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Best course #84104
09/06/06 11:30 AM
09/06/06 11:30 AM
Joined: Feb 2006
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fin. Offline OP
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I was under the impression that there are an infinite number of "best" courses to the weather mark. The higher you sail the slower the boat goes, but it travels less distance and, if done equally well, all would get you to the top of the course in the same amount of time.

Also, I had heard or read, somewhere, that it is better to take the headed tack first, when going to weather. The belief being that less distance is traveled. Further, that belief could be demonstrated trigonometrically.

True or false?

-- Have You Seen This? --
Re: Best course [Re: fin.] #84105
09/06/06 11:58 AM
09/06/06 11:58 AM
Joined: Dec 2005
Posts: 443
Edmonton, Alberta, Canada
bobcat Offline
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I know that this is going to get a bit more technical but believe that I can tell you that you are wrong on both assumptions.

A chart referred to as a polar plot can be generated for a boat. It indicates where optimum VMG (velocity made good) is made for a particular craft. This is the point where the tradeoff from footing for increased speed balances against the increased distance travelled. In your example, the higher a boat sails the slower it goes. True and therefore the slower the fluid flow over the foils. This potentially means more leeway. The boat is pointing higher but the course isn't.

In regards to the headed tack, the tactics vary depending on if its an oscillating or persistent shift.



F16 Blade 716
Re: Best course [Re: bobcat] #84106
09/06/06 12:06 PM
09/06/06 12:06 PM
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fin. Offline OP
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Thanks Bobcat! Great logo!

Can you get down for Tradewinds? Can't be more than 6 or 7 thousand miles round trip!

Re: Best course [Re: fin.] #84107
09/06/06 12:08 PM
09/06/06 12:08 PM
Joined: Jul 2001
Posts: 146
Crofton, MD
Todd Berget Offline
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Tiki,

Upwind, indeed there are infinite courses, however typically there is only one optimum course (in some cases there are more but they are usually very similar). Upwind, you can sail at different courses (angles) to the true wind (ig. 30 deg. true, 35 deg. true, 40 deg. true). For each of these you will have a certain velocity. Now you do the trig. for each course and velocity and get the component vector towards the windward mark (0 deg. true). Now, based on the speed you can achieve for each course, there will be one optimum component velocity (Velocity made good). The course off of true wind with the highest velocity made good is your optimum course. These all may differ for different windspeeds. This is typically how Target boat speeds and courses are derived on big boats. They also have the advantage of a polar diagram usually created from a velocity prediction program which essentially does all of the math for them. Conversely, you can figure the same downwind.

Now, the second question - Upwind you want to sail towards the shift. I think i've typed too much on this response already so you could read Rick's book for a more thorough explanation...


Todd Nacra 20 www.wrcra.org
Re: Best course [Re: fin.] #84108
09/06/06 12:20 PM
09/06/06 12:20 PM
Joined: Sep 2001
Posts: 254
Gower, Wales, UK
sailwave Offline
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Quote
Also, I had heard or read, somewhere, that it is better to take the headed tack first, when going to weather. The belief being that less distance is traveled. Further, that belief could be demonstrated trigonometrically.

True or false?


True if the wind is steadily tracking one way; if it's going right, go right first, and visa versa.

Re: Best course [Re: Todd Berget] #84109
09/06/06 12:23 PM
09/06/06 12:23 PM
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Posts: 3,348
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fin. Offline OP
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Thanks Todd, haven't read Rick's book in years! Maybe it's time to get back to basics.

Re: Best course [Re: Todd Berget] #84110
09/06/06 12:33 PM
09/06/06 12:33 PM
Joined: Sep 2005
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38.912, -95.37
_flatlander_ Offline
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So who gets out the GPS (with the VMG function) and actually plots the chart for their catamaran? Anyone? Of course you'd need to mount a compass to utilize the findings. Is a compass class legal in most catamaran classes for buoy racing?

We raced a PHRF mixed fleet event last weekend and noticed the wind heading posted at every start.

From Hobie rules; "The use of navigation and speed
metering equipment is illegal unless specifically
allowed in the individual boat rules or by the Notice
of Race for the particular event or regatta."
I've heard the wind heading will be posted at the 18/20 Nationals but nothing in the NOR allowing compasses. Why then display wind direction?

Is the catamaran that much faster that you can "feel" VMG and it's not worth plotting, whereas changes in a larger/slower boat are more subtle and therefore less apparent?


John H16, H14
Re: Best course [Re: fin.] #84111
09/06/06 12:37 PM
09/06/06 12:37 PM

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Pete:

This old 27 year cat sailor learned a lot from "Catamaran Racing for the 90's". <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" /> I got the seminar tapes too. Roll Tacking tape is a must. <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />

Doug

Re: Best course [Re: ] #84112
09/06/06 02:05 PM
09/06/06 02:05 PM
Joined: Jun 2001
Posts: 12,310
South Carolina
Jake Offline
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Doug, just using the word "tapes" really dates you. <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />


I've never understood the reason behind that exclusion in the Hobie rules. I'm just beginning to learn how vital a compass is for competitive sailing around the bouys. It's less about understanding what you're best angle of sail is (you really need to learn to feel that through competitive experience) than it is to give you concrete information about what pattern the wind is following on and around the course.


Jake Kohl
Re: Best course [Re: Jake] #84113
09/06/06 02:20 PM
09/06/06 02:20 PM
Joined: Jun 2004
Posts: 393
Syracuse,N.Y
pbisesi Offline
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Compasses are allowed per IHCA rule 16.3 and have been for a while.
They can only give a heading.
John:
When they post a compass heading and then do a change mark with the new heading you then know which way the wind is going. That can be handy.


Pat Bisesi Fleet 204
Re: Best course [Re: pbisesi] #84114
09/06/06 03:55 PM
09/06/06 03:55 PM
Joined: Mar 2002
Posts: 984
2017 F18 Americas Site
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This is from the International Hobie Class Association Rules for Tigers (I think only Tigers):
[color:"blue"]6. EQUIPMENT
6.1 Compasses, navigation and speed metering
equipment [color:"red"]of any type[/color] are permitted.[/color]

Later,
Dan

Re: Best course [Re: ] #84115
09/06/06 04:08 PM
09/06/06 04:08 PM
Joined: Jul 2006
Posts: 1,147
Bay of Islands, NZ
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warbird Offline
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I agree, cat racing for 90s is a great leg up on this task.

Compasses [Re: Dan_Delave] #84116
09/06/06 06:23 PM
09/06/06 06:23 PM
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Posts: 454
Syracuse, NY Hobie Fleet 204
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Tom Korz Offline
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HCA Rule 16.3 General Rules

Compasses with brackets or electronic devices
that provide timing and heading memory but
which do not transmit, transfer or receive data
are permitted. The use of navigation and speed
metering equipment is illegal unless specifically
allowed in the individual boat rules or by the Notice
of Race for the particular event or regatta.

Compass are OK on any boat!!

Re: Compasses [Re: Tom Korz] #84117
09/06/06 10:37 PM
09/06/06 10:37 PM

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Jake:

Unfortunitly Rick didn't have them on DVD then. I still don't think he does. If anyone want a Tacktick Mirco I will make to a good deal.

Doug

Re: Best course [Re: pbisesi] #84118
09/07/06 08:29 AM
09/07/06 08:29 AM
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_flatlander_ Offline
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Quote
Compasses are allowed per IHCA rule 16.3 and have been for a while.
They can only give a heading.
John:
When they post a compass heading and then do a change mark with the new heading you then know which way the wind is going. That can be handy.


Umm, good point, verifies the shift direction, thanks Pat.

Who's buoy racing a cat with a compass and why?

Dan?...you have one on that jack-rabbit?


John H16, H14
Re: Best course [Re: _flatlander_] #84119
09/07/06 10:55 AM
09/07/06 10:55 AM
Joined: Nov 2003
Posts: 130
CA
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Quote
So who gets out the GPS (with the VMG function) and actually plots the chart for their catamaran? Anyone? Of course you'd need to mount a compass to utilize the findings.


You don't need a polar plot for a GPS to be useful for upwind/downwind training. Velocitek packages the concept nicely, but many existing GPS's can do the same thing (but on a smaller display), when used correctly.

Here's how I make my GPS + compass do the Velocitek thing in a matter of seconds:

Head into the wind or sail dead downwind to get the wind heading. Scroll the GPS map cursor 1000 miles away on this bearing. (My Magellan-based GPSs show the distance and heading on screen as I move the cursor.) Hold down GOTO(MARK) to create a waypoint there and GOTO the new waypoint. Display VMG, and this will give your true VMG to windward/leeward. The only caveats are that the wind may shift, and that the VMG is updated every second or two, which is really too frequent, especially downwind, where you would prefer averages over 15 to 30 seconds, IMHO, since good performance is much more dynamic than just selecting a heading, especially downwind.

Your GPS will now give you objective upwind/downwind feedback for training, and you will quickly learn what the boat feels like when you are sailing your best, so you won't need the GPS or compass to reproduce the performance when racing. And when you're in the fleet, nearby boats serve as excellent performance references.

Re: Best course [Re: Glenn_Brown] #84120
09/07/06 12:02 PM
09/07/06 12:02 PM
Joined: Feb 2006
Posts: 3,348
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fin. Offline OP
Carpal Tunnel
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Since I started this mess, I will take the liberty to get back on course and start a little [censored] at the same time! <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

If you are not an evil techno-demon, bent on destroying the purity of our sacred avocation, with obscene microchips, batteries and wires. How do you choose the best course up wind.

I'd be interested in hearing from the sailors out there, if there are any! <img src="http://www.catsailor.com/forums/images/graemlins/shocked.gif" alt="" />

btw- Egyptian cotton is the only "true" sail cloth!

btwbtw- Mary you should do away with that [censored] thing. It is much too scary and serious sounding. How 'bout [OMG! You won't believe what he said! <img src="http://www.catsailor.com/forums/images/graemlins/shocked.gif" alt="" />]

Last edited by Tikipete; 09/07/06 12:07 PM.
Re: Best course [Re: _flatlander_] #84121
09/07/06 12:15 PM
09/07/06 12:15 PM
Joined: Mar 2002
Posts: 984
2017 F18 Americas Site
Dan_Delave Offline
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John:

I do not have the compass on there but I do have the Velocitek with the VMG model.

I was out sailing so much without other boats to pace with and I liked the concept. This way I can go out and at least get the feel of what the boat angles should be for best direction upwind and downwind. I think it has helped me to know the feel of the boat in many wind conditions. I have not yet raced with the device on the boat. The time that I was going to try it the batteries were dead and I had no extras. I have talked to the designer to try and get one with a readout on both sides so it can be mounted on the boom making it is easier to read and use, but I have not heard back about that project. I do not like to mount it on the spinnaker pole for a couple of reasons. One you have to hit the buttons to set it and if it is way out at the bridles it is a task. The other is that you could wrap a line on it and then....

I have designed and not yet built a mount that would automatically swivel the readout to the new tack. I may be looking at the more closely soon.

I would recommend this device if you are in the position of practicing without others to pace against. I have only used and only care about VMG for practice. Never used the straight line speed function. Do not have the Compass version. May or may not get a Tacktick.

Later,
Dan

Re: Best course [Re: fin.] #84122
09/07/06 12:22 PM
09/07/06 12:22 PM
Joined: May 2003
Posts: 4,451
West coast of Norway
Rolf_Nilsen Offline
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To pick the "best" course upwind, you need to understand what the wind are doing (and will do) over the course. If you can gain this knowlegde, you can pick the shortest and fastest course. Then you will have to decide how many tacks you will need to do, and compromise.

Of course, not many are able to predict what the wind will do accurately enough to win every time. Just look at what Bundy wrote in the "Tiger smack" thread.
If you want a write up on meteorology and wind strategy, you will have to buy some books as the subject is huge. Perhaps you will get some to the point answers if you can be a bit more spesific.

Myself, I find it hardest to pick the right way to go in oscilliating winds and when there are narrow channels of wind. Having incredible boatspeed and perfect manouvers helps a lot when you make a mistake <img src="http://www.catsailor.com/forums/images/graemlins/laugh.gif" alt="" />

Re: Best course [Re: fin.] #84123
09/07/06 12:42 PM
09/07/06 12:42 PM
Joined: Feb 2006
Posts: 3,348
F
fin. Offline OP
Carpal Tunnel
fin.  Offline OP
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Quote
Since I started this mess, I will take the liberty to get back on course and start a little [censored] at the same time! <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

If you are not an evil techno-demon, bent on destroying the purity of our sacred avocation, with obscene microchips, batteries and wires. How do you choose the best course up wind.

I'd be interested in hearing from the sailors out there, if there are any! <img src="http://www.catsailor.com/forums/images/graemlins/shocked.gif" alt="" />

btw- Egyptian cotton is the only "true" sail cloth!

btwbtw- Mary you should do away with that [censored] thing. It is much too scary and serious sounding. How 'bout [OMG! You won't believe what he said! <img src="http://www.catsailor.com/forums/images/graemlins/shocked.gif" alt="" />]


You guys are no fun at all! <img src="http://www.catsailor.com/forums/images/graemlins/frown.gif" alt="" />

Where's Wouter? I'll bet I could start some [OMG! You won't believe what he said! <img src="http://www.catsailor.com/forums/images/graemlins/shocked.gif" alt="" />] with him! <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Last edited by Tikipete; 09/07/06 12:44 PM.
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