Sloop Yawl Rig and Selected Balance Calculator

Posted by Robbie Dickson on

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For selected longitudinal reference positions measured from the bow, normalized offset is 100(XCLR − XCE)/LWL. Applying the same calculation to selected sloop and yawl CE positions gives their exact arithmetic difference, but does not predict helm.

Sloop–Yawl · Selected Longitudinal Balance

Compare selected sloop and yawl longitudinal CE/CLR references without predicting helm or performance.

0°

Selected Sloop Offset
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Selected Yawl Offset
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Selected CE Shift
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Offset Change
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Equation Used

offset=100(XCLR−XCE)/LWL; shift=XCE,yawl−XCE,sloop.
Exact selected geometry only; aerodynamic/hydrodynamic centers and helm response are not solved.
  • All longitudinal positions share a bow-origin reference.
  • LWL is positive.
  • CE and CLR inputs are selected comparison positions.
  • Sail areas, trim, heel, leeway, forces, moments, helm response and safety are excluded.
FIRGELLI Automations - Interactive Mechanism Calculators

The separate chart shows selected distances from the bow on one common scale. The rig illustration has fixed proportions.

A sloop-yawl rig and selected balance positions

The illustration shows a jib, gaff mainsail and small stern lug sail. The separate chart maps the selected waterline, CLR and two CE positions on one common scale; the drawn sails do not determine those positions.

What the calculator determines

Select waterline length, CLR position and sloop/yawl CE references. The calculator reports both normalized signed offsets, CE shift and the percentage-point change between offsets.

Selected longitudinal positions

offset = 100(XCLR − XCE)/LWL; CE shift = XCE,yawl − XCE,sloop; offset change = sloop offset − yawl offset.

Selected-input arithmetic

For LWL = 9.6 m, XCLR = 4.85 m, sloop CE = 4.05 m and yawl CE = 4.30 m, the selected offsets are about 8.33% and 5.73%, with a 0.25 m CE shift.

Geometry only

Actual aerodynamic and hydrodynamic centers vary with sail area, trim, heel, leeway, hull, keel, rudder, wind and speed. This calculation does not determine weather or lee helm, rudder angle, stability, performance or safety.

Questions

Are these solved centers of effort?

No. They are selected longitudinal comparison positions.

Does positive offset guarantee neutral helm?

No. A complete force-and-moment model is required.

References & Further Reading

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