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#QuickTips - Boating in Waves

By: Captain Bill Jennings

Captain Bill Jennings gives you the best tips on how to have a swell time


Large waves are often measured in seconds because it can be more accurate than quoting the Beaufort Scale. The system uses time between the passing of two consecutive wave crests measured in seconds. As you would expect, a higher seconds number indicates larger waves and conversely, fewer seconds between waves indicate smaller waves. Smaller waves can be just as deadly as large, but today we are addressing large waves – not the sort that build up and “break” onto beaches, but the ones found in open seas and at the entrances to harbours. What is the best procedure to safely traverse these waves and swells?


Large swells at sea are usually less dangerous than swells encountered at entrances to harbors and rivers because sea swells are more consistent and have a rhythm to them, whereas harbour swells are inconsistent in timing, height, and intensity. The severity of harbour swells is also greatly affected by the tides. You may exit a harbour in the morning through flat water, only to encounter on your return, large nasty lumps. The bottom line is -- you need to treat harbour swells with respect.


When planning to challenge harbour swells, the obvious place to start is at home. Check the tides and any marine notices for the location you will cross. Be sure to pack things you might need – specifically some dry towels.


Once underway, set your tabs in a neutral setting, with both parallel to the bottom of your boat. As you approach the disturbed water at a harbour entrance or a series of swells in open water, look closely at the water you plan to cross and make a conscious “Go-or-No-Go” decision. Nobody is ever accused of being a wimp for playing it safe and returning home. Well, I was once, but the people that objected had been drinking.


Next, determine if your track across the upcoming swells will be head on, or if you need to cross them on a slight angle. If crossing the swells at an angle, you can put more of your boat’s V-bottom into the swells by setting a tab so that your boat slightly leans away from the direction from which the swells are coming. For example, if the swells are approaching from your portside, lowering your port tab slightly will lean the boat to starboard. This action will reduce the spray factor.

If possible, hold your boat in one spot before crossing an area of swells and watch other boats as they cross. This will give you a first-hand idea of what to expect, identify the best route to cross, and provide a few laughs.


Before heading into swells, you should be on plane but not charging at high speed. As with many boating conditions there is always one optimum speed that delivers the smoothest and safest ride.


What makes safe passage through swells more difficult than eating ice-cream is that you must operate your throttle(s) and trim control at the same time and in harmony with the swells. You also need to steer. To look at this in more detail, an oncoming swell of any type will slow your boat and cause your bow to dig in. To keep your speed constant, you must throttle up. Knowing that as you tip over the top of the swell your boat will have a tendency to do air-time, you should at this point trim down. As you tip over the crest of the swell and head down the backside, you can anticipate a rapid speed increase, so you must throttle back. Knowing that when you get to the base of the swell you just crossed, your boat will have a tendency to stuff into the next swell or wave, you should at this point trim up. While performing these driving steps you need to navigate with the wheel to stay on your heading and to avoid severe dampness. This same process is repeated to cross each wave or swell. Remember the process in these simplified terms: Going up = power up – bow down. Going down = power down – bow up.


Now let’s turn around and travel in the same direction as the swells. The above process is identical except for one important thing -- You must keep your speed up to a level that is higher than the speed of the swells. The reason for this is to prevent the swells from causing your boat to “broach,” which can end your trip in a most unpleasant manner.


If you are having difficulty running waves at even a slight angle turn directly into the oncoming water and place your tabs in neutral. While this will take you in a direction that is not exactly where you want to go, it will also take one variable out of the process and you can deal with the difficult water movement head on. Once through the more difficult water, you can “tack” through the remaining less difficult water to arrive at your desired destination.


Should you find yourself in over your head – but not literally – it is possible to turn back, but such a turn in swells requires perfect timing. Wait for a good-sized swell and power into it. The instant your bow lifts to climb the swell, quickly turn the wheel completely in one direction. Your boat will pivot 180 degrees and you will be heading back. I did this once on a trip from Florida to the Bahamas and when we got back to the dock my passengers thanked me. I thought they would be annoyed because I didn’t realize they were nervous.


Following these driving tips will prevent an unscheduled trip to your dentist and allow you and your passengers to have a swell time.


#tips #quicktips

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