设计比率

比較設計比率Jay E. Paris |2015年12月13日

考慮到所涉及的無數變量，在兩個不同的帆船設計之間進行任何客觀的比較可能，起初，似乎是不可能的。然而，在設計比率的幫助下，你不僅可以比較和對比不同的設計，但得到一個很好的主意，看不見，如何一艘船將如何執行帆。

其中第一個，排水量長度比（D / L）是一條船相對於其水線長度有多重的無量綱表達式。AD / L比通過將長噸（2,240磅）的船的排水量除以水線長度（以英尺計）立方​​的一百分之一來計算。因為長噸位中的排水量可以表示為體積（海水的立方英尺），並且由於長度立方也是體積的，所以D / L公式的結果是無量綱的，即，它不再與特定物理尺寸。

這意味著D / L可以用於比較船隻的相對“沉重”，無論它們的大小。例如，如果具有相同的D / L比，具有25英尺水線的船和具有50英尺水線的船相對於它們各自的水線長度同樣重。船的相對重度通常分類如下：

這些等級適用於當前設計，其趨向於比早期船更傾向於減少懸垂和更長的水線。20世紀30年代到20世紀60年代的大多數帆船設計具有高於300的D / L（通常稱為），但隨著它們的長懸伸，它們的航行長度隨著它們的傾斜而增加，從而導致“有效的”D /遠低於其計算值。

排水量 - 長度比的意義是，船相對於其水線長度越輕，其速度勢越高，特別是在排水量模式下。如果有較少的水被推向一邊，波動阻力減小。一些超輕型船隻，或ULDB，足夠輕，以像一個動力艇平面，在這種情況下，低D / L給出了一個設計如何快速和容易地轉換出排水量模式。（雖然船體形狀也很重要。）

雖然起初可能似乎希望總是具有盡可能低的D / L，如在遊艇設計的大多數方面中存在權衡。一般來說，D / L越低，船舶在海上航行的運動越不舒適，船舶越重則越敏感。

另一個重要的設計參數是  帆面積 - 排量比（SA / D），另一個無量綱計算，表示船的帆面積和其排量之間的關係。傳統上，它是通過將平方英尺的標稱帆面積除以以立方英尺為單位的船的排量到三分之二的功率來計算的。

在這種情況下，排量通過將其除以64，即1立方英尺的海水的重量從磅轉換成立方英尺。大多數設計人員用於比較目的的標準排水量是半裝載排水量，船上裝備的船隻和船上的一半消耗品（供應，水，燃料，用品）計算。

標稱風帆面積計算為前三角形面積（底部的一半或J尺寸乘以高度或I尺寸）和主帆面積（腳的一半或E尺寸乘以提昇機或P尺寸）。然而，重要的是要注意，海軍建築師（和海洋記者）越來越多地使用實際的風帆區域作為主帆，特別是，因為名義面積未能解釋經常在現代鑽機上飛行的更大的蟑螂。

SA / D也是無量綱的，因為平方英尺中的帆面積除以已經從立方角轉換成平方英尺的排量項。該數學處理導致再次與舟尺寸無關的參數。因此，具有SA / D為20的30英尺將具有與具有相同SA / D的60英尺一樣強大的鑽機。

一般來說，具有小於15的風速面積排量比的船將被認為是欠冷的; 高於15的值將表明性能相當好; 並且任何高於18至20的性能表現出相對高的性能，只要船具有足夠的穩定性和足夠低的排量 - 長度比以利用其豐富的帆面積。

SA / D類似於汽車的馬力重量比，其中帆面積是功率的度量，並且排量指示波浪阻力。阻力的主要成分是摩擦和波動; 因為波動製造隨速度不成比例地增加，所以SA / D表示中 - 重 - 大氣條件下的性能。

當比較不同船的SA / Ds以確定每個船的帆面積和排量值以相同的方式測量時，這是重要的。在SAIL的新帆船評論中，我們通常使用主帆和100％前三角區域計算比率。

在場合，船廠可以公佈大於和小於標稱值的航行區域和排量，以使船隻的SA / D比率最大化，以使得看起來具有更高的性能。這是通過引用重疊的熱那亞的區域，或在移動的情況下，出版從建造者運輸的船的輕型船舶重量，而不是半負載排量。

最後，有壓載比，或設計承載的壓載量。與前兩個比率不同，這一個不需要花費單位的轉換：簡單地將鎮流器的重量除以半載荷排量，然後乘以100.數字越高，矯正力矩越大，即，抵抗傾覆的能力。

通常，40或更大的壓載比轉換成更堅硬，更強大的船，將更好地站立到風。然而，注意到壓載物的放置在起伏時刻也起到重要作用是非常重要的：例如，相同重量的內部壓載物將提供比在深的龍骨的尖端更少的正確力矩。因此，壓載比比前兩個壓載比確定得稍微少些。

雖然平衡的時刻，如果顯然重要的良好的航行表現，這是另一個領域，可能有太多的好東西。具體來說，具有積極合理時刻的船在海上將具有更快，更積極的運動，這對船員來說可能是困難的。如果你只是花一個下午在浮標周圍游泳，那麼舒適可能不是特別重要。然而，“seakindliness”的所謂，可以在一個漫長的通道在世界上所有的差異。

Comparing Design RatiosJay E. Paris | December 13, 2015

Given the infinite number of variables involved, making any kind of objective comparison between two different sailboat designs might, at first, seem impossible. However, with the help of design ratios, you can not only compare and contrast different designs, but get a pretty good idea, sight unseen, as to how a boat is going to perform under sail.

The first of these, the Displacement-Length Ratio (D/L) is a nondimensional expression of how heavy a boat is relative to its waterline length. A D/L ratio is calculated by dividing a boat’s displacement in long tons (2,240 pounds) by one one-hundredth of the waterline length (in feet) cubed. Because the displacement in long tons can be expressed as a volume (cubic feet of seawater), and since length-cubed is also volumetric, the result of the D/L formula is nondimensional, i.e., it is no longer tied to a particular physical size.

This means the D/L can be used to compare the relative “heaviness” of boats no matter their size. For example, a boat with a 25-foot waterline and one with a 50-foot waterline are equally heavy relative to their respective waterline lengths if they have the same D/L ratio. The relative heaviness of boats is often categorized as follows:

These gradations are applicable to current designs, which tend more toward reduced overhangs and longer waterlines than earlier boats. Most sailboat designs of the 1930s through the 1960s had D/Ls (as they are often referred to) above 300, but with their long overhangs their sailing length was increased as they heeled, resulting in “effective” D/Ls at speeds that were well below their calculated values.

The significance of the displacement-length ratio is that the lighter a boat is relative to its waterline length, the higher its speed potential, especially when in displacement mode. If there is less water to push aside, wavemaking drag is reduced. Some ultralight-displacement boats, or ULDBs, are light enough to plane just like a powerboat, in which case a low D/L gives some indication how quickly and easily a design will transition out of displacement mode. (Although hull shape is also important.)

While at first it might seem desirable to always have as low a D/L as possible, as in most aspects of yacht design there are trade-offs. In general, the lower the D/L, the less comfortable the boat’s motion will be in a seaway and the more sensitive the boat is to overloading.

Another important design parameter is the Sail Area-Displacement Ratio (SA/D), another nondimensional calculation that expresses the relationship between a boat’s sail area and its displacement. Traditionally, it is calculated by dividing the nominal sail area in square feet by the boat’s displacement in cubic feet to the two-thirds power.

In this case, displacement is converted from pounds to cubic feet by dividing it by 64, the weight of a cubic foot of seawater. The standard displacement used by most designers for comparative purposes is the half-load displacement, calculated with the boat equipped for sailing with the crew and half the consumables (provisions, water, fuel, supplies) on board.

The nominal sail area is calculated as the sum of the foretriangle area (one-half the base, or J dimension, multiplied by the height, or I dimension) and the mainsail area (one-half the foot, or E dimension, multiplied by the hoist, or P dimension). It’s important to note, however, that naval architects (and marine journalists) are increasingly using actual sail areas for mainsails, in particular, because the nominal area fails to account for the larger roaches often flown on modern rigs.

The SA/D is also nondimensional because sail area in square feet is divided by a displacement term that has been converted from cubic to square feet. This mathematical manipulation results in a parameter that again is independent of boat size. Therefore, a 30-footer with a SA/D of 20 will have just as powerful a rig as a 60-footer with the same SA/D.

In general terms, a boat having a sail area-displacement ratio under 15 would be considered undercanvased; values above 15 would indicate reasonably good performance; and anything above 18 to 20 suggests relatively high performance, provided the boat has sufficient stability and a low enough displacement-length ratio to take advantage of its abundant sail area.

The SA/D is analogous to an automobile’s horsepower-to-weight ratio, with sail area being a measure of power, and displacement being indicative of wavemaking drag. The principal components of drag are friction and wavemaking; since wavemaking increases disproportionally with speed, the SA/D is indicative of performance in moderate- to heavy-air conditions.

It is important when comparing the SA/Ds for different boats to be certain that the sail area and displacement values are measured in the same way for each boat. In SAIL’s New Sailboat Review, we typically calculate ratios using the mainsail and 100% foretriangle area.

On occassion a boatbuilder may publish sail areas and displacements that are larger and lower than nominal so as to maximize a boat’s SA/D ratio in the interest of making appear to be higher performance. This is done by quoting the area of an overlapping genoa, or in the case of displacement, publishing the light-ship weight of the boat as shipped from the builder rather than the half-load displacement.

Finally, there is the Ballast Ratio, or the amount of ballast a design is carrying. Unlike the first two ratio, this one requires no fancy conversions of units: simply divide the weight of the ballast by the half-load displacement, and then multiply by 100. The higher the number, the greater the righting moment, i.e. the greater to ability to resist heeling.

Typically, a ballast ratio of 40 or more translates into a stiffer, more powerful boat that will be better able to stand up to the wind. However, it’s imporant to be aware that ballast placement also plays an important role in righting moment: for example, the same weight of internal ballast will provide far less righting moment than at the very tip of a deep fin keel. Therefore, ballast ratios are somewhat less determinent than the first two.

While righting moment if obviously important to good sailing performance, this is another area in which is it possible to have too much of a good thing. Specifically, a boat with an aggresive righting moment will have a faster, more aggresive motion in a seaway, which can be hard on crews. If you’re only spending an afternoon racing around the buoys, then comfort may not be especially important. However, “seakindliness” as it’s called, can make all the difference in the world on a long passage.

比較設計比率Jay E. Paris |2015年12月13日

考慮到所涉及的無數變量，在兩個不同的帆船設計之間進行任何客觀的比較可能，起初，似乎是不可能的。然而，在設計比率的幫助下，你不僅可以比較和對比不同的設計，但得到一個很好的主意，看不見，如何一艘船將如何執行帆。

其中第一個，排水量長度比（D / L）是一條船相對於其水線長度有多重的無量綱表達式。AD / L比通過將長噸（2,240磅）的船的排水量除以水線長度（以英尺計）立方​​的一百分之一來計算。因為長噸位中的排水量可以表示為體積（海水的立方英尺），並且由於長度立方也是體積的，所以D / L公式的結果是無量綱的，即，它不再與特定物理尺寸。

這意味著D / L可以用於比較船隻的相對“沉重”，無論它們的大小。例如，如果具有相同的D / L比，具有25英尺水線的船和具有50英尺水線的船相對於它們各自的水線長度同樣重。船的相對重度通常分類如下：

這些等級適用於當前設計，其趨向於比早期船更傾向於減少懸垂和更長的水線。20世紀30年代到20世紀60年代的大多數帆船設計具有高於300的D / L（通常稱為），但隨著它們的長懸伸，它們的航行長度隨著它們的傾斜而增加，從而導致“有效的”D /遠低於其計算值。

排水量 - 長度比的意義是，船相對於其水線長度越輕，其速度勢越高，特別是在排水量模式下。如果有較少的水被推向一邊，波動阻力減小。一些超輕型船隻，或ULDB，足夠輕，以像一個動力艇平面，在這種情況下，低D / L給出了一個設計如何快速和容易地轉換出排水量模式。（雖然船體形狀也很重要。）

雖然起初可能似乎希望總是具有盡可能低的D / L，如在遊艇設計的大多數方面中存在權衡。一般來說，D / L越低，船舶在海上航行的運動越不舒適，船舶越重則越敏感。

另一個重要的設計參數是  帆面積 - 排量比（SA / D），另一個無量綱計算，表示船的帆面積和其排量之間的關係。傳統上，它是通過將平方英尺的標稱帆面積除以以立方英尺為單位的船的排量到三分之二的功率來計算的。

在這種情況下，排量通過將其除以64，即1立方英尺的海水的重量從磅轉換成立方英尺。大多數設計人員用於比較目的的標準排水量是半裝載排水量，船上裝備的船隻和船上的一半消耗品（供應，水，燃料，用品）計算。

標稱風帆面積計算為前三角形面積（底部的一半或J尺寸乘以高度或I尺寸）和主帆面積（腳的一半或E尺寸乘以提昇機或P尺寸）。然而，重要的是要注意，海軍建築師（和海洋記者）越來越多地使用實際的風帆區域作為主帆，特別是，因為名義面積未能解釋經常在現代鑽機上飛行的更大的蟑螂。

SA / D也是無量綱的，因為平方英尺中的帆面積除以已經從立方角轉換成平方英尺的排量項。該數學處理導致再次與舟尺寸無關的參數。因此，具有SA / D為20的30英尺將具有與具有相同SA / D的60英尺一樣強大的鑽機。

一般來說，具有小於15的風速面積排量比的船將被認為是欠冷的; 高於15的值將表明性能相當好; 並且任何高於18至20的性能表現出相對高的性能，只要船具有足夠的穩定性和足夠低的排量 - 長度比以利用其豐富的帆面積。

SA / D類似於汽車的馬力重量比，其中帆面積是功率的度量，並且排量指示波浪阻力。阻力的主要成分是摩擦和波動; 因為波動製造隨速度不成比例地增加，所以SA / D表示中 - 重 - 大氣條件下的性能。

當比較不同船的SA / Ds以確定每個船的帆面積和排量值以相同的方式測量時，這是重要的。在SAIL的新帆船評論中，我們通常使用主帆和100％前三角區域計算比率。

在場合，船廠可以公佈大於和小於標稱值的航行區域和排量，以使船隻的SA / D比率最大化，以使得看起來具有更高的性能。這是通過引用重疊的熱那亞的區域，或在移動的情況下，出版從建造者運輸的船的輕型船舶重量，而不是半負載排量。

最後，有壓載比，或設計承載的壓載量。與前兩個比率不同，這一個不需要花費單位的轉換：簡單地將鎮流器的重量除以半載荷排量，然後乘以100.數字越高，矯正力矩越大，即，抵抗傾覆的能力。

通常，40或更大的壓載比轉換成更堅硬，更強大的船，將更好地站立到風。然而，注意到壓載物的放置在起伏時刻也起到重要作用是非常重要的：例如，相同重量的內部壓載物將提供比在深的龍骨的尖端更少的正確力矩。因此，壓載比比前兩個壓載比確定得稍微少些。

雖然平衡的時刻，如果顯然重要的良好的航行表現，這是另一個領域，可能有太多的好東西。具體來說，具有積極合理時刻的船在海上將具有更快，更積極的運動，這對船員來說可能是困難的。如果你只是花一個下午在浮標周圍游泳，那麼舒適可能不是特別重要。然而，“seakindliness”的所謂，可以在一個漫長的通道在世界上所有的差異。

Comparing Design RatiosJay E. Paris | December 13, 2015

Given the infinite number of variables involved, making any kind of objective comparison between two different sailboat designs might, at first, seem impossible. However, with the help of design ratios, you can not only compare and contrast different designs, but get a pretty good idea, sight unseen, as to how a boat is going to perform under sail.

The first of these, the Displacement-Length Ratio (D/L) is a nondimensional expression of how heavy a boat is relative to its waterline length. A D/L ratio is calculated by dividing a boat’s displacement in long tons (2,240 pounds) by one one-hundredth of the waterline length (in feet) cubed. Because the displacement in long tons can be expressed as a volume (cubic feet of seawater), and since length-cubed is also volumetric, the result of the D/L formula is nondimensional, i.e., it is no longer tied to a particular physical size.

This means the D/L can be used to compare the relative “heaviness” of boats no matter their size. For example, a boat with a 25-foot waterline and one with a 50-foot waterline are equally heavy relative to their respective waterline lengths if they have the same D/L ratio. The relative heaviness of boats is often categorized as follows:

These gradations are applicable to current designs, which tend more toward reduced overhangs and longer waterlines than earlier boats. Most sailboat designs of the 1930s through the 1960s had D/Ls (as they are often referred to) above 300, but with their long overhangs their sailing length was increased as they heeled, resulting in “effective” D/Ls at speeds that were well below their calculated values.

The significance of the displacement-length ratio is that the lighter a boat is relative to its waterline length, the higher its speed potential, especially when in displacement mode. If there is less water to push aside, wavemaking drag is reduced. Some ultralight-displacement boats, or ULDBs, are light enough to plane just like a powerboat, in which case a low D/L gives some indication how quickly and easily a design will transition out of displacement mode. (Although hull shape is also important.)

While at first it might seem desirable to always have as low a D/L as possible, as in most aspects of yacht design there are trade-offs. In general, the lower the D/L, the less comfortable the boat’s motion will be in a seaway and the more sensitive the boat is to overloading.

Another important design parameter is the Sail Area-Displacement Ratio (SA/D), another nondimensional calculation that expresses the relationship between a boat’s sail area and its displacement. Traditionally, it is calculated by dividing the nominal sail area in square feet by the boat’s displacement in cubic feet to the two-thirds power.

In this case, displacement is converted from pounds to cubic feet by dividing it by 64, the weight of a cubic foot of seawater. The standard displacement used by most designers for comparative purposes is the half-load displacement, calculated with the boat equipped for sailing with the crew and half the consumables (provisions, water, fuel, supplies) on board.

The nominal sail area is calculated as the sum of the foretriangle area (one-half the base, or J dimension, multiplied by the height, or I dimension) and the mainsail area (one-half the foot, or E dimension, multiplied by the hoist, or P dimension). It’s important to note, however, that naval architects (and marine journalists) are increasingly using actual sail areas for mainsails, in particular, because the nominal area fails to account for the larger roaches often flown on modern rigs.

The SA/D is also nondimensional because sail area in square feet is divided by a displacement term that has been converted from cubic to square feet. This mathematical manipulation results in a parameter that again is independent of boat size. Therefore, a 30-footer with a SA/D of 20 will have just as powerful a rig as a 60-footer with the same SA/D.

In general terms, a boat having a sail area-displacement ratio under 15 would be considered undercanvased; values above 15 would indicate reasonably good performance; and anything above 18 to 20 suggests relatively high performance, provided the boat has sufficient stability and a low enough displacement-length ratio to take advantage of its abundant sail area.

The SA/D is analogous to an automobile’s horsepower-to-weight ratio, with sail area being a measure of power, and displacement being indicative of wavemaking drag. The principal components of drag are friction and wavemaking; since wavemaking increases disproportionally with speed, the SA/D is indicative of performance in moderate- to heavy-air conditions.

It is important when comparing the SA/Ds for different boats to be certain that the sail area and displacement values are measured in the same way for each boat. In SAIL’s New Sailboat Review, we typically calculate ratios using the mainsail and 100% foretriangle area.

On occassion a boatbuilder may publish sail areas and displacements that are larger and lower than nominal so as to maximize a boat’s SA/D ratio in the interest of making appear to be higher performance. This is done by quoting the area of an overlapping genoa, or in the case of displacement, publishing the light-ship weight of the boat as shipped from the builder rather than the half-load displacement.

Finally, there is the Ballast Ratio, or the amount of ballast a design is carrying. Unlike the first two ratio, this one requires no fancy conversions of units: simply divide the weight of the ballast by the half-load displacement, and then multiply by 100. The higher the number, the greater the righting moment, i.e. the greater to ability to resist heeling.

Typically, a ballast ratio of 40 or more translates into a stiffer, more powerful boat that will be better able to stand up to the wind. However, it’s imporant to be aware that ballast placement also plays an important role in righting moment: for example, the same weight of internal ballast will provide far less righting moment than at the very tip of a deep fin keel. Therefore, ballast ratios are somewhat less determinent than the first two.

While righting moment if obviously important to good sailing performance, this is another area in which is it possible to have too much of a good thing. Specifically, a boat with an aggresive righting moment will have a faster, more aggresive motion in a seaway, which can be hard on crews. If you’re only spending an afternoon racing around the buoys, then comfort may not be especially important. However, “seakindliness” as it’s called, can make all the difference in the world on a long passage.