Daggerboards, how to modify to adjust when loaded

Discussion in 'Multihulls' started by Dave_S, Sep 15, 2018.

  1. Dave_S
    Joined: Sep 2018
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    Location: Brisbane Australia

    Dave_S Junior Member

    To adjust my daggerboards, I have to stop. They are a simple 2:1 pulley/rope system up and down. The boards just run glass on glass in a casing, through the hull.

    Ideally, I would like to be able to adjust them on the move with a slight change of tack to reduce the load.

    I'm hoping it can be done as a simple-ish retrofit.

    How is it normally done ?

    Thanks
    Dave
    Ps
    It is a Schionning Waterline 1480
     
  2. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Welcome to the forum.

    Many, many ways.
    Least invasive: increase purchase system to 3 or 4 to 1.

    Reduce friction by lining dagger trunk with HDPE. You will probably need to replace dagger board or trunk, possibly both

    Good luck
     
  3. Dave_S
    Joined: Sep 2018
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    Location: Brisbane Australia

    Dave_S Junior Member

    Thanks

    The boards are in tight when loaded, I tried to move them with the winch and had a fair amount of load on it, probably equal to 10:1 by hand without success so I'm sure I'm left with fitting some kind of runner.

    I was thinking of strips and buttons of low friction material like HDPE on the pressure points but worried it might not be enough. Are the ones that slide under load completely lined/wrapped with this ? That is probably easier than my idea. What sort of clearance should I have.

    Does anyone use rollers?
     
  4. Doug Lord
    Joined: May 2009
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    Location: Melbourne, Florida

    Doug Lord Flight Ready

    I've seen a Farrier rudder with what appeared to be artificial grass bonded to each side of the inside of the trunk so the rudder could retract vertically. I don't know how good it is...
    Another system: HH Catamarans Choose Vesconite for Daggerboard Bearings http://www.sailingbreezes.com/sailing_breezes_current/articles/jul16/hh-catamarans-choose-vesconite-for-daggerboard-bearings.html
    ========================
    Go to p 90 here for some info on an F boat daggerboard:
    http://corsairmarine.com/sites/default/files/FAQ/How To Maintain a Corsair_0.pdf

    ======================
    You might try companies like APS that may stock friction reducing material made for daggerboards. The biggest problem I see is whether or not you have the clearance for any material?
    If none of the above works and you have to rebuild the trunk I'd try to find a catamaran foiler-A Cat, Flying Phantom etc and look at the system they use for their daggerboards. Those boards have to move up and down- sometimes under load- as well as having to be raked under load.
    Good Luck!

    Osprey foiler daggerboard system-I think the upper sliding block is something like Delrin:

    OSPREY 9-16-11 non-sailing 010 - Copy.JPG
     
    Last edited: Sep 15, 2018
  5. Dave_S
    Joined: Sep 2018
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    Location: Brisbane Australia

    Dave_S Junior Member

    Thanks Doug, sounds like the right stuff.

    Do you imagine T guides, I don't want to introduce more turbulence underwater if possible. The lateral load hopefully is greater than the drag and I'm not sure how to counter both loads without some guide tracks below the waterline.

    Oooops, sorry for some reason I couldn't see the second part of your post. I'll have a look for some foilers .

    I'm happy to rework the existing boards but don't fancy reworking the cases other than attaching to it.
     
    Last edited: Sep 15, 2018
  6. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    White delrin isn't as UV stable as black , it is good to use , I've used it in rod form and cut it as washers to separate metals [tremsetters site]. It may be as simple as giving them a spray with say lanolin or preferred lubricant and polishing the dagger boards when they start to get stiff. It seems unlikely they wouldn't function properly considering its worth. unless they are damaged/ buckled.. my 2 bobs worth ,cheers, ...just looked them up, nice lines. Those daggerboards must take some serious load, perhaps they are flexing more now after taking some whacks.
     
    Last edited: Sep 16, 2018
  7. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Had a second thought.
    How stiff is your board? Could it be flexing and wedging tight?
    New stiffer board with low friction surface.
     
  8. Dave_S
    Joined: Sep 2018
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    Location: Brisbane Australia

    Dave_S Junior Member

    It's possible but even if I head straight to wind with more than 3 or so kn I can't budge them but if I go up and "wiggle" them they may move.
     
  9. Dave_S
    Joined: Sep 2018
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    Dave_S Junior Member

    Not sure what the loads could be but on beam reach except for windage losses they (and the rudders) are trying to cope with the same loads that are pushing 7.5t, 18kn through the water. It's a bit scary when you think of it like that. The case seems to have more clearance at the top than the bottom. The boards tapper off at the top so a guide at the top wouldn't support the board at the back end when it's down.
     
  10. UpOnStands
    Joined: Nov 2015
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    Location: Sydney

    UpOnStands Senior Member

    Sounds as if the aft tapers of the board and case are really well matched. When stationary, do the boards have a fair amount of fore-aft wriggle at the bottom exit of the case?
     
  11. Dave_S
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    Location: Brisbane Australia

    Dave_S Junior Member

    I haven't been under to have a look but it seems, when I wiggle it "eyeball engineering" makes it look to pivot at, or near, the hull exit at the bottom.
     
  12. UpOnStands
    Joined: Nov 2015
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    UpOnStands Senior Member

    just a suggestion. Remove the boards, take a 3-4 mm dia synthetic rope (scrap) long enough and run it down the aft end of the case so a little bit projects underneath. Secure the upper end. Reinsert the boards. hopefully you have enough clearance and they don't jam. See if the temp fix eases removal under load.
     
  13. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    Perhaps a some marine grease around the bottom of the casing where most of the friction and load is being taken up will solve it.
     
  14. Dave_S
    Joined: Sep 2018
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    Location: Brisbane Australia

    Dave_S Junior Member

    Thanks all

    I have some 3mm dyneema onboard, I'll give it a go.

    I tried a dry spray on without any luck, I'll try a heavier marine grease. The spray on drylube came with good recommendation but I think it is more suited for lighter loads.
     

  15. Dave_S
    Joined: Sep 2018
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    Location: Brisbane Australia

    Dave_S Junior Member

    Does anyone have a link to the design of foiling guides.
     
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