The application of science in sailing is undeniable. The sciences of fluid dynamics, Newtonian laws of motion, conservation of energy, Aerodynamics and lift, friction, leverage, driven harmonic systems, weather, Astronomy, Mathematics, electromagnetism, curved space and non-Euclidean Geometry, it's all here in sailing.
There have recently been some lively debates about some of these aspects of sailing; what surface is fastest on the bottom of a hull, how to correct and correlate varied navigation systems, what does Hull Speed actually mean, balancing lateral resistance with center of effort, even how much, if any, flotation is needed in your boat, have all recently been debated. Then there is the whole problem of epistemology, how do we know what we know and if it is reasonable to question what is often considered "settled science".
I recently stated that science should never be settled. There were a couple of very good rebuttal points brought up around that statement. Example: it is considered settled that the Earth is not flat. Great point. Then there is the response that "settled" or not, we treat certain well developed ideas as settled because they hold true with use and they have acceptance from the science community. Absolutely.
I know there are a lot of great minds and an amazing level of education floating around on sailboats. I am astonished at the number of engineers and scientists on this forum. I am hoping to tap into some of that resource for some discussions into the "reality" or "myth" of science around sailing.
To kick it off, I thought it would be interesting to explore a little about the science of lift.
It has always seemed counter intuitive to discover that the fluid racing through a restriction in a pathway, the curve of a full sail, the displacement of a moving hull, can actually cause a lessening of pressure such that lift is created.
I wonder if the atmospheric pressure on the convex side of a sail is really lower than the pressure on the concave side or is it only experienced by the surface over which the air is racing? What I mean is, obviously the pressure on the convex surface of the sail is lower than the surface on the concave side of the sail because the sail is drawn into the low pressure area to equalize that pressure variance, but if a pressure gauge were flowing freely along with the air moving over the surface (no appreciable air movement relative to the gauge), would it feel the same drop in pressure as is felt on the surface of the sail?
You see, it had been explained to me that the directed flow of air meant that the sum total of pressure vectors could not push as hard or as long on the surface of the sail because of its movement across it, resulting in lift. However, some of the images I've seen in a couple of threads here on SBO, show regions of low pressure independent of air movement across the surface. That would mean there was a very real loss of atmospheric pressure for any object, regardless of its movement with or against the air flow. So, why? Why does a dynamic that seems to compress the gas by forcing it through a restriction, actually result in lowers psi and ultimately, lift?
- Will (Dragonfly)
There have recently been some lively debates about some of these aspects of sailing; what surface is fastest on the bottom of a hull, how to correct and correlate varied navigation systems, what does Hull Speed actually mean, balancing lateral resistance with center of effort, even how much, if any, flotation is needed in your boat, have all recently been debated. Then there is the whole problem of epistemology, how do we know what we know and if it is reasonable to question what is often considered "settled science".
I recently stated that science should never be settled. There were a couple of very good rebuttal points brought up around that statement. Example: it is considered settled that the Earth is not flat. Great point. Then there is the response that "settled" or not, we treat certain well developed ideas as settled because they hold true with use and they have acceptance from the science community. Absolutely.
I know there are a lot of great minds and an amazing level of education floating around on sailboats. I am astonished at the number of engineers and scientists on this forum. I am hoping to tap into some of that resource for some discussions into the "reality" or "myth" of science around sailing.
To kick it off, I thought it would be interesting to explore a little about the science of lift.
It has always seemed counter intuitive to discover that the fluid racing through a restriction in a pathway, the curve of a full sail, the displacement of a moving hull, can actually cause a lessening of pressure such that lift is created.
I wonder if the atmospheric pressure on the convex side of a sail is really lower than the pressure on the concave side or is it only experienced by the surface over which the air is racing? What I mean is, obviously the pressure on the convex surface of the sail is lower than the surface on the concave side of the sail because the sail is drawn into the low pressure area to equalize that pressure variance, but if a pressure gauge were flowing freely along with the air moving over the surface (no appreciable air movement relative to the gauge), would it feel the same drop in pressure as is felt on the surface of the sail?
You see, it had been explained to me that the directed flow of air meant that the sum total of pressure vectors could not push as hard or as long on the surface of the sail because of its movement across it, resulting in lift. However, some of the images I've seen in a couple of threads here on SBO, show regions of low pressure independent of air movement across the surface. That would mean there was a very real loss of atmospheric pressure for any object, regardless of its movement with or against the air flow. So, why? Why does a dynamic that seems to compress the gas by forcing it through a restriction, actually result in lowers psi and ultimately, lift?
- Will (Dragonfly)
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