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Nautical Slide Rules and Calculators

Link to our celestial navigation pages for a selection of celestial navigation calculators.

Weems & Plath Nautical Slide Rule

Derive an immediate solution to all speed-distance-time problems for answers in nautical or statue miles.  Calculate speed in knots or miles-per-hour; time in hours, minutes or seconds; and distance in nautical or statute miles (or yards if desired).  It's a standard for the U. S. Navy.


Weems & Plath Vectormaster

Vectormaster permits rapid solution of problems involving vectors, such as those encountered in current sailing, the determination of true wind direction and force, and the apparent wind to be expected on other headings.  Given the position of a storm and the direction and speed of its advance, you can quickly determine the course which will put maximum distance between your vessel and it.  A circular slide rule is located on the reverse for the quick solution of time, speed, and distance problems.  Instructions included.



Weems & Plath LIGHTrules

If you’ve ever been on the water at night and wondered if the lights you see are from an approaching or fleeing vessel, or if you wonder if the vessel is a fishing trawler or super tanker then LIGHTrule is for you.  It's a durable two-sided black PVC slide rule with lights and shapes displayed in patterns for identification.

This simple-to-use vessel identification tool shows the actual view of vessels for Port, Starboard, Bow and Stern lights. LIGHTrule identifies all the light configurations in a magnified viewer to make vessel descriptions easy to read. It also displays audible signals for restricted visibility, maneuvering and warning. It's inexpensive security for night travel and should be an essential part of the equipment found on any boat.It's also an excellent aide for navigation classes and Coast Guard exams, too.

Versions available for U. S. and International lights and signals. Constructed of extremely durable plastic and stored in a vinyl sleeve. Dimensions: 16” x 5 ¼”



Weems & Plath ROADrules

ROADrule  identifies the most common aids to navigation, rules of the road, and maneuvering and warning signals for U.S. or international waters. This simple-to-use identification tool shows the actual view of maritime buoys with corresponding chart symbols. It describes bridge lighting and waterway markings. ROADrule takes a large amount of complex information and makes it easy to understand and quick to refer to. Whether in a classroom or at the helm, it provides valuable assistance to make critical navigation decisions quickly and with confidence.

ROADrule is constructed of durable two-sided black PVC. Its design is similar to a slide-rule. The various buoyage markers are drawn in color to match the chart symbol.  It complements the recently introduced LIGHTrule that has become an instant success.

 Versions available for U. S. waters, European Inland Canals, and International Waters. Dimensions: 16” x 5 ¼”.


Ordering Information:
122091 Nautical Slide Rule $19.95
122264 Vectormaster $32.95
122648 LIGHTrule COLREGS
For U. S. and international waters
129865 LIGHTrule CEVNI
For European Inland Waterways
129863 ROADrule USATONS
For U. S. Coastal waters and the Intercoastal Waterway
129862 ROADrule IALA
For International waters according to the IALA Buoyage System
129864 ROADrule CEVNI
For European Inland Waterways

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