Hardest Part Of Learning To Sail

Nov 8, 2010
11,385
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
BTY: Someone earlier suggested the concept of lift was difficult. I would suggest the only reason it is difficult, is that every diagram trying to explain it, is simply wrong. All diagrams show lift with the arrow on the leeward part of the sail, which implies something (wind) is grabbing onto the sail and pulling it. Lift always comes from the windward side and is pushing against the sail. What happens on the leeward side is only an absence of pressure.
Huh?? That is EXACTLY how lift works in sail.

The lift force vector is absolutely on the leeward side of the sail. The fact that is ahead of the beam allows the boat to move forward.
 
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Apr 16, 2017
841
Federation NCC-1701 Riverside
BTY: Someone earlier suggested the concept of lift was difficult. I would suggest the only reason it is difficult, is that every diagram trying to explain it, is simply wrong. All diagrams show lift with the arrow on the leeward part of the sail, which implies something (wind) is grabbing onto the sail and pulling it. Lift always comes from the windward side and is pushing against the sail. What happens on the leeward side is only an absence of pressure.
IMG_20181125_202114.jpg


Hardest part of sailing is knowing when you are being hustled.

There is a spectrum between all drag and mostly lift. The lifting sail is pulled like th...forget it. Google it
 

weinie

.
Sep 6, 2010
1,297
Jeanneau 349 port washington, ny
Both arguments are somewhat correct and somewhat incorrect.
The best source I've seen to clarify this is here.
There are several pages here... make sure to click next at the bottom.
https://www.grc.nasa.gov/www/k-12/airplane/lift1.html

Note a couple of the pages talk about incorrect theories and particularly why the simplified bernoulli explanation is incomplete without taking into accounts newton's 2nd law.
 
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Nov 8, 2010
11,385
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
Both arguments are somewhat correct and somewhat incorrect.
The best source I've seen to clarify this is here.
There are several pages here... make sure to click next at the bottom.
https://www.grc.nasa.gov/www/k-12/airplane/lift1.html

Note a couple of the pages talk about incorrect theories and particularly why the simplified bernoulli explanation is incomplete without taking into accounts newton's 2nd law.
What argument are you talking about??
 
Oct 19, 2017
6,936
O'Day 19 Littleton, NH
Daveinet makes a good point about the diagramming of lift being problematic for beginners. However, that is typical for a force diagram. Arrows are used to represent the direction and magnitude of the force, not necessarily the origin. They are placed at the central point of mass to show the effects of the force on that mass. In the case of an explanatory diagram for lift, they choose to place the arrow's origin at the outer curve to help suggest that is where the action is. But, it takes both the lower pressure surface and the higher pressure surface to achieve lift.
Lift is achieved because there is a difference in pressure on one side of the sail from the other. The explanations are generally designed to show how there is a drop in pressure over the convex surface dispite the apparent compressing of air across the that surface. They teach as if that surface is the only surface that matters. The concave surface can't experience the same drop or there would be no sum difference between those two sides and lift wouldn't exist. A sail isn't exactly like an airplane wing in that it is moving forward due to lift while an airplane's lift is not for forward motion. Air movement on an airplane wing comes from directly ahead. Therefore, the air moving over an airplane wing only holds the plane up, not propel it forward. This also leads to a misrepresentation of lift with regards to sailing dynamics.
A sailboat can't sail directly into the wind because it's goal is forward motion for the vessel, not lift lateral to the foil. There are points of the wind that won't be achievable. So you get wind that come from the concave side of the sail and appears to push when it is "lift" that actually moves the boat. When sailing with the wind, the dynamics change a little, but there is still the same pressure variance between the two sides. It's just that the variance is not achieved by the same directional airflow over the convex surface. There is added complexity to how sails work than for airplane wings.

Is lift the hardest lesson to learn in sailing? Maybe, for some. However you can sail and race and circumnavigate the globe in a sailboat successfully without ever understanding lift.

-Will (Dragonfly)
 
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weinie

.
Sep 6, 2010
1,297
Jeanneau 349 port washington, ny
What argument are you talking about??
I believe daveinet was referring to the argument that differences in pressure alone was not the sole factor in the creation of the lift force. I think he was getting at the fact that wind is 'pushing' on the windward side. This, of course is not the reason, as one of the pages I cited will show. However, the picard facepalm implied that the flow of air around the sail creating a pressure differential (bernoulli's) is the reason lift is created.
I posted to show that while daveinets solution to the lift problem was somewhat incorrect soley by the application of newtons third law, so is bernoulli's equations alone when you don't a apply newtons laws. (More accurately, the second law of force = change in momentum with respect to time: the foil is changing the direction of the wind and hence a vector component of its momentum).
What I'm trying to say is that the elementary school answer using bernoulli's principle does not provide a complete understanding of how lift works. You must apply newtonian principles as well to give a complete answer.
 
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Jan 1, 2006
6,073
Slickcraft 26 Greenport, NY
I think Sail Newport (Or is it Newport Sailing Center) has a better approach to teach sailing. The worst thing you can do is put a newbie in a classroom with a caulk board and vectors. The best thing you can do is put the newbie in a boat with sails.
 

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Nov 8, 2010
11,385
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
I believe daveinet was referring to the argument that differences in pressure alone was not the sole factor in the creation of the lift force. I think he was getting at the fact that wind is 'pushing' on the windward side. This, of course is not the reason, as one of the pages I cited will show. However, the picard facepalm implied that the flow of air around the sail creating a pressure differential (bernoulli's) is the reason lift is created.
I posted to show that while daveinets solution to the lift problem was somewhat incorrect soley by the application of newtons third law, so is bernoulli's equations alone when you don't a apply newtons laws. (More accurately, the second law of force = change in momentum with respect to time: the foil is changing the direction of the wind and hence a vector component of its momentum).
What I'm trying to say is that the elementary school answer using bernoulli's principle does not provide a complete understanding of how lift works. You must apply newtonian principles as well to give a complete answer.
I understand what you're saying here and agree. I also agree that diagrams about lift have no place at all in teaching beginning sailing... just enough background and get them on the water ASAP. But trying to simply a complex interaction to the point where the explanation is wrong serves nobody.
 

weinie

.
Sep 6, 2010
1,297
Jeanneau 349 port washington, ny
I understand what you're saying here and agree. I also agree that diagrams about lift have no place at all in teaching beginning sailing... just enough background and get them on the water ASAP. But trying to simply a complex interaction to the point where the explanation is wrong serves nobody.
Hah!!! Maybe this is why sailing is hard to learn!!!
The physics is not at all intuitive so perhaps the brain has difficulty in assimilating all the concepts.
Think of it like learning to walk. Walking involves so many factors. You must understand balance. So many muscles and so many joints must be used at exactly the right moments to walk, to run, to turn, to climb steps, etc. Yet we don't even consciously think of walking when we do it. We just do it and we never remembered how we even learned to do it as toddlers.
I think learning to sail is the same way. Enough time behind the wheel and sails will tell you that if you pull the mainsheet in, the boat will react so and so way. It only becomes intuitive after you do it and have done it over and over that you don't think about it.
 
Oct 19, 2017
6,936
O'Day 19 Littleton, NH
I once had a science teacher who was teaching a lesson in trajectory and gravity. He was explaining the math to calculate where a ball launched at a given angle with a given amount of force would land at a calculable distance from the launch point. He then pointed out that the brain performed all these calculations automatically and unconsciously in the case of an outfielder running to intercept a pop fly. My response was, no. The outfielder used experience and trial and error to intercept the ball. No numerical math was going on in his head.

-Will (Dragonfly)
 
Oct 22, 2014
16,087
CAL 35 Cruiser moored EVERETT WA
The science is fascinating and it supports the improvement of the sailing skill.

But the issue for the beginner is to introduce him/her and to create an experience that will make them want to return and try again. I believe that can best be accomplished in a boat with a single sail. A simple pram or dinghy with the sailor wearing a PFD on a warm sunny day. Solo sail in a controlled water with support folk providing encouragement and yet there to help should it be needed.

Isn’t that how it was when baby first walked? No physics/biomechanics/math about muscles, joints, dangers just mom/dad encouraging while reaching out with encouragement.

Once hooked and wanting more, the new sailor can be introduced to jibs, mainsheets, spinnakers, lift, drag. All the elements that drag down the process of fun for many new sailors.
 
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Kermit

.
Jul 31, 2010
5,506
AquaCat 12.5 17342 Wateree Lake, SC
The hardest part for me has been learning to relax. As much as I enjoy it I find it to be stressful more often than not. A good stress but stressful nonetheless.
 
Aug 1, 2011
3,959
Catalina 270 255 Wabamun. Welcome to the marina
I remember taking a NorthU performance course some years ago, and at no time did any of this kind of topic come up in this manner - the courseware was focused on trim, all the way up the sail with an emphasis on what the airflow does, and why, but without a lot of heavy terminology that does little but put people to sleep.

What matters is what the airflow looks like, and what you need to do to make it go.
 
Mar 20, 2015
2,253
C&C 30 Mk1 Silver Harbour, Lake Winnipeg
The hardest part for me has been learning to relax. As much as I enjoy it I find it to be stressful more often than not. A good stress but stressful nonetheless.
You may have hit the nail on the head. Keeping calm, and thinking things through, is something that many seem to have a problem with.

That's similar to another lesson that people have a hard time with. Based on my observation, it appears some people operating the same boat don't mix.

It never ceases to amaze me that we were able to hook up to a mooring ball, with no verbal interaction (two hand signals only), the first week we sailed together, and others do it for years, and still yell and swear at each other.

My wife and I still joke about a couple we encountered at a dock in Desolation Sound. When in skinny water, either she or I says exactly what we heard when a couple was docking and yelling at each other..... "There's rocks here !!!!"

So far, the only time we have yelled at each other, is when I thought we were screwed, and a strong cross wind was going to push us into a cat. She looked at me with saucer eyes, from the bow holding a roving fender, and I resignedly yelled "I think we are *ucked !!" 2 seconds later I was fiercely determined for one last attempt on getting the bow through the wind as we were being blown down the docks in tight space, on an unfamiliar charter boat. We made it with a few inches to spare.

Maybe it's the headspace that is the hardest thing to learn.
 
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