Top Speed?

David

New Member
I'm just wondering, whats the highest speed achieved in a laser? the only way to find this (that I can think of) is to take a handheld GPS with a speedometer on it, and put it in in waterproof container, then go sailing

Has anybody tried this?
I would, if I had a GPS :(
 
Howdy Ya'll
Now this is a subject I like, Perhaps this winter I'll get a chance to find out how fast a Laser can go (or me in a Laser anyways). I've got the hand held GPS and I'll need a good blue norther with 30-40 mph winds, the hard part will be finding flat water along with high wind to get the highest speed possible. Also what will be even harder will be trying to read the small screen on the hand held while on a screaming reach and still keep the boat under control. I was out this last Sunday on the Intercostal canal, it was blowing 25ish or so, and the water was pretty darn flat, darn good time broad reaching back and forth.
Check ya laters,
FishingMickey,
178894/150087
 
GPSes (and esp. the hand-held units) are quite prone to false readings. There was an excellent article in the May 2004 IDNIYRA (DN iceboat class association) newsletter on the topic by Bob Dill (who has spent some time measuring the speed of sail-driven craft - including his own 108 mph land-speed record). Unfortunately, the article isn't on-line, but the synopsis is pretty simple: don't rely on any single reading. Bob suggests using a GPS that can collect a series of data-points (i.e. a track), downloading them to a computer and throwing out any outliers before celebrating.

Cheers,

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

http://www.nalsa.org/speed record.htm
http://www.nalsa.org/Sept_News/spdreg.html
http://www.nalsa.org/nov_99_newsletter.htm
 
I've heard the laser's top speed is about 12 knots. I learned this from a Tornado sailor, who also told me the top speed of his boat: 33 knots UPWIND!!!!!!!!!!!
 
Well, it's not a cat, but it sure as hell isn't a keel boat either!!! Maybe the Laser 28 top speed is 12 knots, but I even doubt that in the right conditions. Tell your Tornado friend to try a Laser in something over 15 knts of breeze. He'll be surprised.

MCneill said:
I've heard the laser's top speed is about 12 knots. I learned this from a Tornado sailor, who also told me the top speed of his boat: 33 knots UPWIND!!!!!!!!!!!
 
I have driven many boats (motorized) with spedometers on them, and I can assure you I was going much faster than 12 knots in the 35 knot winds last week, seemed more like 20.
 
I was clocked at 19knots by the local Wildlife Commission, he pulled up beside me at a full plane and asked if I needed assistance, I smiled and asked how fast I was going, he said 19 knots. :D
 
i was sailing in about 35 knots of wind gusting at 40 and i swear i was going about 15-17 knots and it really sucked when my tiller extension fell off.
 
My guess would be around 14 knots, I look at the speed the swell is moving at, when I am overtaking it downwind i would guess I am doing slightly better then 14knots, not a very accurate system. When are we going to get some real data?:) GPS should be accurate enough for our purposes, most units these days use parallel satelight tracking, up to 12 at once though it is unlikely to track 12 at any one time, more like 8. Some cheap GPS receivers use serial tracking, not much use for velocity measurement.
A Tornado goes upwind at about 15knots, 33knots is downwind.
 
I think one of the most accurate ways to measure your speed would be to have a powerboat tailing you. I really want to try this now, it'd be interesting to know how fast you're moving.
 
i think the only way to be fully accurate is to use the US Military's GPS because they are the ones who own all the GPS satellites & they have made the GPS's that we get not as accurate as theirs, but i doubt we will ever get to use their stuff! ha ha ha ha.
mmm, if you were to use a powerboat that was tailing you, they have to have their speedo calibrated. i dont think there is any 100% accurate way of measuring the speed, but you can probably get pretty close.
just my 2 cents worth.
 
I sailed about 12 miles last week with the tide in a force 5 and it took about an hour, so i can tell you that 12 knots is easy.

and great fun.
 
Mmm, this is what they tell us, but still, our GPS's that we buy from the shop aint going to be as good as theirs, i only put that in for a joke anyway (thats why i put the ha ha ha at the end of that sentence). yes, ours might be close, but it will never be as good, unless we can afford the stuff that they get & i doubt we would be able to get it because it would be top secret stuff.
 
Some time a go the USMO, removed the time error for the Coarse Acquisition mode of GPS. This meant the commercial time signals, and hence GPS precision was the same as the encrypted time signal used by the US military and other allied organisations.

Your hand-held Garmin, Magnavox or other commercially available GPS can be used to accurately positions vs time information, and can therefore be used to measure speed. One point to remember though, GPS measures speed across the Earth, not speed through the water. If the body of water itself is moving across the Earth, GPS will include this speed vector as well. This will distort any measurement of the speed of the laser through the water, which is the important number sought.

For informatin on GPS etc, try:
http://www.navcen.uscg.gov/gps/default.htm
http://tycho.usno.navy.mil/gps.html
http://www.exn.ca/FlightDeck/News/story.cfm?ID=20000502-53
http://www.wsrcc.com/wolfgang/gps/accuracy.html

and there are many, many more..

Puft 'n' Stuft
 
mm, you still forget what i am saying, because the us mil has done a shit load more research & development into making accurate GPS's the ones that we can buy aren't as accurate compareds to theirs. even with their really accurate stuff, they still can't drop bombs accurately. always like 10-20 ft off, this may not seem big to us, but it can mean, depending on the type of bomb that it doesn't hit the intended target. ohh & they can still make your readings inaccurate by creating an error, but this only happens when they are at war & bombing places, such as iraq.
i have done a ton of researching GPS's cause i did a school project on them.
 
yachtie2k4 said:
...the ones that we can buy aren't as accurate compareds to theirs...

Once the time signal has been transmitted by the satellite, it is as accurate as its going to get. The only way it becomes inaccurate is for someone to interfere with the signal (jamming / spoofing) or for the signal not arrive 'cleanly' at your reciver antennae (multipath interference etc). Every GPS unit measures the error between the received time signals, and by knowing what satellite the signals come from and the almanac data of that satellite, the position can be calculated. Every unit (except the really really cheap units) will have the same precision. If you want a full precision GPS unit you only need to buy one from the local chandler; some of the cheaper versions dont have the same precision because they don't calculate the time error to the same number of decimal places as the expensive ones!

yachtie2k4 said:
...always like 10-20 ft off...
If you are dropping 1000lbs of HE, the 10-20ft that you missed the target by will fail to exist the instant the weapon detonates.

yachtie2k4 said:
...i have done a ton of researching GPS's cause i did a school project on them...
whereas I just navigate for a living!
 
man, that only means that people in australia aren't allowed to jam them, but anywhere else people are ha ha ha suck on that. i see that there are a lot of other people that aren't from australia on this forum.
 
my father has a high end garmin hand held GPS and when were driving down the highway it is more acurate than the spedometer on teh actual vehical, plus it is able to tell me exactly how high i am above sea leval (pretty cool when going up a hill) and the leval of incilne were on...... so i would lay my trust in it
 
Wow....

A lot of misinformation has been spread regarding the use of GPS....

From a guy who makes his living with one.....


There are basically 2 kinds.... The smaller handheld units which vary in price from $180Cdn to $1800Cdn. They measure the time difference in broadcasted clock signals from each of the sattellites to triangulate your position. (yes, it is slightly more complicated... but this is essentially what they do).

Then there are the larger, more expensive, survey grade units which lock onto the satelites the same way, but then count wavelength differences in the carrier signals to improve the accuracy of the measurement. these units start at about $40,000Cdn, and do not give real time positional accuracy... so I assume that everybody is using the former kind.


Selective Availability is the US governments name for their control of how many decimal places are broadcast on the time signal. They can allow users to receive very accurate information, or heavily rounded off information. The only difference between US military GPS units, and the ones I can buy at Walmart, are that theirs read the 'scrambled' time signals to full decimal precision.


There are also several methods to "correct the signal", using differences in position at a known point receiving the same signals to 'move' the reading in individual units.....


But for speed calculations: The GPS unit calculates speed just like everything else in the world. The Difference in distance between 2 points, divided by the difference time it took to get there. If the points are 20m out of whack form real world coordinates, it does not matter. They will both be 20m out of whack. In this way, the 'relative' accuracy of the 2 readings is good, and GPS is the best way ever to calculate speed. Especially if you can average the speeds over say 300 different points in a 5 minute span.


Wabbit is the only one here with a valid point. If you are riding a current... you will only get a speed relative to the earth, not the body of water you are riding. But hey.... just ride the current in several different directions, and average your speeds......

I sail on a lake, so it does not matter.

I also sail very poorly, and slowly (hey, I am a beginner), so any speed I measure would be WAY off (of the Lasers max speed)

I just had to register and post on this, however..... as I hate to see popular misconceptions about GPS spread accross the internet.



Fantastic site, by the way.... I have learned an immense amount about my boat from you guys. Pretty much every question I had concerning rebuilding my old laser was answered here..... as was everything I could possibly want to know about saling it....

(yet I still can;t seem to gybe without dragging my boom through the water and capsizing.... what's up with that?)
 
mmm, you cant gybe without draggin your boom, you need more practice. practice doesn't make perfect, perfect practice makes perfect he he he :p but what is perfect practice?
 
Darryn said:
Concentrate on holding boat flat during gybe, cross the boat as the boom swings through


Those sound like good ideas...

What I usually end up doing instead, is:

Cower on the floor of the boat, desperately trying to avoid getting smacked by a swinging boom (I became kinda 'boom-shy' my first few outings)...

Consequently, when the boom does swing over, I am slow to get to the other side for weight, unable to sheet in effectively, and slow on the rudder. So, the sail swings from wide angle on one side of the boat, to a wide angle on the other, which, combined with my poor tiller control starts the boat heading straight up on the new tack.

Luckily, it never makes it straight up into the wind. The sail crosses a point where the wind is perpendicular, heeling the boat far over. In a panic, I usually let out too much sheet, which drops the boom into the water, which then starts acting like a rudder keeping the boat on its course (with sail perp to wind, heeled right over, too much slack in sheet now to recover)...

This is usually where I drop the tiller extension to start grabbing handfuls of sheet while sitting on the rail of the boat looking down at the sail.


eventually, I right the boat, swim back around, climb in, and sail off on the new tack.


Eventually I will work out the timing on when to cross the boat under the boom.... other people make it look SOOO easy.

But this probably belongs in another thread.
 
Try double handed sheeting to initiate the gybe, this will also stop the sheet snagging on the transom corner, drop the sheet once the gybe starts. Once you get the hang of it stop dropping the sheet and hike out on the new windward side for a nice speed increase, deadly if you mess it up though.
 

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