WEEMS & PLATH Marine Parallel Ruler for Chart Plotting — 15" Aluminum Arms, Protractor & Beveled Acrylic

Built for chartwork on sailboats, motor cruisers and in ship pilothouses, this parallel ruler combines rigid brushed aluminum arms with polished aluminum handles and a precision-milled acrylic crosspiece. At 15 inches long and just 0.22 inches thick, it balances reach and control while weighing only 7.5 ounces—compact enough for crowded chart tables yet long enough to span typical chart scales. A built-in protractor and beveled acrylic edges make angle transfer and sighting straightforward, and the included protective plastic sleeve keeps the unit scratch-free in storage.

How does this ruler improve accuracy when transferring bearings?

The rigid aluminum arms resist flexing so the ruler holds its alignment while you slide it across the chart, reducing parallax and cumulative error. The milled acrylic crosspiece with beveled edges provides a clear sightline and stable contact with the paper.

• Brushed aluminum arms minimize bending under normal charting pressure
• Polished handles give a secure grip for precise movement
• Beveled acrylic edges reduce snagging and enable exact placement
• Integrated protractor scale lets you read and set angles directly

Is the 15-inch length appropriate for small vessels and bench use?

Yes—the 15-inch span is a practical compromise between portability and reach. It covers common chart scales used by recreational mariners while fitting easily into chart lockers or a bag.

• 15 inches (38.1 cm) covers most coastal chart plotting needs
• 0.22-inch thickness keeps the tool slim for tight work areas
• 7.5-ounce weight makes it easy to handle without slipping
• Protective sleeve preserves edges when stowed aboard

What construction features enhance durability for marine conditions?

Materials and machining were chosen to stand up to regular onboard use. Brushed aluminum arms resist corrosion and show wear less visibly, while the polished handles are engineered for repeated handling and positive control.

• Brushed and polished aluminum resists seawater exposure with proper care
• Milled acrylic crosspiece is dimensionally stable and impact-resistant
• Beveled edges reduce chipping and maintain straight lines
• Includes a protective plastic sleeve to prevent scratches during storage

How do I care for and store the parallel ruler to keep it accurate?

Rinse with fresh water after heavy salt exposure and dry thoroughly to minimize corrosion or spotting. Store in the supplied plastic sleeve in a dry location and avoid dropping the tool or placing heavy objects on it to preserve alignment.

• Freshwater rinse after salty spray or prolonged sea use
• Wipe dry and store in the included protective sleeve
• Do not bend or clamp tightly to prevent alignment shifts
• Periodic inspection of edges and protractor keeps readings reliable

Who is this for: Recreational and professional mariners who need a dependable, easy-to-use plotting instrument for coastal navigation and routine chartwork. It’s suitable for skippers, navigators, sailing instructors and anyone who prefers manual plotting alongside electronic navigation aids. The Weems & Plath 15" parallel ruler is an especially good match for boats with limited chart-table space where a balance of reach, durability and portability matters.