We had 3581 out today in a bit of a blow and were a little disconcerted by the amount of bend in the mast when going downwind with the kite up. If we ploughed into the back of a wave the jib would end up flapping in the breeze with the forces in the rig.

Is this normal? 

The rig was fully raked with the same tension as we were using upwind... i.e. the leeward stay wasn't slack. lowers were off quite a bit and teh puller was on hard.

Are we missing a trick or is this just what happens?

Cheers
Ian

try de-raking the mast downwind, letting shrouds off.

Did you have your puller on?
Also let off the shrouds to allow the mast a little more upright.
I never noticed this problem when I owned the boat.
Regards John

Yup puller was on hard.

When I say flapping I mean that the jib halyard tension had gone completely and the jib was blown well forward. I'm used to seeing floppy rigging in extreme conditions but this rigging was very loose. I can see that standing the rig up might help but not just letting it off. (I don't have a true one string system on the boat)

Note the same rig tension was used on the beat with no sign of the leeward shroud going soft so I don't think the tension was to low... however should I be running even more down wind?

It was only F4-5 in general but with some evil gusts every now and then. (the Sheppy weather station that is at the end of our estuary, we sail on the Medway, was showing 30knt spikes so I guess the boat is allowed to struggle a little in those.

It stood up to it well though and in a handicap fleet we finished second only to a Blaze, a known bandit in that sort of wind, so we were quite happy... if a little tied!

Ian

I used to own Prologue.  In a blow the last thing you'd want to do would be to let the rig tension (shrouds) off downwind.  However, you should try to adjust the rake so the mast is more upright.  Generally speaking, on a downwind leg the stronger the wind the more the jib luff is likely to go slack.  We found this at Whitstable in the strong winds on the Thursday and Friday.

Good sailing!

Apologise for digging around old threads...!

Has anyone else noticed this...???

And is anyone concerned that the one string rake system could ease in a big gust?

I don't think anybody is suggesting that the one-string system 'eased' in the gusts, more that the forces on the mast where causing it to close the distance between jib halyard sheave and mast foot/jib tack, thereby slackening the jib luff. The debate seems to be whether it is due to the spinnaker pole forcing the lower mast backwards (despite the best efforts of the puller) or the top of the mast flexing forward due to insufficient shroud tension. My one-string system (standard Winder set-up) wouldn't self-adjust, even with both cleats undone; definitely requires positive application of effort to either fwd or back string.

If the puller is on likely causes would be (in no particular order...)

Spreaders swinging forward (not fixed in position)
Not enough spreader angle to deflect the mast
Too little rig tension (acts via the spreaders to keep the mast bending the correct way)
Letting too much kicker off
Sailing very quickly into the back of a wave

One stringing will help prevent to some extent this as you spend less time adjusting individual controls and it is the individual controls not the one string system (which is just a method of linking them together) that affect the mast bend

I wasn't considering that the one-string system uncleared, more that with the "winder special block system" most people are using, that as the one string part has less purchase than the rig tensioning controls, that it therefore has more strain and more elasticity.

Slight movement on the special block could easy the forestay in a gust.

I've had two Winder boats with one string systems. As long as I've had the correct rig and puller tension I have never had a problem with the rig "easing in a big gust". So, no, I have not been concerned.