Kickup rudder questions

Discussion in 'Multihulls' started by Scuff, Jun 22, 2021.

  1. Scuff
    Joined: Nov 2016
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    Location: Richmond VA

    Scuff Senior Member

    I've got a design for a kickup rudder that was included in the plans and had some questions. I included a file that shows the rudder.
    1. This is the first one I've seen that uses a hold down rod with a friction lock to keep the rudder down and still allow it to kick up. Has anyone ever used this approach? It seems it may be hard to force the rudder back down due to leverage.
    2. The tiller goes over the rear deck and it seems it would interfere with the traveler. The spade uses a linkage and the tiller mounts aft in the cockpit floor. I'd like to use this approach .. what would be a good way to implement that?
    3. Does the angle of the transom complicate using a linkage to control the rudder?
    4. I was thinking of using the newick "fuse" and still keep the rod to allow resetting the rudder. Does that seem doable?
     

    Attached Files:

  2. wet feet
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    wet feet Senior Member

    It seems perverse to me to use a skinny rod to hold the rudder down.I suspect that if you ever grounded the rudder,the rod would buckle and be of no further use.I have no idea what a Newick fuse might be-other than coming from the mind of Dick Newick.As we don't have any clues about the size and displacement of the boat it is a bit difficult to make recommendations.I have to admit to a strong preference for a Spectra/Dyneema rope downhaul led to a CL 257 Clamcleat.The rope won't stretch and the cleat will release if the rudder hits anything.You would have to work out a way to lead the rope from the rudder to a cleat on the tiller.
     
  3. Scuff
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    Scuff Senior Member

    The boat is 28' and displacement is 3500 lbs. The fuse is a wooden dowel drilled through the cheeks and rudder. Upon grounding the fuse breaks.
    I've seen the rope downhaul in some pictures/posts. To use that approach doesn't the pivot need to higher up? Thanks.
     
  4. wet feet
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    wet feet Senior Member

    I don't see why you would need to change the geometry.A hole through the rudder blade could house a piece of plastic tube in which a stop knot could live and you would need to lead it through to the outer surface of the curved portion.You could route a groove to the head of the rudder stock and insert a sheave to lead the rope forward to a cleat on the tiller and my preference is for the underside of the tiller.You do need to be aware that while Dyneema is exceptionally strong,it does need stretching initially.
     
  5. Kayakmarathon
    Joined: Sep 2014
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    Kayakmarathon Junior Member

    As long as the drag on the rudder is less than the torque from the weight of the rudder; then the rudder will naturally return to the down position. I've used an aluminum kick-up rudder in kayaks. Since aluminum is light, I use a bungee cord (spring) to get the rudder to return to the down position.
     
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  6. Scuff
    Joined: Nov 2016
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    Scuff Senior Member

    Ah I remember seeing the setup you're describing. I'll look and see if I can find some additional info. Based on the length/displacement is the cam cleat you referenced suitable? Any thoughts on the linkage question? Thanks for the help.
     
  7. guzzis3
    Joined: Nov 2009
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    guzzis3 Senior Member

    Those clam cleats are neat. Before I heard of them there was the "old" method of mounting a cam cleat on a flexible fiberglass plate. cleat one end fix to tiller or whatever at the other. Too much pull the glass base flexes and allows the line to release.

    Is that the only size they are available in ? or is there a bigger version ?
     
  8. wet feet
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    wet feet Senior Member

    A couple of points: first the cleat is a Clamcleat and I am attempting to attach an image below for the benefit of people who have never seen one.Second,why would you want a larger one?Given the strength of Spectra/Dyneema a 6mm rope is quite sufficient.If you have a rudder that is a hydrodynamic disaster area you may be imposing large loads all the time and the easy fix is to use a bullet block on the downhaul line to allow a doubling of the purchase.

    I understand the point about the metal rudder from a kayak point of view,but those rudders seem to be about the size of the palm of my hand.The rudder under discussion by the OP is many times larger and I would imagine it will be wood and may be glass sheathed.For a production boat it would possibly be GRP with a foam core.

    [​IMG]
     
  9. guzzis3
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    guzzis3 Senior Member

    I suppose 6mm is enough but if fitted to say a 30' cat I wouldn't want my rudder to flip up if it just banged a branch in the water, not if I'm in a critical situation. A strong cruising rudder will take that. I imagine there is a limit to it's adjustability ?

    If you are referring to my post I used the terms clam cleat and cam cleat as I intended to. If I were making the flexible fiberglass type I would use a cam cleat. YMMV.
     

  10. wet feet
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    wet feet Senior Member

    As I wrote,you could add a purchase.Which leads to the question of whether you would rather have your rudder flip up or have a hole in the transom.I know the CL257 will stay down at speeds up to around 15 knots because I have used them since they first became available and trapezing dinghies can reach that sort of speed and may well go faster.I have yet to need more retaining force than they provide.
     
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