How a Boat Sails in Apparent Wind

Captain John with 25+ years of experience shows you the no-nonsense cruising skills you need for safer sailing worldwide. Visit his website at https://www.skippertips.com and sign up for his highly popular Sailing Tip of the Week. Discover how you can gain instant access to hundreds of sailing articles, videos, FREE e-Books and much more!

How a Boat Sails in Apparent Wind sentiment_very_dissatisfied 33

Sailing 15 years ago 233,494 views

Captain John with 25+ years of experience shows you the no-nonsense cruising skills you need for safer sailing worldwide. Visit his website at https://www.skippertips.com and sign up for his highly popular Sailing Tip of the Week. Discover how you can gain instant access to hundreds of sailing articles, videos, FREE e-Books and much more!

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Most popular comments
for How a Boat Sails in Apparent Wind

Leonardo Po
Leonardo Po - 7 years ago
what about angle of attack?
Captain John's Skipper Tips
Captain John's Skipper Tips - 7 years ago
Leonardo, go here: Genoa Luff Telltales: https://youtu.be/sW9lbZSAMrM
dontrell iommi
dontrell iommi - 7 years ago
? I do not get it at all
Captain John's Skipper Tips
Captain John's Skipper Tips - 7 years ago
Dontrell, did you have a question on the apparent wind video?
jp400motox
jp400motox - 7 years ago
I have been researching designs for building a sailing rig for my kayak. also i need to learn some about sailing before i head out and your simple and to the point explanation here has helped allot. I will probably be sailing mostly rivers so a good understanding of how much into the wind and sail position for sailing into the wind will help allot. Thank you.
Captain John's Skipper Tips
Captain John's Skipper Tips - 7 years ago
Thanks for your comments. Good luck with your kayak!
Jeffrey 1957
Jeffrey 1957 - 7 years ago
Thank you.
Captain John's Skipper Tips
Captain John's Skipper Tips - 7 years ago
You're welcome!
EpicFishFingers
EpicFishFingers - 7 years ago
1:41 in both of those examples the sail is parallel to the wind, so how the hell does the sail move the boat forward when it's directly against the wind? Why wouldn't you turn the sail anticlockwise a bit to tack, or whatever?
Never sailed in my life and I still don't see how you can physically sail into wind, at all.
Captain John's Skipper Tips
Captain John's Skipper Tips - 7 years ago
Most of the flow over the sail creates side force when sailing to windward or on reaches. Lift to windward comes from the keel, which provides lateral (sideways) resistance. This results is forward motion. See this article: http://physicsbuzz.physicscentral.com/2015/05/the-physics-of-sailing-how-does.html
Somendra Kharola
Somendra Kharola - 7 years ago
Hello Sir,

I would be grateful if you could address the following questions:

1. If I wished to set sail in an African dhow (non-motorized) with a fixed lateen sail, in which direction should I point my sail for maximum speed, and in which direction should I point my sail for maximum stability?

2. Is it possible to sail faster than the true wind in such a crude sail-boat (7m in length) if I was to trim my single lateen sail close-haul?

Thanks
Somendra Kharola
Somendra Kharola - 7 years ago
Thank you!
Captain John's Skipper Tips
Captain John's Skipper Tips - 7 years ago
Somendra, on most sailboats, beam reaching will be fastest. I am not familiar with the dhow, but you might keep provisions in the center and low in the boat, the crew to windward, and reef the sail to increase stability. That applies to most boats. Ease the mainsheet if you need to spill more wind in in gusty conditions. On your second question, close hauled sailing is exciting, but not that fast. You are sailing more to the side than ahead (leeway). Reaches are always faster. You can sometimes sail faster than the wind when running (called "surfing").
Max Stevens
Max Stevens - 8 years ago
you are talking about boat wind when motoring and you keep doing so , are you saying this demo is done with the motor running contantly because if the motor is off naturally the boat wind should not be there right. Thanks.
Captain John's Skipper Tips
Captain John's Skipper Tips - 8 years ago
No worries. Glad to help.
Max Stevens
Max Stevens - 8 years ago
Got cha that makes since, forgive me just learning this stuff.
Captain John's Skipper Tips
Captain John's Skipper Tips - 8 years ago
You produce boat wind if you are moving through the water by any means of propulsion. Boat wind is the result of boat speed. So, if your sails are up and you are generating just 1/10th of a knot of speed, you have boat wind. Same with an engine, oars, paddle, etc. Boat wind is simply produced by the forward motion of a boat moving through the water. Whether in a dead calm or raging storm.
Boobe Bee
Boobe Bee - 8 years ago
Why is that when the apparent wind is parallel to the sail it reaches max lift? Is there still pressure difference on both sides of the sail (driving force)?
Ro Ro
Ro Ro - 8 years ago
Captain John's Skipper Tips
Captain John's Skipper Tips
Captain John's Skipper Tips - 8 years ago
You build high pressure on the windward side and low pressure on the leeward side.  The lift component on a sail is quite small. Keep your sails trimmed to maximize lift.  This generates speed and your keel will provide a lot of lift to windward. Sailing is about getting all of your foils working in harmony. The result is a fast boat with less heel and weather helm.
Coast Life
Coast Life - 8 years ago
So... Is apparent wind what happens when true wind and boat wind interact?
Captain John's Skipper Tips
Captain John's Skipper Tips - 8 years ago
Exactly. Apparent wind is a result of boat wind and true wind. Your boat sails in apparent wind. You trim your sails to the apparent wind. There are only two times in sailing when the apparent/true wind line up with one another.: when you are headed directly into the wind (i.e. to hoist or lower a sail or getting stuck 'in irons') and when running dead downwind.

10. comment for How a Boat Sails in Apparent Wind

Mary Cate O'Malley
Mary Cate O'Malley - 9 years ago
Great information.
GaryChap
GaryChap - 9 years ago
Why do you say to angle the boom parallel to the apparent wind.  That's going to flap, collapse and generate no drive forces - only drag. Also, I thought your explanation of 'three winds' rather than 'components' could be a bit confusing to some.

Most of your other videos are truly wonderful. This one just felt a little poor.
john jamieson
john jamieson - 9 years ago
+GaryChap Gary, thanks for your comments. More accurate might be to state to trim the sail to the apparent wind.
Don Monnot
Don Monnot - 10 years ago
Nice explanation, but I see a minor problem with the diagram. If your boom lines up with the apparent wind, you'll be luffing your sail. The boom needs to be pulled in to prevent luffing. It needs to be pulled in to get the leading edge of the sail to be lined up with the apparent wind. How far that is depends on the draft of the sail.
Armando Palha
Armando Palha - 11 years ago
Dear Captain

     Besides your simple and highly effective explanations I love the drawings showing the events.
   I wish I had it on a single dvd
   Thanks, Cap
Armando Palha
Captain John's Skipper Tips
Captain John's Skipper Tips - 11 years ago
Armando, thanks much for your comment. I have been thinking about doing that. Perhaps this would make a good project for the new year. 
Best - Captain John
Captain John's Skipper Tips
Captain John's Skipper Tips - 11 years ago
Thanks for your comment!
Bugod i
Bugod i - 11 years ago
Great vid
Adnan Medic
Adnan Medic - 11 years ago
Good videos my friend ...
rs8684
rs8684 - 11 years ago
Captain John, I know the masthead fly shows the APPARENT wind. But where is the TRUE wind, when sailing, in relation to the masthead fly while moving? I assume that if the wind is forward the beam, it is in front (toward the nose) of the indication of the fly, but if the wind is behind you, then the true wind is aft of the direction of the fly. But I've never been sure, and I can't comprehend it in my head...
rs8684
rs8684 - 11 years ago
When I am out sailing, I am always confused with where my masthead fly points - is the true wind before the fly or after the fly? I have a hard time figuring that one out.
spelunkerd
spelunkerd - 11 years ago
I didn't expect to learn anything in this video. But, to my surprise, it clarified the important detail about how the sail actually works. Good job!

20. comment for How a Boat Sails in Apparent Wind

Hayden
Hayden - 11 years ago
thx for the video this helped me a lot. I am learning how to sail right now I got my first boat a few weeks ago after helping my dad sail his boat for 10 years I figured it was time to get my own so I got a 19 foot y flyer and fixed it up. its a fast boat!
Angus McIntyre
Angus McIntyre - 11 years ago
'Similar' is an understatement. Wings and sails use exactly the same principals to generate lift. One just happens to be made from cloth...generally. Consider the solid 'wing sails' on the AC72s!
Frank Newcomb
Frank Newcomb - 11 years ago
Oh ya ok ,so my boom should line up with the flag then ,thank you for that : )
Frank Newcomb
Frank Newcomb - 11 years ago
I put a small flag on top on the mast so all i have to do is look up for TW .
Nautical PappyStu
Nautical PappyStu - 11 years ago
It sounds like you are saying the sails work like a wing of an aircraft rather than being pushed along, (note: I'm a power guy not a sail one so on a learning curve even with 40 plus years on the water LOL)
DrTTube
DrTTube - 13 years ago
Awesome, thanks!
frank0067
frank0067 - 13 years ago
lol .. man in all my years i never yet seen anyone who could teach how a one sails against the wind.. they ALways suppose the wind is in back pushing where ya wanna go.. well how about if where ya wanna go is straight against the wind?
Pedroskini
Pedroskini - 13 years ago
Love the videos. Thanks for making them and sharing them.
rusty keller
rusty keller - 14 years ago
There's a fourth kind of wind. That's the wind that blows when your Captain is speaking! Actually, I enjoyed your presentation. I've been sailing for a long time, and I found your description of wind effect very knowledgable and helpful. Thanks.
gkel365
gkel365 - 15 years ago
Great explination...Thanks for your help. Keep up the good work

30. comment for How a Boat Sails in Apparent Wind

ZipTumbleFast
ZipTumbleFast - 15 years ago
This video will totally changed my sailing habits. For whatever reason, I have always thought the main had to be perpendicular to the apparent wind (or as close as possible). What an eye opener. Oh, and I joined your SkipperTip site too. Thanks!

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