Laser Speeds

W

will162878

New Member
Does anybody have speed graphs for a laser (full, radial or 4.7)??
I'm looking to find "polar" graphs of the laser's speed for different wind/boat angles in different conditions. Raw data would be just as good though. Can anybody help or tell me of a website with them on?
 
LASER POLAR DIAGRAMS

Hi, Will,

Those "speed graphs" are referred to as "Polar Diagrams", or "polars" for short.

A "polar diagram" is a particular way of plotting the boat speed generated at all angles to the wind for various wind speeds. (The term "polar" is used because the boat speed curve is plotted using "polar coordinates".)

The short answer is, as far as I know, "no polar diagrams are publicly available for the Laser". (They are available for some other one-deigns.)

Significant "polars" related discussion took place on the NA Laser Mailing List. You can find them by searching the List for "polar" at the URL
http://www.laser.org/archives/
Some initial inquiries actually date back to January 1995! Later attempts at developing a "consensus based" polar diagram (organized by yours truly) date back to 1997.

In 1977, I had contacted all companies that had "Velocity Prediction Programs" (VPP's) that can handle a boat like a Laser. Such a VPP must be able to handle a) a lack of heeling equilibrium, b) planing and surfing conditions, c) Variable lever arms (crew weights and positions), d) By-the-lee wind angles, e ) Variable foil depths. This was a tall order!

Later, I privately tried to get comments, coopereation and participation by various world class designers and sailors (such as designer Frank Bethwaite, Ed Adams - then the US Olympic Team Coach, and Dan Herman from PACT 95's Young America, etc.), but nothing significant materialized apart from an understanding of the complexity of the matter and some informal comments by Herman and Adams, as the development of reliable polar diagrams is an expensive endeavour.

It is interesting to note that all the currently familiar and popular downwind Lasering techniques referred to as "Zig Zagging" or "S-curving" etc. that exploit such Laser speed data were developed following these discussions.

The beginnings of a "Laser Polar" for only the downwind angles was first published on January 8, 1997 on the drLaser web site (then called the "Philadelphia Laserfleet Information Server") based on Adams' remarks. Subjective data collection continued for some period close to a full year.

Later, an unreliable but almost complete Laser polar diagram was used by drLaser to develop in 1998 some "course computers" designed to help RCs and PROs set "proper" triangle or windward-leeward Laser race courses in various wind and current conditions. The resulting course computers are currently available in the "Race Management" section of the drLaser web site.

Finally, a related article titled "Polars, Targets, and Bizarre OCKAM U. Steering Methods" (authored by me) was published on the drLaser web site ("Boat Handling" and "Strategy & Tactics" sections) on 1999-05-21.

Incidentally, Will Richards who asked the question above is a "curious" UK youngster who also initiated a project last year to determine the exact power ratio generated by the Laser mainsheet system! Will: we will not let you dive into new uncharted waters before you complete your old project and publish your results :)

Best regards,

Shevy Gunter
Editor, drLaser
.
 
I know they're called polars - I must have forgotton to write the porper name: I thought that nobody would unserstand what I meant! I have read the OKRAM Bizarre steering before now - thats what gave me the idea.
 
Would this method be of any use. I realize its not the same type of testing / specific data but its accurate enough to give general speed indications for various positions of sail in different winds.

http://forum.laser.org/viewtopic.php?t=86
 
Mounting a speed indicator on your Laser and just going out sailing would give you a "personal" polar diagram, reflecting not the potential of the design, but the current capabilities of the particular sailor.

That is, all strategic decisions about, say, how close to the wind to sail upwind, or whether to gybe instead of sailing by the lee, would reflect all the personal errors in sail and hull trim.

The problem, of course, is not just measuring the boat speed but also the wind speed, the wind direction and the angle of attack of the sail at the moment the boat speed is measured, making such experimental data very hard to collect.

That's why they have VPP's (Velocity Prediction Programs) to determine this information based on boat data.

Bottom line: The approach, if it could be fully implemented, would be much better than the currently available data (mostly based on guesswork and some approximate OTW mesurements). It would at least complement it nicely.

If we could get Robert Scheidt and Roope Suomalainen, etc. to participate in these experiments, then we would of course have data that more closely approximates the potential of the design.

Shevy
 
[quote:f10c232415="drLaser"]Mounting a speed indicator on your Laser and just going out sailing would give you a "personal" polar diagram, reflecting not the potential of the design, but the current capabilities of the particular sailor.

That is, all strategic decisions about, say, how close to the wind to sail upwind, or whether to gybe instead of sailing by the lee, would reflect all the personal errors in sail and hull trim.

The problem, of course, is not just measuring the boat speed but also the wind speed, the wind direction and the angle of attack of the sail at the moment the boat speed is measured, making such experimental data very hard to collect.

That's why they have VPP's (Velocity Prediction Programs) to determine this information based on boat data.

Bottom line: The approach, if it could be fully implemented, would be much better than the currently available data (mostly based on guesswork and some approximate OTW mesurements). It would at least complement it nicely.

If we could get Robert Scheidt and Roope Suomalainen, etc. to participate in these experiments, then we would of course have data that more closely approximates the potential of the design.

Shevy[/quote:f10c232415]


I'll call rob up tonight and we'll drive to your house for some early PA sailing..... :D :D :D

All in good fun.!! :D
 
But surely a relative polar diagram is just as good as an actual one if looking at VMGs etc... So a regular racer proficient in by-the-lee sailing would be a suitable candidate for speed testing?
 
A "relative" polar could surely be useful. Everything beats zero information.

However "relative" is defined (which I still do not understand but do not need to), just lika a normal polar diagram, a relative polar would be useful only if wind (speed and angle) and sea conditions are recorded to some degree of precision with each boat speed observation.

Even qualitative observations on the wind state are better than none.

Otherwise, whether points which are actually on different polar curves (i.e., for different wind speeds) are joined to end up with a hybrid (and false) curve can not be ascertained.

Depending on your location in the UK and the month of the year, it may be quite difficult to catch test days during which the wind speed and direction will stay about constant duringthe tests, without gusts and lulls and oscillations, especially if you are interested in measuring speed not by marine electronics but by practical but slow means such as covering the distance between two fixed buoys.

As conditions change, you will need to catch additional test days to replicate the conditions of previous measurement days, to be able to complete the points necessary for approximating a given (wind specific) polar curve.

(Before the Sydney Olympics, I was told the Australian Laser team, even with high tech windspeed and direction instrumentation, had spent MONTHS on the water to be able collect data under consistent wind and sea conditions.)

One way of minimizing this effort and increasing the reliability of the polar curves is to use multiple boats simultaneously on multiple headings (multiple crossing legs) at each observation session, plus shortening the leg lengths (to 100 m. or less).

If using the multiple boat method, multiple observations recorded after rotating the boat assignments to the spokes of the crossing legs result in significantly more reliable data.

Shevy Gunter


PS. If your sailing area is subject to tidal and/or river currents, measurement becomes much more complicated. The desire to avoid this complication by measuring only during the slack may restrict the time available for measurements to a few minutes.
 
Potentially, I can use 3 boats simultaneously.
The tidal effect is big in the deep water channel but in the areas outside of this, there is less than 0.1kt tide anytime 2 hours each side of each tide.
It is getting late in the year to start such tests but i can try.
If anyone has any data it is of use to me aslong as I know the following:
1) Boat Speed
2) Wind Angle
3) Wind Strength
4) +A quick description of how the data was obtained/estimated reliability.
I know lots of poeple, especially coaches, time boats over set distances to compare speeds, so I know lots of you have this data - not enough for a whole polar but every piece adds to it.
If you have any data of this sort, or even reliable knowledge of what shape the polar curve will be in certain localised areas, please e-mail me:
[email protected]
 
In the last days I did some GPS speed measurements, the environmental conditions were steady winds about 15kt, flat water and no tide. The fastest upwind speeds were about 5.4kt, the hull speed of a Laser is approximately 5kt. Is it possible to sail faster than hull speed on an upwind course ?
 
Just an FYI on GPS speed measurements. Bob Dill knows something about measuring the speed of ice and land yachts (he's been doing it for a few years, and is a principle of the team that holds the current sail-powered land speed record at 116.7 mph - Bob only went 112.3 mph himself). He recently wrote an article for the DN Association's newsletter, Runner Tracks, about the latest technolgy available to mere-mortals:
http://www.idniyra.org/articles/IceboatSailingPerformance.html

While the specifics are targeted at ice and landyachts, the principles are pretty generic.

Cheers,

Geoff S.
DN US-5156/Laser 145234/Renegade 510
 
Hi,

You might be interested to know that Bob Schumacher, working with Dill, is the pilot who holds the land speed record of 116.7 since 1999. He is also the local Laser/Vanguard dealer in Burlington, VT, as co-owner of Canoe Imports for 30 years or so.

116 and on PORT! http://www.nalsa.org/speed_record.htm

Al Russell 182797(bought from Bob yesterday!)
 
Will,

I have a polar graph like you describe. It is in a booklet by Frank Bethwaite that he sent me a couple of years ago. The booklet is titled "Dynamic Advances in the 90's: Sources of Speed: Apparent Wind Sailing". I have emailed Frank asking for permission to scan the graph and post it.

A few data points from that graph (the columns line up using a fixed-width font):

Wind Speed Close Hauled Beam Reach Broad Reach Downwind
6 kts 4 kts 5.4 kts 5 kts 4.1 kts
9 kts 4.8 kts 6.3 kts 6.1 kts 5.5 kts
12 kts 5 kts 7.3 kts 8 kts 6.7 kts

David

David Gardiner, Ph.D.
[email protected]

will162878 said:
Does anybody have speed graphs for a laser (full, radial or 4.7)??
I'm looking to find "polar" graphs of the laser's speed for different wind/boat angles in different conditions. Raw data would be just as good though. Can anybody help or tell me of a website with them on?
Click to expand...
 
With Frank Bethwaite's permission, here is the graph from "Dynamic Advances in the 90's: Sources of Speed: Apparent Wind Sailing" by Frank Bethwaite.

It is in a JPEG attachment.

David
 
can anyone explaintop me how i shud be reading this graph, i don't see where u get the info from, i'm missin something ( my brain probs)
 
Imagine that you are in a helicopter high over a bunch of Lasers that are all together. All at once, the Lasers take off on different points of sail ranging from close hauled to dead downwind, all on port tack, all sailing a straight course. After 1 minute, you take a picture straight down, getting all of the boats in the picture. The starting point is the center of a circle. The positions of the boats are points on a curve. Different concentric circles correspond to different boat speeds - the boat furthest from the starting point after one minute is obviously the fastest.

Curve A is what you would get with 6 knots of wind, curve B is at 9 knots, and curve C is at 12 knots. Sorry - I neglected to include that last bit of information on the graph.

David

144679 said:
can anyone explaintop me how i shud be reading this graph, i don't see where u get the info from, i'm missin something ( my brain probs)
Click to expand...
 
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