Single handed - improve initial stability?

Discussion in 'Stability' started by PeterCC, Feb 22, 2021.

  1. PeterCC
    Joined: Feb 22, 2021
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    Location: Cape Cod. Ma

    PeterCC Junior Member

    sailing a 19 foot West Wight Potter on Nantucket Sound. Hard chined boat with a 300 lb cast iron "dagger board" style centerboard. Mostly sail single handed conditions are frequently 15kts plus 3-4 waves. In those conditions you quickly get to 20+ degrees of roll. To keep this closer to 15 degrees i need to depower the sailplan. When i do that then she has difficulty making decent headway to windward . Pinching the boat to weather as it approaches a wave crest and bearing away again as it sails down the back of the waves helps a bit.

    With another person on the rail there are NO issues. I'd like to improve the single handed situation

    Some possible solutions: become a better sailor, buy a different boat, sail somewhere else, find someone willing to crew, tweak the existing ballast. At the moment the last option , seems to at least be worth investigating as the others solutions are not likely in my circumstances,

    I am looking for comments and critique on a proposed solution. i'm an engineer, but not a naval architect ... i know enough to be dangerous.

    My thinking: Lowering the CG of centerboard will not help the very initial stability as much as more beef on the rail. However it should help quite a bit as i get closer to 20+ degrees of roll. The thinking was to replace the centerboard and reinforce the CB trunk. I've also ASSUMED that as long as i'm not out with a full crew in heavy weather the stress on the rig "should" be well within original design limits. The goal would be to minimized changes so that i can revert to the stock configuration should the changes end up having untended consequences. The new Centerboard would be the same weight as the original and consist of a "off the shelf" sheet of G-10 Fiberglass laminate with a lead torpedo shaped bulb split in half and thru bolted to the fin. The "fin" would have a minimal amount of fairing. This configuration adds about 8" to CB up draft but not enough to interfere with trailer. There is no additional weight so existing CB winch will be fine.
     
  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Welcome to the Forum Peter.

    This is probably a silly suggestion, but would it be feasible to have portable water ballast that can be transferred from side to side, rather like the IMOCA 60 class of singlehanded offshore race boats?
    IMOCA https://www.imoca.org/en
    You could maybe have a water tank up under the side deck on each side, and have them connected with a hose.
    Use a manual bilge pump for pumping water in or out, and / or for transferring between tanks.

    Although more realistically, most boats are starting to get a bit overpowered in 15 knots of winds - West Wight Potters are not unique here.
    Reefing down is probably a more prudent move.
    I presume that you have an outboard engine for your boat?
    Very often when motor sailing you can get a 2 + 2 = 5 scenario, if you are reefed down, and have the motor just pottering along.
     
  3. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Are you hiking out in those conditions?
     
  4. PeterCC
    Joined: Feb 22, 2021
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    Location: Cape Cod. Ma

    PeterCC Junior Member

    @bajansailor - thanks for the reply, I considered it, but frankly there's more than enuf enough to do without having to manually pump 100+ lbs (15+ gals) of water . I have two good sized batteries, mostly to keep weight forward to balance out a heavy 4 stroke outboard., which is off unless i'm just about back to home port where i need to negotiate a very narrow channel with a lot of current (never in my favor) . i will reconsider water ballast again, but i worry about the water ending up on the lee side and exacerbating things. I tried reefing, but usually that actually depowers way too much, so usually i just depower using mainsail twist.... until iot gets really windy.
     
  5. PeterCC
    Joined: Feb 22, 2021
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    PeterCC Junior Member

    @gonzo - yes hiking, out as much as possible, there is a railing that limits this,. it might be possible to shorten/remove the railing...but that might have unintended consequences for when i need to be NOT hanging over the rail in a really heavy blow.
     
  6. gonzo
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    gonzo Senior Member

    I was looking at images of those boats, and they don't show reef points in the main. Is that the way all are?
     
  7. tlouth7
    Joined: Jun 2013
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    tlouth7 Senior Member

    With that hard chine some fixed ballast should really help. 100kg or so should bring her down to her lines a bit and so submerge more of the chine at lower angle. Make sure you secure it!

    Also see if there is an owners' association and if you can speak to other people who are likely to have experienced this already and found the solutions.
     
  8. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    If you have batteries on board, a water ballast arrangement like bajansailor suggests, appears the obvious solution, with a switch connected to a bilge pump in each side tank. Easy enough to set up with valves so the water can't transfer from one side to another unless pumped.
     
  9. PeterCC
    Joined: Feb 22, 2021
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    Location: Cape Cod. Ma

    PeterCC Junior Member

    @tlouth7 - i ASSUME you mean fixed ballast as low as it will go ... likely to either side of the keel/CB trunk. I'm liking that idea as a first step. I though about this but dismissed it as having not a lot of direct impact on righting moment ... wasn't thinking so much about submerging chines a bit more.. will also help a bit with momentum. I have had this 'single handed stability " discussion with other owners, but very few sail it single handed and there is NO problem with at least one more person on board.

    @gonzo - most do have at least one set of jiffy reef points ...i have two sets.

    @Mr Efficiency - the water ballast system seems like a big reliability risk . So many points of possible failure (bad switch, weak battery, failed pump, human error :) with a big down side if you end up with a couple of cuFt (62 lbs/cuft) water on the lee side. Seems like it would be prudent to have a manual backup pump and/or some way of manually dumping.Then there is the issue of where to fit tanks that need to hold a couple of cuFt - a 6"x6" tank would need to be 6-8ft long

    Do they make tanks/bags for this purpose? I can see where a DIY tank would undoubtedly end up leaking and/or take a fair amount of time to construct in a workman like fashion.Seems like by the time you are done it would end up costing more in time and money than a new fin and bulb.
     
  10. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Would it be feasible to maybe bolt a couple of lead bars to the bottom of the daggerboard, one of each side?
    By being so low they would have a good positive effect there?
     
  11. gonzo
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    gonzo Senior Member

    If you don't want to reef down to get better control, the solution is to hike further out. You can either have a hiking board or a trapeze.
     
  12. Howlandwoodworks
    Joined: Sep 2018
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    Howlandwoodworks Member

    I think gonzo has the best solution. Reefing would safe. cheep, wise. and DYI.
     
  13. PeterCC
    Joined: Feb 22, 2021
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    PeterCC Junior Member

    @bajan - yes, but the you put more load on the winch...and the crew member who has to crank the winch:) It's already quit a chore with the 300 lb stock daggerboard. My thought on a workaround for this was to replace the cast iron daggerboard with a lighter but equally strong material and put all the saved weight in a torpedo shaped bulb. If the experiment failed i could easily revert to the stock daggerboard and maybe use the lead as fixed ballast per @tlouth7 Other people have lightened the daggerboard by cutting material out of the daggerboard to save weight ....but disinclined since it's hard to judge what the affect it will have on the integrity of the daggerboard and it's not straightforward to undo.

    This is a good discussion and gotten me to think a bit harder about ways to mitigate the problem and consider other things like the effect of a displacement change as usual every solution has it's plusses and minuses. I've read up a bit more on water ballast that you and @Mr Efficiency mentioned and not feeling quite as negative about it.
     
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  14. Mr Efficiency
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    Mr Efficiency Senior Member

    I wouldn't be too worried about a bilge pump failing, if one did and you couldn't equalise the tanks, the solution would be to have a connecting hose with a stop valve on it, that is otherwise always closed, open it till they equalize, then close again. A bit of plumbing, but if you are going to worry about a switch failing, get a good waterproof one. With decent sized bilge pumps, transfer would be rapid, but the tank shape would need a little thought, so you get little residue left in a tank you want emptied.
     

  15. tlouth7
    Joined: Jun 2013
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    tlouth7 Senior Member

    Yes something heavy (some old chain could work) as low down as possible inside the boat. Around the daggerboard trunk sounds ideal.

    I wouldn't add anything to the daggerboard itself - firstly you will mess with the hydrodynamics which could have a surprisingly big impact, and secondly you will be subjecting the board and the trunk to vastly bigger loads than they are designed for. In the worst case this could compromise the integrity of your hull if the trunk moves.

    One thing that hasn't been mentioned is that old, baggy sails will tend to accentuate this issue.
     
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