Capt Ronrico
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- Oct 23, 2015
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Magic Number for Boats = 61.8 ?
I stumbled on this notion while reading "The Silent War" by John Craven. Craven was the U.S. Navy's Chief Scientist during the Cold War era. The things he and his crew got up to are mind-blowing: like wire-tapping the Soviet High Command's private phone lines' underwater cables; developing the Polaris submarines; and sorting out the Thresher & Scorpion disasters.
Anyway, he mentions that if you look at an aerial photograph of any large body of water with boats on it, you will see that the wakes left behind by the boats all measure 61.8 degrees. This is true, he says, of all boats in all waters - fresh or salt - at all times of the year in all parts of the world in all non-stormy conditions. Pretty interesting, I think.
I'm pretty sure that this number has something to do with the molecular geometry of water itself. So I started thinking of 61.8 degrees as the cleavage angle for water. I simplified it to 60 degrees (for convenience - 60 deg is so familiar to work with) and started wondering if this applied directly to boat design: that is, if the included angle of the bow from tip to widest beam was 60 deg or less, would the boat be very efficient; and if the included angle were greater, would the boat be inefficient?
That is: is the design of the boat working with or against nature in terms of slicing through water? If so, then 61.8 qualifies as a magic number for hydraulics.
If true, then if you want a boat to go fast and slice through a wave, make the bow angle 60 deg or less. If you want the boat to breast an oncoming wave, make the bow angle bluffer than 60 deg, for example.
Then I started to think: this has got to be some universal fact that every boatnik but me knows and takes for granted. It must be basic to all boat design, all marine engineering.
So - finally - my question is: is it an open secret and how does it affect boat design?
I stumbled on this notion while reading "The Silent War" by John Craven. Craven was the U.S. Navy's Chief Scientist during the Cold War era. The things he and his crew got up to are mind-blowing: like wire-tapping the Soviet High Command's private phone lines' underwater cables; developing the Polaris submarines; and sorting out the Thresher & Scorpion disasters.
Anyway, he mentions that if you look at an aerial photograph of any large body of water with boats on it, you will see that the wakes left behind by the boats all measure 61.8 degrees. This is true, he says, of all boats in all waters - fresh or salt - at all times of the year in all parts of the world in all non-stormy conditions. Pretty interesting, I think.
I'm pretty sure that this number has something to do with the molecular geometry of water itself. So I started thinking of 61.8 degrees as the cleavage angle for water. I simplified it to 60 degrees (for convenience - 60 deg is so familiar to work with) and started wondering if this applied directly to boat design: that is, if the included angle of the bow from tip to widest beam was 60 deg or less, would the boat be very efficient; and if the included angle were greater, would the boat be inefficient?
That is: is the design of the boat working with or against nature in terms of slicing through water? If so, then 61.8 qualifies as a magic number for hydraulics.
If true, then if you want a boat to go fast and slice through a wave, make the bow angle 60 deg or less. If you want the boat to breast an oncoming wave, make the bow angle bluffer than 60 deg, for example.
Then I started to think: this has got to be some universal fact that every boatnik but me knows and takes for granted. It must be basic to all boat design, all marine engineering.
So - finally - my question is: is it an open secret and how does it affect boat design?
