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 Post subject: too much twist in sail
PostPosted: Tue Mar 11, 2008 9:24 pm 
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Joined: Thu Mar 23, 2006 1:20 pm
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Location: Atlanta, GA
I'll have some pics up soon as soon as the site theyre on starts working again. But after seeing them it became ridiculously clear why I couldn't point for sh*t at performance midwinters. There was way way too much twist in the sail, and aside from downhaul I'm thinking the mast was raked way too far back. Is there something I'm missing here that caused so much twist in the sail and caused me to tack 5 times to get to A mark because I couldn't point?

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 Post subject:
PostPosted: Tue Mar 11, 2008 9:57 pm 
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Location: Atlanta, GA
Image


Image


We are the white Tiger sail

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 Post subject:
PostPosted: Wed Mar 12, 2008 4:07 am 
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Try sheeting in a lot more.


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 Post subject:
PostPosted: Wed Mar 12, 2008 5:12 am 
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Joined: Mon May 09, 2005 10:25 am
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Location: Jersey Shore
Definitely undersheeted. Sheet the main in harder and the boat will naturally point higher and drop into "the groove".

If you don't have them already, you would probably benefit from putting tell-tails in the upper panels of the mainsail. In light to medium wind, they will tell you when you are over or under sheeted. In higher wind, they will probably always be showing some twist.

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 Post subject: rot
PostPosted: Wed Mar 12, 2008 7:31 am 
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Location: Raleigh, NC
Where was your mast rotation set?

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 Post subject:
PostPosted: Wed Mar 12, 2008 8:57 am 
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I think that is a bad photo to look at your trim. It was right at the start and it looks like you just went out on the wire and are getting settled in. You also are in a bad air zone from the other boats and are footing to get cleaner air.
Come find me at Spring Fever and we can look at your settings.


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 Post subject:
PostPosted: Wed Mar 12, 2008 9:21 am 
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Location: Jersey Shore
Simply based on the photos you provided I agree, this is probably shortly after a start or definitely at some point during the upwind leg. So one question would be if it's after the start, why is everyone else already fully trapped out and you're just getting out on the wire. Or, if this is at some point during an upwind leg, it looks like maybe you just tacked and are getting going after the tack.

In either case, you've positioned yourself in bad air. In the first pic there is one boat direcly ahead and to windward and in the second pic, there is a line of boats ahead and to windward. Being stuck in dirty air will greatly effect you're ability to point upwind and diminish upwind performance overall.

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 Post subject:
PostPosted: Wed Mar 12, 2008 1:17 pm 
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Location: Northfield Minnesota
In the first pic, the boat furthest to the right: Holy cows thats a flat sail!


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 Post subject:
PostPosted: Wed Mar 12, 2008 8:52 pm 
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Location: Atlanta, GA
It was just after the start and I believe I had loosened on the blocks just a bit to get on the wire, sheeting back in as I lean back. The reason I wasn't already out was the boat was still fairly flat and I had a 225 lb crew already out. This was the first time I used this sail and I blew up a quick release pin when I sheeted in tight on the way out from the beach so I was honestly a little wary of sheeting block to block the rest of the ride and kept it sheeted out just a tiny bit more than I probably could have gone. But we were fast on the reach and fast with the spin, just stalled out when trying to point.

The mast rotator was pointing at the shroud. We had a combined crew weight a little over 400 so I was looking for all the power I could get (was very happy we had high enough wind that a 225 lb crew was to my advantage)

Just wanted to check up and see if there was a predominate cause for the sail twisting too much on these boats. Wasn't thinking too much about the footing when I posted but I realize how that can dramatize the twist a little. Glad I found you (David) and Mike that night, I'm looking forward to your help and getting the boat dialed in (and thanks for listening to my crying about having to tack so much to get to A 8) )

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 Post subject:
PostPosted: Mon Mar 17, 2008 12:12 am 
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Location: San Diego
Try handing the mainsheet to the crew to sheet once the crew is on the wire. Also, take the quick release anything off the main sheet. The quick shackles are too long and are not intended for this type of load.


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 Post subject:
PostPosted: Mon Mar 17, 2008 5:09 am 
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Location: Seattle, Washington
Quote:
Try handing the mainsheet to the crew to sheet once the crew is on the wire. Also, take the quick release anything off the main sheet. The quick shackles are too long and are not intended for this type of load.


See this web site.
http://en.lewmar.com/products/catalog/1-143.pdf
It lists the specs between D shackles and Lewmar Quick Shackles.

Basicly a 1/4" pin size D Shackle has a safe working load of 2500# and the Size 72 Synchro Snap Shackle with a 1/4" pin size has a safe working load of 2420#. Breaking loads are 5000# and 4840# respectively.

With regards to stack height I believe the Snap Shackle is about 1/2" taller. I use the Quick Shackle to connect to the strap on the main sail clew. On my Tiger the stack height is not an issue.

Image

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 Post subject:
PostPosted: Mon Mar 17, 2008 8:30 am 
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Location: Atlanta, GA
I'm pretty sure that while rushing to get off the beach I grabbed the wrong pin, one from the old 16, so its not unlikely the pin was as old as I am.. I like those snap shackles though thanks for the link.

I had to keep the mainsheet on this trip. My cousin raced with me, it was only his third time sailing and he was so uncoordinated on the wire he probably woulda hung himself with it, not to mention the 4 times he lost balance and his ogre a$$ came crashing into me like a wrecking ball... Watching him flail around trying to climb back on was well worth it though

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 Post subject:
PostPosted: Mon Mar 24, 2008 10:59 pm 
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Location: Palm Beach Sydney Australia
My experiences may help you with this issue. We have been struggling for height and speed and generally we where over powered in anything over 10 knts. After much testing and advice, in 15 - 20 knts of constant sea breeze here are the settings that worked for us:

1. Mast Rake - Side - 2nd from Bottom - top 2nd Hole down - very tight rig
2. Spreader depth 80mm (approx 3 inches)
3. Pre-Bend - approx 45mm (approx 1 3/4 inches (did say 2 3/4 - wrong conversion :? )
4. Rotater - (this will cause a bit of a stir) well forward of the stay and in fact its now always set to that. The leech of the jib just misses the spreader arm (on the beat). We now never touch the rotater, up or down wind.
5. Cunningham - on as HARD as humanly possible even harder than that!
6. Mainsheet - pull on to the max - your crew should only need to let off 6 to 9 inches of sheet - and you can head up slightly in very strong lifting gusts. In fact the main is so light you can hold it with ease, so when the crew has to pull on a heap more cunningham he can hand it to the skipper and its not going to pull out of your hand.
7. Hard battens in the top two - all battens just snug - not shoved in hard - just take out the wrinkles

On an STX this will invert the main on the beach and be dead flat and on the water the top twists off just like the Tiger on the far right hand side of the photo you included in this post. Its un-believeable - totally transforms the Tiger into an absolute weapon in 15kts plus

The only other point is I am running 10:1 on the main (As I am old and daughter is crewing for me) - we are using the new Nacra 5 sheave Harken top block - down to the usual triple and a double on the top of the triple.

If you get one I can help with the sheet threading as it is a bit different.

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Last edited by kylea on Tue Mar 25, 2008 4:57 pm, edited 1 time in total.

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 Post subject:
PostPosted: Tue Mar 25, 2008 10:27 am 
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I think there's a type-o in your measurements...45mm is not 2 3/4"

Form the pictures...you just to sheet harder ...and keep down hauling till the head pulls out of the sail! then pull a little harder...that should be just about right.... :)

All kidding aside - the harder you pull the luff normally you won't really point higher...the boat just gets faster and easier to control - but if you are light you have to do that - if you are a heavier crew you won't have to - keep in ind to go into a higher pointing mode you will need less down haul - but if you are good and can steer well - with a flatter sail...it s a narrow grove - but with more speed across the daggerboards you'll actually sail a higher angle - just not stuffing up and pointing the boat at a higher ... but rather allowing the boat to go faster by actually steering a couple degrees lower to get the speed up that will generate a higher angle.
There have been many posts lower down on the Tiger forum that you might read up on about tuning this thing.

80mm of spreader rake sounds like allot! (maybe that works good for someone sailing with his daughter) but for a crew anywhere near a normal two male crew size...over 330 lbs combined you'll want to stay at around 2" or less of sweep and 1 3/4" total prebend.


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 Post subject:
PostPosted: Tue Mar 25, 2008 12:11 pm 
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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) ?


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