Equinox: Designing the Hull
Steam Happens #26
Click on the photo below to view a new Equinox movie
Will and Equinox at Lees Mills August 2014
Pictures and illustrations from the article in order of appearance
plus a few extras
A spar-mounted torpedo
torpedo-boat attack. As dangerous for the attacker as the target
Various confederate stealth torpedo-boats. These were usually called "Davids" as opposed to their "Goliath" targets
Herreshoff's Lightning with two spar torpedos
Turbinia at speed
Turbinia on display
Herreshoff's Stiletto, capable of launching a free-running torpedo
and Herreshoff's Lotus Seeker (below), a private fast commuter capable of launching a great gin and tonic
Oberon, a beautiful modern fast launch from U.K.
Click here to view Oberon running at speed. You must view these videos:
The Prismatic Coefficient:
easily driven hull the prismatic coefficient ranges from just under to just over
A boat with a Cp of 0.525 or less is usually considered a very “fine” hull and is optimized for speed in a displacement (non-planing) hull....
V is the immersed volume or displacement of the hull in cubic feet
A is the maximum cross-sectional area in square feet
L is the waterline
length in feet.
The Cp thus indicates the longitudinal distribution of the underwater volume of a yacht's hull.
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Will's hull designing illustrations. Evaluating a hull design with simple tools. Please refer to article
Figure 1 Calculation of the cross sectional area at any station by counting squares
Figure 3 The area below the waterline
Figure 4 Locating the center of bouyancy
Figure 5 Graphically calculating the righting moment by tilting the waterline
Figure 5b, a healed version of Figure 5. Graphically calculating the righting moment by tilting the hull and keeping the waterline level
Figure 6 How the height of the center of gravity affects heel stability
Figure 7 Round profile vs hard chine with the same cross section area
Figure 8 Comparing the heel stability of a round bilge vs a single chine hull.
Stern. Note hard chine aft of skeg
Hull on trailer. Note balance on single axle and angle of repose to facilitate easy one man launching and loading.
To download the above CAD file of the Equinox hull "hull.EPRT" click here
Download eDrawings Viewer (it's free) to view, rotate, and
closely examine the hull
drawing file click here.
Install it on your computer and use it to open the drawing hull.EPRT