The Newport cat-boat carries a single mainsail extended by a boom and gaff. Explore the rig described by Hiscox and compare entered longitudinal positions for the centre of effort (CE) and centre of lateral resistance (CLR), measured from one bow datum.
Newport Cat-Boat Reference-Position Calculator
Enter a declared waterline length, CE station and CLR station measured from the same bow datum, plus a board display angle. The worksheet reports the two stations and their signed separation only; it does not predict helm, stability, performance or safe design.
Equation Used
- All longitudinal stations use the same declared bow datum along the entered waterline length.
- The CE and CLR percentages are declared inputs; neither point is predicted from hull, sail or appendage geometry.
- The board angle changes only the drawing and is not used to infer CLR.
- Hydrostatics, sail aerodynamics, heel, trim, leeway, rudder effect, dynamic balance, structure, scantlings, rig loads, handling, performance and safety are excluded.
The entered CE and CLR positions set the reference lines in the drawing. Their signed separation is a distance calculation; the calculator does not derive either centre from sail or hull geometry.
A single gaff mainsail defines the documented rig
Hiscox item 766 describes the Newport cat-boat with its sail bent to the mast and extended by a boom and gaff, plus a forestay leading to a short bowsprit. The period Book of the Ocean describes the typical American cat as a broad, shallow-draft centre-board boat with one large sail.
The viewer identifies that topology and keeps the entered station arithmetic separate from the historical drawing.
A historical American cat-boat type
Period literature associates the Newport catboat with American recreational sailing and describes the broader catboat type as a centre-board craft. The diagram illustrates this historical rig rather than the dimensions or capabilities of a particular modern boat.
Longitudinal reference-position calculations
Both percentages use one declared bow datum. This arithmetic does not locate either centre from physical geometry and does not prescribe a target lead.
Declared station example
For a 6.4 m waterline, CE at 42% and CLR at 55% from the bow datum, the declared stations are 2.69 m and 3.52 m. CLR minus CE is +0.83 m, or +13.0% of waterline.
Reference positions and sailing balance
Sailing balance depends on the hull, appendages, sail and operating conditions together. The separation between two entered reference points alone does not determine helm response or a suitable design target. The board-angle control changes the illustration only; it does not recalculate CLR.
Newport cat-boat calculator questions
Does this calculator find CE or CLR?
No. Both are declared inputs.
Does a positive separation guarantee weather helm?
No. The result is only signed distance between two declared stations.
Does board angle move the entered CLR?
No. It changes the schematic only; a real CLR requires the complete underwater geometry and condition.
Newport cat-boat references
- Hiscox, Mechanical Movements, page 218, item 766: public-domain plate and caption identifying the mast-bent sail, boom, gaff, forestay and short bowsprit.
- Ernest Ingersoll, The Book of the Ocean: period public-domain discussion and illustration of the Newport catboat and the American centre-board catboat type.
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