Weather Helm / Skeg and Rudder

[BAD ORCA]

Do sailboat designers when designing a new sailboat (monohull) always try to design with a very slight amount of weather helm or is the intended goal of the designer to always try and build a balanced sailing boat?

My gut feeling is that they might try to design in a very slight amount of weather helm with a 100% genoa since large 100+ genoas seem so popular but my thinking may be way off.

My second question is...is it possible that a skeg and rudder (fin keel monohull / dinghy type flattish bottom) could be too large for a particular sailboat and actually cause some weather helm as well, independent of the sails?

[sck5]

You should be able to balance pretty much any sailboat. Having said that, it is a good idea to sail with a slight weather helm so the boat will fly up into the wind if you let go rather than gybing. Which could be quite unpleasant.

[tkeithlu]

Mast rake is probably the easiest way to adjust to a minimal weather helm. For an explanation of the principles, see:

https://www.northsails.com/sailing/e...your-sail-plan

[Bill O]

Originally Posted by BAD ORCA

Do sailboat designers when designing a new sailboat (monohull) always try to design with a very slight amount of weather helm or is the intended goal of the designer to always try and build a balanced sailing boat?

My gut feeling is that they might try to design in a very slight amount of weather helm with a 100% genoa since large 100+ genoas seem so popular but my thinking may be way off.

My second question is...is it possible that a skeg and rudder (fin keel monohull / dinghy type flattish bottom) could be too large for a particular sailboat and actually cause some weather helm as well, independent of the sails?

Is there a particular boat that you are looking at or own that is exhibiting excessive weather helm?

Sometimes boat designers get it wrong and can put the mast in the wrong place. When Perry made the Valiant 47, he put the mast in the wrong place. He had to move ~13" forward and add a bow sprit to reduce WH. The modified boat eventually became the Valiant 50 .

[SteveSadler]

All monohulls will have weather helm under full sail because as it heels over the hull has more of one side in the water, less of the other. This creates an assymetric hull shape. The side with more curved surface in the water will push the bow the opposite way. This is then corrected by reefing the mainsail which creates an opposite assymetric force.

[KadeyKrogen38]

Outside of a bad design, excess weather helm is usually the result of having too much sail up or bad trim of the mainsail. Mast rake may be off and needing readjusting if the bad weather helm is not sail/ trim related.

[zstine]

weather helm is largely dependent on the amount of heel. In light air or when over-reefed and sailing with little heel, the helm should be neutral. you should not have lee-helm. When the boat is fully powered and well heeled over, you should have some weather helm. This is faster since both the keel and rudder share the load to 'lift' the boat toward the wind. It also makes the boat self-steering since you can lock the helm a few degrees off center and as the boat turns up and flatens, the helm turns the boat down. as you fall off and heel, the boat turns up.. it finds a balance

[foufou]

Another thing that can produce weather helm is an old sail where the draft has moved aft and the leech is still tight. A properly shaped sail does make a difference.

[Cwens]

Originally Posted by SteveSadler

All monohulls will have weather helm under full sail because as it heels over the hull has more of one side in the water, less of the other. This creates an assymetric hull shape. The side with more curved surface in the water will push the bow the opposite way. This is then corrected by reefing the mainsail which creates an opposite assymetric force.

Additionally, independent of hull shape, as the boat heels, the center of effort of the sailplan moves to leeward. Even if you had a cylindrical hull, with no asymmetry created by heeling, as the boat heels, the forward thrust of the sailplan is acting on the boat somewhere to leeward of the center of drag of the hull, causing weather helm.

[SAMUELBURNS]

No one has addressed BOrca’s concern about rudder & skeg contributing to weather helm. Sailboat designers use the term ‘lead’ to mean the length between the centerof effort CE of a sail ‘plan’ and the center of lateral resistance CLR of the hull.
When helm is used to counter weather helm, the CLR of the hull moves astern.
And when the boat heels, the CE moves away from the centerline of the boat and
out over the water. Imagine the CE as some point of the sailplan where a single ‘vector’
could be attached (in place of the sails) pulling the same force as the sails. The ‘lead’
of a heeling boat acts in part to ‘crank’ the boat around the CLR and into the wind. Reducing this ‘lead’ reduces weather helm; using more helm only increases ‘lead’.
Moving CE forward and down effectively reduces ‘lead’ and weatherhelm. Reefing the
mainsail and unrolling jib sail both accomplish this while avoiding loss of boat speed
resulting from countering weatherhelm with rudder.

[BAD ORCA]

Originally Posted by Bill O

Is there a particular boat that you are looking at or own that is exhibiting excessive weather helm?

Sometimes boat designers get it wrong and can put the mast in the wrong place. When Perry made the Valiant 47, he put the mast in the wrong place. He had to move ~13" forward and add a bow sprit to reduce WH. The modified boat eventually became the Valiant 50 .

Hi Bill. Well i started reading 'Desirable and Undesirable Characteristics of Offshore Yachts'. Im in the third or fourth chapter where he starts to explain weather helm. I know what it is and have experienced with it sailing my boat and my friends boat, but i realize i still dont fully understand it.

I have a Peter Canning Mariner36. My sails are on the old side for sure. To give an example of its weather helm, when we take her out in the bay in 15ish kts of wind, with full genoa up (its a 130 or 150, overlaps mainmast), i can steer my boat with very little effort. If i take my hand off the wheel she will round up slowly into the wind within about 50ish yards. Assuming water is reasonably flat with genoa and mainsail sheeted in pretty tight. On my friends little Ranger 29, we can sail in the same conditions, maybe slightly furled in jib, and i can take my hand off the wheel and the boat will follow a strait course for 30 minutes unless large waves.

I really dont have much more experience than that. I'd like to swap out my large genoa for a 100% jib. If i do i'm assuming weather helm will get worse. In fairness to my boat, I havn't known how to properly trim to alleviate it. We always furled in the jib, which does help de-power the boat but simply letting out the main might have been all that was needed.

Im just trying to learn and sort of 'evaluate' my boat by comparison to try and asses where she falls. I dont know if what i described for my boat would be considered 'excessive' weather helm or pretty normal.

[BAD ORCA]

Originally Posted by tkeithlu

Mast rake is probably the easiest way to adjust to a minimal weather helm. For an explanation of the principles, see:

https://www.northsails.com/sailing/e...your-sail-plan

Iv'e read somewhere in some rigging book (sorry i cant remember which) that heavy single spreader masts on offshore boats should not be raked. I read it quickly in passing and cant remember why that is though.

[BAD ORCA]

Originally Posted by SAMUELBURNS

No one has addressed BOrca’s concern about rudder & skeg contributing to weather helm. Sailboat designers use the term ‘lead’ to mean the length between the centerof effort CE of a sail ‘plan’ and the center of lateral resistance CLR of the hull.
When helm is used to counter weather helm, the CLR of the hull moves astern.
And when the boat heels, the CE moves away from the centerline of the boat and
out over the water. Imagine the CE as some point of the sailplan where a single ‘vector’
could be attached (in place of the sails) pulling the same force as the sails. The ‘lead’
of a heeling boat acts in part to ‘crank’ the boat around the CLR and into the wind. Reducing this ‘lead’ reduces weather helm; using more helm only increases ‘lead’.
Moving CE forward and down effectively reduces ‘lead’ and weatherhelm. Reefing the
mainsail and unrolling jib sail both accomplish this while avoiding loss of boat speed
resulting from countering weatherhelm with rudder.

Does adding another jib on an inner stay have a similar effect? Could a smaller jib be raised on the inner stay allowing the main to be kept fully up and un-reefed?

[Kd9truck]

The only time I accept weather helm with out adjusting/reducing sail is when I am trying to “pinch” closer to the wind, or when the vessel is experiencing a gust over the upper limit of the current sail adjustment.
As a unconscious rule I trim sail to balance the boat. Especially if I am looking to hand the Helm to the auto pilot. My experience for the past 45 yrs is almost exclusively with fractional production line sloops ranging in size from 23 to 57 feet.

[rhubstuff]

Originally Posted by ChrisOwens

Additionally, independent of hull shape, as the boat heels, the center of effort of the sailplan moves to leeward. Even if you had a cylindrical hull, with no asymmetry created by heeling, as the boat heels, the forward thrust of the sailplan is acting on the boat somewhere to leeward of the center of drag of the hull, causing weather helm.

The CE cannot move to leeward or to weather. It can only move fore and aft.