Performance Results 
(Seconds per Nautical Mile)


There eight (8) outputs charts defining the race results between the aluminum version of 'Lighting Strike'  designated as   (Boat A), and the steel versions of 'Lighting Strike' designated as Boat B). 



Understanding the Velocity Prediction Charts:

  1. Each output chart  represents a different (BTW) or the track angle with respect to the true winds direction.  BTW= 0 is dead to windward. BTW =180 is dead downwind.   The BTW's start with the boat heading  45- degrees to the wind, then BTW's of  60 degrees, 75-degrees, 90-degrees, 120-degrees, 135-degrees, 150-degrees, ending with a BTW of180-degrees or directly downwind.
  2. Each output chart will calculate the speed of the hull, in seconds per nautical mile, for six (6) different True Wind speed in knots ranging from 6 to 16 Knots.
  3. The next row (Base Sec/NM - Boat A), (the aluminum version of 'Lighting Strike'),  calculates the seconds that Boat A takes to travel one (1) nautical mile for each of the above True wind speeds.
  4. The next row (Differences - Boat B), (the steel version of 'Lighting Strike'), calculates the difference in seconds per Nautical Mile from the Base Sec/NM -Boat A.
  5. A 'Positive' (Difference) is added to Boat-A's time.  Making Boat B slower than Boat A.
  6. A 'Negative' (Difference) is subtracted from  Boat A's time.  Making Boat B faster than Boat A. 

45
60
75

The first three Performance predictions are the Windward and Close Reach results.  Here is how I read the results:

  1. At the lower true wind speeds the steel version is a bit slower.
  2. At the higher true wind speeds the steel version is a bit faster.

90

On a Beam Reach:

  1. At the lower to middle true wind speeds the steel version is still a bit slower.
  2. At the higher true wind speeds the steel version is still a bit faster.
120
135
150
180

On the Broad Reaches to Downwind:

  1. At all true wind speed the steel version is slower


  1. Generally speaking, I do not see reason to build the aluminum version over the steel version over concerns of speed.
  2. Especially if my aluminum welding skill were lacking.
  3. I encourage the reader to review the Static Hydrostics,  Dynamic Stability, Center of Gravity location, Weight Distribution, Hull Scantlings, and Sailplan Ratios and Coefficients for both aluminum and Steel construction by clicking on the below links.

Aluminum Version- Engineering Details

Steel Version- Engineering Details



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New - Ongoing

The redesign of the classic sailboat Dark Harbor for Aluminum construction

Updated - June 22 2025

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