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PostPosted: Tue Mar 25, 2008 4:51 pm 
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Sorry Jacques your right 45mm = 1 3/4 - could not read the Inch to Metric ruler very well :? So we have the same pre-bend

Our Crew weight was 357lbs (162kgs) (had a mate on) normally we are 348lbs (162kgs) with Emily.

Jacques is also correct its the speed that gets generated and the feeling of control - the boat never felt over powered and we could just head up into the stronger lifts slightly, to wash off any extra power. And the faster the boat moves the more lift the centreboards can generate - much less leeway is experienced. So it all starts to work together.

We were pacing against the current Tiger World Champion and on Saturday we could not get anywhere near his height nor speed. We talked about the settings and on the following Monday we had basically the same wind strength - 15kts plus - and we where able to achieve the same height and speed. So it was a good benchmark. We'll be training again in two weeks so we will see if its repeatable.

As I noted the use of the rotater is counter intuitive and raises eyebrows. A mate of mine uses the rotater in the normal manner - pulls it to the back of the boat when over powered. We are going to do two boat testing on Sunday and we'll compare performance. I'll update the post following that.

The top is able to twist off as the sail section above the hounds is totally flat, with no batten pressure (using the hard battens) and little or no shape. The leech just opens up, I could not believe it either. The mast section on the Tiger is much the same as a H18 and to flatten a H18 you over rotate. We just have the added luxury of raked spreaders to induce bend in the lower section. I spoke to a mate who sails on 16foot skiffs and he commented that they follow the same method. The top of the sail just winds vanes and as it has no shape to induce lift it just twists off to leeward.

Try it and see its easy to do - but the key is the cunningham.

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PostPosted: Tue Mar 25, 2008 5:50 pm 
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Claus wrote:
How is the top supposed to twist off with so much rotation? I though with wind we want less rotation in order to let the top twist off (the mast is more flexible sideways) ?


It can't. If it is really windy and you really want the top to spill then you have to rotate the mast less. We set the rotator so the spreader is just off the job in light to moderate wind. Once downhaul is maxed out and we are double trapped and the boat still feels over powered then we'll start pulling in on the rotator to depower.

I'd guess from about 18kts upwards we think about doing this, but it's more a feel thing.

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PostPosted: Thu Mar 27, 2008 6:43 pm 
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It does - I'll bring photos....

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PostPosted: Thu Mar 27, 2008 10:00 pm 
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This is a subject that has bug me ever since buying the Tiger. I have gone from one basis of trim to the other and have found under sheeting has been the biggest mistake I have made.

Currently we have been training for the F18 worlds with Mark Laruffa and seen huge increases in speed and have found settings work for some and not for others.

We are set up as follows

2 pin down on the forestay (without furler attached)
3 pin from the bottom on side stays. Relatively tight
80mm spreader rake (M. Booth and others have been tending to do this lately so giving a go)
Diamond stays set at around 38 on the loose gauge


Light air running with little down haul then increasing as the wind does, overall effect flatting sails out as the wind builds

Mast rotation has generally been back on boards but have set it to the rear beam recently and find the boat gets in the grove with less effort. Much easier to steer in gusts and to maintain boat speed.

Purchased a SNU shute system as well and life is much easier hoisting as well.

Hope to see this thread grow as there needs to be more discussion on settings for Tiger and a share of information.

We will have a video camera out this weekend and taking pics of the different setups and will try to post for all to see.


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PostPosted: Fri Mar 28, 2008 9:10 am 
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kylea wrote:
It does - I'll bring photos....

Would be nice!


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PostPosted: Sun Mar 30, 2008 6:19 pm 
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Aside from everything working together, what do you think is the most important part in the tuning or something you'd put emphasis on getting right? is there one thing you messed with that gave significant feedback on the water; i.e. mast rake, rig tension, diamond wires etc...?

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PostPosted: Sun Mar 30, 2008 7:20 pm 
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This has been a slow progression over 20 months of trial and error. Constantly trying to find the one magic thing to make the boat faster and eaiser to handle.

What I was doing was changing too many things at once and never really understanding what to expect. I spoke to an experienced ex hobie tiger sailor and now Nacra guy and his comments where the most telling. He sets his boat up the same way no matter what. Rake & pre-bend, only varing the rotater and obiviously downhaul.

What I needed to do is understand what the sails are trying to do and how the centreboards and sails work together. The Jib curves/deflects the airflow and leebows the main, hence the lower section of the main has to be set to match this deflected airflow from jib. However the mainsail above the jib has the airflow hitting at the same entry angle as the jib (say 45 deg versus 30 deg). Therefore the main must be able to twist off to leeward to match this.

First, the most important thing is to set the mainsail to match the expected airflow. The 4 main leech tell tales 'tell the tale' and the top one tells the most important tale, expecially in light to moderate air.

2nd in light air run the main loose and keep the top from hooking. This may require some light downhaul to flatten the top a bit.

As the airflow increases the sail will naturally be forced to leeward, however if the main is pulled on hard without matching downhaul the top will be still hooked to windward - this results in an un-balanced sail plan and the boat will be overpowered, literally the breeze is pushing the top of the mainsail away from the centre line of the boat - and then you fly a hull.

Think about what the sails are physically doing - and then relate that to what you are experiencing on the water. The main twists the boat to windward as the action of the force created acts behind the centreboards. The boat rotates towards the breeze. The jib force is in front of the centreboards - hence it rotates the boat away from the breeze. These two need to be balanced.

Once the boat starts moving the lift created by the centreboards increases and the main can be pulled on harder. You can tell when its working as the rudders will tend to stall if there is too much main tension.

Third, in strong breeze (above 15knts) - if in doubt pull on more downhaul and then more. Match this with the main and jib, set up a jib cunningham you can control from the front beam and use it to flatten the luff of the jib, just like the main. (This is a nice to have - not essential as you can always send the crew to the front :shock: )

Fouth, Pre-bend - set to recommended settings for crew weight.

Fifth, Rig tension - follow the recommended settings - once again think about the rig's purpose - in light air a tight rig will not allow the mast to rotate very well, so set the rig a little looser, as per Mitch Booths comments. As the Breeze increases you want the rig to be tigher so its not creating stress when you tack and gybe, otherwise the rig is crashing back and forth, things break. If is likely to be very strong then set the tension very tight, if you know for sure its going to be light all day and you cannot get to the beach to adjust the tension - set it light. Otherwise set it firm for medium conditions

Sixth, the rotater - I'll upload some images they tell the story. The top and bottom left are with over rotation. The right top and bottom are with the rotater to the back cross beam. Top set downhaul on hard, bottom downhaul lighter.

Image

On the bottom right notice how the mainsail leech is "hooking" - it has more shape but in a strong breeze this would be an over-powered sail. The Top right is better - with more downhaul applied - but it still has more shape than the left side. Using these images you can see effect of the three controls, sheet tension, downhaul and rotater.

The sail shape on the left allows the top section to fall off to leeward (it "twists" the main - the result is a very fast sail - HOWEVER - you cannot start off with this shape - you need to get the boat moving and then starting trimming and downhauling.

I now use the settings noted above for all conditions and then vary the mast rake:

1. If its around 15 - 18 go to the 2nd from the bottom on the side, 2nd from top on front - rig is very tight
2. Over 18 top hole on front and bottom on sides
3. Very light 3rd from top and 4th up.

Image courtesy of joclo

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Last edited by kylea on Sun Mar 30, 2008 10:30 pm, edited 1 time in total.

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PostPosted: Sun Mar 30, 2008 10:02 pm 
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So bring the rotator back to get going, then let it out to flatten the sail and find speed.. Used to think bringing the rotator in depowered, glad that is cleared up.

Great pictures man understanding whats going on is exactly what I need.

Quote:
This has been a slow progression over 20 months of trial and error. Constantly trying to find the one magic thing to make the boat faster and eaiser to handle.

Well, glad you and the others here have taken time to post, you're helping me and everyone else in my position to cut that time in half. Thanks for the effort guys. Image

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PostPosted: Mon Mar 31, 2008 2:58 am 
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See a small movie we shot on the weekend, sailing down Sydney Harbour.

Kyle has the Black Shute in front of me and the red kite and windward stuff is me and my wife. http://youtube.com/watch?v=37wKwT0Fquk

James


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PostPosted: Mon Mar 31, 2008 6:23 am 
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Kyle, I can see you get a flatter main with overrotated mast as the mast top easily flexes back when sheeting in, curving the mast mostly at the top. I suppose by "twisting off" you only refer to the leech as the mast in this position can only flex very little to leewards?


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PostPosted: Mon Mar 31, 2008 7:58 pm 
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Claus wrote:
I suppose by "twisting off" you only refer to the leech as the mast in this position can only flex very little to leewards?


Exactly - the sail is now as flat as possible - the top third has little or no aerodynamic shape and the leech is 'pushed' off to leeward, actually it just wind vanes.

Give it a try and let us know. It really only applies over 15 - 18 knts

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PostPosted: Thu Apr 03, 2008 10:18 am 
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Gotta wait to get these winds here, usually we are between 10 and 15.

Would you mind another question? I see you use 80mm of spreader rake, which seems a lot. I wonder how it comes the fast guys have used 55mm during a few years and now they use 80mm? Nobody ever tried that setting before? Especially as you employ the same prebend as always.


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PostPosted: Thu Apr 03, 2008 2:24 pm 
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Claus wrote:
how it comes the fast guys have used 55mm during a few years and now they use 80mm?


I had a discussion with Darren Bundock about it and he said he uses 65 and that Mitch Booth uses 80 - but I think these settings are a red herring (for us).

The mainsheet and the downhaul and rotater are the main controls that dramatically affect the shape of the sail. Pre-bend sets the minimum base shape the sail will have without any downhaul or mainsheet pressure. It also affects the way the luff is presented in terms of the amount of curve and initial draft position. This will vary between sails. But who knows how you can decide this setting, I don't.

For the rest of us, who just make up the numbers for the hot shots, I reckon it is not that critical. Use the recommended settings and concentrate on the main and the downhaul and rotater. These three are more than enough to play with. Once you can get the boat moving fast and flat consistently you can then start to experment with the pre-bend.

Adjusting the pre-bend to some magic position might make a slight difference if you are really competitive but I would bet for most of us it doesnt. We make so many mistakes with basic settings and boat handling its not relevant for the moment.

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PostPosted: Thu Apr 03, 2008 3:09 pm 
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Completely agree on that! For the beginning we just want a basic setup for this advanced stuff, but the existing data makes you a bit uncertain: How comes that the basic setup changes from about 50mm http://www.hobie-cat.net/download/manue ... _tiger.pdf to 80mm with the same boat/mast/sail, only 2 years later? At least intriguing. I guess I´ll set it to 70 to be in between the two ;)

Thanx for the discussion! Your last comment about mast rake a few months ago helped us a lot. We now sail with much more rake, it even feels a bit like sailing the H16 I was used to :)


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PostPosted: Thu Apr 03, 2008 3:31 pm 
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The MOST important thing to do it to get a buddy of equal or slightly better performance and agree settings and then try and pace each other - varying ONE setting at a time, switch roles after say 30 mins.

You need to take time out from racing and train / practice - remember, we have stepped from billy carts (H16, H18) to formula 1 (F18) - we cannot expect to get serious results without putting in the preparation.

Make notes (wind strength, direction, crew weight etc) and build up a diary.

And then share the results. That way we can improve the whole communities performance and start to counter-act the Nacra invasion.

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