How fast ?

[JoeVacs]

I dont quite understand hull speeds etc, however i regulary see 7 knots on my 26S in only 17-20 knot wind and have seen on occasions 11 knots..noy many people beleive me but i think my gps is quite accurate.

Also i have raced my mate who has a 26X 2002 and he cant keep up with me..

Dont know if thats of any use??

Madguy

Your GPS speed is how fast you're moving across the globe, not how fast you're moving in the water. If your hull speed is 6knots you aren't going to go any faster than that. If the current or water speed is running at 5 knots and your in the stream, you could in theory be going 12 knots on your GPS, but your actual speed through the water is still only hull speed. Here's a hull speed calculator
http://www.sailingusa.info/cal__hull_speed.htm

Also Knots and miles per hour are not the same, and all the GPS I've seen show mph not knots. http://www.grc.nasa.gov/WWW/K-12/WindTu ... s_mph.html

Ive managed to figure out what the actual speed is taking into consideration the speed of current etc,,however. i sail on an inland man made lake.. taking this into consideration and the fact that there is no current are you then saying that my gps is incorrect in telling me that i am travelling at 11 knots when there is no current to consider. and if my hull speed is only 6 knots i therfor cannot sail at anything more than 6 knots under any curcumstances??...

My gps is the standard horizon cp180i which gives the speed ov the vessel in knots as far as im aware!!

Just want to clarify??

Maadguy

Hey dude, don't get "mad" at me. I'm not questioning the speed of your boat. I was just trying to be helpful with information that I have read, by people that are much smarter and more qualified than me on these matters. If you don't believe their findings, take it up with them, or better yet, thumb your nose at 'em as you pass 'em on the water in your speedy little boat.

[bubba]

Is your S setup for crusing. Are you carring the same gear ( weight ) as the X , food, water, extra anchors, ect ??

[DaveB]

I always refer to speed on water as Knots but since this post was in MPH I didn't want to confuse anyone. But you are correct. for 6.1 knots equals 7 mph.
Why all sailers should be useing Knots instead of MPH when posting or on the water.
Dave

D's and S's hull speed is around 6.2 mph but they well exceed that often.
In 15 knots of wind on a broad reach can exceed 6.8mph and can do 7.2mph or more surfing....

Dave do you mean knots? I've seen 6.5-6.8 knots quoted different places for the hull speed on S and D's. That would be 7.48 mph to 7.83 mph.

While that S is running circles around you, you are probably down below standing up walking around making lunch, while is is all hunkered over down there trying to put a peanut and jelly sandwich together ,

Sum and Ruth (owners of a spacious (not) S)

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[Sumner]

..............6.1 knots equals 7 mph.
Why all sailors should be using Knots instead of MPH when posting or on the water....Dave

I'm trying to think in knots more and nautical miles, but it is hard as my mind is still pretty tied into mph and miles, and if you happen to be from north of the 49 and younger it will be KPH and Kilometers. Now if you are from up there and older you might still have some of the MPH and miles in the back of the head to deal with also.

c ya,

Sum

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[Boblee]

Mostly our chartplotter is set at knots but occasionally I switch it to kph to get relevance but as has been already said when the tide changes or the wind comes up it pays to switch to the paddle on the transducer instead of satelite signals if you want to get a closer idea of how your boat is performing.

[madguy]

Your GPS speed is how fast you're moving across the globe, not how fast you're moving in the water. If your hull speed is 6knots you aren't going to go any faster than that. If the current or water speed is running at 5 knots and your in the stream, you could in theory be going 12 knots on your GPS, but your actual speed through the water is still only hull speed. Here's a hull speed calculator
http://www.sailingusa.info/cal__hull_speed.htm

Also Knots and miles per hour are not the same, and all the GPS I've seen show mph not knots. http://www.grc.nasa.gov/WWW/K-12/WindTu ... s_mph.html[/quote]


Ive managed to figure out what the actual speed is taking into consideration the speed of current etc,,however. i sail on an inland man made lake.. taking this into consideration and the fact that there is no current are you then saying that my gps is incorrect in telling me that i am travelling at 11 knots when there is no current to consider. and if my hull speed is only 6 knots i therfor cannot sail at anything more than 6 knots under any curcumstances??...

My gps is the standard horizon cp180i which gives the speed ov the vessel in knots as far as im aware!!

Just want to clarify??

Maadguy [/quote]

Hey dude, don't get "mad" at me. I'm not questioning the speed of your boat. I was just trying to be helpful with information that I have read, by people that are much smarter and more qualified than me on these matters. If you don't believe their findings, take it up with them, or better yet, thumb your nose at 'em as you pass 'em on the water in your speedy little boat. [/quote]




Hmmm.....

Im a bit confusede now.....not really sure why you think im mad with you, im just trying to give all the information i have to get the correct information to go forward with..
i know that when i was sailing on a river and the current was moving at apox 5 knots and i was travelling with the current my gps said i was doing 9 knots therefore i know i was doing actual 4 knots...

what i didnt understand is when i sail on a lake with what i thought was no current and i got 11 knots for over 4 mins constant that i cant be doing actual 11 knots...

or is my 21 year old scuba diving nickname "Madguy " that you find threatening???

i didnt think the way i wrote my comments were offensive, abusive or in a harsh manner and can only opoligise if you took it that way.

Madguy

[Nautek]

Hi Madguy

Please read my post over page re currents in a lake

Allan

[kadet]

A GPS is a great tool but do not take them as gospel.

They are affected by many many things, Atmospheric conditions, signal reflection, interference, availability of satellites etc.
Mine constantly tells me I am at 45metres altitude when it is mounted on top of my s helm which is about 2.5 metres above sea level. As for the post that said most GPSs only measuring miles go into the settings they can normally be configured for any unit you choose, miles. knots, kilometres.

Madguy of more interest is in what conditions, point of sail, and how much canvas did you have up to get this 11 knots. I don't doubt that a Mac could reach 11 knots given they are a planning hull and not restricted to hull speed. IMHO it is the conditions that would allow for 11 knots would be bloody terrifying.

[madguy]

OK. the day i saw 11 knots on my gps.

There were about four of us ready to launch, my 26s, a26x a Janeau 21 and a benatue about 22ft.

The day was very windy averaging between 28-35 knots(on my nasa2 wind vane at mooring). we decided that we would still go out even though most were staying off the water.

we got into a little bit of a race(as you do) so i rolled out all the canvas i had.( i know very stupid)
150 genoa full out. full main. keel up motor out of the water and a very empty boat with just me and the missus onboard.the wind was coming from about 4-5 o,clock, (not quite a run, sorry cant remember the name for it) when the wind gust rose to about 45 knots. we hung on for dear life and ran the lenght of the north arm( appox 5 k) in no time..watching the gps and reached 11 knots for about 4 mins.

I left the 26x by quite away but the janeau 21 was off like a greyhound.

he said he had two instruments giving him a reading of 12.3 knots and the 26x said he got 9.1 fastest.

we have to admit that it wasnt a good day to sail as it was far to windy however the wind was sitting about 8 ft off the water which seemed very calm considering the wind.

Cant really say much more than that. ive not been sailing to long so dont know all the technical jargen. i do know that i would,nt choose to go out in that again but it was an adrenalin rush at the time.


hope this makes some sense to someone, im still trying to figure out what all the buttons do hence the reason for trying to clarify information so i can understand it.

Madguy

[JoeVacs]

Hey "Madguy" I was just having a little fun with your screen name. Not offended or threatened. Just a poor attemp at humor

[kadet]

Yep that would do it as I said terrifying though hopefully on small man made enclosure you were not facing 3-4 metre waves as well

[Sumner]

........... I don't doubt that a Mac could reach 11 knots given they are a planning hull and not restricted to hull speed. IMHO it is the conditions that would allow for 11 knots would be bloody terrifying.

The "S" is a displacement hull unlike the X and M that are planning hulls. I think under the right conditions like he has mentioned it must be possible for an S evidently to go that fast. It would be about 3 1/2 mph over the hull speed. The shape of the waves that were running more or less with him might have also helped.

c ya,

Sum

[DaveB]

Go for MPH, makes you think your moveing faster!
Dave

..............6.1 knots equals 7 mph.
Why all sailors should be using Knots instead of MPH when posting or on the water....Dave

I'm trying to think in knots more and nautical miles, but it is hard as my mind is still pretty tied into mph and miles, and if you happen to be from north of the 49 and younger it will be KPH and Kilometers. Now if you are from up there and older you might still have some of the MPH and miles in the back of the head to deal with also.

c ya,

Sum

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[DaveB]

28-35 knots of wind will knock you down in any sail area more than 40 sq. ft.
When the wind rose to 45 Knots you would be knocked down under bare poles in a Mac.X and most trailerable sailboats.
Are you cranking My Tractor or yours?
Dave

OK. the day i saw 11 knots on my gps.

There were about four of us ready to launch, my 26s, a26x a Janeau 21 and a benatue about 22ft.

The day was very windy averaging between 28-35 knots(on my nasa2 wind vane at mooring). we decided that we would still go out even though most were staying off the water.

we got into a little bit of a race(as you do) so i rolled out all the canvas i had.( i know very stupid)
150 genoa full out. full main. keel up motor out of the water and a very empty boat with just me and the missus onboard.the wind was coming from about 4-5 o,clock, (not quite a run, sorry cant remember the name for it) when the wind gust rose to about 45 knots. we hung on for dear life and ran the lenght of the north arm( appox 5 k) in no time..watching the gps and reached 11 knots for about 4 mins.

I left the 26x by quite away but the janeau 21 was off like a greyhound.

he said he had two instruments giving him a reading of 12.3 knots and the 26x said he got 9.1 fastest.

we have to admit that it wasnt a good day to sail as it was far to windy however the wind was sitting about 8 ft off the water which seemed very calm considering the wind.

Cant really say much more than that. ive not been sailing to long so dont know all the technical jargen. i do know that i would,nt choose to go out in that again but it was an adrenalin rush at the time.


hope this makes some sense to someone, im still trying to figure out what all the buttons do hence the reason for trying to clarify information so i can understand it.

Madguy

[Sumner]

Go for MPH, makes you think your moving faster! Dave........

That is why I hate meters when you refer to elevation. What sounds more impressive when talking to some one, "I climbed a 3962.4 meter mountain or I climbed a 13,000 foot mountain." I realize once you get use to it 3900 meters probably sounds high, but I'm not use to it......yet .

Same thing about temperatures. When it is really hot say in Phoenix you can say I was out in 115 deg weather yesterday vs. I was out in 46 deg weather (Celsius). Heck at 46 I might still have my long johns on.

We were out in the Mac in over 50 mph winds, but at the time..........

http://purplesagetradingpost.com/sumner ... ll-09.html

........... we were tied to shore with four shore lines and the dingy was flying up to the life lines. We still weren't sure things were going to hold.

We are still green and when the wind gets over about 20 knots (noticed I used the right term) our sails usually come down and we are on the motor looking for shelter. Now saying that I'm hoping this next year to have the boat setup where if the wind is higher that that we can at least sail to shelter if the motor wouldn't work for some reason or there was no place close to go to.

c ya,

Sum

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