Cruisingfoiler, "Mind you, I don’t know for sure what inertial frame you are referring to when you speak of maintaining altitude control. Given you refer to the requirement for 3m deep foils to keep the boat level in 2+ m seas, I believe my critique serves to demonstrate that your altitude maintenance claim is not sound.
Wave profiling: once the wave length is significantly greater than the foil spacing, the craft can more comfortably profile the wave section. Ocean wavelengths far exceed foil separation, so hull clearance does not need to exceed wave height. Offshore foiling is dynamic. Pitch and heave stability become dynamic with respect to the sea state. The sea state becomes the inertial frame in which the dynamics of pitch and heave stability operate. Chop is a different matter, and fetch in storm conditions. Clearance is required for both dynamic wave profiling and chop. The confused sea states found in storm conditions are another matter, but I’d only choose to foil in these conditions if the craft was more seaworthy by doing so (unlikely)."
I think you answered your own question, but I will try and clarify a little. Altitude control refers to keeping the boat horizontal to the horizon and keeping the primary lifting portion of the foil at least two feet below the surface of the water.
The CFly controls altitude by virtue of its triangular shape, the deeper the foil is in the water the more lift it has. The Canard portion of the Cfly stops lifting when the bottom plate is out of the water and planing and the main foil is still submerged. It works nicely as long as the waves are less than the height of the front foil (swells are not waves).
So it looks like CFly can handle 2 foot waves just fine and by scaling up it could probably handle much larger waves and therein lies the problem. As the boat is scaled up weight increases faster than size so the engineering becomes 'challenging'. Nothing time and money can't solve.
Talador
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Posted by: taladorwood@yahoo.com.au
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