Preparing for Offshore: Know Your Boat


Before heading offshore, take some time to know how your boat responds in various conditions  (published October 2016)

While sailors often think first of checking the condition of all the gear on their boat, making sure they have all the latest gadgets, checking weather, going through checklists and thinking of storm tactics and emergency procedures, there is another step that should be taken. That is to make sure you really know your boat, and how it will behave offshore. I will run through some of the basic functions you should pay attention to.


Let’s start with the speed of your boat. You have sailed her in nice conditions around the Chesapeake for years, or around Long Island Sound or Penobscot Bay and along the coast. You have even been caught in some thunderstorms or squally conditions with some three or four foot waves, and thought you had seen pretty rough conditions. In most of your sailing, you have found your boat has sailed to windward at a pretty good six knots, on a broad reach at seven and downwind at a nice, lazy five knots. Maybe add a few knots if you have a faster boat. You are now planning your offshore passage from the Chesapeake to the Caribbean, and Chris Parker suggests that boats could leave tomorrow if they can make seven knot boat speed to get across the Gulf Stream before the winds turn northeast against the stream. No problem, you think.

But do you really know your boat speed offshore? I am sorry to break the news that the speeds you saw on the Chesapeake, or Long Island Sound, or Penobscot Bay will not be reached routinely offshore. Residual waves from different directions, counter-currents, building seas ahead of a storm, all have a dramatic effect on your speed. Count on seeing boat speeds a good bit less than what you have experienced in your coastal cruising. Plus, the forecast can call for favorable winds, but in reality local weather effects, or changes in the forecast (it is not an exact science) could cause you to experience an adverse wind direction or less supportive wind speed, and thus lower sailing speeds. So be conservative in planning what speeds you will attain. Be realistic.


img_9598   Invariably in an offshore passage, a weather system moves through followed by a light period as a high pressure system settles in. In your coastal cruising you may have gotten into the habit of firing up the diesel auxiliary when the winds lay down. On a long offshore passage you need to know very precisely how much fuel you have available and how much you burn just motoring, or motor sailing. Figure out your burn rates while doing your coastal cruising. You need to have this information when looking at the overall forecast for your passage route. It is always best to try to do as much sailing as you can early in your passage. Put up light air sails. It is ok to go slow—save that fuel!

If along the way there is very light air and you feel your fuel supply is good, try motor sailing with the engine going slow at 1,600 to 1,700 rpm. You’ll find your burn rate is one-third to half of what you’d burn motoring only at cruising speed. I often hear boats on the radio running short of fuel. In summary, know your capacity and burn rates under different conditions, use the fuel sparingly early in the passage—go slow, and motor sail at lower rpm to stretch your supply.


Of the sail inventory you have, select a set of sails that will give the best helm balance in moderate to strong winds. A significant issue when sailing offshore is to keep a good balance on the helm. Significant weather helm, twentyfour-seven, puts large loads on the rudder, steering system and autopilot and can lead to premature failure of those components. You can get by with some weather helm for an afternoon sail, but it can hurt you over a long passage. That oversized genoa may work well in the shifting light airs of coastal cruising, but in steady winds around a front and in the trades, the steering system and boat may have to work too hard. And when leaving sails set without checking their trim over a long passage, you can again be loading up with weather helm.

So what do you do? It starts with reasonable sail selection—know on your boat what sails give you a well-balanced helm over a wide range of wind speeds. Also, know what sail trims give you a well-balanced helm. A large roached main may require you to depower the main in anything but the lightest winds. When sailing offshore, check your sail trim periodically, and just as importantly—check your weather helm indications. This is most easily done by checking the autopilot control. If it is showing the rudder has to be turned seven degrees or more to windward to hold its heading, then you have too much weather helm. Well less than seven degrees is even better. It is normal to have just a few degrees. Change the sail trim to get the helm back in balance.

The more you know your boat, the shape of your wake will also tell you when you have too much weather helm. More turbulence than when trimmed correctly, or a cylindrical rolling turbulence in the middle of the wake can be indicative of substantial weather helm. For catamarans if the leeward hull wake begins to take on the form of a small rooster tail, you are over-canvassed. Know what the indications are on your boat for being over-canvassed or incorrectly trimmed.

Of course hull shape of a monohull will cause weather helm when sailing close hauled. Don’t confuse that effect with sail trim. The designer will usually allow for a small amount of weather helm when close hauled, and that should present only a moderate load on the steering system. Usually just a few degrees. But, as the wind fills in and you are pushing the rub-rail into or close to the water, if over-canvased for the wind strength, you will get added weather helm from the hull shape. Reduce sail, straighten up, and you’ll have a happier helm.

Also, before going offshore, make sure your rudder position sensor is accurately set for the neutral, straight-ahead position. For boats with a rigid chain and cable wheel steering system, place a piece of tape or a decorative Turk’s head knot on the top of the steering wheel when the rudder is in the straight-ahead position. These will help when checking weather helm.


img_7676     Before going offshore, know at what apparent wind speeds to windward and what speeds off the wind require a reef in the sails for your boat and sails. Some input for this may come from your sailmaker, keeping sail loads below what the fabric is designed for. But, knowing your boat you may find the boat sails better, more comfortably, or easier on the autopilot at wind speeds even lower than the maximum suggested by your sailmaker. Make note of these speeds for on the wind and off the wind directions, and log them in your boat manual.

Also, know how to reef efficiently when offshore. Practice this in some larger waves inshore. Try to set-up systems on your boat to ease the procedure. In rough conditions there is a lot of noise and commotion, and you are trying to get things set quickly. Make it easy. Put marks on reefing lines for a slab reefing system so you know easily when the line is set correctly, and you don’t have to climb up on deck with a flashlight to check the line position.


Chafe is the bane of offshore sailors. It is one of those things you don’t plan on, often can’t predetermine where this might occur, and can be debilitating when it occurs. It is not practical to carry spares for every length of running rigging aboard. The best medicine is prevention.

Long offshore passages with big seas provide opportunities for chafe, so be on guard. The primary materials of concern are your sail cloth and running rigging. And the conditions that most often lead to chafe problems are long periods of big seas. The first step is to routinely go around the rig and check—look for lines that are crossing standing rigging, reefing lines or the topping lift pulling tight against the sail, looking for conditions that could lead to chafe damage.

As the sails, halyards, outhauls, topping lift or boom pump from boat motion in big seas, one creates conditions that can lead to chafe. I always check at least twice a day. Use a strong flashlight at night. And be sure to stay clipped in to jack lines if you go out of the cockpit (of course it is wise to be clipped-in when in the cockpit as well, particularly in big seas).

Adjust lines to remove the potential areas of concern. Relax non-used reefing lines or topping lift, trim in the outhaul to minimize mainsail pumping, re-tension the main or genoa halyard if there has been some stretch—looseness in these can allow pumping of the halyard.

If over the period you have had your boat, you have experienced some wear of particular halyards, topping lift, or a common problem—the mainsail outhaul, before going offshore you might do a special inspection and corrective measures to hone in on the chafe causes. Because, if wear and chafe have happened over several summer seasons of coastal or protected water sailing, it will happen over just a matter of days offshore and you will lose that halyard or outhaul. Steps you can take are: placing chafe gear at particular problem areas, going to low-stretch line for halyards and outhauls to minimize sail and halyard pumping in big seas, and adding restraints (similar to a preventer, but rigged as a downhaul) to keep the boom from lifting and pumping in big seas. This last one can be as simple as moving your traveler car to a point directly below the boom when the sail is trimmed where you want it, and tension the mainsheet well, or if that option is not available, add a restraint similar to a preventer that can tension the boom downward in big seas, and can be released under load.
In short, be sure to know your boat and how it will behave offshore to better prepare for the offshore passage. In doing so, you will enjoy the passage more fully and arrive at your destination as planned. Safe Sailing!

     Hank has been an active sailor for the past 45 years, and logged over 140,000 blue water miles. He has owned monohulls from 22 to 52 feet, and now sails Flash, a Catana 471 performance cruising catamaran, with his wife Seale. Hank is one of the Directors of the Salty Dawg Rally, and has contributed articles to several sailing publications.


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