Most depthfinders are historical instruments. They collect and display information from the recent past-not the best arrangement for the sailor. By the time the sounder indicates a shoal, its already beneath you. But this is changing rapidly.
Beginning in March 2014 with a review of wind sensors, Practical Sailor embarked on a series of articles on wind instruments. The series kicked off with a look at mechanical, mast-mounted sensors (see PS March 2014 online); Part II compared the various ways that wind data is computed and displayed (see PS May 2014 online); and Part III sought to find the ideal system, matching sensors and displays from different brands (see PS August 2014 online). The ink had hardly dried after the first round of testing, when readers began asking about ultrasonic wind sensors, which appear to offer a number of advantages over conventional mechanical sensors and their revolving-cup sensors.
Whether youre contending with the violence of an abroholos or the gentle puff of a zephyr, it helps to have an idea of wind intensity. For the last several months, testers have been closely examining the tools sailors use to measure and display wind information. This article wraps up our review of mechanical vane sensors and displays, focusing specifically on choosing the best combination to meet your needs. Future reports will look at ultrasonic wind sensors, which have no moving parts, and a build-it-yourself wind sensor that uses an Arduino open-source electronics platform.
To wire, or not to wire? This is a good question, and there are certainly some pluses and minus to consider. For sailors with wiring-unfriendly masts, the wireless approach is a good one. These include wooden spars, ones with conduits that are already full with other wiring, and masts that are regularly unstepped. The downside of going wireless is that the batteries will need to be changed on occasion, and in some cases, signal interference is possible.
Before we plunge headfirst (again) into the world of multiplexers with this test report, heres a quick review of what exactly were talking about. If you have older instruments or a GPS networked to send information to other devices (a multi-function display, laptop, etc.), the information is likely in NMEA 0183 format and is sent in sentences in a set order. For example, the NMEA sentence $GPAAM,A,A,0.10,N,WPTNME*32 is an arrival alarm sentence sent by a GPS to various networked devices upon arrival at a waypoint.
NMEA 2000 (aka NMEA 2K or N2K) is the communication standard replacing NMEA 0183. It is a technical standard (IEC 61162-3) used for connecting marine sensors and display units within a boat. The major differences from NMEA 0183: NMEA 2K operates at 250 kilobits-per-second, about 100 times faster than the 4,800 baud of NMEA 0183.
Its dusk on an overcast, gusty day, and raw data is pouring into your wind display from the masthead, GPS, and the knotlog. Can you clearly see the information on the display, and more importantly, is it meaningful? Can your gloved fingers push the buttons? Can you easily change the way wind data is collected, processed, and displayed so that it best reflects the conditions? These are among the things testers examined for this report, Part 2 of our wind-sensor evaluation, which focused on the display and user interface. In Part 1 (PS, March 2014) we focused on accuracy and durability of the anemometer and vane sensors that feed into the displays.
For better or for worse, the modern cruising sailor is becoming more like an airplane pilot. Safely ensconced out of the wind, the helmsman relies on instrumentation to provide him with information about our environment. Should he bear off for more speed, set the screecher, or tuck in a reef? Increasingly, were seeking these answers in digital display rather than strips of yarn in the rigging and the hair on the back of our neck.
Nobeltec, a marine-navigation software developer based in the U.S., recently released a new chartplotting app for the iPad: Nobeltec TZ. We took it for a weeklong test cruise and found it to be a good basic nav program with some significant strengths, and some notable shortcomings.
So, a couple of years back, you acquired a good old boat at a pretty good price-thanks to the market-but now youre wondering how many coats of bottom paint it has. And what kind? Youve put on a few coats of ablative antifouling since youve owned the boat. It has adhered well and has done its job. But each year, the bottom looks rougher and rougher-with big recesses where paint has flaked off. You sweated out some extra prep-work this season, and thought you had a nice, durable subsurface for painting, but each pass of the roller pulls up more paint. Whats going on here?