Boat & Sailing instruments

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 The Marine instruments - Articles & helpful information

Instruments and Systems

Regardless of whether you are a sailor or operate a power boat, the information gained from basic instrumentation is vital to proper navigation.

Boat Instrument systems relay important navigational information to the captain and crew. The most common instruments found on boats are depth sounders and speed logs, and many sailboats supplement these with wind speed and direction instrumentation.

These instruments can function independently or they can feed data to each other, producing information such as Velocity Made Good (term in sailing - VMG) which requires boat speed, wind speed and wind direction instruments to talk to each other.

The navigational instruments

Transducers are the heart of your navigational instruments.

They take the input of one form of energy and produce an output of energy in another form (usually an electric output signal), with a known, fixed relationship between the input and output. Transducers are either reinforced plastic or bronze. Use plastic transducers on aluminum or steel hulls to reduce electrolysis problems and use bronze on fiberglass boat hulls.

Boat/Sailing instruments

Apparent wind direction and wind speed are the two basic functions of any wind instrument. Additional sensors can expand these functions to include true wind direction, true wind speed, true wind angle and leeway, perfect for racing sailors.

Wind Speed & Direction sailing instruments have three primary components; a wind vane, an anemometer, and transducer.

The wind vane detects the apparent wind direction, the anemometer measures the wind speed and the transducer receives this data, transforming it into an output signal which is presented on either an analog or digital display.

With 55 years of development the Ockam Sailboat Wind Instruments
provide the best solution for sailors.

To Learn more: What is Vmg, True wind speed and direction or Understanding wind shear visit

Sailboats offer a particular challenge for accurate wind data. A heeling, rolling, pitching sailboat causes data errors. Wind speed is relative to the height above the water's surface and that distance changes each time the boat rolls. When the vane and anemometer can no longer sense the wind parallel to the water's surface, the readings are changed and incorrect. There are systems that will correct for these errors but they are expensive.

Wind speed instruments

Wind speed instruments are found primarily on sailboats, especially racing sailboats, but they're finding their way more and more onto cruising sailboats and power boats because of the ability to integrate instruments. The data from a wind speed instrument can be correlated with a speed instrument's data to determine the VMG (the average speed to a point directly upwind or directly downwind), giving you the ability to determine the fastest angle of attack relative to the wind.

Speed instruments

Speed instruments indicate the vessel's hull speed through the water and many incorporate a log and trip log. The reading you see on the speed display is not compensated for current and a boat moving at 10 knots directly into a 5-knot current would read 5. For actual Speed over the Ground (SOG) a speed instrument must be connected to a GPS.

The IS20 Combi Marine Instrument by Simrad (on photo below) is a modern digital instrument showing combinations of depth, Speed and temperature. The IS20 come with Multiple Language Options and choice of Data Units for only $400.

Pitot tubes

Pitot tube sensors are often used on small power boats and planing boats. Pitot tubes sense the pressure created by the flow of water past the boat's hull, translating it into a vacuum in a tube run to a gauge, the display is actually reading the vacuum. This type of speed sensing device has an analog display and cannot be integrated with other instruments.

Paddle wheels

Paddle wheels may either protrude from the hull or be bracket mounted off the stern. Protruding paddle wheels are usually found on sailboats, trawlers and other larger non-planing power boats while stern bracket-mounted paddle wheels are commonly used on planing boats.

Paddle wheels measure hull speed by counting the rate at which the wheel rotates as water flows past, sending the data to a transducer which then sends information to the display and other instruments such as a chart plotter. These type sensors often have a second sensor with the ability to measure water temperature.

Inside Displays

Display types include digital or graphic displays, although a few analog display models are still available. This one feature can determine your satisfaction with the instruments you select.

Digital displays are usually monochrome LCD, providing rapid and current numerical depth information without showing the bottom's contours. This type of display is commonly used for depth, speed and wind speed instruments.
Graphic displays show the bottom's contours using either color or monochrome LCD or CRT display screens and are used more on fish finders than depth, wind and speed instruments.

Display screens are measured on the diagonal as are TV screens and can range in size from 2.5 inches up to 7 inches. Screen size, type, resolution and contrast are factors that will influence how well you can read the screen in a variety of light conditions. High-resolution and high-contrast monochrome displays with back lighting offer good visibility in a variety of lighting conditions but all displays are best used in subdued lighting. Another contributory factor to visibility is the screen type; LCD or CRT.

LCD Displays

Monochrome LCD (Liquid Crystal Display) screens are the most commonly used for instruments but they are also available in color. The color display will have readability limitations in daylight conditions, especially direct sunlight. Because LCDs are thin and lightweight, they're suited to locations where space is at a premium. Most LCDs are described in the manufacturer's specifications as either full VGA (Video Graphics Adapter) or VGA. Full VGA consists of 640 X 480 pixels usually found in the larger displays, and VGA offers only 320 X 240 pixels found on the smaller units. The LCD monochrome screen is a good choice for use most lighting conditions.

CRT (old technology) Displays

CRT (Cathode Ray Tube) displays are more often found on fish finders and have a higher pixel count (full VGA) than LCD screens with bright, high-contrast screens that are readable in most light conditions except bright sunlight. Determine the amount of space you have for mounting instruments with CRT displays as they take up more space that the LCDs. Color CRT displays draw more power as wellbe sure your house batteries can support the current draw.


SeaTalk is a data interchange system developed by Autohelm/Raytheon (now RayMarine) and used exclusively in their instrumentation systems. It is a single cable, three wire, asynchronous, bi-directional data communication system, which also carries sufficient power supply to operate other "SeaTalk" compatible instrumentation connected to it.

National Marine Electronics Association (NMEA) 0183 is the standard for interfacing marine electronic devices.

In Fact: Even though the standards are in place, if at all possible avoid trying to interface instruments from different manufacturers, select a complete system from one manufacturer.

The NMEA 0183 standard is based on "Talker" devices which send data in the form of sentences to a "Listener" device about once each second. Most marine navigation instruments such as GPSs, knot meters, compasses, etc. are Talkers, while others, such as GPSs are also Listeners.


Review the manufacturer's specifications for power carefully. There are three power terms that are, or should be, stated in all product specifications: power output, peak power and current draw. Power output is the rating in watts that the manufacturer assigns the transducer. What's important is the duration that the output power is supplied.

A higher AC power transducer with shorter pulses won't necessarily offer the same detail as a unit with less output power with longer pulses. The current draw is important because that's the amount of power your batteries need to supply the instruments per hour. Usually the current draw is minimal unless you have color CRT traditional displays.

Selection of instruments

The selection of speed instruments should be based as much on the type of boat you have as what your needs are. High-speed powerboats require different instruments than sailboats or low-speed trawlers.

Purchase instruments with specifications tailored to your boat and the way you use it. For example; what's the maximum depth reading you need with a depth sounder? Don't buy a sounder that reads to 500 feet if your lake is only 30 feet deep.
Decide what additional functions you need with the instrumentation system you're buying. Do you also need water temperature, shallow and deep alarms, anchor alarm and keel offset, or is a simple depthsounder enough to suit your needs?

Wind Instruments can provide data ranging from apparent wind direction and speed for the day sailor to a host of other wind data for the racer. If you own a sailboat, perhaps some of the systems that have sensors to compensate for heel and pitch should be considered if wind speed and direction are important to you.

Salt water reduces the depth-reading capacity of a depth transducer by 20 to 50 percent. If you boat primarily in saltwater, consider buying a low-frequency depth transducer.

For a compass

a Plastimo Iris 50

handbearing compass by Plastimo


• Two functions : handbearing and traditional compass.
• Graduation : every 1°
• Clearance : ±12°.
• Field of view : 20°
• Built-in photoluminescent lighting
• Red lubber lines
• Weight : 105 gr

For a compass, you can use a Plastimo Iris 50. Its a hand bearing compass which you could use velcro or an upturned lid to mount on the thwart or foredeck. With the added bonus you could lift it up to the eye and use for taking bearings. It's clever, the prism somehow lets you read the bearing even without putting your glasses on. You can buy your for $50.

New Sailboat Electronics

Solar-Powered, Wireless SailTimer Wind Vane

Learn how Apps and Appcessories are Changing Sailboat Navigation

The wireless new SailTimer Wind Vane communicates directly with an IPad

From the makers of the Sailing GPS comes the SailTimer Wind Vane and app. The wind vane is a wireless anemometer that communicates with your iPad/iPhone, sending wind data ( wind direction and speed). The free SailTimer app uses this plus the iPad's GPS boat position data to calculate optimal tacking accurate time and angles to destination. Unlike other GPSs and brands, it takes into account a sailing boat's inability to sail straight into the wind.

Requiring no wires to run down the mast,Solar-powered it's a good and new solution if you don't have any other anemometer on your board. SailTimer communicates via a small blue box which runs on two M batteries, and lets you use your iPad as a passage-planning and navigation tool without shelling out for expensive wind instruments. Apps for older Nokia and others phones are also available, and iPad apps such as iNaxX wibe able to use the data.

You can purchase full UK Admiralty Charts in the app for about $15, while polar plots can also be created in the app. It looks like a useful and interesting alternative to more traditional nav instruments, and we'll be trying it out over

the winter months.

Take 5 seconds to check that Amazon is REALLY cheapest spot for some kind of sailboat instruments. Get free shipping and low prices in a huge choices of type and models for your boat.

The Navy App (NavilyPro software)

Free application guides helps boaters in selecting their stopovers, reference moorings Navily added by boaters and marinas.

Its content is entirely collaborative. Boaters share and choose their moorings from reviews and pictures added by the community. The partners also ports complement the information provided in the application. Navily app also used to organizing the call in the marinas.

Since the implementation, boaters send requests of stopovers (along with their complete profile) that is received and managed directly by the ports.

This system is already available in the ports of Cannes, the Embiez, Port-Vendres or Saint Malo.

Navily, available on Android and iOS.

The new 7.4 inches SailTimer sailboat instrument

The new solar-powered wind instrument for sailboats from SailTimer(online for about US $ 500) features an innovative wind-cup design that maintains wind accuracy even when the
boat's heeled.

The company, notes that SailTimer new wind solar-powered instrument is another example of innovative marine electronics that are now accessible for many sailboats of all ages and sizes.

Masthead anomometer, redesigned for accuracy Anemometer

Wireless and Smaller than traditional masthead-mounted electronic units, the new SailTimer just over 8 inches wide, is only 7.4 inches tall, and weighs just 9 ounces. Wireless data is transmitted via Bluetooth, it is XMEA 0183 compliant and will work with a variety of other apps.

For more details visit: |