POINTING & WEATRHERHELM ~ from C&C Yacht
From time to time, skippers and owners ask how to better optimize the pointing ability of their boat
. The question often carries the unstated hope and/or belief that there is an easy/quick fix that will magically cure the pointing problems that the questioning skipper
is experiencing. I surely wish that it was this easy; but, unfortunately the solution comes in the blend of nearly two dozen different interrelated factors. These factors include, but are not necessarily limited to the following list: Sail Shape, Overall Shape and "Newness", Mast
Bend, Main Halyard
Tension, Main Cunningham Tension, Main Outhaul
Tension, Mainsheet Tension, Main Leach Line Tension, Boom Vang
Tension, Jib Halyard
Sheet Lead Position Fore or Aft, Jib Sheet Lead Position Inboard or Outboard
, Jib Sheet Tension, Jib Leach Line Tension, Jib Foot Line Tension, Sail Selection, Sail's Angle of Attack to the Wind
(footing or pinching), Boat's Angle of Heel, Boat's Balance Fore 'n Aft, Boat's Speed Through The Water
, Clean Bottom, Wind
Velocity, Size of the Waves, and Steering
Skill of the Skipper
. Unfortunately, for the skipper who is trying to improve the pointing characteristics of his/her boat
this is not like Economics 202 where we can say "All other things being equal….." if we change this, such-'n-so should happen. All of the above factors contribute to the boat's overall performance - and that includes pointing ability.
But, let's look at each factor to see if some general thoughts can be derived. Remember that all these factors work
with each other to produce good boat speed, pointing ability, et al. No single
factor is the most important.
- Overall Shape and "Newness"
in a way very similar to an airplane's wing. And, like an airplane wing, the overall "roundness" of the sail shape is important to developing lift
. For slower wind velocities a rounder shape is needed. For higher wind velocities a less round shape is more efficient. In addition, the placement of the maximum roundness (fore & aft on the sail) is important.
In general, most sails
are designed with the maximum roundness (called the maximum draft) at between 40% and 60% of the way aft on mainsails and at about 33% aft on jibs sails. You can move the position of maximum draft
forward or aft by increasing or decreasing the tension on the sail's control lines. As the wind increases in strength, the position of maximum draft
moves aft because the fabric
of the sail stretches. To keep the position of maximum draft close to the designed position you will need to increase tension along the luff edge of the sail. Halyard tension and cunningham tension are the most common means for changing the position of maximum draft.
As sails age, the fabric
stretches out of its original shape. The sail becomes much more rounded and the position of maximum draft moves further and further aft on the sail. So, as the sail ages, it becomes increasingly more difficult to keep the position of maximum draft in the most efficient place. Plus, the sails overall roundness becomes more pronounced making the sail somewhat better for lighter breezes and for reaching; but, much less efficient for pointing and for moderate or stronger breezes. If you are trying to point with a skipper who has newer sails than you have, you may be in for a frustrating day.
Having the option of bending your mast
by using some sort of adjustable backstay tensioner
gives you the advantage of being able to adjust the amount of maximum draft in the mainsail
. For lighter breezes more draft is generally preferred (lighter backstay tension). While stronger breezes call for less maximum draft (increased backstay tension). The luff of the middle sections of the mainsail
is pulled forward when the backstay is tensioned and the middle of the mast is bent forward. Bending the mast effectively decreases the amount of maximum draft and flattens the mainsail for better efficiency in stronger breezes.
In addition, when you tension the backstay adjuster
you increase the tension on the forestay. This will keep the jib sail luff in the best position and not allow the jib to change shape when the wind gusts. By keeping the jib sail in its best position and by changing the maximum draft on the mainsail, you do two good things for your boat. You keep the boat driving to windward and reduce heeling, making the whole system more effective.
Main Halyard, Cunningham, and Jib Halyard Tension
The position of maximum draft moves aft on sails as the wind increases in strength and/or as the sail becomes older and the fabric stretches. The farther aft this maximum draft position moves, the less efficient the sail is for pointing. The lift changes from lift in a forward direction to sideways lift. Sideways lift heels the boat and creates more leeway (sliding sideways in a downwind direction). Increasing the tension along the luff edge of the main or jib sail will reposition the maximum draft forward on the sail. So, as the wind increases or as the sail ages, more tension is adjusted along the luff (forward) edge of the sail.
You can increase the tension along the sail's luff by increasing the halyard tension or (in the case of the mainsail) increase the cunningham or gooseneck downhaul tension. Effective tensioning of the halyard often requires a winch
. Adjusting a downhaul line is almost impossible while sailing; but adjusting a cunningham is often easily done while under sail. In general, there is a visual reference for luff adjustment. Pull the lines tightly enough to just pull out the horizontal creases along the sail's luff.
Main Clew Outhaul Tension
Whether you have an adjustable backstay or not, you have a clew outhaul for the mainsail. Originally, this was just a short piece of 1/4" line that connected the mainsail clew and the end cap on the boom. The original 1/4" line was not easily adjusted to increase or decrease tension along the mainsail foot. If you have a pulley and cleating system, you can easily adjust the tension on the mainsail clew and effectively along the mainsail foot. By increasing the clew outhaul tension you flatten the bottom 1/3 or so of the sail making it more efficient in stronger breezes for upwind sailing. Decreasing tension on the mainsail clew outhaul effectively increases the amount of maximum draft and makes the sail more efficient for lighter breezes.
Your mainsail and perhaps some or all of you jib sails may have a leach line. This is a small line that is sewn into the fold of fabric along the sail's leach. There is normally a small cleat near the sail's clew so that you can secure the leach line after you've adjusted the line's tension. The leach line is a precaution line that better sail makers add with the idea of the sail lasting longer.
As the sail ages and stretches, the leach often becomes "soft" and begins to flutter even when the breeze is perfectly flowing on the rest of the sail. Increasing the tension on the leach line controls leach flutter. Leach flutter can disturb the air flowing on your sail - making the sail less effective, especially for upwind points of sail.
Many jib sails also have leach lines that act similarly to the leach lines on mainsails. Any time you see the leach of either a mainsail or jib start to flutter, increase the tension on the leach line.
of adjusting the leach lines is that some skippers tighten these lines too much and actually cup or hook the leach of the sail causing the sail to stall and become less efficient. Watch the tension on the leach lines so that you have smooth air flow from both sides of the sail.
Jib Sail Foot Line
Some jib sails have foot lines similar to the leach line. These are sewn into the fold of fabric at the sail's foot. Pulling the foot line snuggly tends to calm the fluttering of the jib's foot. Over tensioning the foot line can cause the jib sail to have an inefficient sail shape.
One condition that many skippers create that diminishes the pointing ability of their boat is to over tension the mainsheet. Tightening this control line tightens the leach and can even hook it to windward. This causes the sail to stall and become very inefficient. With this inefficiency, the boat tends to slow down and develop leeway. The old saying "When in doubt, let it out" really comes into play with mainsheet tension. In light to moderate breezes, you won't go faster or point higher with max tension on the mainsheet.
Mainsheet Traveler Position
One thing that many skippers can do to help pointing ability is to center or even move the traveler car to windward. Sheet out the mainsheet till the boom is centered or even slightly to leeward. If your maximum draft in the mainsail is at about 40% aft and your leach is smooth the mainsail should lift nicely. As the breeze pipes up, let the traveler down to compensate for heeling caused by the wind.
Boom Vang Tension
For windward sailing your boom vang
doesn't do much. The mainsail is pretty close to the centerline of the boat and your mainsheet is the primary control line in use. There is a problem though with over tightening the boom vang. You can tighten the vang to the point that the mainsail's leach will hook to windward in just the same way as over tightening the mainsheet will hook the leach. This, of course, stalls the mainsail and your boat will soon slow down and also develop additional leeway.
Many skippers don't realize that the vang can be the problem. They start fiddling with the mainsheet, traveler position, etc…..all to no avail. So, from a practical point of view, efficient upwind sailing is best done with minimal tension on the boom vang.
Jib Sheet Lead Block Position Fore and Aft
For most conditions, the jib sheet lead block needs to be at a position that allows the sheet to bisect the angle of the jib's clew. Even pressure will be applied to both the foot and leach of the jib with the sheet lead located in this position. An excellent guide to make sure that the jib sheet lead block is in the correct position is to watch the telltales along the jib sail's luff. If you head
up nearly to a luff, all the telltales should "break" at the same time. If the top telltales "break" before the lower ones do, the car is too far aft. If the lower telltales "break" before the top ones do, the lead car is too far forward. Jib sheet lead car position fore and aft is very important to pointing, boat speed, and overall performance.
Strong Breeze Tip:
If you are experiencing strong winds and want to depower the sail plan (but without changing sails) you can move the jib sheet lead blocks aft 6" to a foot. This allows the bottom half of the jib to continue to work
, but the top half spills wind and is less of a heeling factor.
Jib Sheet Tension
Your jib sheet acts somewhat like the clew out haul on the mainsail, AND like the mainsheet for positioning the jib with relationship to the centerline of the boat. If you tighten the jib sheet too much the sail will become too flat and loose lift. If you loosen the jib sheet too much, the jib sail will luff and loose drive. Watch your jib luff telltales. Try to adjust the jib sheet so that all of the telltales are flying straight aft all the time when sailing upwind. This will tell you that the jib is pulling as hard as it can for the wind you're experiencing.
Most skippers are "stuck" with the same mainsail for all conditions. But, there often is a choice with regard to the jib sail. Depending on the boat, the jib sail sizes may range all the way from storm jibs at the smallest end of the scale all the way up to 165% drifter jibs for light breezes. Unfortunately though, many skippers have only one working 110% jib and perhaps a 150% genny. These two sails are good for many wind conditions, but not ideal for all.
The problem from a pointing standpoint is that if the sail is too small for the wind velocity, the boat sails too slowly. The slower the boat goes, the less it can point effectively. There just isn't enough water
flowing alongside the keel
to make these two foils efficient. As keel
efficiency decrease, the boat slides to leeward. Many skippers "feel" this and try to point the boat higher (sometimes even tighten up on the main and jib sheets). The sails become even less effective and more leeway occurs. A "catch 22".
Not having small enough sails for strong winds can be just a tough for pointing. As the wind pipes up, the sails tend to heel the boat more and more. The mainsail can be reefed, but at some point the jib is just too big. If the skipper decides to tough it out with a jib that's too large, the boat will heel past 25 degrees and the keel looses its bite on the water. Leeway occurs. If the skipper takes in the jib, there's often not enough sail to drive the boat effectively. The boat slows down and leeway occurs.
So sail selection directly can affect the boat's pointing ability.
A word about roller furlers:
I have not seen a jib sail yet on a roller furler
that points well when partially furled. The part of the sail that is rolled around the forestay causes a big bulge and inefficient airflow. The jib sheet leads are seldom (if ever) moved to compensate for the new clew position, so sail shape and clew tension is all wrong. And, the part of the sail that is left deployed has very little draft, so there's virtually no real lift. These all lead to the boat sailing more slowly than reasonable, and more leeway developed by the boat. Again a "catch 22".
Don't get me wrong here. I think that roller furlers are a wonderful bonus for recreational and cruising sailors. They just don't let the boat point well if the jib is partially furled, and that's what we're talking about.
Angle of Attack of the Sails To the Wind
The angle of the sails relative to the apparent wind is called the angle of attack. It is similar to the angle of attack that an airplane's wing has as the plane moves forward. Sails can be trimmed closer to or farther away from the centerline of the boat by adjusting the sheets
. This can affect angle of attack. The skipper might sail the boat closer to the wind by pinching or farther off the breeze by footing. Inexperienced skippers will tend to either pinch or foot. These skippers often complain that they can't point with other boats, but it's not their boat's fault. By pinching, the sails loose efficiency and the boat slows down and gathers leeway. By footing, the skipper sails a longer course than is necessary. Sailing alongside a boat with an experienced skipper will often give you clues regarding angle of attack, sail trim, and more.
Boat's Angel of Heel
The amount of heel that a boat has will affect the efficiency of the keel to bite into the water. If the boat is heeled more than 25 degrees of so, the keel is not able to hold the boat as well. The boat develops leeway and slides sideways. Reefing the main or shifting down to a smaller jib is usually the answer. In strong winds, a smaller sail plan will actually allow the boat to sail faster and point higher.
Boat's Balance Fore and Aft
Another factor that directly affects pointing ability is the balance of the boat on a fore and aft plane. If there's too much weight aft, the transom squats into the water and actually causes significant drag. This slows the boat down and leeway is developed very quickly. Having too much weight aft might be as a result of stowing heavy gear
in the cockpit
lockers or in the quarter berth areas. It might be caused by the skipper sitting back next to the stern rail. Or, having too much weight aft might also be caused by the current
trend toward higher horsepower 4-cycle engines. Adding 15hp 4-cycle engine
that weighs 115 lbs. to replace a 7.5hp 2-cycle engine
that weighs 75 lbs. is like coiling 60 feet of 1/4" chain on the stern pulpit. Allowing a 100-lb. child to ride in the stern rail seats is like adding 150 feet of 1/4" inch chain to the stern rail. In either case, the stern is pushed down by the extra weight and the boat's ability to point is decreased rather dramatically.
Having a clean bottom and the ability to sail close to the boat's maximum potential helps the boat point higher. Windward lift is generated by the keel and rudder if the boat is sailing close to hull speed
, which helps pointing. Conversely, a dirty bottom that slows the boat also decreases the pointing ability as the boat develops leeway.
The strength of the wind directly affects a boat's ability to point high. In light breezes, there just isn't enough wind power to give the boat sufficient speed to point well. So, if you sail in an area where there is light or moderate breezes, you might be frustrated in your boat's pointing ability.
Size of the Waves
Wave size can push a boat off course. Often this push is to leeward. But, because of the big waves, it is difficult to average a course that points high. When a skipper tries to sail higher in big waves, the boat often slows down and actually develops leeway in addition to being pushed by the waves downwind.
Steering Skill of the Skipper
Some skippers are really good at anticipating wind and water conditions. These skippers look ahead all the time to see where the smallest waves are. They actively sail toward these smaller waves so the boat isn't pushed to leeward by the larger waves. The boat also sails in relatively smoother water, so sails at a faster speed allowing the keel and rudder to develop more efficient lift. And, experienced skippers often know the trick of "scalloping" their boat upwind. These skippers actually turn the boat toward the wind and allow the boat to coast for a moment to windward before heading back off to the proper course. These scalloping maneuvers move the boat progressively to windward better than simply relying on the boat to do everything on it's own.
By-the-way, if you are sailing close to a skipper who is scalloping upwind on every puff, you might look at that boat just as the skipper scallops. The other boat is certainly "pointing" higher at just that moment. If you try to sail steadily on that higher course, your sails will simply not be able to maintain boat speed and your boat will develop leeway (sliding farther downwind from the boat your are comparing to). A very frustrating situation for you and a real chuckle for the other guy.
Your eyes can play tricks on you if you are trying to compare your boat's pointing ability to others. Because the deck
joint is curved and this is the general reference that you eye may use for comparison, your eye can be tricked. You may be pointing just as high as the next boat, but your eyes don't see it that way. So, you try to point higher, loose your efficient angle of attack, sail more slowly, and develop leeway…..Actually not pointing as high any more. Another one of those "catch 22's".