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Weather Helm/Lee Helm -What's The Diff?

Discussion in 'Sail Trim with Don Guillette' started by Don Guillette, Apr 26, 2018. Add this thread to a FAQ

  1. Don Guillette

    Don Guillette

    Joined May 17, 2004
    1,896 posts, 65 likes
    Other Catalina 30
    US Tucson, AZ
    Over the last 17 years just about about every sail trim topic of interest to most beginners to intermediate sailors has been discussed. It's becoming more difficult to come up with topics that will interest the sail trim forum lister's. I trawl the various forum sights looking for topics -- if I was looking for maintenance subjects I'd have a ton of them. Another source I use is conversation I have with sailors.

    Weather helm & lee helm came up the other day in a phone conversation. The following is the way I described it to the beginner Hunter sailor from Florida, who is experiencing mild weather helm. A understanding of CE (center of effort) and CLR (center of lateral resistance) would have made the discussion easier but if I started off with that I'd have lost the beginner sailor inside of a minute so I approached the topic from a non scientific standpoint, which I prefer anyway. Additionally, the terms lee helm & weather helm were established when tillers were in vogue rather than wheels. Weather helm is when you have to PULL the tiller to weather or the windward side of the boat in order to sail in a straight line. Lee helm is is when you PUSH the tiller "to lee" in order to sail in a straight line. The turning action is opposite with a wheel.

    So weather helm means that the boat left alone would want to turn into the wind and lee helm means the boat wants to turn downwind. Without getting into a discussion on how to correct weather helm/lee helm by moving the CE & CLR, which might be another good topic, I explained why some weather helm is a good thing from a safety standpoint and why a perfectly balanced boat, which he was looking to establish, is not completely ideal.

    If one of your beginner sailing friends asked you why weather helm is a safety factor and why a perfectly balanced boat is not completely ideal what would you tell them?


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  2. GorillaToast

    GorillaToast

    Joined Sep 2, 2011
    1,009 posts, 50 likes
    Hunter 27 Cherubini
    US Alum Creek State Park
    I'd just tell them because some old f%#t in the Sail Trim forum says so.
    :rolleyes:
     


  3. jon hansen

    jon hansen

    Joined May 25, 2012
    941 posts, 422 likes
    john alden caravelle 42
    us sturgeon bay, wis
    so an out of control sailboat will go into '"IRONS" there by stopping the vessel
     


  4. victorhoisington

    victorhoisington

    Joined Jan 22, 2008
    173 posts, 27 likes
    Islander Freeport, 41 Ketch
    US Longmont, CO
    A perfectly balanced boat is nice on a calm day but still requires attention, puffs, lulls, wave action all impact the balance and so minor tweaks are always required. The boat with just a bit of weather helm provides some feedback to the helms person as well as noted, if the helm is neglected or something happens the boat will head up into irons thus stopping the boat, whereas a boat with lee helm will head further downwind and "run away" if the helm is dropped.

    Always a good topic and one that can be expanded upon to discuss the static as well as working trims to affect balance. You could spend a whole year on just this topic and probably not cover every aspect, rig tension, mast rake, sail size and balance, and of course the interactions between all of these. its as much an art as it is a science and if it was easy we would all be America's cup skippers :)

    Thanks for the topic It will be interesting to see the responses.
     


  5. Jackdaw

    Jackdaw

    Joined Nov 8, 2010
    8,768 posts, 2,100 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    Well for a beginner:

    You've answered the safety question. If a puff comes and even if the driver freezes, the boat will naturally turn up and luff. Much safer than her turning down and presenting closehauled sails to breeze building on the beam.

    As for performance, I might leave that alone for now (why overload them), but it pressed I'd them them the truth; that the 3-5 degrees of windward tiller angle helps make the rudder a better foil so it can create better lift.
     


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  6. Rick486

    Rick486

    Joined Oct 1, 2007
    937 posts, 146 likes
    Hunter 44DS
    US Pt. Judith
    Yes. I was always taught, and experienced in my sailing lifetime, that a bit of weather helm is helpful and very desirable. Helps to point higher. :)
     


  7. Joe

    Joe

    Joined Jun 1, 2004
    6,431 posts, 316 likes
    Catalina 27
    US Mission Bay, San Diego
    I tell them.... think of the boat in terms of sail area ahead of the mast and sail area behind it... if forces on both sails are balanced, the boat will want to track in a straight line. If the power of the headsail is greater than that of the mainsail the excess pushes the bow of the boat down wind, that's lee helm.. meaning the boat left on it's own will want to turn downwind. Conversely, if the mainsail is more powered than the headsail then that excess will want to push the stern to leeward, turning the boat upwind. That's weather helm.

    At it's very basic core... sailing is all about balancing the power of the sail plan so the boat is under control. All adjustments we make to our sails and hull(such as ballast placement) are focused on this end.
     


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  8. weinie

    weinie

    Joined Sep 6, 2010
    1,163 posts, 181 likes
    Jeanneau 349
    US port washington, ny
    Steering is actually easier because you can steer by feel and not by any sight cues such as objects on land or compass headings or even telltales (to a certain extent).
     


  9. TomY

    TomY Alden Forum Moderator

    Joined Jun 22, 2004
    1,151 posts, 659 likes
    Alden 38' Challenger yawl
    US Rockport Harbor
    I guess I might use the analogy of a cars tendency to understeer in corners; the resistance of the wheel providing a feel for the vehicle to help keep you out of a skid.

    Then parallel that with a boats weather helm, the gentle force of which is trying to make it round up into the wind, and come to a stop. For the beginner, I'd say rounding up is always preferable to a crash jib and whatever else a boat under lee helm, left on it's own, will do.
     


  10. Bill Roosa

    Bill Roosa

    Joined Jun 6, 2006
    6,965 posts, 140 likes
    Hunter 40.5
    US Harrington Harbor North, MD
    you go faster with a little (3 degrees) weather helm.
    The full non-scientific explanation I use is the teeter-totter analogy. The boat is a teeter-totter with the keel as the center, the foresail and mainsail are the people on the ends A fat guy main (too much power) causes weather helm. A fat guy jib causes lee helm. Also the terms weather and lee are better explained (imho) as "to the weather" or into the wind and away from the weather or down wind. FWIW
    The reason you go faster with a little weather helm is both the keel and the rudder are helping stop side slip to leeward. Lee helm has the rudder actually making the keel supply more lateral resistance aka drag----and slows you down.
     


  11. shemandr

    shemandr

    Joined Jan 1, 2006
    3,422 posts, 527 likes
    Marblehead Skiff 14'
    US Greenport, NY
    I don't ever remember sailing a boat with lee helm (When sailing upwind). It would be weird. I supposed some blue water cruising boats would do well sailing downwind with lee helm.
     


  12. Don Guillette

    Don Guillette

    Joined May 17, 2004
    1,896 posts, 65 likes
    Other Catalina 30
    US Tucson, AZ
    Andrew: You must have a tap on my phone!! That's exactly what the FL sailor asked me : "suppose I encounter lee helm, what do I do to remedy the situation?". I told him, in a nice way, that his boat is set up pretty well and unless a person knows exactly what they are doing to not tinker with mast rake as he's messing with CE & CLR, which I never did explain. Maybe jackdaw could take a shot at explaining those terms and what a new boat owner sailor could do to correct the situation on the boat he just purchased.

    Garhauer Marine gave me a backstay adjuster, which I never used -- it looked trick (like chrome hubcaps) so I just left it there. The "telephone pole" mast on my C30 worked just fine when it was straight up.
     


  13. shemandr

    shemandr

    Joined Jan 1, 2006
    3,422 posts, 527 likes
    Marblehead Skiff 14'
    US Greenport, NY
    I agree that production sailboats are generally designed to have a bit of weather helm and you have to make an effort to mess it up.
     


  14. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    2,571 posts, 1,057 likes
    O'Day 19
    US Littleton, NH
    You are talking about downwind, but not dead downwind? What would lee helm or weather helm feel like in dead downwind sailing? CLR is not a consideration, at least the 'L' wouldn't be.
    For most sailboats, especially modern fin keel boats, the CLR is usually located just aft of the keel. With the current trend for plumb or reverse bows and little or no rocker, that is moving forward a bit more, but the rudder still represents a significant proportion of lateral resistance below the waterline. The general concept of Center of Effort is the average center based upon the center of each flying sail (I suspect that is not actually the case when real lift forces are considered for different trims and cuts of sail, but it is the simple explanation usually given) Rake, boom length, roach, luff tension will all have an effect on Center of Effort. Then, there is not only sail trim but points of sail as well. As the boat heels, the Center of Effort moves to leeward as well as forward or aft depending on factors like hull trim in the water. If you are exceeding hull speed, the boat is climbing the bow wake and the Center of Effort moves aft. Heeling moves the Center of Effort outboard to leeward and the Center of Resistance moves to windward so that an increase in weather helm should be experienced. A balance helm in 12 knots of wind is not likely to remain a balance helm in 25 knots of wind.

    -Will (Dragonfly)
     


  15. victorhoisington

    victorhoisington

    Joined Jan 22, 2008
    173 posts, 27 likes
    Islander Freeport, 41 Ketch
    US Longmont, CO
    Getting into the technicalities now. We have to remember that our modern sloops have 4 foils each with a center of effort, 2 above the water and 2 below the water. As we move over the ground each foil has a CE. The CE for our below water foils moves based upon our speed and heeling angle, for the above water foils its all about how we set the mast (rake, bend)by tensioning the shrouds, backstay, etc. as well as the sail trim, (cunningham, outhaul, vang, sheets, etc.) as mentioned balanced helm at 12 knots will not be a balanced helm at 25. Now back to the multiple CE's, when you combine the CE for each foil you get a CE for the boat, depending upon where this CE is you end up with some degree of weather, or lee helm. You can try to do the math but it gets pretty complicated very fast. Pick up a one of Herreshoff's books on yacht design and you can see the what I mean. For most of us I would say tune the rig as best you can, go sail, play with your sail controls until you know what happens. Every time we go out the conditions are slightly different, maybe a bit more wind or we adjusted the outhaul tighter or an extra crew. All of these will change the way the boat sails, when first learning weather helm is your friend. As we progress we think less about that and more about how she is performing and what we want to tweak to get better performance.

    Fair winds.
     


  16. Jackdaw

    Jackdaw

    Joined Nov 8, 2010
    8,768 posts, 2,100 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    If CE and/or CLR comes up in a discussion with a beginner, you lose.
     


  17. Jackdaw

    Jackdaw

    Joined Nov 8, 2010
    8,768 posts, 2,100 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    As I'd just posted, dragging out CE and CRL with a beginner is going to be non-productive. I really suggest staying with what they can see and feel, and leave the abstract terms for a later day.

    Now on to Lee Helm, the reason most have never experienced it is because it is wholly undesirable. Designers work hard to design boats without it, and if it shows up in the prototypes, builders jigger with the rig to fix it.

    If you encounter it when sailing, that's not a beginner fix. The first thing to do is make sure that boat and sails are in proper trim, and set up upwind mode. If the boat wants to bear away and you need to apply steering correction to keep the boat straight, you indeed have lee helm. And now we need to introduce terms.

    While simplistic, the Center of Effort of the sails (CE) is calculated by marking the intersection of two lines, both which leave the two leading edges of the sail and bisect the other side. If a boat has two sails, the combined CE is in the middle of the line (actually proportionally) that connects them. That we can adjust.
    A-CE.jpg

    The CLR is for the most part unadjustable, its based on the hydrodynamic effects of the keel and rudder. Unlike CE, its not as easy for a sailor to figure out where CLR because of the complex interaction of the hull and keel in lift generation. Some boats will adjust centerboard rake (OK), or how much they lower a swing keel (not so OK).

    The big tool in your box is mast rake, which can be adjusted by forestay length, and by mast foot position of the mast is keel stepped. Raking the mast back moves the CE back. Extending it (0.5 inch at a time) and then re-tuning the rig will show changes.
    A-rake.jpg
     


    Last edited: Apr 27, 2018
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  18. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    2,571 posts, 1,057 likes
    O'Day 19
    US Littleton, NH
    Old school designers would calculate the CLR by cutting out a profile view of the boat below the waterline and then find the balance point. Where it balances would equal the CLR, assuming only cross-sectional friction. Surface area friction changes that a little and adds much more complexity to the calculations.

    - Will (Dragonfly)
     


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  19. Jackdaw

    Jackdaw

    Joined Nov 8, 2010
    8,768 posts, 2,100 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    Indeed. But this method is incredibly simplistic, mostly because it does not take into account that the Center of Lateral Resistance is the center of pressure of the hydrodynamic forces on the hull of a boat. Its about lift, not just area. Nowdays with fin keels that general much more lift than simple areas of the hull, that technique does not work. Indeed, the CLR typically moves forward when the boat moves, due to generated lift.
     


  20. Don Guillette

    Don Guillette

    Joined May 17, 2004
    1,896 posts, 65 likes
    Other Catalina 30
    US Tucson, AZ
    Jackdaw: Thank you for taking the time to post the info.
     



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