Talk:Sail

message: How is a sail a vertically oriented wing? A sail works by air pushing against it, a wing works by pressure differences from the wing cutting through the air.
:That's the difference between some kinds of downwind sail-setting and all the rest: In extreme downwind sailing the sail, as an aerofoil, has indeed stalled and the wind is simply 'pushing against it' - in that case setting a spinnaker or 'tacking downwind' will improve performance and boat stability.  In all other cases, from beating upwind to broad reaching, each sail works by exactly the same mechanism of pressure differences as a wing and an aerofoil. The luff is the leading edge and the leech is the trailing edge.  A well-set spinnaker or criuising chute works as an aerofoil too, but the aerofoil is vertically oriented with two leading edges beginning at the head and the foot being the trailing edge.  The same is true of square-rig sails, when off the wind.  When on the wind, a square-rigger's windward tacks are hardened down and the two side edges of the sail become leading and trailing edges respectively.  Can we work these ideas into the article somewhere? --Nigelj 10:38, 13 November 2005 (UTC)
replies: text: I edited the Wing entry to include sails as a kind of wing, I'll try to do as you suggest NigelJ
TonyClarke 16:08, 13 November 2005 (UTC)

text: Sorry, Zitchas, but this is wrong, wrong, wrong.  Sails are aerofoils and, when they are not stalled, they do produce lift exactly like aircraft wings do, although often in directions other than 'up'.  When sails are stalled they produce a little lift and lots more drag, just like wings too (though the drag is often in directions other than 'backwards', and so can power a boat downwind).  Instability of the turbulent air behind a stalled sail often amplifies the rolling of a boat downwind, and is very inefficient on all other points of sail, so skippers avoid it if at all possible.  The tosh about lift resulting from higher wind speeds due to thick aerofoil shapes is fully debunked in Lift (force)#Common misconception.  As I understand it, the benefit on aircraft of 'rounded' leading edges and 'thickness' in the aerofoils is to broaden the range of angles of attack that do not result in a stall.  This range of angles is minimal for a very thin aerofoil like a sail, although this is then mitigated slightly by the fact that the sail cloth is not rigid and so can adapt slightly (e.g. luffing).  Nonetheless, this narrow range of good angles for each sail is what keeps sail-trimmers busy when racing. --Nigelj 15:46, 10 December 2005 (UTC)
replies: text: Not that this is particularly relevant to the discussion, but the lower surface of a rigid wing is not a necessity, it just improves performance.  A rigid wing consisting only of only one surface works: it can be flat or curved.  Some cheap balsa model gliders use such wings.--Gautier lebon (talk) 07:18, 10 June 2011 (UTC)

text: Birds may have something different to say about non flapping  hard wings! Bcebul (talk) 21:58, 9 June 2011 (UTC)
thread_title:  What 

message: I think that this might be an oversimplification of the matter, as it depends largely on both the type of rigging being used and the direction (relevant to the wind direction) that one wishs to go.
For instance, many of the large square rigged ships did move essentially through the force of the wind pushing on the sail. I suppose technically the wind is piling up behind the sail (thus high pressure area) and the difference in pressure between the higher and lower pressure areas on opposite sides of the sail causes it to move, which is the same principle as that which generates lift. However, unlike in the case of aerofoils (aka wings) there is *not* a higher wind speed going across the back of the sail than the front.
In short, while the pressure differential as cause of movement remains valid, the cause of these pressure differences is not the same as for wings.
Lift (force)
Anyway, hope this helps.
I suppose another question would be for information sources explaining this. Anyone have any good sources of information to base this on? The one link provided on the page (Perfect sails or something to that effect) is a bit overtechnical, and I'm not sure about it.
Zitchas
:Sorry, Zitchas, but this is wrong, wrong, wrong.  Sails are aerofoils and, when they are not stalled, they do produce lift exactly like aircraft wings do, although often in directions other than 'up'.  When sails are stalled they produce a little lift and lots more drag, just like wings too (though the drag is often in directions other than 'backwards', and so can power a boat downwind).  Instability of the turbulent air behind a stalled sail often amplifies the rolling of a boat downwind, and is very inefficient on all other points of sail, so skippers avoid it if at all possible.  The tosh about lift resulting from higher wind speeds due to thick aerofoil shapes is fully debunked in Lift (force)#Common misconception.  As I understand it, the benefit on aircraft of 'rounded' leading edges and 'thickness' in the aerofoils is to broaden the range of angles of attack that do not result in a stall.  This range of angles is minimal for a very thin aerofoil like a sail, although this is then mitigated slightly by the fact that the sail cloth is not rigid and so can adapt slightly (e.g. luffing).  Nonetheless, this narrow range of good angles for each sail is what keeps sail-trimmers busy when racing. --Nigelj 15:46, 10 December 2005 (UTC)
replies: text: Not that this is particularly relevant to the discussion, but the lower surface of a rigid wing is not a necessity, it just improves performance.  A rigid wing consisting only of only one surface works: it can be flat or curved.  Some cheap balsa model gliders use such wings.--Gautier lebon (talk) 07:18, 10 June 2011 (UTC)

text: Birds may have something different to say about non flapping  hard wings! Bcebul (talk) 21:58, 9 June 2011 (UTC)
thread_title:  Sails as wings? 

message: This article could use a simple diagram showing how a sail works. Qutezuce 08:08, 27 May 2006 (UTC)
thread_title: Diagram

message: I've just removed this from the article. If someone who knows about this could incorporate it back, it would be nice, but as it stands it reads like a comment and contradicts the preceeding paragraph.
''
:: The statement above is not correct. 
::As the boat moves downwind is is moving forward (relatively)and the apparent wind moves from 
::directly behind the boat to foward as indicated by streamers and indicators located at various points on the boat. 
::The sails are actually creating lift thus allowing the boat (in some cases)to move along faster than the wind.
::The keel creates a righting moment, like gravity and the sails are resisting the forces of gravity on them, 
::that resistance is converted to a forward motion of the boat.
''
--Aioth 13:14, 30 October 2006 (UTC)
thread_title:  Contradiction 

message: I'd appreciate something on the history of sails, who invented them & when (I've seen Egyptians credited, c3000BC), what materials were used (canvas? silk? cotton?), when the rigid wingsail was invented & by who, so forth.  Trekphiler 14:38, 21 November 2006 (UTC)
thread_title: Sailing against the wind

message: Take a minute to read the comments at Talk:Sailing#Re-write effort -- non how-to et seq. Some of us a working on re-organizing the sailing-related articles. See if you agree with our approach and give us some help. Mrees1997 19:41, 29 December 2006 (UTC)
thread_title:  [[Sailing]] re-organization effort 

message: I have the impression, that new boats have larger sails.
In the past many small sails were used, now two big one suffice?
Where is the limit?
Arnero 21:02, 7 July 2007 (UTC)
thread_title:  Scaling 

message: First of all, I'd like to ask, where the bugger is the square rig?
Square riggings where used in a large part of the history of sailing in Europe and also in the medderterainan till the bysantins where beaten by the Arabs that where using Latin sails...
And as the sqear riggings are main competitors to the fore and aft rigs it should atleast be mentioned in a article about sailing.
As for the scaling part of everything...
The square rigs have one major disadvantage compared to fore and aft rigging, and that is that you require a larger and more experienced crew on a ship with that rig to be able to perform comparable with a ship with a fore and aft rigging.
The larger the sails where the harder they where to handle so at least in the beginnings it was usual to have small sails as each sail then becomes manageable with a smaller crew.
This also was a advantage in naval battles as losing one sail was afecting the overall performance of the ship less, you hopefully had other sails remaining.
Later one people invented new ways to manage the sails new ways using ropes and stuff..
And later then that the fore and after rigs being more managable by a small crew also al owed a larger sail.
Well that's what I can think of any ways.. might not be what you where looking after thou...
Luredreier 19:09, 5 October 2007 (UTC)
thread_title: My two cent

message: A sail is any type of surface intended to generate thrust by being placed in a wind—in essence a vertically-oriented wing. 
Isn't that exactly what a windmill sail does? The sail is so designed that the thrust produced is converted to rotary motion. Does this need adding to this article or as a new article?  —Preceding unsigned comment added by Mjroots (talk • contribs) 09:51, 21 January 2008 (UTC)
thread_title: Windmill sails

message: Something to clarify: No sail has any bits of engine or motor? --Menchi 02:32 8 Jun 2003 (UTC)
:Flettner rotors (I may not have that spelled right) do have motors, but they are rarely used on purely sailing vessels.  The are found (when found at all) on hybrid motor/sailing vessels that use the windpower to increase efficiency.  The rotors work much like a golf ball; they are cylinders with a dimpled surface that is rotated at high speed.  As the wind passes across the moving surface, the side going with the wind pulls the air further than the side going against the wind, which generates lift at 90 degrees to the wind.  Reverse the direction of rotation, and you reverse the direction of lift.  I don't know that any energy is lost (other than normal frictional losses) when generating the lift; if there is no additional energy loss, then the motor is not putting any energy into the generation of lift, and you coud consider the rotors to be "pure" sails.  scot 14:09, 22 Apr 2005 (UTC)
thread_title: Sails with motors?

message: Just a second, what does air pressure have to do with simple pushing? I'm not creating a difference in pressure on something when i kick it, am i?
: Pressure being force over area, yes you are, if only for a short time. PeteVerdon 10:14, 1 November 2005 (UTC)
thread_title: Pressure?

message: How can "The Arabs [have] invented the sail in about 2,000 BCE" be true when "The first written attestation of the ethnonym "Arab" occurs in an Assyrian  inscription of 853 BCE" (from wiki page on Arabs). I believe that the Arabs invented lateen (triangular) sails but did it much later - square sails had been around for a while.  —Preceding unsigned comment added by Laetoli (talk • contribs) 23:03, 14 June 2010 (UTC)
thread_title:  Arabs invented sails?? 

message: The first sentence of this page is unhelpful, and I feel a more readable imtroduction would be useful.  As it is, it reminds me of the Dickensian horse, " Quadruped. Graminivorous. Forty teeth, namely twenty-four grinders, four eye-teeth, and twelve incisive. Sheds coat in the spring; in marshy countries, sheds hoofs, too. Hoofs hard, but requiring to be shod with iron. Age known by marks in mouth.' Thus (and much more) ".  Arrivisto (talk) 22:35, 31 August 2012 (UTC)
thread_title:  Introductory definition 

message: The differences can be seen here:  https://en.wikipedia.org/w/index.php?title=Sail&diff=593265260&oldid=590826912
I do not find that the edits, taken as a whole, improve the article.  In particular, the first sentence "Air viscosity, acting parallel to the sail surface, and air pressure differences acting perpendicular to the sail surface are related to aerodynamic" is difficult to parse and doesn't seem to advance the article.  Other opinions?  Mr. Swordfish (talk) 17:14, 31 January 2014 (UTC)
replies: text: I agree with Swordfish.--Gautier lebon (talk) 13:51, 1 February 2014 (UTC)
replies: text: Seeing no disagreement, I'm going to revert the changes.  Mr. Swordfish (talk) 18:35, 6 February 2014 (UTC)
thread_title:  recent changes to sail aerodynamics section 

message: The reference on the section "Movable sails" does not seem very expert. The information does not make sense. Something on Kite rigs may belong here, if User:HopsonRoad agrees, but unless this section can be re-written and re-sourced to make sense, it needs to be removed. HLHJ (talk) 05:19, 27 November 2017 (UTC)
replies: text: I concur with your assessment, HLHJ. Clearly Egyptian sails could move well before the date cited. Also, the source cited does not appear to be reliable—it's a puff piece. As to kite rigs, they are mentioned in the lead as being beyond the scope of this article, but have two links to take the interested party to that topic. Thanks for discussing this matter here, first, before deleting a good-faith contribution Cheers, User:HopsonRoad 14:56, 27 November 2017 (UTC)
thread_title:  Moveable sails 

message: The article states:  This really perpetuates a common misconception. 
First, the reference for this statement: Sloop of War, pg 288. According to Amazon, this book only has 256 pagesso the page number immediately looks wrong. I have an electronic version of this book (without print edition page numbers) and various searches do not reveal anything to confirm the statement in the article. (There is some discussion about the problem of balance with two masted square rigs, but that is as close as I can get to finding something relevant.) I am not saying the source does not support the article, but it certainly needs checking.
Second, the general principle. When the two rigs, fore-and-aft and square, are compared, it is important to compare similar hull shapes, sizes and, most importantly, dates. The fact that a modern fore-and-aft rigged high performance yacht sails better to windward than a 19th century square rigger with natural fibre sails, a bluff-bowed hull and either a large cargo or lots of heavy guns is, at best, unhelpful. We do not have modern square riggers, so the comparison has to be historic. For that we have the opinion of James Cook and Frederick Marryat (who, as following reference states, is taken to be an RS on ships of that era by maritime historians). Both thought that a brig had better performance than a schooner, including to windward. This is a view that was widely held. It is discussed in a book review, where the reviewer (reasonably emphatically) supports the author's view to this effect.To explain further, it is not so much that one rig was better than the other to windward, it was that fore-and-aft rig was not very good for long downwind passages. Firstly you got a lot more chafe with fore-and-aft. Then there was the ever-present risk of an unintended gybe. (Those who sailed the huge multi-masted schooners lived in terror of this.)
Thirdly, the exact article content is plain wrong as square rig is actually at its most efficient when reaching (?just like for-and-aft?). This is because you get the least amount of blanketing of the various sails. I would hope the aerodynamics is pretty obvious.
Does anyone want to make a case for what the article's reference says before this is fixed? ThoughtIdRetired (talk) 22:16, 1 January 2024 (UTC)
replies: text: I concur. The link to the reference includes no statement, supporting the claim. Unless there is a reference that discusses efficiency of the rig on various points of sail, I recommend that the entire sentence be removed. Any discussion of efficiency of sails on various points of sail should encompass a range of sail types, be discussed in the body of the article (not solely the lead section) and be supported. by references. Cheers, HopsonRoad (talk) 15:21, 2 January 2024 (UTC)
replies: text: Comment from User:HopsonRoad noted and largely agreed. However, this is not the lead, but the section after the lead which seeks to separate sails into two categories: square rig and fore-and-aft rig. So the difference between the two does need to he covered in the article. It is simply a case of coming up with a concise explanation based on some good quality references. So there is a little bit of homework to do there before making any changes. ThoughtIdRetired (talk) 14:06, 6 January 2024 (UTC)
replies: text: I have gone ahead and removed the seriously wrong statement from the article. This section is the place to explain the differences between square and fore-and-aft rig, which needs sourcing. ThoughtIdRetired (talk) 14:10, 6 January 2024 (UTC)
thread_title:  Problem statement