Cure for weather helm

Discussion in 'Boat Design' started by peleg7, Jan 31, 2021.

  1. peleg7
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    peleg7 Junior Member

    Hi, my 1972 ‘38 sailboat has quite a strong weather helm. A famous designer told me that the cause is that the mast has been positioned too aft and the keel too much forward. An obvious solution would be to mount a bowsprit , but this would destroy boat’s aesthetic, so I don’t like it. Increasing the rudder area could contribute to solve or at least reduce the problem?
     
  2. bajansailor
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    bajansailor Marine Surveyor

    Hi Peleg - what make / class is your boat?
    And how strong is the wind when she starts to develop noticeable weather helm?
    What is the wind speed when you have to start reefing down from full working sail, and how much is your typical angle of heel then?
    What type of rudder do you have - eg is it a cantilevered spade type, or supported on a skeg?
    Extending the rudder, or building a new one, would be a big job.
     
  3. peleg7
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    peleg7 Junior Member

    Here’s a photo of the rudder and the keel. The weather helm start at 12/15 knots, with an heel angle of 20/25 degrees. The solution I’ve found right now is not to reef the main (which is just quite small) but ease the sheet. Some friends switched from sloop to cutter rig, and they found they experienced less weather helm.
     

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  4. rangebowdrie
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    rangebowdrie Junior Member

    Right, adding some sail area forward of the CLR.
    I don't have a simple solution, (without moving the tack of the jib forward).
    Here in my area the Cascade sailboats are common, and you see lots of them with short bowsprits/anchor platforms, being used to extend the headstay forward.
    Making the boom shorter has been done, but that was usually on the older CCA types that had lower aspect mains.
     
  5. bajansailor
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    bajansailor Marine Surveyor

    Thanks for this additional info Peleg - but what make of 11.50 yacht is this?
    She looks like a Sparkman & Stephens design (similar to a Swan 36?).
    When you ease the mainsheet, your weather helm is reduced - but are you still getting any drive from the mainsail?
    I am wondering if maybe most of the sail is then back winded, and just the leech is actually driving?
    Re your friends who switched from sloop to cutter rig - I presume that this was by the addition of a bowsprit to get the jib forestay further forward?
     
  6. rangebowdrie
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    rangebowdrie Junior Member

    My very first thought when looking at the pics.
    In looking at the pics,, kind of hard to tell, but do I detect a bit of a "bustle" right at, or just in front of where the WL is in the aft sections,, perhaps not.
    As a '73 year, that was an "interesting" period for design, when, (largely due to rule changes,) designers had a tendency to forget that the mainsail was supposed to be the "Main" sail, and were designing boats that used headsails as the predominate driving force,, using a little ribbon of a mainsail as more of an aerodynamic "trim tab" to balance the jib.
    The pics don't show the sail plan, so without personal knowledge of that particular model it's hard to make a guess.
    You see a lot of pics of racing during that period where the leech of the main is fluttering, the jibs doing most of the work.
     
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  7. fastwave
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    fastwave Senior Member

    Many people confuse load on the tiller with a weather Helm problem.
    The rudder is unbalanced on that drawing. It will always have a high load tiller in stronger winds.
    Focus on the rudder angle instead of load.
    If this is the case then you need to add rudder area infront of the rudder or just accept it
     
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  8. DCockey
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    DCockey Senior Member

    Good advice. The swept back rudder will always have need a much stronger force on the tiller than if it was not swept back and had some area ahead of the rudder shaft.
     
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  9. rangebowdrie
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    rangebowdrie Junior Member

    If one cannot move the CE of the sailplan forward,, perhaps the CLP can move aft.
    Ok, this may be a long shot, but,, looking at the pics, could the rudder have a section added to its leading edge so that it could have a heel fitting that was in line with the existing rudder shaft,
    Then, could the skeg be deepened to allow the heel fitting to be attached to the bottom of the skeg.
    And, the skeg itself could have some area added to its leading edge, tapering up into the V section that runs between the aft edge of the fin and the existing skeg .
    Taken as a whole, the rudder would have much greater support, and the added skeg depth and area would move the CLP aft.
    Similar to many of the profiles we've come to see in several designs by Ted Brewer,, a better and stronger profile for a cruising boat.
    The existing rudder with its unsupported lower half, together with the swept-back shape is not all that great for a cruising boat.
    Several NAs/designers/builders on this forum who are knowledgeable about working out the tech details concerning strengths/methods/materials/and laminate schedule(s).
    I shouldn't be all that great of a job,, (I guess that's easy for me to say, sitting in an armchair).:rolleyes:
    Edit; I'm going to go out on a limb here, but I believe that more of a "Brewer" skeg/rudder set-up with added skeg area will produce a better boat for uses other than "round-the-marks" racing.
     
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  10. tlouth7
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    tlouth7 Senior Member

    If your main genoa has a lot of overlap (140 or 150% is not uncommon from this era) then counterintuitively moving to a smaller genoa may actually help reduce weather helm. A decent number 3 can do wonders. Assuming you have a masthead rig then it is common to sail with a surprisingly large backwinding bubble along the luff of the mainsail when going upwind in any reasonable breeze. It is possible you have already found the correct solution which is to trim the main properly!

    The simplest and best solution is to speak to other owners with the same rig and find out what works for them. Good luck!
     
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  11. peleg7
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    peleg7 Junior Member

    This is the sailplan, the mainsail foot has been reduced in the next versions due to the weather helm.
     

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  12. bajansailor
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    bajansailor Marine Surveyor

    Thanks for providing the sail plan Peleg.

    Is she an Alpa 11.50?
    Here is one for sale in Greece -
    Buy Alpa Yachts ALPA 11.50 | Alpa Yachts ALPA 11.50 for sale https://dailyboats.com/boat/83582-alpa-yachts-alpa-1150-for-sale#google_vignette

    I agree with tlouth, re how a smaller genoa can reduce weather helm - the rig on our 35' sailing boat is not as extreme as yours (our mainsail is relatively bigger in relation to the foresail), yet she still has more weather helm with the genoa than she has with the smaller jib.
     
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  13. gonzo
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    gonzo Senior Member

    If you are heeling 25 degrees, the boat is overpowered.
     
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  14. Will Gilmore
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    Will Gilmore Senior Member

    How old are your sails?

    Blown sails have deeper camber that moves aft, giving them more lift, but less drive. They heel the boat and don't increase forward power. 25 degrees heel then puts the CE farther at and outboard to leeward and the center of resistance on the opposite side, windward. What little driving force there is then focuses on bringing the boat up into the wind.

    With flatter sails, you get a better shape forward, your CE moves forward and less heel, resulting in a better helm balance.

    Mast rake and a good vang can all help.

    Of course, if these boats are known for an unbalanced helm...

    -Will (Dragonfly)
     
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