Velocity 
Predictions
( Double Hard Chine vs True Round Hull)

The following Velocity Predictions compare two steel versions of 'Thunder Cloud'.   

The 'Velocity Predictions Charts' 

  • Results are given  in 'Seconds per Nautical mile - (Sec/NM).
  • The BTW is the Track angle with respect to the true wind direction.
  • Six True Wind  speeds are listed (Knots)
  • Boat A is the True Round version of the hull.
  • Boat B is the Double Hard Chine version of the hull.

Example One:

What would be the speed in  (Sec/NM)for the True Round version - Boat-A, in a ten (10) knot True Wind Speed, at a BTW of 45-degrees?

897.82 = (Sec/NM)

Example Two:

What would be the speed in  (Sec/NM) for the Hard Chine version - Boat-B, in a ten (10) knot True Wind Speed, at a BTW of 45-degrees)?

(879.82 - 11.18) = 868.64 (Sec/NM)


Looks like the Hard Chine hull is a bit faster than the True Round version at a 45-degree Btw in a ten knot wind speed.


True Round vs Hard Chine

(Speed Comparison Cart

Looking at the above Cases, this is what I see:

  •  There is no real difference the Double Hard Chine and the True Round hull as far as speed is concerned.·        
  •  From a Stability point of view the Double Hard Chine hull is a bit more tender than the True Rounds hull.·         
  • The true round hull has a bit more maximum stability than the Double hard Chine hull.·         
  • The Double hard Chine hull has a higher Angle of Vanishing Stability at, 127-degree then the True Round hull at 122-degrees.·        
  •  The only meaningful difference and probably the most important to most sailors is:  One is True Round and the other is not.


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New - Ongoing

The redesign of the classic sailboat Dark Harbor for Aluminum construction

dark-harbor-model-file.jpg

Go to Dark Harbor Redesign



Steel and Aluminum True Round Plans

Click Here for Plans


Demystifying the weight factor

By way of a VPP Race between two versions of 'Lighting Strike' (One steel and the other Aluminum)

The weight factor Demystifed

Go to Lighting Strike's Velocity Predictions


How to layout and fabricate Hull Intergrals

Fabricating Hull Intergrals such as a Hatch Coaming is the next stage of boat construction.

The below pics is an initial dimensioned hand sketch - The first step in the layout process.


Click here to continue the process.


English Wheeling

This is not your Father's 'English Wheeling' method.

See how the 'True Round' shell platting is reduced to a flat pattern. These Flat Patterns take the mystic out of English Wheeling.


Click Here for Details



Converting an existing Hard Chine Design to a True Round Design

Followed by a Race via a 'Velocity Prediction Program.

Click Here

conversion1.jpg

The top pic is the orginal design - The bottom pic is the converted True Round version.

conversion2.jpg