Daggerboard seating methods

Discussion in 'Sailboats' started by saltnz, Oct 4, 2010.

  1. saltnz
    Joined: Feb 2010
    Posts: 19
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    Location: New Zealand

    saltnz Junior Member

    I created a thread about 6 months ago about whether to repair existing swing keel system or convert to dagger board.
    To cut a very long story short I have decided to go for the daggerboard option. I have made a mock up of the whole system and happy with what I am doing (well aware of pros and cons).

    One thing my mock-up does not answer is how do you seat the daggerboard when fully down. To elobarate more on that, where the the foil shape ends and meets the square edge at the top of the daggerboard the square edge rests/seats onto the skeg part of the centercase (please see included photos for exactly what I am talking about). Because I do not know what you call this I am going to refer to them as "plates"
    The daggerboard is going to weigh about 190kg in my mockup I just cut out a piece of ply and glued it on to the mockup keel so it has a nice flat "plate" and that mates quite nicely to my mockup skeg/sole section. However in the real situation as soon as you exert the full weight of the real keel in this area I believe there will be compression followed by cracking of fibreglass and then water seeping into places I do not want it to go. What kind of materials/methods do people usally use in this area? I was thinking maybe 2 StainlessSteel plates one to mount on the keel and one on the skeg (with the centercase structure welded onto it) so that when they meet the bottom plate bears the entire weight if the keel and provides a flat robust surface for the top plate to mate to (with the help of garvity and a locking pin).
    Also how much clearance should I have on the "plate" from the fattest part of the foil to the edge of the "plate". Are there any guidelines or magical formula to use?
    In the 2 example photos I have included the white one (2nd one) Is made out of rolled stainless sheets and has plenty of clearance. I spoke to the guy who did this at the beginning of the year and he was very pleased with how that seated. The 1st example, the wooden one is a bit more reflective of how my keel is being made (laminated timber with a recess cut out at the top aft section). It only has a "plate" on the rear section of the keel, it (the plate) appears to be made out of timber and does not have much clearance at all and I have no idea how this is turning out for him. I have no idea what either of these two examples are using on the surface on the skeg "bottom plate".

    I know my question is really heading into the realms of an engineer, but as everyone can guess I am already well over budget and not very good at explaining things technically.
    Any advice would be appreciated thanks

    Attached Files:

    Last edited: Oct 4, 2010
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