You can get empirical relationships from this link:
The height relationship at 16.35 gives similar results to the table I sent.
The wave celerity is given at 16.33.
From the celerity you can use the well known relationship between gravity wave celerity and wavelength used to determine "hull speed" for displacement craft.
Using these relationships you can determine the maximum wave slope is constant at 1 in 12 irrespective of wave size. These are deep water waves. Waves get steeper in shallow water. My understanding is that peak slope before breaking is around 1 in 7 and that is a better value for determining clearance of structure over the water.
With the model for a sailing boat I do not consider approaching waves perpendicular. The wave heights and celerity are a function of the windspeed and I use the same value, for convenience, to produce the drive. I can change sail parameters to adjust for apparent windspeed if I choose. I usually have minimum angle of 40 degrees to the waves. Also I do not have large angles to apparent wind creating maximum drive when I have high angles to the wave. These conditions could exist if the wind was changing direction rapidly. However in those circumstances the prudent skipper will not be chasing maximum speed.
I developed the model to see how reserve buoyancy affected drag and to see how hard a boat could be pressed before diving.
The model only considers a single hull and I only consider motions in the vertical plane on the longitudinal axis of the hull. Its gives realistic results for the Harryproa.
On 01/05/2016, at 3:06 PM, "lucsimard@ymail.com [harryproa]" <harryproa@yahoogroups.com.au> wrote:
Rick,
Thanks for the links!I saw Beaufort scale before, what it does not give me is the distance between waves, I know it can vary a lot depending on swell and wind, etc. but the mathematical model need a number ...I figure that with a 15 m boat, if waves are close together, it would ride quite leveled supported by many wave crests. But at some point, the wavelength will increase with wind force and just as the boat is at it's maximum pitch and velocity going down, the bow will hit the next wave and burry ... Rotation inertia and speed would make this worst. Also worst case would be Wave length close to boat length I guess ?But my question is much simpler, does the simulation/calculations you use for the number you gave me consider all this ? (worst case boat length vs wave length, speed, etc ?)... understood that dynamic lift or wave pressure on top of the bow is not considered.Wondering since I can predict but really never know when crossing the sea what I could be getting. Also can give me a good idea when to safely take the sea anchor out :-)
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Posted by: Rick Willoughby <rickwill@bigpond.net.au>
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