Wednesday, August 20, 2014

New Seine Skiff Based on Tug Boat Design

In June, 2014, Seattle-based Snow Boat Company delivered a new 24-foot by 13-foot seine skiff to King Cove, Alaska for the area M salmon fishery. The boat is one of the largest seine skiffs in Alaska, and almost begs not to be considered a skiff due to the size and power.

Over the years, the rails on seine skiffs have been getting higher, thus creating a need for a higher tow post. This height can lead to instability and poor towing characteristics. Bringing the tow point down was the primary goal in the new design.

The new skiff is more like a tug than a traditional skiff, and many design features are a departure from traditional skiffs known throughout Alaska.

There are no bulwarks in the stern of the boat, and the towing point is much lower, giving the boat great stability when towing and turning. Using a large 4-blade 40-inch wheel provided by Sound Propeller with a fixed nozzle designed and built by Snow, a 3.8:1 Twin Disc 5091 deep case gear, and 300-HP QSL9 Cummins, the boat has more bollard pull than other skiffs with 500-HP. Behind the wheel is a large Deflector Marine Rudder capable of spinning the boat in just a little more than one boat length. With 11,000 lbs. bollard pull, the 300-HP engine is almost never running at full speed. The boat is pulling much harder than the 200-HP skiff it replaced, using half the fuel.

Eight-inch HDPE pipe surrounds the boat as a bumper, set in a channel with 2-inch thick polyethylene foam behind the pipe, this type of bumper is very durable and not "sticky" like rubber bumpers are. It slides along the hull of the seiner without grabbing.

The bulwarks in the bow rake inward for better protection from banging on the overhanging portions of the seiner when fishing in rough weather. There are bulwarks across the vessel just forward of the tow post. There were no attempts in the vessel design to keep water off the aft deck, and it is assumed that waves will roll across the stern in a heavy sea.

Two 350-gallon water ballast tanks keep the boat deeper in the water, adding stability and towing power. The ballast is pumped in and out with a hydraulically driven pump.

The sea trials in Seattle gave the impression the design is successful, with great towing and turning qualities, and the first few weeks on the fishing grounds are proving the design a success, with stability, operator safety, and economical pulling.


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