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Downwind techniques


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#1 aro

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Posted 10 July 2014 - 07:54 PM

Yo! When sailing a multihull which typically do between 7 and 15 knots depending on how you steer, what techniques are helmsmen and trimmers using to maximize downwind VMG?

Set genacker and steer to it (up in lull, down when speed climbs)?

Maybee trim sails too?

How much speed variation should you see when running?

What is the best way to climb over those waves that slow us down?

Does anyone have good reading to find tipps to test?

 

Cheers, Anders (I just want to go faster)



#2 tomfla

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Posted 11 July 2014 - 01:10 PM

Lots of issues, probably too many to address.

 

But back when I was boardsailing seriously I attended a clinic before the Olympic trials.  One of the better ladies there use to shake her finger at me and say 'Tomas, you must learn to play with the waves'.

 

While it is easy to say hitting the back of a wave will slow you down the result is usually to shift the apparent wind aft and increase the speed of the apparent wind, which is usually a good thing.  On the other hand when you are surfing down the face of a wave you are shifting the apparent wind forward and decreasing the apparent wind speed which is often a bad thing.

 

I try to minimize the time I spend climbing up the back of a wave and maximize the time I spend surfing down the face of a wave.  This is done by a combination of changing course and trimming the sails as the apparent wind shifts.

 

But I could be wrong about all of this.



#3 kgw

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Posted 11 July 2014 - 02:56 PM

I've heard that getting the apparent wind 90 degrees to the main is a good starting point... ;-)

#4 sail(plane)

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Posted 11 July 2014 - 03:36 PM

Yo! When sailing a multihull which typically do between 7 and 15 knots depending on how you steer, what techniques are helmsmen and trimmers using to maximize downwind VMG?

Set genacker and steer to it (up in lull, down when speed climbs)?

Maybee trim sails too?

How much speed variation should you see when running?

What is the best way to climb over those waves that slow us down?

Does anyone have good reading to find tipps to test?

 

Cheers, Anders (I just want to go faster)

 

I´m a beginner, I have the same questions

regarding waves: in my Weta, in 10-12 kt winds and corresponding chop, maximizing VMG downwind: I try to "put the bow in the holes" (well everybody tries to do that right?), while at the same time trying to keep the apparent wind

that is the best way to describe it, put the bow in the (water) holes, the boat starts to plane and stays there for a while until I loose it and start again. I have to actively helm to do this and it´s only worth if there is enough wind to plane.

maybe this doesn´t apply to a cat and only to a planing hull like the weta´s?



#5 B30

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Posted 11 July 2014 - 04:16 PM

The answers you are looking for will vary somewhat depending on the type of boat and the conditions at the moment.

 

What kind of boat are you sailing?



#6 aro

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Posted 12 July 2014 - 08:55 AM

Thanks guys! Like the responses.

 

We are sailing a Dragonfly 28 Sport (i.e. tall rig). This is a very (for a tri) heavy boat at 2 220 kg's. We have the same sail area as a SeaCart 30 at more than twice the weight. 

 

We need quite a lot of wind to really get going. Or a nice wind angle. When we get planning life is good but like Tomas and Sail(Plane) say, it is a question of playing the waves and finding the holes.

 

Apparent wind at 90 degrees seems to be the Hobie mantra. Yes, it is a good starting point. But then when the speed is up, I wish to maximize VMG down wind.

 

I find myself steering to the speedometer mostly. Which feels a little bit wrong. 

 

We have a rudimentary polar diagram for two wind speeds. But speed varies very much on a trimaran.

 

Maybe one could start from the target boat speed, go up, go faster, go down, go lower than the angle at target boat speed, go up when speed is down to target boat speed. And repeat. (are you with me?). This will have us below target boat speed when we accelerate again but we are pointing below target angle so the price is not without benefit. What do you people think?



#7 BeachbumII

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Posted 12 July 2014 - 07:50 PM

Steer to vmg. Use GPS waypoints to learn whats the best angle + speed combination for different conditions. Try out new ways and wrtie them down with results.

 

Probably without seeing the polars nor driving the boat my guesstimate is that at the 2220 kg of weight the boat is more a majestetic one than a rally car. You must steer gently and let the boat accelerate. Also on  a Heavier boat feeling  the rythm of the waves  helps you foresee what you should do on the next gust.

 

First i would try to drive constant speeds without too much variation.  Its not the high peak speeds that give you a good average, but the reducement of the low speed-moments.



#8 aro

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Posted 14 July 2014 - 02:37 PM

OK, let me put it a little bitt different.

 

How much variation in speed and how much zig zag (variation in angle) would you expect depending on wind strength?

 

Lots of wind (20 kts) may give very low angle, 150 degrees true perhaps. Speeds in 12 - 18 kts, almost no zig zagging. As the wind drops there comes a time when the boat does not make it over the next wave if I don't luff. How far should I turn to get the speed? Or should I? Would you always luff for speed?



#9 BeachbumII

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Posted 14 July 2014 - 08:29 PM

I can only aswer this, the rest rest is boat dependant:

 

If I dont make over the next wave, and it is possible to be faster than the wave, I Luff for speed as much as is needed.






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