Avoid rock, bottom

By: 

Michael Crowley

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FarSounder's sonar detects lurking navigation hazards

Going bump in the night is never fun. Though that’s what a lot of fishing boats do when they make the run up Alaska’s Inside Passage. It’s especially true in early spring when the rivers are running high, pulling logs off the banks and then dumping them into the narrow waterways lying between the shores of British Columbia and Southeast Alaska and the bordering coastal islands.
A big enough log — night or day — stops a 70-footer in its tracks. Then you hear it bump, roll and slide down the length of the boat’s bottom. You pray it misses the keel cooler, prop and rudder. Logs lying horizontally in the water are bad enough, worse are the deadheads — not to be confused with fans of the San Francisco rock band.
Deadhead logs are pretty much straight up and down in the water. Run over that log and it’s driven down toward the bottom until its buoyancy takes over, and then it’s driving straight back to the surface, wanting only to go through the boat’s hull, fish hold, main deck and anything else in its way.
Other parts of the country have their own uncharted hazards: rocks, wrecks, pilings, and bottom altered by undersea activity.
A possible answer to such unpleasant encounters with these obstacles is the sonars from FarSounder. These are 3-D
sonars that scan ahead of the boat, providing a full-color view with range, depth and bearing information. The sonars have nothing to do with fishfinding but everything to do with warning of approaching underwater objects.
FarSounder has two models, FS-3 and FS-3DT. Both are mounted in the bow, facing forward and present a real-time view with updates to the monitor every two to three seconds, says FarSounder’s Ian Bowles.
The FS-3 sonar has a 90-degree field of view, 45 degrees off each side of the boat, says FarSounder’s Matthew Zimmerman. It has a range of 1,000 feet.
The FS-3DT features the company’s dual-transmission technology. That gives it the same range capability as the FS-3,
plus it can reach out to 1,400 feet with a 60-degree field of view. Both sonars go down to 165 feet.
Roll and pitch stabilization allow the sonars to compensate for 20-degree movements without compromising the image. Both sonars operate at 60 kilohertz and draw less than 1 kilowatt of power.
Contact FarSounder, 43 Jefferson Blvd., Warwick,
RI 02888; tel. (401) 784-6700; www.farsounder.com.