rig tension .. up or down

Another point worth making for boats that cannot easily adjust rig tension on the move.  When you rake the mast back for strong winds use two (2) pins, one above the other and both through the eye of the shroud.  Then if the wind drops you slaken the rig enough to remove the lower of the 2 pins and re-tension.  This decreases the rake and there is no risk of letting the rig fall over the side.

When it gets windy you want the mast to bend more to flatten the sail, so putting the rig tension off or on depends on weather the spreaders tend to straighten or bent the mast with increasing tension.

It is important to understand that the length of the forestay controls the rake and the length of the shrouds controls the rig tension (at a particular rake)

From some of the above comments it shows that for some types of boats having a saggy luff is less important than raking the mast back when the wind increases and you are on the water and can't change the shrouds.

Take redback's point about mast deflection.  Slacker rig should give better gust response by allowing the middle of the mast to bend at a lower wind force (lowers permitting). 

But also, less tension = less mast prebend and a fuller more powerful main.

As for rake, less tension = more rake, with the usual effects of a bigger slot, a lower mast tip and hence less power and less heeling force. 

But when setting up on the beach (rather than adjusting on the water), surely the way to get more rake is to go down on the shrouds, pulling the mast back, not to reduce the rig tension (ie simply lengthening the forestay)..

Still confused.

Edited by NickA

The 5000s is the same when the wind is over twenty knots you let off the rig tension which in turn let the mast go back a bit.

 

Well that depends.  On my boat, a 4000, the spreaders deflect the mast forwards so by putting plenty of tension on I can put some luff curve into the mast which seems to suit the sail and it locks the mast into that sort of shape up to a certain wind strength.  Above that wind strength the leeward shroud can no longer help control the mast and so it moves a little up to windward in the middle and opens the slot and lets the top bend off a bit this coincides with having to ease the main which again pushes the mast to windward in the middle but this is controlled by the lowers.  This all works nicely with the amount of spreader deflection, luff curve, crew weight etc. that I have in my boat.

If I let the tension off the bend to windward in the middle happens at a lower wind speed.  We don't adjust it whilst sailing.  If its very windy we rake the mast back and re-tension to about the same amount or possibly a bit less especially if its gusty.  The luff sag is minimal but then we are using quite a lot of tension.  Anyway the mainsheet tension is also keeping the jib luff tight.  If the main were to flog the mainsheet is no longer helping with the luff tension but anyway this generates such a lot of drag the boat is horrible so luff sag is going to be a minor issue.

I suspect 400 and 5o5 crews ease the rig tension as a way of raking back the rig in strong winds and ideally would like to have the same rig tension or there abouts but losing it is a price they pay for more rake.  I seem to recall when I sailed a 400 regularly that the jib went very slack when the kite was up and it was very windy.

Finally if your jib luff is sagging noticeably I suspect you don't have enough rig tension.  Walk up to another well sailed 3000 and ping the shroud - I bet its tighter than yours.