Weather Helm Vs Lee Helm – What is it? How to use it?

Jul20
2011 Written by Grant Headifen

This learn to sail article was written by Grant Headifen, Educational Director of NauticEd. NauticEd is an online sailing school and Sailing Certification Company providing sailing courses and sailing certifications for beginner to advanced sailors.

During the Americas’ Cup campaign in New Zealand in 2003, I saw one of the best explanations of this on a TV interview with the Greg Butterworth, the Tactician for the Alingi Team.

Most of us sort of understand the concept and we’ve been left with the answer of “Well – weather helm is better because it’s safer.” But few explanations go into how it gives your boat a sailing advantage. This concept is also explained in our Sail Trim Sailing Course on-line.

The definition of weather helm and lee helm is simple and it is easy to remember which is which. If you have a tiller, weather helm is when you have to pull the tiller to weather (toward the wind) in order to keep the boat going in a straight line. Lee helm is when you push the tiller to lee (downwind) in order to keep the boat going in a straight line. We’ve probably all felt this slight pressure required on the tiller when underway. If you’re just learning to sail, remember next time you’re out to feel for this on the wheel.

Your boat can be tuned to give weather helm or lee helm. Rake the mast forward  and you move the center of effort of the wind forward which causes your boat to want to turn downwind. Rake the mast back and you move the center of effort of the wind back causing your boat to want to go upwind to weather.

When your boat gets rounded up – you just experienced massive weather helm. No matter how much you pull the tiller to weather, you can’t stop the boat going to weather. Dumping the main sail moves the center of effort forward thus reducing the weather helm.

The basic perception of weather helm being safer comes from this effect: if you let go of the tiller, it will automatically go to center because of the water flowing over the rudder and because the rudder is pivoted at its leading edge. Now there is no rudder force to counter the desire of the boat to turn up wind to weather so the boat does exactly that. It turns to weather and rounds up thus  slowing the boat down and reducing forces on the rig. Conversely, lee helm  means that if you let the tiller go the boat will turn away from the wind, heel over more increase forces on the rig.

So from a safety point, weather helm is good. BUT there is another advantage that we’re not generally taught. Holding the tiller to weather means that there is a slight pressure on the rudder to windward. This actually MOVES THE BOAT TO WINDWARD as it slices through the water. And we all know what that means, race advantage!

The illustration shows how the water pressure from weather helm creates a sideways force on the rudder tending to push the boat to weather.

Hydrodynamic Advantage from the Rudder

Hydrodynamic Advantage from the Rudder

Now Greg Butterworth went on to explain that there are other cool things you can do. One is to put a little trailing edge swinging control surface on the keel.

Trim Tab on the Keel

Trim Tab on the Keel

The illustration below shows this effect too. For us pilots, this is much like a trim tab on a wing of a small airplane. The trim tab creates the ability to adjust the lift at that point on the aircraft and thus create a balance of forces. The issue to remember here is that you’d need to trim the tab the other way when you tack over.

So there you have it. While we’ve all been understanding the lifting effects of the wind over the sail, the other fluid that we’ve ignored is the water under the boat and how we can gain lift from it too.

Next time you’re out sailing on a nice steady 10 knot breeze, come up on a close haul, trim the sails perfectly so that all your tell tails are flying smoothly. Then notice what pressure you’ve got on the helm. Note that if you’ve got a wheel, weather helm will be a tendency to apply downwind turning pressure on the wheel (which is the same as pulling a tiller upwind right?). Ideally you should have slight weather helm. If not, you should probably not jump right in and start raking your mast back. Talk to a mast tuning specialist in your area first.

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Trimming the Mainsail and Preventing Rounding Up

Jul07
2011 Written by Grant Headifen

This article was written by Grant Headifen of NauticEd Sailing School.

As you learn to sail and advance your knowledge, it’s important to learn the finer point of sail trim and understand what is going on with the wind in the sails.

We approach this topic by looking at the condition created by an incorrect trim setting of the mainsail causing rounding up. Rounding up is when your sailboat, against your will, automatically turns up into the wind. If you understand how your sailboat should not round up then you will understand the proper trim of the mainsail.

Rounding up is caused by many factors. One is too much wind and force aloft which tends to heel the boat over. This reduces the amount of rudder in the water and thus the rudder’s effectiveness. According to Pythagoras’ theorem a 30 degree heel will loose you 29% of your rudder effectiveness. This means you’ll need more helm to weather to control the boat. More helm to weather creates more drag. More drag slows the boat. As the boat slows the rudder becomes far less effective by the square of the reduced velocity. So with over heeling you’re loosing rudder area and velocity. A cubic reduction in effectiveness to control a round up.

Another factor in rounding up is the center of pressure of wind on the sails moves far aft which then pushes the aft of the boat downwind and thus the front of the boat up wind.

The NauticEd SailTrim clinic discusses this topic and so what we wanted to do was test it out for sure. So last weekend we took out a friend’s Beneteau 373 to test out an anti-round up theory. Read on to find out the results of our experiment.

First though, we must first understand wind shear. The phenomenon of wind shear is pretty easy. Wind moves faster at the top of the mast than is does at the water level because the stationary water slows the down the wind in close proximity.

Secondly, consider the concept of true wind vs apparent wind. Which is best understood by imagining driving your car in a cross wind with your hand out the window of the car. The faster you go, the more the apparent wind moves towards coming from the front of the car. But when a gust of wind comes (which is just an increase in true wind speed) then the apparent wind shifts back more to the side. When relating this to a sailboat, if your boat was standing still, the wind at the top of the mast would be the same apparent direction as at the cockpit level albeit, faster. However as your boat picks up in speed the apparent wind moves forward BUT because of wind shear it shifts forward less at the top of the mast. IE at the top of the mast the wind tends more to the direction of true wind direction because the true wind speed is higher. Thus at the top of the mast the true wind is more aft than apparent wind. Aft means it is coming from a direction further towards the back of the boat. Get it?

So – whether you get it or not. The fact is: at the top of the mast the wind is higher in speed and more aft than at the cockpit level.

true wind vs apparent wind

true wind vs apparent wind

Figure A and B show the boat speed, true wind and apparent wind vectors for cockpit level and top of the mast. Obviously in both cases, the boat speed vector must be the same. The true wind vector is obviously the same direction but due to wind shear it is longer (faster) at the top of the mast. This results then in the apparent wind direction being more aft. IE in this case from 135 deg to 125 deg.

Thirdly, you should understand that if a sail is sheeted in to tight it creates more heel. This then is exactly what is happening at the top of the mast. The sail is sheeted in too tight against higher wind speed. No wonder you’re getting excessive heeling. And excessive heeling creates round ups.

This is now quite a revelation! It means that the top of the main needs to be “out” further than the bottom of the sail for it to operate efficiently. This is usually indicated by the top telltale. Often the leeward telltale will be stalling at the top of the sail. Especially in high wind because of the phenomena above.

Thus the top of the mainsail needs to be let out further so that the leeward telltale can fly smoothly. This is commonly referred to as twisting the sail out at the top. Except people believe you are just spilling out (wasting) the wind at the top. Not quite so now, as you’ve just learned. Twisting out the top of the sail is letting the top of the sail fly according to the direction of wind it is feeling.

Tell tales on the sail

Tell tales on the sail

In the illustration, you can see the top telltale on the downwind side is fluttering. If you let out the main at the top, the wind can reattach to the sail on the leeward side and the telltale will fly smoothly.

Understanding all the above. How do we stop rounding up?

Option one: Obviously the first and safe option in higher winds is to reef the sail but the options below will still apply.

Option two: Let out the traveler, which is what most people do when hit by a gust. Just so long as you realize what you’ve done is not twisted the top of the sail out – all you’ve done is let out the mainsail from top to bottom and thus depower the mainsail. This reduces the force aloft and thus the heel. It also moves the center of effort of wind on the sails forward which reduces tendency to round up. The trouble is that you spend all day fighting gusts with still quite a few involuntary round-ups.

Option three: Let out on the mainsheet. Here again you’ve depowered the entire mainsail to handle the gust. Still, it works.

Option four: Permanently reduce the force aloft by letting out further on the mainsail and tightening up on the traveler. The trick here is to bring the mainsail bottom back in again using the traveler. Yes, bring the traveler to windward up past the center point. Most sailors are reluctant to do this because they’ve been taught that it detaches the wind on the leeward side. But not when you’ve let out the mainsheet. In effect, by letting out on the mainsheet, you’ve allowed the boom to rise up and the leech of the sail to slacken. This creates the desired twist at the top and allows the top of the sail to fly according to its apparent direction. At the same time, the bottom of the sail can fly according to its apparent direction.

What happened on our 15 knot gusty sailing day? Well, not one round up.

So to summarize, the sailing lesson here is when in higher winds bring the traveler up and sheet out the main. You’ll also need to release the boom vang a little. Letting the boom vang out allows the boom to rise which loosens the leech (trailing edge) of the sail and allows the top part to “twist out”.

Posted in Learn to Sail

Learn to Sail Series: How to Reef the Headsails

Jun12
2011 Written by Grant Headifen

This is a continuing  learning how to sail article on Reefing the Sails. This has been written by Grant Headifen of NauticEd Sailing School.

In the last Learn to Sail article on reefing we convinced you pretty hard on why you should reef the sails. So now let’s first learn how to reef the headsails.

The five most common sails on a sailboat are mainsail, jibsail, genoa, spinaker and genaker.

We’ll deal with the spinnaker and genaker first in regards to reefing because it’s pretty simple. Take them down and replace with a smaller one if available or take down entirely. Don’t push the limits with these sails. They are made of very fine and fragile fabric because they need to be light. If you over power these sails they will tear. Even if they don’t tear, one slight misjudgment or distraction when flying these in high winds can lead to a broach and broaches are bad.

A broach is when the wind force slams the boat over sideways, you loose control, the boat tries rounds up but the wind continues to fill the sail and hold the boat down – potentially capsizing it. It’s the last thing you want to do as you learn to sail because you probably don’t have the experience to get out of this situation other than swimming. You’ll most often see this in yacht club regatta racing when a captain is reluctant to reduce sail area because he wants to win the race. Experienced skippers know to NOT put a stopper knot in any of the working lines of a spinnaker or genaker. If you broach, you will need to dump these lines completely out of any blocks or fairleads that guide these lines with in seconds or face potential capsize.

The next sail set to discuss is the jibsail and the genoa. Or they can correctly be referred to as the head sail in both circumstances. These two sails are essentially the same except by definition. A headsail is a genoa if the clew (bottom aft eyelet) extends aft past the mast. A head sail is a jibsail if the clew does not extend past the mast.  People refer to a jib or genoa size by the percentage of distance from the forestay to the mast. If the Genoa extends past by 10% then it is called a 110 genoa. If a jibsail extends only 90% of the distance from the forestay to the mast then it is called a 90 jibsail.

Some jibsails and genoas are raised and lowered and some roll up (furl) around the forestay. If they are furled around the forestay then it is very simple to reef them. You simply roll them up a little in order to decrease their size. Typically there will be two stripes marked on the foot of the jib/genoa. Each one marks where the sail should be rolled to for the respective reefing point.

There is a safety and rigging protecting method that is VERY important to note when reefing a roller furling sail. It’s a classic mistake that is commonly made when you learn to sail because you’re not familiar with the rigging and their forces. The point is simple, you must tighten the sail after reefing with the jibsheet. Don’t use the inhaul to tighten the sail. A roller furling jibsail/genoa has a drum at the bottom of the forestay. This rolls up by pulling on the inhaul line and rolls out by pulling on the jibsheet. The inhaul is a line that runs back to the cockpit. You pull the inhaul to wind it up while managing the slow release of the jib sheets.

To unwind the head sail you will release the inhaul line and lay it out so that it will uncoil smoothly with out getting caught in the inhaul clutch or cleat. Then pull the leeward (downwind) jibsheet all the time ensuring the smooth uncoiling of the inhaul, plus keeping a watch out on traffic and crew etc.

When you are reefing a roller furling headsail, slowly let out the jibsheet while heading the boat slightly to wind to slacken the jibsheet. Roll up the sail the desired amount making sure that the jibsheet always has some slack to it. Then tighten the headsail back up with the jibsheet only. Do not cleat off the jibsheet and tighten the sail by further hauling in on the inhaul. This will certainly damage the drum and furling system.

For additional safety, do not completely let go the jibsheets then begin winding the inhaul. This causes the jibsheets to whip wildly and, from experience, they really REALLY hurt. Control the jibsheet tension at all times. Controlling the jibsheet tension also ensures a firmly wound headsail.

When you want to let out a reef in the headsail, first wrap the inhaul around a winch two to four times depending on the wind strength. Then release the inhaul clutch/cleat and control the let out of the inhaul. Once it is at the point you want it or it’s all the way out, cleat the inhaul and tighten up on the jibsheet.

If the headsails are not of the furling type then you will most likely hank (clip) them onto the forestay and then raise the sail with the jib halyard. In this case there is no way to furl or reef that sail. Reefing the headsail then means removing the current headsail and raising a smaller one. It’s not that difficult but you have to be aware of whipping lines and inherent dangers of being on the bow in rough and rolling seas with waves potentially breaking over the foredeck. Under poor weather conditions, the prudent sailor will be clipped into jacklines with a harness. Jacklines are safety lines that run on the deck from forward to aft. A crew member can clip in and walk to the foredeck and back whilst all the time being attached to the sailboat.

As you learn to sail, we sincerely hope that you take note of this sail reefing series as it is very important to your crew, yourself and your vessel. This article is not the be all and end all. You absolutely should get out sailing with a knowledgeable friend or instructor from a NauticEd Affiliated sailing school on a boat and practice reefing under various weather conditions.

This learn to sail article was written by Grant Headifen, Educational Director of NauticEd. NauticEd is an online sailing school providing sailing courses and sailing certifications for beginner to advanced sailors worldwide.

NauticEd Sailing Certifications are accepted by most large yacht charter companies including The Moorings, Sunsail, Kiriacoulis, BVI Yacht Charters, Sailing New Zealand, Gulf Charters Thailand.

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Learn to Sail Series: How to Reef the Mainsail

May18
2011 Written by Grant Headifen

This is a continuing  learning how to sail article on Reefing the Sails. This has been written by Grant Headifen of NauticEd Sailing School.

In the previous Learn to Sail article on reefing we convinced you pretty hard on why you should reef the sails. So now let’s learn how to reef the mainsail.

When getting underway, mainsails are either hoisted up the mast or unfurled (unrolled) out of the mast. When reefing the mainsail, you are reducing the size of the sail area presented to the wind. If the mainsail is hoisted, then to reef, you will be lowering the sail slightly. If the mainsail is typically furled into the mast, you will be furling the sail into the mast a little to reef it.

Reefing the Mainsail by Furling Into the Mast

This is simple. You first must take the wind load off the sail. You can either motor into the wind or use the jibsail to head onto a close haul or close reach and let the mainsheet out until the load disappears from the mainsail. Then wrap the mainsail outhaul around the winch and release the clutch holding the outhaul. Leave the outhaul wrapped once around the winch to create some back tension. This is important so that the mainsail wraps up tightly inside the mast. Otherwise, if it is too loose, a loosely wrapped mainsail will not fit into the mast and will over wrap on it self creating a huge problem when you next try to unfurl. Now furl in the mainsail using the inhaul or infurl line to the desired amount. Usually there is a 1st reef and 2nd reef position marked on the sail. It is VERY important to only tension the sail back up using the outhaul line NOT the inhaul line otherwise you will damage the inhaul system. This is a classic mistake by new sailors as they learn to sail.

Reefing the Mainsail by Lowering the Sail.

Note that if you have a mainsail inmast furling system do not use this method. Although in an emergency you probably could but the sail should be all the way unfurled before you attempt it. More than likely however there will be no reefing grommets in the sail anyhow.

Here you are lowering the sail a little into a boom furling system, a stac pac – which is a long bag on top of the boom or you’ll just lash the unused portion of the sail to the boom using lines that run through grommet holes along the sail at the reefing points. And by the way, this is where the reef knot is so named. You’ll use the reef knot to lash the sail to the boom.

To reef then, take the load off the mainsail by motoring into wind or by using the jibsail to head onto a close haul or close reach and then let out the mainsheet until the load is removed from the mainsail. Wrap the main halyard around a winch and release the clutch for the halyard. Lower the mainsail to the desired reefing point.

At the mast there will be a hook system to hook into reefing grommets along the leading edge of the main sail. Or there will be lines running up to those reefing grommets. Either way, you will be using these to pull down the sail. Some sailboats are rigged with a Cunningham which is a pulley system which gives you more leverage.

The Main Sail

The Main Sail

At the leach (trailing edge) of the mainsail there will also be grommet reefing holes and most likely there will be lines to also pull those down to the boom. Ensure that you pull down the luff (leading edge) first before you pull down the leach otherwise you can damage the sail. As you learn to sail you’ll begin to gain a real appreciation for the order of performing such tasks.

The leach reefing lines sometimes will run down along the boom to the mast end. The first and second reef lines are usually distinguished by being different colors.

Now re-tension the halyard. If the boat is fitted with a Cunningham, now use it to further adjust the tension of the luff.

Once the luff and leach are secured, and if you don’t have a stac pac, lash any loose sail down using the reefing grommets.

If you boat is fitted with a boom furling system, most of the above is relevant except instead of pulling down with the reefing lines, you’ll just furl (wind) the sail into the boom. You’ll need to keep a little tension on the halyard to ensure the sail wraps firmly into the boom. Do not down tension the mainsail luff using the boom furling system. Rather use the halyard and Cunningham to do your tensioning.

We hope you enjoy this learn to sail series on reefing the sail. Please continue to read our other articles.

If youre serious about learning to sail, consider the NauticEd Skipper Sailing Course.

This learn to sail article was written by Grant Headifen, Educational Director of NauticEd Sailing School. NauticEd is an online sailing school providing sailing courses and sailing certifications for beginner to advanced sailors.

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Learn to Sail Series – Reefing the Sails – why?

May10
2011 Written by Grant Headifen

This is another Learn to Sail Artical is a series on the sails. The articels are written by Grant Headifen, Educational Director for NauticEd Sailing School. NauticEd is the World’s Most Advanced Online Sailing Education and Sailing Certification Company.

Reefing the sails is such and important safety aspect of sailing that it’s one of the first things you should understand as you begin to learn to sail.

Now is a good time to discuss something a tiny bit technical – force from the wind. Force imparted onto the sailboat is multiplied by four every time the wind speed doubles.

So if you go from 5 knots to 10 knots the forces quadruple. Then if you again go up to 20 knots, the forces are 16 times higher than at 5 knots. And 40 knots? 64 times. To put that in more perspective if it takes about ½ your strength to pull a line at 5 knots, at 20 knots you would feel 8 hefty guys pulling against you in a tug of war. You’ve got no chance. Now also think of the stress on the rigging and how 16 times more force aloft is heeling your boat over. Sixteen times!!!!

I hope you’re getting the point.  The quadrupling effect comes from the well established Bernoulli’s equation which says the pressure applied is proportional to the square of the velocity. And by definition, force is equal to pressure multiplied by area.

So if we halve the area we halve the forces. Makes sense right? And that is what we are doing by reefing. We’re reducing the area while the velocity is increasing in our best attempt to manage the forces.

And one more thing – when you’re heading up wind, your boat speed is somewhat additive to the wind speed and so the forces increase even further.

The mast on your sailboat is probably supported by shroud lines attached to the sides of your sailboat and by a forestay and aftstay. They are designed to hold certain forces aloft. Should the forces become higher than design or the connections deteriorate which on a boat they are guaranteed to do over time, then you’re going to have some serious problems with a dismasting.

In reality and practice, you should start to think about reefing the sails at about 12 knots of wind. At 15 knots, you should definitely be reefing and at 20 knots, you’re crazy if you don’t have 1 or 2 reefs in. The boat will be uncontrollable if you haven’t reefed and you’ll be probably breaking items on your boat due to high forces from the wind. At 30 knots, the boat will probably explode. Well, not quite, but I’m making a point to reef reef reef and get comfortable with the process especially when you are starting out in your learn to sail quest. And get a sailing school instructor or practiced sailing friend to teach you how to reef your sails.

The process should not be intimidating. What can be intimidating however is if you leave it too late. A good professional captain of mine who would sail across the Atlantic had a saying. If you think you should be reefing – you should have reefed yesterday and if you are thinking about “shaking out the reef” (unreefing (if that is a word)) wait until tomorrow.

Leaving the reefing until it is too late means that there are excess forces already on all of the lines you’re going to want to be handling which is a safety issue for you and your crew. So reef early. An additional incentive to reefing is that actually, you can make your boat go faster anyway.  So if you’re trying to be mucho and waiting to reef, you will be going slower and loosing the race (there is always a race).

Not reefing causes rounding up. One of the best things to see in a race is when the boat that is ahead of you has too much sail aloft and they get over powered and round up into the wind. This is so awesome because in doing so they will have lost 50 meters of lead on you.

Rounding up is a wee bit technical but essentially it is when the wind force takes over your boat with out your ability to counter act using the rudder. The boat just turns up into the wind. It’s dangerous because you can be turned right into other traffic. And it’s just a pure waste of good sailing.

When you begin to learn to sail, you’ll find that the boat is trimmed so that the rudder balances the turning force of the sails. The force from sails want to turn the boat up into the wind and the force from the rudder wants to turn the boat down wind. This is done for two reasons. (1) For safety: if the tiller or wheel is released the boat will round up into the wind and loose  power. And (2) if the rudder is pointing slightly up wind the boat gets a lift to windward from the force of the water on the rudder.  However this balance is lost as the boat heels over too much. If you imagine that the boat has heeled over 30 degrees then according to Pythagoras, you are down to 70.7% of your rudder counteracting forces. So too much heeling is bad.

On top of all that, as you begin to learn to sail and understand the forces, you’ll learn that the sail relies on efficiency of the wind over the sail to create lift. This requires that the wind on the back side of the sail flow evenly across the sail (stays attached to the sail) to create the low pressure and thus lift. When the wind speed is too high and as the boat heels over, the wind has great difficulty in staying attached to the sail. Thus the wind peels off and you loose efficiency. A smaller sail requires the wind to stay attached for a shorter distance and thus increases the efficiency.

We sum all this up to say when you reef in high wind conditions your boat can go faster with less heeling and less likelihood of doing serious damage to your sailboat. That’s good.

In the next learn to sail series we’ll cover how to reef the sails.

This article was written by Grant Headifen, Educational Director of NauticEd. NauticEd is an online sailing school providing sailing courses and sailing certifications for beginner to advanced sailors.

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