Low and Fast in Heavy air downwind

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Postby Guest » Mon Sep 23, 2002 5:35 am

After three years I just about have the boat worked out. The last big challenge is to go low and fast downwind in heavy air.
I still struggle to beat the mixed fleet downwind in moderate to heavy air. I go faster for sure, but the end up before me at the leeward mark. On all the other points of sailing I am now thanks to the help of Steve the president and many others very, very competitive. Please give me a few pointers on going low, very low with a A-kite. The rest of the fleet is going around 8.5knots but straight to the mark, it should be possible to beat them. I started easing the tackline and heeling to windward. Would twings help or are they less effective in heavy air?
I guess goosewinging the kite is a bit hairy in 20 knots of wind. What is the upper limit on flat water in dirty air you would consider goosewinging the kite? Would it work and more importantly would it be save? I am very tempted to give it a go...
What about boat trim? If you deep would you move the weight forward more?
I have learned to improve my boatspeed upwind with the help of same Cuben Fibre Sails (High and very fast) and arrive at the windward mark mostly in the top 3 boats and need a way be fast on the dead square downwind leg. Long and a lot of other boats behind ahead and everywhere. Going high and plane does not seem to work. Any comments please.
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Postby Guest » Mon Sep 23, 2002 11:49 am

Bob,

At a certain point in wind velocity it is best to...... as your sons are used to doing in their skiff's ....head up and plane. This varies by wind and waves but is around 20 knots. Before that developing good rotation of the spinnaker is paramount to "bleeding" down low. Heel to windward helps. Slightly less vang helps increase flow to the spinnaker on the backside of the main. Crew weight forward is good in light to medium wind. Surpentine downwind as the puffs hit. If your A-spinnaker is close to the 12m class luff max easing the tack may not help that much.

One last thought. When you plane move the weight back. In 25+ knots move someone behind the skipper.

Jay Lutz
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Postby Guest » Mon Sep 23, 2002 7:47 pm

Jay,


what is the "12m class luff max" and how do I know if my chutes are or not. I have played with the tack line in light air but we were not near anybody to notice a change in speed.

thanks
Guest
 

Postby Guest » Tue Sep 24, 2002 2:09 am

Thank you Jay,
you are right sometimes during dinner discussions with my sons I forget that the J/80 is not a 100lbs honeycom/carbon skiff hull which builds up apparent wind so fast and so much that even if you start high, as the apparent wind move foreward you just go lower and lower. I guess the same priciple applies but 2900lbs just take a bit longer...
I know it is a feel thing to go lower in the pressure and head up in the lulls. My boat has AWA instrument and I wondering if you could recommend me a range of high and low points to move in say 15-20 knots? To what minimum angle AWA would you head up in flat water to build pressure and speed? Is 90 degree too high? How low would you go trying to bleed down 170 degree? If I read you note correctly you are saying in approx less than 20knots it is not worth chasing the speed which comes from hot angles,so what angle you you recommend 135 being the max on the polar? Would you move up and down say only 10 degree either way trying to build the apparent wind?
As I obviously sail to hot angles I would appreciate to have a high and low point when trying to maximise VMG downwind. You help is much appreciated.

Regards

Bob
I noticed in you old shore sail trim guides you recommended goose winging the kite in certain conditions. It this still an option and under what conditions would you recommend it.
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Postby Guest » Tue Sep 24, 2002 12:57 pm

Jud,

The actual class max for spin luff length is 12.2m. What I mean is that length is fairly generous so if a spin is designed max then there is potentially less need to ease the tack line ..or for that matter the spin halyard in order to get rotation of the luff to windward and away from the blanket effect of the main. A good example of too short a max luff length was in the J105 77sqm class sail. The max luff was so short that you needed to ease the tack a foot or more as well as the halyard to allow the luff to rotate. On a properly designed J80 spin you don't need to ease much ...or at all. I don't because I don't like the sail to bounce around.

Jay
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Postby Guest » Tue Sep 24, 2002 1:29 pm

Bob,

I think that in a J80 using exact numbers to go by is too technical. Wave height and direction often changes how you sail downwind. It needs to be more "seat of the pants". When you get a puff and a wave at the same time you can bear away much more then just a puff or just a wave. So try dumping the instruments for day and sail by "feel".

Jay Lutz
PS- the "wing and wing" is a good thing to position yourself for mark rounding or right of ways but not for an entire leg.
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Postby Guest » Tue Sep 24, 2002 4:36 pm

Okay Jay dont tell us the "exact numbers" but just some guidelines like :
flat water, less than 10 kts : windex at 90° ?
flat water, 10 - 15 kts : windex at 100-110° ?
flat water, 20 kts : windex at 130° ?
...possible ?

Ciao
Massimo Polo
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Postby Guest » Tue Sep 24, 2002 5:53 pm

Bob,

Back to Jay's point about wing and wing. While approaching the leeward mark on starboard jibe, try bringing the main across right before the mark and heading straight downwind, then doing a Mexican take-down of the spin on the port side while jibing around the mark. We used this a few times during J-Fest with good success and it set us up better than a leeward take-down on a port approach. Not a long wing and wing, but long enough...

Chip
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Postby Guest » Tue Sep 24, 2002 7:35 pm

Chip
I have also found the windward takedown as you round the mark to be very effiecient if executed properly(1 in 5 on my boat). But, be carfull not to lose your right of way by moving your boom to starboard if you are outside the two boat length circle.
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Postby Guest » Tue Sep 24, 2002 7:38 pm

Ok Jay,
Good point. Next Saturday I dump the instruments and sail by feel only. Forecast 15-18 knots.What do I at the windward mark. The rest of the fleet goes dead square 180 degree to the leeward mark.
Tell me how it feels when I am too high? What are the tell tales signs? I think I know how it feels when I am too low.
I asked for the numbers just for a rough guide I try to sail by feel, but not having another a-symetrical boat in the fleet makes it hard sometimes to know whether you could do better by sailing different angles.

Kind regards

Bob
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