Recently I have read interesting article in a sailing world, It was about the best boat I have ever seen, Mari-cha IV Well it mentions a boat speed; “Mari-Cha had two reefs in the main, two in the mizzen, and a tiny Code 4 headsail in 25 knots of breeze. Boat speed was 28 knots.” Does any one can explain how that works? I have to mention that Mari-Cha is a monohull.
- Status
- Not open for further replies.
M
Mark Burrows
From Someone Smarter than Me (I?)
Your question has to do with a phenomenon called apparent wind. Apparent wind is the wind you feel on your face as you move forward. True wind is the wind that is blowing naturally. If you can imagine riding your bicycle on a day when there is no wind whatsoever, you still feel wind on your face (apparent wind) and it gets stronger as you go faster. That is because your forward motion is creating its own wind. If you were to ride your bike on a day when there was a 5 mile per hour wind behind you and you were pedaling at 5 miles per hour, the two winds (true and apparent) would cancel each other and you would not feel any wind at all. Boats that are able to sail faster than the true wind are "creating their own wind". Generally these are fast catamarans and iceboats, although some racing monohulls may be able to achieve this. The apparent wind is the wind that the boat sails in. Usually, you can sail faster at 70° to 80°off the apparent wind (called a "close reach") than you can with the wind directly behind you. This is because you can trim the sails so that the wind flows over them to create a lift, much like an airplane wing, that propels the boat. There is a positive force against the inside of the sail, and a negative force pulling the outside of the sail. (You can try this by holding your hand out of the window of a moving car (With your parent's permission, please!). Rotate your hand to feel how the wind pushes and pulls on it at different angles.) Under optimum conditions, the apparent wind is greater than the true wind. Let's say you are on a fast catamaran and sailing in a true wind of 10 knots. By moving very fast through the water you may be able to create an apparent wind of 20 knots which may allow you to sail at 12 to 13 knots, which is faster than the true wind. (Friction will keep you from moving as fast as the apparent wind.)
Your question has to do with a phenomenon called apparent wind. Apparent wind is the wind you feel on your face as you move forward. True wind is the wind that is blowing naturally. If you can imagine riding your bicycle on a day when there is no wind whatsoever, you still feel wind on your face (apparent wind) and it gets stronger as you go faster. That is because your forward motion is creating its own wind. If you were to ride your bike on a day when there was a 5 mile per hour wind behind you and you were pedaling at 5 miles per hour, the two winds (true and apparent) would cancel each other and you would not feel any wind at all. Boats that are able to sail faster than the true wind are "creating their own wind". Generally these are fast catamarans and iceboats, although some racing monohulls may be able to achieve this. The apparent wind is the wind that the boat sails in. Usually, you can sail faster at 70° to 80°off the apparent wind (called a "close reach") than you can with the wind directly behind you. This is because you can trim the sails so that the wind flows over them to create a lift, much like an airplane wing, that propels the boat. There is a positive force against the inside of the sail, and a negative force pulling the outside of the sail. (You can try this by holding your hand out of the window of a moving car (With your parent's permission, please!). Rotate your hand to feel how the wind pushes and pulls on it at different angles.) Under optimum conditions, the apparent wind is greater than the true wind. Let's say you are on a fast catamaran and sailing in a true wind of 10 knots. By moving very fast through the water you may be able to create an apparent wind of 20 knots which may allow you to sail at 12 to 13 knots, which is faster than the true wind. (Friction will keep you from moving as fast as the apparent wind.)
L
larry w.
A
Alan
Mark is right, except
..for a small error. He said,"Boats that are able to sail faster than the true wind are "creating their own wind". In fact, all boats create wind as long as they are moving. The difference is the amount of wind. Mari-Cha makes so much wind that she has no need for a spinnaker. A spinnaker is a downwind sail and she never sails downwind, her apparent wind is always forward of the beam and therefore needs no spinnaker.
..for a small error. He said,"Boats that are able to sail faster than the true wind are "creating their own wind". In fact, all boats create wind as long as they are moving. The difference is the amount of wind. Mari-Cha makes so much wind that she has no need for a spinnaker. A spinnaker is a downwind sail and she never sails downwind, her apparent wind is always forward of the beam and therefore needs no spinnaker.
F
Fred Ficarra
Wow, this was a first (for me)
Did anyone tune in to this thread earlier. It was rude. Phil took it out. *x
Did anyone tune in to this thread earlier. It was rude. Phil took it out. *x
B
Bob
J
Jeff M.
HOLY COW!!!
Thanks Bob, for the Harken link. Now that's a boat! Can you imagine? 525 miles in 24 hours! That must be one serious adrenaline rush. Soon as I win the lottery I'm definitely gettin' me one of those!
Thanks Bob, for the Harken link. Now that's a boat! Can you imagine? 525 miles in 24 hours! That must be one serious adrenaline rush. Soon as I win the lottery I'm definitely gettin' me one of those!
J
Jack
Harken claims 40kts
This is nearly 3.4 times the square root of the waterline length even if LOA is all waterline. This seems like a real stretch. 28 knots would still be 2.36 LWL.
This is nearly 3.4 times the square root of the waterline length even if LOA is all waterline. This seems like a real stretch. 28 knots would still be 2.36 LWL.
F
Fred Ficarra
S
Steve
Now that IS Equipped
Yeah, I will write a check out of "petty cash"! Interesting thing is that that boat can go faster than most power boats! So much for the "blow boat - slow boat" image of sailing boats. Only way someone can afford something like that is to win races with it an have a company like Harken put it together financially and equip it! Beautiful! Steve
Yeah, I will write a check out of "petty cash"! Interesting thing is that that boat can go faster than most power boats! So much for the "blow boat - slow boat" image of sailing boats. Only way someone can afford something like that is to win races with it an have a company like Harken put it together financially and equip it! Beautiful! Steve
B
Bob
There is a story from squarerigger days
that the standard ships carried logs that would read to 12 kts, and the clippers ones good for 16. One blustery night the first mate on a clipper was checking the ship's speed so it could be entered in the logbook. He tossed the "log" off the stern, started the 30 second "glass", and watched the line as it zinged off the reel. Just before it hit the stop he handed the reel to a Chinese steward who was standing on the poop beside him. The terrific pull of the line was more than the poor steward could counteract on the wet deck, and he began slipping toward the after rail. Knowing that to let go of the reel was an unforgiveable offense, he held onto it as he was swept over the rail and fell into the ship's wake. Meanwhile, the mate calmly walked over to the binnacle, where the captain asked him what speed they were making. His reply was classic: "16 knots and a chinaman, sir."
that the standard ships carried logs that would read to 12 kts, and the clippers ones good for 16. One blustery night the first mate on a clipper was checking the ship's speed so it could be entered in the logbook. He tossed the "log" off the stern, started the 30 second "glass", and watched the line as it zinged off the reel. Just before it hit the stop he handed the reel to a Chinese steward who was standing on the poop beside him. The terrific pull of the line was more than the poor steward could counteract on the wet deck, and he began slipping toward the after rail. Knowing that to let go of the reel was an unforgiveable offense, he held onto it as he was swept over the rail and fell into the ship's wake. Meanwhile, the mate calmly walked over to the binnacle, where the captain asked him what speed they were making. His reply was classic: "16 knots and a chinaman, sir."
- Status
- Not open for further replies.