Fossati's Aero-Hydrodyamics

If we increase the Angle of Attack ...

we can build 1 Wing ...

with 3 elements

 

America ... Schooner ...

America (yacht) - Wikipedia https://en.m.wikipedia.org/wiki/America_(yacht)

was a Cutter, haha

Joking aside: it is 1 Wing built with 3 elements

On the other hand, the Cutter vs. Sloop controversy was and is a discussion about two types of Hulls.

 

Force produced by a Sail can be recreated quite well as the Sum of

High pressure on a flat board

plus

Low pressure of a bow with its arrow (a) and string/chord

Cl2d = Lift Coefficient in two dimensions

CL3D = Lift Coefficient in three dimensions

AR = Aspect Ratio

Force = Coefficient x Dynamic pressure x Reference area

Dynamic pressure = 1/2 x density of the fluid x Velocity squared

 

Something moves and creates Low pressure, suction

Be that as it may, the truth is that high pressure is something natural to us because it is like a kind of push and, on the other hand, the suction, the low pressure, seems wrapped in an aura of mystery, could it be the fear of emptiness and nothingness (?)

 

Something is moving ... e.g. the curved stern of a sailboat seen in profile

First pedagogical attempt

The stern creates a hole and the stern falls into that hole

Second pedagogical attempt

The stern creates a gap or hole, the water wants to fill that hole or void and in doing so pulls back the water in front of it and makes it move at a higher speed, and the higher speed creates a lower pressure.

 

Home exercise

Yacht A seen from above sailing heeled

where is the Lateral High pressure, and where is the Lateral Low pressure

Yacht B seen from the side/Profile

where is the Vertical High pressure, and where is the Vertical Low pressure.

 

Why the stern of a Contessa 32 performs reasonably well

Answer

Because it moves more water from bottom to top than from side to side, in other words: the low pressure of the stern has more Vertical component than Lateral component

 

The case of this sailboat is prodigious (a motorsailer for more joke) and shows the power of the Low pressure, Suction.

It sailed at 4 knots of speed and with the waves the small boat made momentary peaks at 7-8 knots, the wind continued to rise and sailed at 5 knots and with the waves that had increased in size made peaks of 10-12 knots, at the end with very big waves it made a tremendous surf that concluded reaching a peak of 20 knots with 19.19 (!) feet LWL and 300 (!) D/L Carene

That the least important thing is the speed. Speed is just an index of dissipating energy in a good way. The tremendous thing is that it sank the stern in the wave and so bow up rode, flew, in a controlled manner instead of giving three somersaults after nailing the bow and run into a wall of resistance of destabilizing lateral forces.

 

Low pressure, suction

Low pressure, suction, is the number 1 enemy of the fast ship.

And the great friend of old airplanes, sails and small sailboats on the high seas.

 

Who can rid us of the pesky @CarlosK2 who is adding nothing to the discussion about Fossati's Appendix 1?

The arrow in question raises significant concerns due to several anomalies:

• Excessive Length: The length of the arrow, signifying the relative pressure strength, is considerably larger than all the others. This significant difference is a cause for suspicion.
• Divergent Direction: The arrow points in a direction markedly different from the rest. Since arrow direction indicates overpressure or underpressure, this deviation is a red flag.
• Lack of Data Point: The arrow's location coincides with a point where no pressure tap was present, suggesting an absence of any experimental data to support its inclusion.
• Perpendicular Consistency: Despite these anomalies, the arrow, like the others, maintains a perpendicular angle to its attachment point on the surface. This single consistency is not enough to alleviate the concerns raised by the other discrepancies.

These anomalies cast doubt on the validity of the arrow and its source. It's concerning that:

• Fossati uses a figure that appears to be unrelated to the actual experimental data obtained from the manometer and the pressure point diagram.
• He incorporates Marchaj's figure without a clear explanation of its relevance or how it aligns with the presented data.

 

After six pages,the discusssion still continues?Clearly there is a strong desire to get to grips with the workings and I believe it is the only aspect of boat design that you have any posting history with.For what it's worth,there are many,many people in the aircraft world who debate the precise reasons why wings work,but not the pressure differentials on the surfaces-and yet planes fly.Maybe finding a forum where they congregate would allow the collective brain power to be accessed.In the mean time,are you enjoying sailing regardless of how it works?

 

You are right, a very strong desire. I have been searching for such a forum, but no joy yet. PhysicsForum eventually banned me. aviation.stackexchange is not getting any traction. I was hoping for a connection with a fellow european (my heritage) and am encouraged by your response. And yes, I am enjoying yacht racing - delighted to find a high level, active, intellectually challenge sport that I can engage in approaching my 80th birthday.