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John Rousmaniere in his book "The Annapolis Book of Seamanship" defines weatherhelm as "A boat's tendency to head up, into the wind, unless checked by the tiller or wheel". Most skippers want their boat to have a little weatherhelm because the "feel" of the boat seems right, and because the boat will naturally head up and stop if the tiller is left unattended. This is better than having the boat sail off downwind doing a series of unexpected jibes if the reverse situation (leehelm) is allowed to persist.
Some of us have had experiences where no amount of checking will prevent the boat from rounding up. And, sometimes this rounding up has been uncontrolled and possibly dangerous. After this happens once or twice, we really want to do anything and everything to prevent it from happening again, because:
a) the crew looses confidence in the skipper and may not want to sail again, EVER!
b) the skipper is wondering if the boat can take many more of those maneuvers before something expensive breaks, AND the skipper was secretly scared ____tless.
c) the folks at the marina have started asking embarrassing questions regarding "positive floatation" and insurance.
d) possibly, all of the above.
For some, the answer will be to take the sails down, start the motor, and never sail on those windy days again. For most of us, though, we will accept the challenge of figuring out how to prevent uncontrolled rounding up.
The first question is, "What caused the excessive weatherhelm"? Easy answer = The Wind. However, it's not just the wind, but how the wind acted on the boat. So the solution is in adjusting how the boat reacts to the wind; and making the adjustments before the wind has a chance to affect the boat in an unwanted way. The appropriate adjustments are made based on a knowledge of sailing theory and an understanding of your boat. Your boat's tendency toward weatherhelm may be affected by the size of sails, the placement of crew and cargo, the rake (fore/aft tip) of the mast, the amount of heel, or any combination of these.
Uncontrolled weatherhelm is almost always accompanied by excessive heeling to leeward. As your boat heels more and more away from its "at rest" balance, the windward waterline becomes effectively straighter and the leeward waterline becomes much more curved (see fig #1). As this happens, the boats forward motion forces the water to pack-up on the leeward bow and effectively try to push the bow toward the wind. While this effect is being felt by the bow of your boat, the rudder becomes less and less effective. At a 45 degree heel, the rudder is about equally trying to lift the transom out of the water as well as trying to steer the boat. Of course the more the rudder tries to lift the transom, the more the bow is effectively "pushed" down - allowing more water to pack-up and make the boat more prone to steer toward the wind. Steering becomes difficult, if not impossible, at this angle of heel. Heeling angles of 30 to 35 degrees, in fact, are often difficult to handle without serious rounding up by many skippers.
Controlling the excessive amount of heel is required to prevent uncontrolled weatherhelm. Some of the ways available to control heeling are:
a) Weight distribution could be changed.
b) Sail controls could be adjusted.
c) The sailplan could be altered.
You might try one or all of these on your boat. Let's take a look at each.
Weight Distribution Can Be Changed
Changing the weight distribution on your boat is probably the easiest of the adjustments you can make to reduce your problems with weatherhelm.
Part of your weatherhelm problems may be because you have too much weight aft. The aft locker may be loaded to capacity. The quarterberth too may be loaded "to the max" with all sorts of stuff. Or, you and your crew may simply be sitting too far aft in the cockpit. Any of these transom squatting conditions tend to induce weatherhelm even in light breezes; and when the wind increases in force, they tend to amplify their affect on your boat.
After adjusting the "at rest" weight distribution, and as the wind increases and your boat begins to heel more, you may want to have your crew sit on the windward side of the boat (either on the weather rail on deck or on the weather settee seat below). You may want to install a tiller extension so that you can join your crew on the weather rail.
Adjusting the Sail Controls
Both your mainsail and your jibsail (genoa) have sail control lines. These include: the halyard, clew outhaul, cunningham, boom vang, mainsheet traveler, and mainsheet for the mainsail; and the halyard, backstay adjuster, jibsheets, and jibsheet lead blocks for the jib. By adjusting the tension on these controls it is possible to make the sails more powerful (create more lift for light wind conditions) or less powerful (the wind is already supplying an abundance of power). Most of us want the sails to be more curved for light wind days and to be flatter on windier days. In other words, we will adjust the control lines to lighter tensions for less wind and increase the tension on the controls as the wind velocity builds.
As the wind builds, you may want to try some or all of the following to "de-power" and flatten your sails:
a) Tighten the clew outhaul
b) Tighten the Cunningham
c) Tighten the Boom Vang
d) Tighten the Mainsheet
e) Adjust the traveler car to leeward
f) Sheet out in the gusts and sheet back in for the lulls
Jibsail a) Tighten the jib halyard
b) Tighten the jibsheets
c) Move the jibsheet lead blocks to an outboard position (the newer Catalina 25's show the lead block tracks on the deck next to the cabin side instead of on the toerail as in the older models) through the use of a barberhauler or another track on the toerail
d. Increase the tension on the backstay adjuster - this reduces the amount of "sag" along the luff of the jib not really bending the mast like a Capri 22 adjuster will.
e) Move the jibsheet lead block aft on the track - this flattens the bottom of the jib while allowing the top of the sail to twist off and spill wind. This should not be used as a long term solution though if the leach of the sail is flapping continuously.
As the wind decreases is force, the reversing the adjustments you made above will "power-up" your sails for the lighter conditions.
Altering the Sailplan
If increasing the tension on your sail controls is not sufficient to reduce your boat's weatherhelm, then you need to do something more drastic to the sails....REDUCE SAIL AREA. Again, there are options (just like with the control lines) and your knowledge of your boat and how you like to sail will determine what you want to do first. However, there are really only two choices you're dealing with here - Reefing the Mainsail or Changing the Jibsail to a smaller size.
If you tend to be more to the bold side of things, you will probably carry your large sail area longer and then reef the mainsail, leaving the jib alone. You reason that you can reef (thereby lowering the center of effort in the sailplan - Fig 2) more quickly than doing a "tap-dance" around the foredeck trying to change down the jib. If this is you:
a) Make sure that your jiffy reefing gear is in good working order and ready to go - including your main boom topping lift.
b) Practice reefing in calm weather so that you'll have the bugs worked out and you will know what to do when the wind really is blowing the mailboxes down the street.
c) If you have a tall rig, you need two sets of reef points with appropriate jiffy reefing gear for both sets. The single reef only gets you down to about a standard rig size.
d) Realize from the git-go that your crew may not want to either steer OR go forward to the mast to "tuck in" a reef.
If your crew tends toward the timid when it comes to heeling and windy weather (or you do), then you'll be better off changing to a smaller jib (or no jib at all) as your first sail plan alteration. Of course, the 5 P's of good sailing (Prior Planning Prevents Poor Performance) will dictate that you generally opt for a smaller jibsail before leaving the dock or anchorage. If you get "caught out" with an increasing breeze and have your larger jibsail up, resolve to change this sail to a smaller one before all those white-caps get to you. Remember that just changing from a 150% to a 110% jib will effectively move the jibsheet lead block to a wider (outboard) position (Fig 3), decrease total sail area, and lower the center of effort of the combined sails. Keep your eyes peeled to windward. Be aware of changes in weather by watching the clouds, waves, and other boats.
If you don't own a roller furler for your jib, you may want to rig a jib downhaul so that you can quickly (and permanently) douse the jib, leaving only the mainsail up. When there's plenty of wind, my Catalina 25 sails pretty well with just the mainsail (even only a reefed mainsail).
A word of caution here. A sailmaker friend of mine has told me more than once that he makes quite a bit of money every year from sailors who douse the mainsail and leave the jibsail up, instead of the reverse. He says that rigger friends of his do well with these sailors too. He thinks it's because the mast offers more support to the luff of the main than the forestay can give to the luff of the jib in a big gust.
Finally, under this heading, your mast may be tipped (raked) too far aft causing part of your weather helm problems. If so, you will want to adjust the rake of the mast to a more vertical position. Remember that you probably want a slight weatherhelm in light breeze conditions.
So there you are. If you have weatherhelm problems; think about what's going on, move weight distribution, adjust the tension or position of sail controls, or alter your sailplan by changing sails and/or reefing. And remember to sail flat 'n fast, not rail down 'n slow.