Boat-handling in heavy weather

For a larger view of the photos, click on the images. Larry Graff, founder of Glacier Bay Catamarans, knows something about boat-handling in heavy weather as he has set several offshore records with his cats, including the first New York-to-Bermuda record in an outboard-powered boat.

In Cat Connections, a newsletter for Glacier Bay owners, he outlined what he has learned about handling small powercats in nasty seas:

Several Glacier Bay owners have requested a story on best procedures and techniques for running in severe seas offshore, should they get caught in a gale or more. Safety offshore actually starts at the dock, with your choices in the following areas:

• Passengers should be seated and have a hand hold when running in an open
sea. Open sea boating passengers’ should be limited to the number of available
seats.

• Always insure your bilge pumps, all 4, are operational and that your bilges are dry. Should you have one hull partially filled with water, your catamaran (which is typically exceptionally stable) will begin to react like a mono-hull with water in its bilge. As a sea rolls the boat the water in the hull rolls with it, limiting the hulls natural rebound capability. Keep your bilges DRY!

• General boat maintenance; electrical systems, plumbing, proper water sealing
and pre-trip inspections and testing of your systems. Every system MUST be
110% operational, period! Fix it or don’t go.

• Proper safety equipment and easy access to the equipment, should you need it in an emergency. Too many owners (Captains) bury their safety equipment and gear under a wide array of other gear which gets put into the boat later. When you need your safety gear, you will most likely be in a RUSH and the situation will not be easy.
• Cargo – fish coolers should be stored bellow deck in the fish wells, other heavy items must be ratchet-strapped in securely on non-skid mats. Shifting weight is unsafe.

Once you’ve made sound choices before departure, you’re ready to begin your trip offshore. Here are boat handling techniques and special areas I do either for safety or for the comfort of all aboard. These two issues often go hand in hand, I think your best choices typically come when you consider your passengers fun and comfort. If it’s a “Harry or Scary” choice it’s probably the wrong one.

• Keep a continual eye on the seas as you work through them. If the boat’s motion is uncomfortable, trim up or down, change your heading a bit or adjust your speed up or down. The boat should feel good. In large tight seas (5’-10’), you may need to run up sea 20-30 degrees for a period and then run down 20-30 degrees to give the hull a chance to slice steep waves, as the hull moves through it.
• Trim your boat (side to side), level using an equal amount of port and starboard engine trim. Trim just to level, some websites recommend “twisting the boat into the seas”, but this can leave you in an unstable position, should an unexpected wave hit. Do not have more than 3 bars of trim difference between your port and starboard engines.

• In very large seas, when you have long distances to go, I have recently developed the “Lake Illiamna” system that recognizes and uses the fact that LARGE TIGHT seas typically have 2-3 “big ones” and then a series of 6-7 smaller more manageable waves. I set my engines so that one engine is at, say, 3200 rpm. I maintain 10 kts and with both engines at 3200 rpm, I maintain 16 kts. As each large set comes, I pull one throttle back to near idle and let the other engine consistently maintain my chosen “big wave” speed (10 kts), as soon as the big set clears I again match both engines to 3200 rpm (16kts). This system gives me an easy, predictable way to match the current seas without over shooting my desired speed or undershooting. Over a period of time, I will switch which engine I use as the “rest motor” to match the fuel burn rates.
Running Down Swell Into an Inlet - The thing to remember here is that the big
wave you’re on is a spinning bail of water. If you are on the front/down swell
side, it’s rolling forward at 8-12 kts. If your running at 18 kts, your actual speed
through the water is 8-10kts. This is not much to maintain steerage. I like to wait outside the inlet and watch for a period when there is no traffic and then hop onto the back side of ONE swell and ride it through, matching my speed to the swell. My props are always in the water, as are my rudders. The spinning bail of water is working for me rather than against me. Visibility is one problem with this technique, so at times you may need to nudge up for a peak and then back down into the base. You also have to keep an eye on the wave behind you so you don’t get overtaken.

• Watch the horizon for fast moving larger vessels, ships, or military vessels. They can throw exceptionally large and aggressive wakes which can stack/combine with the existing seas to build an exceptionally bad wave set.

• Watch for aggressive wind shifts. If you have winds above 15-20 kts that make a 180 degree swing in direction in a short period of time (20-50 minutes), expect very aggressive steep seas and occasionally a rogue wave-set to build in short order.

These are my personal techniques and don’t come with any guarantees. I recommend you work your way up incrementally in larger seas to familiarize yourself with your boat’s capabilities . . .

The dramatic photos of the Wildcat 36 and 40 used to illustrate heavy weather were shot during sea trials in gale conditions off the Irish coast. For more heavy weather photos and information on the Wildcats, visit Safehaven Marine. For video of the Wildcat 40 in action in Force 7-8, click here or here and hang on.

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