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Hi HopsonRoad, some comments, with due respect:
Perhaps we should not use the expression "Apparent Wind Sailing" since all sailing is use of apparent wind. Did Bethwaite really use this term?
Apparent wind is the difference of wind and boat velocities, ie (True wind velocity - Boat velocity) .. not the sum as you suggest.
I don't think your comments about 18 footers reads well (tripling? of what?), and it lacks acknowledgement of many other sailing craft which performed more efficiently than 18 footers, including windsurfers, kites, tornadoes, etc etc. There were also many foiling craft in the 1980's including one in NZ by David Knaggs.
Your section on "Apparent-wind-angle limit" contains errors and does not read well .. and the claim that 6 times wind-speed may be a theoretical maximum efficiency of a yacht is wrong. AC75 yachts are close to achieving that now, and there are very obvious inefficiencies in their setup, as evidenced by their spray and wake. On inspection of the Beta Theorem, the theoretical efficiency limit of a yacht is more likely to be:
{1/ [1/(foil lift-drag-ratio) + 1/(sail lift-drag-ratio)]}
By example .. a hypothetical "very light" yacht with "negligible" parasitic drag, and with a foil with LTDR 40 and a sail with LTDR 40, will sail at 20x wind-speed when sailing 92.9 deg off the wind.
(1/(1/40+1/40) = 20)
Beta = atan (1/20) = 2.9 deg
By this hypothetical example the efficiency of a yacht is clearly not constrained to 6x windspeed.
Charco21 ( talk) 22:53, 2 August 2020 (UTC)Charco21
This should be clarified. An apparent wind can be separated into two components relative to the sail craft's frame of reference and orientation: an apparent headwind (or tailwind at slower speeds) and apparent crosswind. There is never any benefit to an apparent headwind. All of the thrust is due to diverting the apparent crosswind. Note that for a fixed heading with respect to the true wind, the apparent crosswind is sin(angle between true wind and sail craft's direction), which is constant for a constant true wind and heading, independent of the sail craft's speed. The overall efficiency determines the limit of speed for a given apparent crosswind and heading. Rcgldr ( talk) 23:56, 4 August 2020 (UTC)
Both the aerodynamic force on a sail and the wind velocity are vectors so it is possible to resolve them into components depending on which co-ordinate system you choose to use. Early work in aerodynamics used a co-ordinate system parallel and perpendicular to the wing. Later, the current standard of parallel (drag) and perpendicular (lift) to the wind direction became widespread. I have seen treatments for sailboats that resolve the aerodynamic force into components parallel and perpendicular to the centerline of the boat, resolving the force into drive and heel (or leeway). Similarly, I can see where it might be illuminating to resolve the wind velocity into components parallel and perpendicular to the centerline of the boat, but I've never come across any literature that does this. Using the conventional coordinate system, by definition wind velocity is always 100% in the direction of drag. So, for the purposes of editing this article, the next step would be to find a reference that resolves wind velocity into components parallel and perpendicular to the boat. Mr. Swordfish ( talk) 15:24, 5 August 2020 (UTC)
With regards to the labeling of and differentiating between the antiparallel vectors boat speed and boat wind, there appears on reading and referencing the associated image(without referencing the commons description, it should be noted) to be an identical subscripted labelling for both vectors as VB. While the written section and associated mathematical description do well to detail the apparent wind calculation with regards to boat wind, for those referencing the image to visualize the associated derivation, it can be a bit confusing. As a passerby, it wasn't my hope to unilaterally alter either the section description or the associated media, though it seems to me that the easiest rectification would be to specify that boat wind is antiparallel to boat speed by referencing boat wind as -VB. Though as the associated media was uploaded by HopsonRoad, a modified image might best serve the purpose of the description, but this is to your discretion. The Intervocalic Sigma ( talk) 21:36, 29 May 2021 (UTC)
Needs fixing:
β is magically introduced without any explanation - someone needs to say with this is the FIRST TIME it is mentioned (probably apparent wind angle - so if yes, spell that out).
This is an article about sailing. That implies SAILS. So this phrase needs to be reworded: "If the craft travels at VB = 10 knots with a tailwind of VT = -5 knots" - last time I checked, regular sail boats cannot sail downwind at double the speed of the wind. Introducing examples that are impossible does NOT help anyone understand things! — Preceding unsigned comment added by 110.143.72.26 ( talk)
Would it make sense to change this:
"High-performance watercraft that can exceed the velocity of the true wind include..."
to something like this:
"High-performance watercraft that can achieve VMG in excess of the true wind include..."
When I read the article I was at first questioning if it was talking about exceeding speed of the true wind in its direction of travel or if it meant the direct downwind component of its velocity vector (VMG) could exceed true wind. After reading it over a few times it seems like it is the latter. But only because I've read other things. Seems like it would be clearer if it was explicitly stating that it is VMG we're talking about here. — Preceding unsigned comment added by 50.238.167.160 ( talk) 23:46, 22 August 2022 (UTC)
This is the
talk page for discussing improvements to the
High-performance sailing article. This is not a forum for general discussion of the article's subject. |
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Archives:
Index,
1,
2,
3,
4,
5,
6Auto-archiving period: 90 days
![]() |
![]() | This article is written in Australian English, which has its own spelling conventions (colour, realise, program, labour (but Labor Party)) and some terms that are used in it may be different or absent from other varieties of English. According to the relevant style guide, this should not be changed without broad consensus. |
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A graph should have been displayed here but
graphs are temporarily disabled. Until they are enabled again, visit the interactive graph at
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This page has archives. Sections older than 90 days may be automatically archived by Lowercase sigmabot III when more than 4 sections are present. |
Hi HopsonRoad, some comments, with due respect:
Perhaps we should not use the expression "Apparent Wind Sailing" since all sailing is use of apparent wind. Did Bethwaite really use this term?
Apparent wind is the difference of wind and boat velocities, ie (True wind velocity - Boat velocity) .. not the sum as you suggest.
I don't think your comments about 18 footers reads well (tripling? of what?), and it lacks acknowledgement of many other sailing craft which performed more efficiently than 18 footers, including windsurfers, kites, tornadoes, etc etc. There were also many foiling craft in the 1980's including one in NZ by David Knaggs.
Your section on "Apparent-wind-angle limit" contains errors and does not read well .. and the claim that 6 times wind-speed may be a theoretical maximum efficiency of a yacht is wrong. AC75 yachts are close to achieving that now, and there are very obvious inefficiencies in their setup, as evidenced by their spray and wake. On inspection of the Beta Theorem, the theoretical efficiency limit of a yacht is more likely to be:
{1/ [1/(foil lift-drag-ratio) + 1/(sail lift-drag-ratio)]}
By example .. a hypothetical "very light" yacht with "negligible" parasitic drag, and with a foil with LTDR 40 and a sail with LTDR 40, will sail at 20x wind-speed when sailing 92.9 deg off the wind.
(1/(1/40+1/40) = 20)
Beta = atan (1/20) = 2.9 deg
By this hypothetical example the efficiency of a yacht is clearly not constrained to 6x windspeed.
Charco21 ( talk) 22:53, 2 August 2020 (UTC)Charco21
This should be clarified. An apparent wind can be separated into two components relative to the sail craft's frame of reference and orientation: an apparent headwind (or tailwind at slower speeds) and apparent crosswind. There is never any benefit to an apparent headwind. All of the thrust is due to diverting the apparent crosswind. Note that for a fixed heading with respect to the true wind, the apparent crosswind is sin(angle between true wind and sail craft's direction), which is constant for a constant true wind and heading, independent of the sail craft's speed. The overall efficiency determines the limit of speed for a given apparent crosswind and heading. Rcgldr ( talk) 23:56, 4 August 2020 (UTC)
Both the aerodynamic force on a sail and the wind velocity are vectors so it is possible to resolve them into components depending on which co-ordinate system you choose to use. Early work in aerodynamics used a co-ordinate system parallel and perpendicular to the wing. Later, the current standard of parallel (drag) and perpendicular (lift) to the wind direction became widespread. I have seen treatments for sailboats that resolve the aerodynamic force into components parallel and perpendicular to the centerline of the boat, resolving the force into drive and heel (or leeway). Similarly, I can see where it might be illuminating to resolve the wind velocity into components parallel and perpendicular to the centerline of the boat, but I've never come across any literature that does this. Using the conventional coordinate system, by definition wind velocity is always 100% in the direction of drag. So, for the purposes of editing this article, the next step would be to find a reference that resolves wind velocity into components parallel and perpendicular to the boat. Mr. Swordfish ( talk) 15:24, 5 August 2020 (UTC)
With regards to the labeling of and differentiating between the antiparallel vectors boat speed and boat wind, there appears on reading and referencing the associated image(without referencing the commons description, it should be noted) to be an identical subscripted labelling for both vectors as VB. While the written section and associated mathematical description do well to detail the apparent wind calculation with regards to boat wind, for those referencing the image to visualize the associated derivation, it can be a bit confusing. As a passerby, it wasn't my hope to unilaterally alter either the section description or the associated media, though it seems to me that the easiest rectification would be to specify that boat wind is antiparallel to boat speed by referencing boat wind as -VB. Though as the associated media was uploaded by HopsonRoad, a modified image might best serve the purpose of the description, but this is to your discretion. The Intervocalic Sigma ( talk) 21:36, 29 May 2021 (UTC)
Needs fixing:
β is magically introduced without any explanation - someone needs to say with this is the FIRST TIME it is mentioned (probably apparent wind angle - so if yes, spell that out).
This is an article about sailing. That implies SAILS. So this phrase needs to be reworded: "If the craft travels at VB = 10 knots with a tailwind of VT = -5 knots" - last time I checked, regular sail boats cannot sail downwind at double the speed of the wind. Introducing examples that are impossible does NOT help anyone understand things! — Preceding unsigned comment added by 110.143.72.26 ( talk)
Would it make sense to change this:
"High-performance watercraft that can exceed the velocity of the true wind include..."
to something like this:
"High-performance watercraft that can achieve VMG in excess of the true wind include..."
When I read the article I was at first questioning if it was talking about exceeding speed of the true wind in its direction of travel or if it meant the direct downwind component of its velocity vector (VMG) could exceed true wind. After reading it over a few times it seems like it is the latter. But only because I've read other things. Seems like it would be clearer if it was explicitly stating that it is VMG we're talking about here. — Preceding unsigned comment added by 50.238.167.160 ( talk) 23:46, 22 August 2022 (UTC)