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Discussion Starter · #1 ·
Hey guys, i'm new over here. i am really interested in dinghy sailing and just completed my RYA level 2. this has inspired me to base my 4000 word extended essay on the physics behind sailing.
The question that i'll be researching on is:
'How does the angle of the sail on a sailboat from the direction of wind affect the total drag force on the sail?'
i'm trying to conduct an experiment on the the above with a model of a sail using a table-fan as a constant wind source.

Any ideas or suggestions?..... :confused:
 

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Hey guys, i'm new over here. i am really interested in dinghy sailing and just completed my RYA level 2. this has inspired me to base my 4000 word extended essay on the physics behind sailing.
The question that i'll be researching on is:
'How does the angle of the sail on a sailboat from the direction of wind affect the total drag force on the sail?'
i'm trying to conduct an experiment on the the above with a model of a sail using a table-fan as a constant wind source.

Any ideas or suggestions?..... :confused:
First off, a table fan will produce far too turbulent a flow pattern to get you any meaningful data. You will be better off using a homemade wind tunnel. They're cheap and easy to make using thin plexiglass. Put a box-fan at the downwind end of the tunnel, and have some sort of funnel arrangement at the upwind end to minimize the turbulent flow as the air enters the tunnel. Also, to minimize boundary layer effects, make sure the cross-section of the tunnel is at least twice the longest dimension of the test object.

Second, and undoubtedly more difficult, you'll need some way of simultaneously measuring both drag AND lift on your test foil (as well as some other variables, like flow speed, and projected frontal surface area). The best way to do that is with a three-dimensional force platform instrumented with strain gages and the proper amplifiers (poke around the InterNet a bit and I'm sure you'll find some schematics).

I realize all that probably sounds way more complicated than you were prepared to bite off. But, as someone who has done just this sort of thing (only with marine invertebrates in water), I can tell you that that is that is what you need to do. On the other hand, there is a ton a literature on just this sort of question. How lift and drag vary with angle of attack is a problem dating back to before the Wright brothers. A good place to start is a Dover Science Classics book, by Robert Granger, called "Fluid Dynamics". It's a fairly cheap book (I think it's less than $30, new), but it probably has more than enough info for what you want to do.

Good luck.
 

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If you are interested in the physics of sailing, be sure to check out C.A.Marchaj books:
"Sailing Theory and Practice" (196?), "Aero-Hydrodynamics of Sailing" (1979), "Seaworthiness, The Forgotten Factor" (1986), and "Sail performance" (1990). I haven't seen any more recent books by him...
 

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I found a lot of intriguing stuff just by googling "physics of sailing"
 

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Discussion Starter · #5 ·
First off, a table fan will produce far too turbulent a flow pattern to get you any meaningful data. You will be better off using a homemade wind tunnel. They're cheap and easy to make using thin plexiglass. Put a box-fan at the downwind end of the tunnel, and have some sort of funnel arrangement at the upwind end to minimize the turbulent flow as the air enters the tunnel. Also, to minimize boundary layer effects, make sure the cross-section of the tunnel is at least twice the longest dimension of the test object.

Second, and undoubtedly more difficult, you'll need some way of simultaneously measuring both drag AND lift on your test foil (as well as some other variables, like flow speed, and projected frontal surface area). The best way to do that is with a three-dimensional force platform instrumented with strain gages and the proper amplifiers (poke around the InterNet a bit and I'm sure you'll find some schematics).

I realize all that probably sounds way more complicated than you were prepared to bite off. But, as someone who has done just this sort of thing (only with marine invertebrates in water), I can tell you that that is that is what you need to do. On the other hand, there is a ton a literature on just this sort of question. How lift and drag vary with angle of attack is a problem dating back to before the Wright brothers. A good place to start is a Dover Science Classics book, by Robert Granger, called "Fluid Dynamics". It's a fairly cheap book (I think it's less than $30, new), but it probably has more than enough info for what you want to do.

Good luck.
thnx a lot for the advice. i only wish i could carry it out like that but the problem is that i study at a fully residential school. so i dont actually have much to work with and have to make do with whatever is available. i'm trying to place some card or something like that around the fan so that the airflow will be focused on one direction. i'm gonna use a spring balance to measure the force on the sail at different angles, keeping the boom's movement restricted by 2 poles + or - 2 degrees from the angle being investigated. any improvements that you can offer?
 

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Discussion Starter · #6 ·
hey guys, could you please fill out this tiny questionnaire for my primary research... only a few simple questions... :)

Questionnaire
1. What is your name?
 ________________________________________________

2. How often do you sail in a week?
 During the vacations ___________________________
 For the rest of the year _________________________

3. Do you own a boat?
 ¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬( Yes / No )

4. How many years/months of experience do you have in sailing?
 _____________________________

5. What is the wind speed (in knots) that you prefer to sail with?
 ___________________

6. What type of boat do you prefer to sail in? Choose the appropriate. [More than one response per category is acceptable
Occupancy
o Single
o Double
o Four people
o Six or more people
Sail shape
o Triangular
o Rectangular
Number of sails
o Only mainsheet
o Mainsheet and foresail
o More than two sails
Onboard motor
o Yes
o No
 Name of make and model:_______________________________________________

7. What angle do you prefer to keep your sail at in accordance with the direction of the wind? Choose any one.
o 20-30
o 30-40
o 40-50
o 60-70
o 80-90

8. Do you reef your sail? If yes, at approximately what wind speed?
o Yes
________knots
o No

Thank You!
 

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Discussion Starter · #7 · (Edited)
hey guys, could you please fill out this tiny questionnaire for my primary research... only a few simple questions... :)

Questionnaire
1. What is your name?
 ________________________________________________

2. How often do you sail in a week?
 During the vacations ___________________________
 For the rest of the year _________________________

3. Do you own a boat?
 ¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬( Yes / No )

4. How many years/months of experience do you have in sailing?
 _____________________________

5. What is the wind speed (in knots) that you prefer to sail with?
 ___________________

6. What type of boat do you prefer to sail in? Choose the appropriate. [More than one response per category is acceptable
Occupancy
o Single
o Double
o Four people
o Six or more people
Sail shape
o Triangular
o Rectangular
Number of sails
o Only mainsheet
o Mainsheet and foresail
o More than two sails
Onboard motor
o Yes
o No
 Name of make and model:_______________________________________________
 Weight:______________________
 Length:______________________

7. What angle do you prefer to keep your sail at in accordance with the direction of the wind? Choose any one.
o 20-30
o 30-40
o 40-50
o 60-70
o 80-90

8. Do you reef your sail? If yes, at approximately what wind speed?
o Yes
________knots
o No

Thank You!
 

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Old as Dirt!
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3,491 Posts
...

'How does the angle of the sail on a sailboat from the direction of wind affect the total drag force on the sail?'

Any ideas or suggestions?..... :confused:
Refer to C. A. Marchaj's "Sailing Theory and Practice" (Dodd, Mead © 1964 by C.A. Marchaj), penned by Marchaj while at Southampton University, England, in October 1962, and particularly Chapter 14 commencing on page 202...
 

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3 Posts
Hey guys, i'm new over here. i am really interested in dinghy sailing and just completed my RYA level 2. this has inspired me to base my 4000 word extended essay on the physics behind sailing.
The question that i'll be researching on is:
'How does the angle of the sail on a sailboat from the direction of wind affect the total drag force on the sail?'
i'm trying to conduct an experiment on the the above with a model of a sail using a table-fan as a constant wind source.

Any ideas or suggestions?..... :confused:
Hi there!

I was searching for a question to do my IB extended essay on sailing too can you tell me what was your final question? That would help a lot because im clueless on what question I should write about!

Kind Regards

Rodrigo Costa
 

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Hi there!

I was searching for a question to do my IB extended essay on sailing too can you tell me what was your final question? That would help a lot because im clueless on what question I should write about!

Kind Regards

Rodrigo Costa
Welcome aboard, costar. Unfortunately, that poster hasn't signed on since 2012. Perhaps someone else could help, but I'm not familiar with what you're asking. Maybe if you clarified, someone would be able to help. Good luck.
 

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Farr 11.6 (Farr 38)
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There is a lot of subjects related to sailing that are good topics for an IB Final Essay. Most deal with one science or another:
Aerodynamics:
Hyrdrodynamics:
Structural design
Meteorology,
Ocean science
Contingent planning (If-then analysis used for routing)
and so on,
Many of these are highly technical in nature and take some fairly sophisticated equipment if you plan to do primary research. For example, you might research Manfred Curry and perhaps replicate some of his early experiments. As a teenager in the 1930's, Manfred Curry did some of the earliest experiments in sail aerodynamics. Using comparatively inexpensive and simple equipment he was able to measure the relative air pressure on various parts of the sail His work revolutionized the sailing world's understanding of sail shape and forces. Now then, he had access to the Fokker Aircraft wind tunnel, which did not hurt, so part of duplicating his experiments would require building a small wind tunnel or gaining access to one at a university.

Jeff
 

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There is a lot of subjects related to sailing that are good topics for an IB Final Essay. Most deal with one science or another:
Aerodynamics:
Hyrdrodynamics:
Structural design
Meteorology,
Ocean science
Contingent planning (If-then analysis used for routing)
and so on,
Many of these are highly technical in nature and take some fairly sophisticated equipment if you plan to do primary research. For example, you might research Manfred Curry and perhaps replicate some of his early experiments. As a teenager in the 1930's, Manfred Curry did some of the earliest experiments in sail aerodynamics. Using comparatively inexpensive and simple equipment he was able to measure the relative air pressure on various parts of the sail His work revolutionized the sailing world's understanding of sail shape and forces. Now then, he had access to the Fokker Aircraft wind tunnel, which did not hurt, so part of duplicating his experiments would require building a small wind tunnel or gaining access to one at a university.

Jeff
Thank you for your help Jeff!

My plan was to get a specific model of a boat and explain the physics concepts used to build that boat. I'm not sure if im making myself clear! I would basically analise every feature of the boat and explain it but im not sure how to put that into a question! Do you think its a good idea?

Kind Regards

Rodrigo Costa
 

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Super Moderator
Farr 11.6 (Farr 38)
Joined
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10,696 Posts
Thank you for your help Jeff!

My plan was to get a specific model of a boat and explain the physics concepts used to build that boat. I'm not sure if im making myself clear! I would basically analise every feature of the boat and explain it but im not sure how to put that into a question! Do you think its a good idea?

Kind Regards

Rodrigo Costa
I only have a small amount of experience with the IB program so i am not sure that I fully understand how this is structured. If I were to structure this in the manner that I would for any formal research project, it would look specifically like this:

GIVENS:
1) At any moment, a sailboat under sail is a study in equilibrium that is a balanced resolution of forces in opposition to each other.
2) These forces consist of static and dynamic aerodynamic and hydrodynamic forces, which are both produced and countered by the properties of the boat in question.
3) Modern Yacht design attempts to resolve those forces efficiently in the sails by minimizing side forces and drag while maximizing forward forces (drive), and efficiently in the hull, keel and rudder(S) by resisting sideward motion and heeling while minimizing drag, yet producing adequate carrying capacity, reasonable seaworthiness, and a comfortable motion for the people on the boat.
4) The potential solutions to improving efficiency are often tempered by those last pragmatic requirements, which require that a sailboat perform as a practical and comfortable home transporting humans and their possessions in a changing and sometimes harsh environment.
QUESTION TO BE STUDIED
Using as an example, the PICK-A-MAKE&MODEL-42, which is a specific model of sailboat, what are those forces produced and countered while sailing, and how do the features of this design maximize the desired static and dynamic forces, while minimizing the undesirable byproduct forces?

And at that point I would add a hypothesis to be proven or disproven.

Now then, do yourself a favor and under no circumstance cut and paste what I have written. Do a little bit of research so that you better understand all of that my post is talking about. Then narrow your question to one small part of that topic, since that question as written would require a vast amount of research and produce a very fat book. (At least if I had to answer it).

Jeff
 

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I only have a small amount of experience with the IB program so i am not sure that I fully understand how this is structured. If I were to structure this in the manner that I would for any formal research project, it would look specifically like this:

GIVENS:
1) At any moment, a sailboat under sail is a study in equilibrium that is a balanced resolution of forces in opposition to each other.
2) These forces consist of static and dynamic aerodynamic and hydrodynamic forces, which are both produced and countered by the properties of the boat in question.
3) Modern Yacht design attempts to resolve those forces efficiently in the sails by minimizing side forces and drag while maximizing forward forces (drive), and efficiently in the hull, keel and rudder(S) by resisting sideward motion and heeling while minimizing drag, yet producing adequate carrying capacity, reasonable seaworthiness, and a comfortable motion for the people on the boat.
4) The potential solutions to improving efficiency are often tempered by those last pragmatic requirements, which require that a sailboat perform as a practical and comfortable home transporting humans and their possessions in a changing and sometimes harsh environment.
QUESTION TO BE STUDIED
Using as an example, the PICK-A-MAKE&MODEL-42, which is a specific model of sailboat, what are those forces produced and countered while sailing, and how do the features of this design maximize the desired static and dynamic forces, while minimizing the undesirable byproduct forces?

And at that point I would add a hypothesis to be proven or disproven.

Now then, do yourself a favor and under no circumstance cut and paste what I have written. Do a little bit of research so that you better understand all of that my post is talking about. Then narrow your question to one small part of that topic, since that question as written would require a vast amount of research and produce a very fat book. (At least if I had to answer it).

Jeff
Thank you for the great help Jeff!

I think that I'm going to talk with my physics teacher I'll do something like that! Thank you once again! I'll keep you updated!

Kind Regards

Rodrigo Costa
 
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