Sail forces and sail plan ?

[Rick Willoughby]

Originally Posted by daiquiri

The therms "positive pressure" and "negative pressure" would be alone a sufficient reason to make you fail any serious exam in Aerodynamics.

Regarding your post #36, I've given you a series of explanations on why JavaFoil cannot be used to perform a reliable analysis on a single 2D sail sheet, let alone extending that result to a complete, finite-length, masted sail.

But you don't want to listen, because you refuse to admit to yourself that you don't know everything about anything and that there are still many things to learn.
Or maybe you simply didn't get the point of my warnings about using the software tools for tasks different from what they have been made for, and outside of boundary where the physycal models used by the software are valid.

Remember that thread on inclined propellers? I've learned something new from you over there, Rick, and I had written it and gave you my thanks for that.

I'm plain HAPPY when I can learn something new, that's the main reason why I have joined this forum. In return to that gained knowledge, I'm offering my knowledge in aerodynamics - which is not small at all, though you are reluctant to accept that someone might know more things about some particular field than you do.

Let me end with a following citation - who knows why did it come into my mind...:

"There is no more blind man than the one who doesn't want to see."

As I recall it took me quite a while to get you to see the light on the shaft vibration. But you did eventually see the light.

You are arguing about degrees of accuracy here. You have already stated that JavaFoil produces a good result in the condition of attached flow.

Originally Posted by daiquiri

If you use tufts to make yourself sure that the flow over the sail (and particularly at the leading edge) is attached, then you are basicaly operating at the ideal angle of attack (as explained before) and the flow is well modelled by JavaFoil (for that angle only).

This is the most common state for a sail when sailing to windward under most conditions - highly tuned racers in calm sea aside. The sail will be operating in a very narrow range.

If you can provide fcfc and me a reference to free software that performs the calculations better for multi-element sails than JavaFoil you will have offered some useful education. Otherwise you are simply nit picking and need to get into the drivel thread as it is not improving understanding here.

At no stage have I said that JavaFoil is the perfect solution. All tools have limitations. Testing the validity of the results will either give confidence in the result or impetus to seek something better. I have confidence in the answers that JavaFoil produces over the range I am interested in.

You only offer negative input on why it does not work over a wide rage of conditions beyond those of normal operation.

Rick W

[daiquiri]

Originally Posted by Rick Willoughby

As I recall it took me quite a while to get you to see the light on the shaft vibration. But you did eventually see the light.

This is the thread, check out how much did it take you to make me understand your words and give you thanks and reps for having me taught something new:
Prop Shaft Systems.

You are a heavy person, Rick. Heavy like earth. I'm sorry to see that.
Take a look at this music video, it might help you to ease it down a bit. I wouldn't want you to start using some pills because of JavaFoil and aerodynamics:
http://www.youtube.com/watch?v=7B7bV...eature=related

Originally Posted by Rick Willoughby

You have already stated that JavaFoil produces a good result in the condition of attached flow. This is the most common state for a sail when sailing to windward under most conditions - highly tuned racers in calm sea aside. The sail will be operating in a very narrow range.

I'm leaving this quote to serve as epitaph to your stubborness and deafness.

Originally Posted by Rick Willoughby

If you can provide fcfc and me a reference to free software that performs the calculations better for multi-element sails than JavaFoil you will have offered some useful education. Otherwise you are simply nit picking and need to get into the drivel thread as it is not improving understanding here.

As i have told you, but you evidently haven't read, I am not aware of any simple means to perform that task, apart from N-S CFD codes. And even the CFD codes have many limitations if you don't tune the calculation parameters correctly.
A sail is a tricky, constantly variable geometry made of elastic material, with a mast ahead of it, immersed in a flow with high vertical gradients, both in direction and in intensity.
The flow is never attached on a real-world sails, unless you use a double-surface sails. a separation bubble is always present at the leading edge, and models used by JavaFoil cannot cope with them.

Now, if I'm not aware of any simple and accessible ways to fly you to the Moon, will you keep on trying to reach it with your car?

This is my last post on this topic. Nothing can change your mind, so I will no longer try to do it.

But you have put me on allert with your posts and I will intervene again if I see that you are spreading disinformation and ignorance on any particular issue.

[Rick Willoughby]

Originally Posted by daiquiri

......

As i have told you, but you evidently haven't read, I am not aware of any simple means to perform that task, apart from N-S CFD codes. And even the CFD codes have many limitations if you don't tune the calculation parameters correctly.
A sail is a tricky, constantly variable geometry made of elastic material, with a mast ahead of it, immersed in a flow with high vertical gradients, both in direction and in intensity.
The flow is never attached on a real-world sails, unless you use a double-surface sails. a separation bubble is always present at the leading edge, and models used by JavaFoil cannot cope with them.

......

I believe fcfc is fully aware of this as it is all detailed in the paper he referred to.

His objective of finding a series on sails that gives the required data is not available, at least to my knowledge and apparently everyone else who has offered some useful information here.

He can use JavaFoil to determine plots similar to the attached, taken from his referenced paper, for any rig that can be reasonably reduced to a 2D flow field with empirical compensation for aspect ratio. He could extend it to allow for twist and spanwise chord changes without too much difficulty.

JavaFoil is accurate for the ideal conditions that most trimming sails aim to achieve.

Rick W

[Rick Willoughby]

For interest sake I looked at how well JavaFoil would model the data provided in the chart extracted from the referenced paper and I attached above.

In this case I have orientated identical sail sections in such a way that the airflow is direct left to right (may make it easier for those who have difficulty shifting the reference frame). The sails are freed up to get somewhere near maximum lift from the combination. You could fiddle adjusting the angles for a long time to get the best orientation. The maximum lift occurs somewhere around 30 degree orientation and the Cl is just under 2. I have used an aspect of 4, which is taken from the model used for testing and referred to in the paper - see image.

The second plot shows what can be achieved by placing the camber further forward on the foresail. May not be practical but higher CL is possible if it was achievable.

Rick W

[Rick Willoughby]

Attached shows the highest lift condition I can get trimming the two thin foils with 10% camber and AR of 4. It is achieved with 29 degrees apparent wind.

Best lift is Cl of 2.05 with Cd of 0.35. So lift to drag ratio is 5.9 at highest lift condition.

Rick W

[Ad Hoc]

Funny, in the endless technical papers i read and have in my library, whenever Javafoil is mentioned, it is with a 'simplistic' caution. Great to use for very quick basic 2D flow stuff if you haven't got any of the classic reference books, but they all say over 20 degree AoA is seriously questionable, and produces +/-10% accuracy at best.

Yet you consistently appear to ignore these caveats, and in fact any PC/CFD/FEA program and maintain that the output is an absolute and not to be questioned in any form. Astonishing!

[Rick Willoughby]

Attached shows the result for same sail combination but larger angle to apparent wind. The Cl is now falling off at 1.86 and the Cd is 0.32 giving lift to drag of 5.8.

It is a reasonably labourous task to trim the foils at the various angles of wind to get the best lift condition but it can be done and is not a lot different to what would be done in sheeting sails.

Rick W

[Rick Willoughby]

Tried going at a higher angle to apparent wind. The Cl only falls a small amount as does the Cd. However the 10% camber of the foresail would not be able to be achieved unless it had a boom. Without a boom the sheeting angle would have to be too wide.

The analysis could be carried out for a narrower sheeting angle but it would require giving the foresail more camber to more accurately reflect the actual sail shape.

Rick W

[fcfc]

Sorry, there is no need to flame.

In the lack of sail statistical series, I will simply revert back to principle of yacht design. That's the safest option.

[apex1]

Originally Posted by Rick Willoughby

I took the time to answer the original post with useful information. All you have provided is your penchant for water polo took you away from sailing. That is not very useful to the original request.

If you cannot be bothered to provide an answer or to show where a particular answer is wrong then you should go to the drivel thread. Because that is all you are offering.

In fact you even agreed that JavaFoil is accurate for the narrow range of operation that a windward sail would operate in.

When I see something of value that you can produce and you are prepared to put your name to your claims and opinions you might gain a little more credibility.

Rick W

I am pretty sure you have not a clue about the stage of professionalism you are trying to fight against here! If I was you, I would quickly get me the big eraser and edit ALL the former posts!
You otherwise are in serious risk to loose some of your credibility.
Regards
Richard

[Rick Willoughby]

Originally Posted by apex1

I am pretty sure you have not a clue about the stage of professionalism you are trying to fight against here! If I was you, I would quickly get me the big eraser and edit ALL the former posts!
You otherwise are in serious risk to loose some of your credibility.
Regards
Richard

Richard
I am not fighting against it and have no need to erase useful information so the ignorance shines.

I give credit to Daiquiri that he knows what he is talking about but he rushed in as fools tend to do. He has done it before.

If you look at the images in all my latest posts on this thread you will see I have orientated the wind left to right so it is easier for people who have difficulty adjusting the frame of reference. The Angle of Attack, shown in the upper left hand box of the images, is always at zero. This just means the flow is left to right. In all cases you will see that the flow on the foils is streamline so the theory holds.

JavaFoil is used as a valuable tool in understanding how sails work as has been shown on many other threads here.

I cannot help the ignorance of others who rush in without thinking.

Rick W

[apex1]

Originally Posted by Rick Willoughby

Richard
I am not fighting against it and have no need to erase useful information so the ignorance shines.

I give credit to Daiquiri that he knows what he is talking about but he rushed in as fools tend to do. He has done it before.

If you look at the images in all my latest posts on this thread you will see I have orientated the wind left to right so it is easier for people who have difficulty adjusting the frame of reference. The Angle of Attack, shown in the upper left hand box of the images, is always at zero. This just means the flow is left to right. In all cases you will see that the flow on the foils is streamline so the theory holds.

JavaFoil is used as a valuable tool in understanding how sails work as has been shown on many other threads here.

I cannot help the ignorance of others who rush in without thinking.

Rick W

Well, you may not like this statement, but you desperately asked for it:

YOU ARE THE LAYMAN HERE! and the "others" are well known, well respected and pretty professional nautical architects, doing theyr job on a level you obviously have never seen. Earning a living in the ship design business is not as easy as some may guess. trying that in the "pro´s" world is harder.
Your valuable contribution to many of the threads here, does not make you "immune" to a harsh contrary (and pretty well established) point of view.
The two "rushing in whithout thinking" are daiquiry and ad hoc, both very well respected members of the professional shipbuilding community.... And you?

daiquiry is your main enemy?

This is the thread, check out how much did it take you to make me understand your words and give you thanks and reps for having me taught something new:
Prop Shaft Systems.

You did never reply to "ad hocs" statements. Why? Too professional, you cannot compete,thats it!

You will not mind if I reduce your reputation points a bit? will you?

Regards
Richard

[Ad Hoc]

apex1

Thank you for your kind words (I'm blushing!), unlike RW, I do not seek patronage from others. Like Daiquiri, just provide advice/guidance to those that seek it, based upon our knowledge and experience of real world design, not computer graphics that mean...er...um....you can fill in the blanks.

In his case, certainly reading the above and on many other threads, it is a case of ignorance is bliss!

I occasionally come across "old boy" surveyors like him. Don't question me, I am the surveyor. (I am currently dealing with one right now, wont say where, in case he reads this forum). That's my cue to expose them for being "little Hitler's" whom have very little real experience and technical knowledge, and just want you to respect their position, regardless that they are seriously lacking in technical knowdgle. Just as they hide behind the "surveyor" position, just as others hide behind their "computer programs"...both cut from the same cloth. Very sad...

For someone who consistently bleats....show me your gallery and show me your numbers, i would have expected a plethora of real boats that have been designed and operating world wide, such as: patrol boats, crew boats, passenger boats, tugs, etc yet, in HIS gallery....nah, just little models. The same size we have used in the past for 'model' testing. Little 5m models that perform one task and one task only. Nice to have design brief of just one line...design, ops..., those are just trial and error iterations, last count was 11 he told me.

He clearly feels the need to spread the word in his own way...the definitive word has spoken....anything else, is well, beneath him!

But since this is a "free world/forum" he can say what he likes.....just don't try and earn a living from it!

[apex1]

Originally Posted by Ad Hoc

apex1

Thank you for your kind words (I'm blushing!), unlike RW, I do not seek patronage from others. Like Daiquiri, just provide advice/guidance to those that seek it, based upon our knowledge and experience of real world design, not computer graphics that mean...er...um....you can fill in the blanks.

In his case, certainly reading the above and on many other threads, it is a case of ignorance is bliss!

I occasionally come across "old boy" surveyors like him. Don't question me, I am the surveyor. (I am currently dealing with one right now, wont say where, in case he reads this forum). That's my cue to expose them for being "little Hitler's" whom have very little real experience and technical knowledge, and just want you to respect their position, regardless that they are seriously lacking in technical knowdgle. Just as they hide behind the "surveyor" position, just as others hide behind their "computer programs"...both cut from the same cloth. Very sad...

For someone who consistently bleats....show me your gallery and show me your numbers, i would have expected a plethora of real boats that have been designed and operating world wide, such as: patrol boats, crew boats, passenger boats, tugs, etc yet, in HIS gallery....nah, just little models. The same size we have used in the past for 'model' testing. Little 5m models that perform one task and one task only. Nice to have design brief of just one line...design, ops..., those are just trial and error iterations, last count was 11 he told me.

He clearly feels the need to spread the word in his own way...the definitive word has spoken....anything else, is well, beneath him!

But since this is a "free world/forum" he can say what he likes.....just don't try and earn a living from it!

Well, I am a adult , frank person, meaning what I say. I am impressed, that a "well respected member" reduced my rep. points, awaiting that I would do so.!!!
Rick, you´re a child...................
We do not need your rep. to make our living! And I was giving you a positive just some days ago!

Do what you like... Rick W

But as other "adult" members mentioned above, I will check your "so named" contribution here , and name it as it is: figure playing of a layman!
Mr. numbers.
No... not as a reply... revenge... ,as a personal contribution to all these amateurs you have tried to run into ruin with your software related opinion! Go home and relax, amateur! You do not have the knowledge to contribute here!
Just nice "software produced figures", you dont know whats behind them, thats it.

So, may give me another bad "reputation point"

I SH..T ON THAT!
I make my living with adults... and be fine with it.

Originally Posted by Rick Willoughby

There is considerable discussion on sails in various threads. Here is a sample:
multi element foil sections?
In post #5 I show how a multi-element sail can be set up in JavaFoil.

JavaFoil is quite easy to use. If you take the time to get a grasp on it then you will learn quite a lot about sails.
Rick W

Thats just numbers and nnnnothing else.............

And if you´re clever (which I doubt) , you will not reply to these, my statements.

Regards
Richard

[terhohalme]

Ad Hoc and Apex1, do you really see above adult and professional? How do I see it only arrogant?

I can respect your knowledge and skills, but your attitude makes me feel sad...

I'm not defending RW, just wondering this debate.