things first. The spreader must bisect the angle formed by the rigging at the spreader tip. The top length of cap shroud must be too long. The bottom length possibly too short, but with the adjustment of the bottle screw might be OK. You are going to have to do some cutting and re-termination, would suggest Sta-loks. To make it a little easier you can employ bottle screws at the spreader tip for the upper cap length.
You can do this without unstepping the mast if you are good at working at height for a duration.

 

[Danny]

Are you sure that, when the shroud is in two parts with both parts being terminated at the spreader, it's still important to have the spreader angle bisect the shroud angle?

The reason I ask is that I can understand that, if the shroud is continuous, then, if the spreader is at the wrong angle, the tip would tend to be forced down (or up). The shroud could then slip through the spreader tip when the rig is under load breaking the spreader and endangering the rig.

If the shroud is in two parts and fixed at the spreader tip then I would have thought the worst effect of not bisecting the spreader angle would be a slightly unbalanced load between upper and lower shroud with the difference being transferred to the mast by the spreader.

Waiting to be enlightened....

 

[savageseadog]

Think you are right about that part of it. If it were a very long way out then the spreader would be shortened in effect. The only other objection is how the spreader sits on the spreader root or bar. Both whether it would sit properly on its mount and you would of course have a resultant upward load at the root.

 

[BAtoo]

Can you not lift the spreader tip by taking up the terminal on the upper part at the spreader and letting off the lower - or is there no adjustment there??

On a fractional rig the cap shrouds are there to tighten the forestay (- and to ensure the mast is perpendicular) so that should be your determination if the caps are tight enough This adjustment should be done with the backstay off - the backstay is only there to bend the mast & flatten the mainsail.

Sorry if you know the latter bit - not meant to be condescending.

 

[VicS]

There is very good PDF on the Selden masts web site. Sorry I dont have the url. There is along list of manuals etc and this one is not near the beginning. It is called "Hints and Advice"

 

[joss]

Thanks for all responses. interesting points raised.

Jo