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Increasing mast rake in stronger winds

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Andi View Drop Down
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Post Options Post Options   Quote Andi Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 04 at 8:27pm

RS200 jib leads do not go out sideways unfortunately.  They are quite long fore and aft but they are angled so that the sheeting angle from the centre-line is constant.  We sailed a Lark many years ago and you could adjust the jib sheeting angle in, out, up/down as you choose.  Some people do use a jib cunningham effect in the RS200 ( we are not allowed to have an adjustable jib cunningham but by tweaking the jib luff tie down you can get something of a downhaul effect but it never looks impressive enough to be worth fiddling round with 1mm string in very tight knots.)  I will have a go at this though as I am running out of options.

Yes we do end up in effect pinching but this is the only way of getting both the windward and leeward telltails flying in the higher wind speed with the very flat jib camber.  I would love to have an outward pulling barber hauler or a sideways track ( too much National 12 sailing I guess. )

If we have to ease the jib, it has to be eased a long way until the extra power from the fuller camber is countered by the increased twist and if necessary allowing the luff to lift upto 30% back from the jib luff wire.

We are getting the main nicely flat - we have a good downhaul and kicker and we are getting a nice barn door effect within the limits imposed by a soft mast comparable with the Proctor C on the Lark.  I am interested in your comment about pinching by having the main too far in.  Our pointing angle is surely set by the need to get the jib streaming efficiently and the main then comes in as far as we can get it while still keeping the boat flat.  ( We do sail very flat. )  Am I wrong in taking this approach?  Some one at the recent nationals said we were pinching.

   - Andi

 

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redback View Drop Down
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Post Options Post Options   Quote redback Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 04 at 11:29pm
In the 4000 we ease the jib, but with the power of the trapeze the extra speed more than makes up for the extra distance.   I find pinching a mistake in any boat when its survival conditions.  In the Laser I used to raise the board and try and drive the boat off - the extra speed made the boat more responsive and thus less likely to go into irons.

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Post Options Post Options   Quote Andi Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 04 at 8:21am

Yes, I still race a Laser at times ( usually a Radial at 10.5 stone ) The new Radial rig seems to be able to point high even in seriously windy conditions without stalling and without the need to raise the Dagger board.  Like you, I also used to sail with the dagger board upto 30+% up just to keep the boat moving without it going into irons.

Footing off doesn't pay in a 200 if other boats are still managing to point.  In the 200 pinching works upto about twenty odd mph wind ( as long as the waves are smooth - it doesn't work in a Grafham type chop ) and then as I said above we need to change mode and this is where we seem to go wrong - we end up easing the jib, it then powers up so we have to dump the main out a long way(pointing gone out the window) and then we have ragging sails or we bear away to get them to pull and are instantly over-powerd so we luff to depower and so we sail on the ragged edge, working like maniacs and going slowly with loads of leeway.  Maybe we just haven't enough weight in the boat to do this stuff properly ( 19.5 stone is a little light but not too bad )

   - Andi

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Post Options Post Options   Quote redback Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 04 at 1:18pm
I think you're going to have to murder that main with more downhaul and keep pointing.  I hope you've got the jib fairleads further back than normal but the jib sheeted flat.

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Garry View Drop Down
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Post Options Post Options   Quote Garry Quote  Post ReplyReply Direct Link To This Post Posted: 12 Sep 04 at 5:21pm
Try some of these links to links!

http://www.sailboat-technology.com/links/online_articles.php

http://www.drlaser.org/

http://www.sheridanhouse.com/reviews/physicsofsailingreview. html

http://www.wb-sails.fi/news/98_11_PerfectShape/Main.htm

Garry

Lark 2252, Contender 298

www.cuckoos.eclipse.co.uk
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Post Options Post Options   Quote Andi Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 04 at 12:19pm

Thanks for the links.  Some very frightening tech stuff there and a lot of good ( hours and hours ) of study material.

On Saturday we had an open meeting at our club - Stewartby and I stuck to my "don't rake it back" guns.  It was mega windy - report on rs website and we went like a train.  I used a tad more rig tension - up from 330pounds to probably 380. ( This after reading about the jib luff sag effect.  I DON'T ACTUALLY UNDERSTAND THE EFFECT ON THE JIB LEECH THOUGH)  We kept pointing high with block to block kicker and as much downhaul as I could pull.  In the major gusts we had to ease the jib as well as the main and unlike previously we didn't get instatly over-powered.  Maybe the rig tension is the key?  Apparently our national champion doesn't alter mast rake either so maybe it's just a 200 thing.  Also as one of you helpful guys said, "Every one copies the fastest guy's settings even if he's not got the best ones.  A brilliant sailor with poor set up can still win and then the rest copy his poor settings"  I  paraphrase somewhat.  This was an entirely new idea to me.  Unfortunately it reinforces my "don't rake" stance when what I really wanted was for some one to talk me into believing that raking works so that I don't feel so lonely doing my own thing.

   - Andi

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Post Options Post Options   Quote Scooby_simon Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 04 at 2:21pm

" I DON'T ACTUALLY UNDERSTAND THE EFFECT ON THE JIB LEECH THOUGH" - Bendy at the front = bendy at the back(leach) and so not the correct shape.

 

 

 

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Post Options Post Options   Quote redback Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 04 at 3:11pm

I think if your jib luff sags you end up with a fuller sail and a more hooked leach - not ideal in a blow.

Has anybody had the idea of having the top part of the sail curved the wrong way - ie like the top batten hasn't poped?  If you could sheet it properly you'd have a righting force at the top of the mast, in opposition to the heeling force further down!

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Post Options Post Options   Quote Andi Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 04 at 3:43pm

It is starting to get a bit worrying about the amount of compression force on the mast with rig tension pushing 400pounds per shroud and eye popping downhaul plus bending it as far as the kicker will go!  Yes I know this reduces rig tension.  ( I don't know by how much - I'll have measure on Wednesday )

I'm interested to know if any one has any useful web links regarding rig tension as it affects a dinghy in the form of a more rigid jib luff.  Most books etc talk about jib luff tension in the form of stretching the cloth of the sail around a separately tensioned luff wire - ie a jib cunningham in Lark speak.

I presume that the mid point of a slack jib luff will get pulled aft and to leeward by the wind forces in the sail.  My next statements are questions really as I'm thinking aloud:  The aft deflectiion will create fullness in the mid-height part of the jib - bad.  ( Opposite of depowering the mainsail with kicker induced mast bend.)The leeward deflection would tend to increase the angle of attack at the mid height luff and also result in effectively over-sheeting the mid height part of the jib ( if there's a tight leach ) this would close the slot - bad.  But if the luff gets blown off to leeward maybe the leach goes to leeward with it regardless of leach tension, thia would be good as it opens the slot? No that's wrong probably, inless you can achive very little luff tension.  I guess this would work on a reach though where a wide slot with little jib leach tension and a twisted sail are good.

And I haven't a clue how the jib sheet forces will affect the luff shape.  I'll have to have a look at this by setting up a vey low rig tension and try sheeting the jib on hard.

   - Andi

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Post Options Post Options   Quote redback Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 04 at 8:14am
I look forward to your results.  Have you noticed the forum further down on Rig Tension?
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