Weather helm

[Don Guillette]

Yesterday I was speaking to a newbie sailor about weather helm. It would be very simple to demonstrate on his boat. Talking about many aspects of sail trim over the phone is not easy – it’s like explaining how to be a carpenter or better yet, how to play a musical instrument!!! It can be frustrating.

A lot of sailors don’t like weather helm but there’s nothing wrong with it. It’s a good thing in light wind but can be a pain in heavy wind. Some newbies think that only the rudder turns the boat. It does but so does the mainsail but not as well or as quickly as the rudder. The more you eliminate twist from the mainsail the more the wind turns the sail, which is like turning the rudder.

How much weather helm is desirable when sailing upwind? On my C30 I found that 3 degrees to 5 degrees, which isn’t very much, was just about right but I don’t know the scientific explanation just as I don’t know the scientific explanation of the “lift/drag curve” but I know how to make stuff work for me. If I pushed it to 7 degrees I was still OK but 10 degrees was too much. I think the rudder was creating too much drag but I’m sure RichH can explain it. I measured the degrees by centering the rudder and placed a piece of tape at 12:00.

Do you know a simple way to tell if your boat has a weather helm problem??

 

[25yearslater]

Since I have a tiller boat it is super easy to tell. Your arm gets tired after a while. Generally I keep the trim so that I have no to very light weather helm. I found the speed readout on the laptop could clue me in when drag was building as the speed would start to drop. It is amazing how quickly the speed drops when the rudder is anything but straight.

 

[Paul Mermelstein]

Don, you are quite knowledgeable and I yield to your expertise. But wouldn't I know if I have the "appropriate" amount of weather helm if the sail set and rudder angle combination produced a balanced boat with little pressure on the helm?

 

[Joe]

I never want to "fight" the tiller.... even with 5 degrees the tiller should feel balanced... and it should allow the autopilot to work effortlessly.... so... if you don't have a gauge on your rudder post, then try letting off the tiller or wheel and see how fast the boat wants to round up. If it slowly turns in to the wind then that's a pretty good place to be. If it heads up abruptly... make your adjustments.... sheet or power up the jib, ease or depower the main..... until you feel comfortable.

When setting up for the auto pilot I'll try to get my boat as close to zero weather helm as possible.... if you get it right you'll hear very few corrections being made... it's fun.

 

[Jackdaw]

How much weather helm is desirable when sailing upwind? On my C30 I found that 3 degrees to 5 degrees, which isn’t very much, was just about right but I don’t know the scientific explanation just as I don’t know the scientific explanation of the “lift/drag curve” but I know how to make stuff work for me.

The hydrodynamic surfaces of a boat (keel and rudder) need to generate lift for the boat to go effectively to windward. Because they are symmetrical, they use the boats slight slideslip to give the illusion of asymmetry. But even still they would benefit from being asymmetrical. This however would mean that the appendage would have to be A) designed to work only on ONE tack, or B) could rotate its Angle of Attack (AOA) a few degrees. This is impractical for the keel, but is exactly what happens when you have 2-4 degrees of weather helm.

It's also why lee helm is so bad. Turning the helm the other way DESTROYS any lift the rudder would generate.

 

[Kermit]

It's also why lee helm is so bad. Turning the helm the other way DESTROYS any lift the rudder would generate.

Also scary as all getout when the wind is pushing you where you don't want to go.

 

[Spindrift NH]

This could open up a whole can of worms, but I'm gonna put it out there anyway. I have a catalina 30 with the wing keel, not sure if yours is the wing Don. This past fall, the yard fiberglass guy asked me if I thought my boat has a lot of weather helm. "Why yes" I replied, "I think I have a blown out mail sail, its 15 years old" No he said, you have the wrong rudder. He then informed me that I have the rudder for the fin keel, longer and narrower. And for a price he could modify mine for me and fix the weatherhelm. He would repair it by shortening the depth and lengthening the aft edge. He said later models had the improved rudder. Any thoughts?

 

[Davidasailor26]

This could open up a whole can of worms, but I'm gonna put it out there anyway. I have a catalina 30 with the wing keel, not sure if yours is the wing Don. This past fall, the yard fiberglass guy asked me if I thought my boat has a lot of weather helm. "Why yes" I replied, "I think I have a blown out mail sail, its 15 years old" No he said, you have the wrong rudder. He then informed me that I have the rudder for the fin keel, longer and narrower. And for a price he could modify mine for me and fix the weatherhelm. He would repair it by shortening the depth and lengthening the aft edge. He said later models had the improved rudder. Any thoughts?

I always assumed that a shorter rudder was just out of necessity to keep the rudder shallower than the keel so that groundings would be less likely to damage the rudder post. A deeper rudder should be more efficient as it has a longer leading edge, which is really what generates the lift. I can't think of any reason why a winged keel would make any difference on that.

 

[Don Guillette]

Here's how I explained the method to determine IF the newbie had a weather helm problem. Most boats don't have a weather helm problem -- normally it's the fault of the skipper and the trimmer.

The first thing the skipper and trimmer have to do is set the main and jib sail trim controls for closehauled and 100% efficiency otherwise this whole thing is a waste of time. It may take a few sailing outing because the wind needs to cooperate in a couple of ranges.

In 5 knots of wind closehauled, take your hands off the wheel/tiller and see what happens. If the boat is in balance it should sail straight and slowly head into the wind. Only the slightest bit of rudder is necessary to bring it back to a straight line. In 10 to 12 knots of wind do the same thing and if everything is right only about 3 to 4 degrees of rudder will be needed to bring it back to a straight line. Here's the big test -- in 15 knots do the same thing and you'll need 6 to 8 degrees of rudder to bring it back to a straight line.

If your boat performs as outlined above, you don't have a weather helm problem.

 

[Ken13559]

Can I use the rudder reference angle indicator on the Autopilot display as guide? Would an indicated 10deg means 10deg of rudder? Max is 30deg on my display.

 

[moehorenfeldt]

The rake of the mast has a great influence on "weather helm". The further aft the mast is raked off absolute perpendicular, the more weather helm is induced. Ouyang Matilda 20 sailors were known to have one arm significantly longer than the other due to weather helm. A balanced rudder takes some of the strain off the tiller, but as noted above, some weather helm is desirable, mainly because if you go overboard unintentionally, your boat won't sail away from you, at least not if you are on autopilot. My $.02 anyway.

 

[seasailor55]

I've been told that rudder post rake is also a factor. I have a 1984 Cape Dory 22 with a full keel and an attached rudder that rakes significantly. In anything over 12 knots it will spin into the wind if the tiller is released. A bigger jib and a reef in the main helps, but doesn't eliminate the weather helm. Other Cape Dory boats seem to have the same problem. Design issue I suppose, although I'm definitely not slamming Alberg or his creations. To be honest, I'm a bit disappointed in the performance of the boat, having always felt that straight tracking was a big plus factor of a full keel design. Could it be I've been spending too much time on my Hobie 16?

 

[RichH]

All good comments; but especially when using dacron mainsails with a boltroped luff (the most common configuration) what REALLY controls 'weather helm' once the mast rake is 'close' to the designer's sail plan/design, etc. is .......... mainsail halyard tension !!!!!!

Arriving at correct mainsail halyard tension will cause the overall shape of the sail to change, so that the 'point' at where the maximum amount of draft occurs (fore or aft) results in a 'balanced' output of the mainsail and jib combination, hence balanced 'weather helm' - I like ~3° of helm.
Of course, this is all set up and adjusted by initially sailing closehauled and with enough mainsheet tension applied so that the area of the leech of the mainsail - just above the second from the top batten - is approximately parallel with the boats centerline; then making halyard adjustment until you get the precise amount of weather helm that you LIKE. This is the 'design or sail output goal' of the sailmaker.

Every day on the water will be different from any other day - wind and waves will usually always be different ... so you need to raise and 'stretch out' the luff on a boltroped dacron mainsail differently every time you go out. Here's the basic set up (and the expected problems as a dacron sail begins to 'age') ----- Go to http://forums.sbo.sailboatowners.com/showthread.php?t=120970 see post #1