| T O P I C R E V I E W |
| blouderback |
Posted - Feb 18 2009 : 11:09:40
So I was reading the latest edition of Boating magazine last night, and saw an article talking about some dude who set the latest sailboat speed record at like 52MPH. They said that he AVERAGED 52MPH over a 500 meter course (or something like that - the exact distances and speed are from memory).
Now, here's the kicker: They said the AVERAGE wind speed at the time was 25MPH.
Can someone tell me how you can get a sailboat to go faster than the wind that's pushing it? |
| 16 L A T E S T R E P L I E S (Newest First) |
| Radioactive |
Posted - Jun 20 2009 : 04:01:03
synchronicity,
Yeah, it IS fun. Too much work for me, but it is a blast. ( Ages ago I sailed a 16, as well as owned/sailed an 18 ft Hobie ). It is also a lesson in "flexible structures". The boat you though was a solid, fixed shape changes shape as the stress increases. This is by design, but that alone is a learning experience. And oh, yeah: Fast. And the boat sings to you... |
| synchronicity |
Posted - Jun 19 2009 : 22:32:21
Up on one hull,
Trapped out on a Hobie reaching it feels like
the vessel is about to take flight - and almost
does as you crest a wake or a wave.
Once or twice, I'll swear that the only thing in the water was the rudder.
|
| delan |
Posted - Mar 01 2009 : 18:47:15
A sail works just like the wing of an airplane, the wind on the front of the sail, sucks the boat forward, in the same way the the airflow across the top of a wing travels faster than the airflow under the wing, and creates lift. The lift on top of an aircrafts wing, lifts the plane. The lift on the front of a sail pulls the boat forward, let's say the windspeed is twenty knots. As the boat accelerates to hull speed, the wind appears to increase, this is the apparent wind speed, it's greater than the actual windspeed.
Then, if you have a sailboat with a planing hull, you're no longer restricted to hull speed, when the sailboat pops up onto the plane, the "apparent" windspeed continues to increase.
One more thing, as the boat moves forward, the wind now appears to change direction, this is the "apparent" wind direction, once again, as speed increases the boat can now point further upwind, or closer. A decent fast displacement sailboat may point up 30 degrees to the wind, where a slower cruiser may not be able to do better than 60 degrees to the wind.
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| saltysam |
Posted - Feb 19 2009 : 16:32:24
I've never seen it in any books but I suspect the squareriggers always knew they could trim their many rectangular sails and head into the wind at greater speeds. The issue of square sails was a big factor when one considers the main worldwide trading routes. The fsmous Orient to England routes were such that the prevailing winds held steady for in generally generaly East-West direction and square sails trimmed to the wind did just fine. |
| lanbuilder |
Posted - Feb 19 2009 : 13:42:20
This web site on world records for wind powered craft has some good information and how it works.
http://www.windjet.co.uk/index.php?option=com_search&searchword=boat |
| Prospective |
Posted - Feb 19 2009 : 12:50:35
I've always thought that one of the greatest advancements of the modern world was when the sailors of square rigged boats learned that they could sail to more points of the compass, and indeed, at faster speeds then the prevailing winds just by angling the sails.
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| JimPend |
Posted - Feb 18 2009 : 20:46:56
Hey, Pascal will a cat go that much faster than the wind. Don't go to the apparant(sp) wind. Just a question, you jumped in on a hydro something. |
| PascalG |
Posted - Feb 18 2009 : 20:32:39
indeed it's not complicated, you quickly get a feel for it. |
| JimPend |
Posted - Feb 18 2009 : 20:27:33
It's not hard Flutterby, it's neat, I love it. |
| Flutterby |
Posted - Feb 18 2009 : 18:01:24
That is why I powerboat. That dang sailin' stuff is just too complicated!
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| stmbtwle |
Posted - Feb 18 2009 : 11:54:20
He's not going DOWNwind; he's going INTO or ACROSS the wind, so the faster the boat goes, the more wind it gets. The boat gets it's power from the RELATIVE wind. At 50 mph in a 25 mph wind he could be looking at a 60+ mph relative wind speed. Lots of power to be had.
Directly downwind is another story; the faster the boat goes the LESS wind, and less power available.
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| JimPend |
Posted - Feb 18 2009 : 11:51:44
The wind doesn't push you unless you are going exactly down wind. Sailing is more complicated than it looks. For instance the fastest point of sail is when the wind is coming from the side (abeam), the boat lists (leans) the most going into the wind or almost into the wind. The sail is an airfoil as they said, unless you are going directly down wind. The boat that did the 52 must have been a cat or as Pascal said. He should know if a cat can go that much faster than the wind, it is not a monohull because hull speed would stop you. |
| saltysam |
Posted - Feb 18 2009 : 11:49:05
Think of an airfoil as in an airplane. The curve atop the wing causes a difference in pressure between the top and bottom foil surface. A sail does the same thing. The differences of pressures cause the sail (attached to the boat)to move the boat towards the top of the curved section. This force generates boat speed. Lottsa references on sails and foils available with GOOGLE. |
| blouderback |
Posted - Feb 18 2009 : 11:32:31
HUH? |
| PascalG |
Posted - Feb 18 2009 : 11:20:34
must have been the Hydropter, it runs on foils and the entire boat is out of the water... interesting project. As bill said, sails are like wings, they generate lift so unless you are going downwind, the lift can be such that you go faster than the wind. |
| Radioactive |
Posted - Feb 18 2009 : 11:11:16
Yes. The sail is an airfoil. |
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