The "Sib-Lim" Challenge

  • 19 Nov 2014 17:43
    Reply # 3154493 on 3144241

    We actually discussed this matter (re: NIS 31) last weekend with Robin and I had the idea of adding a (3-6mm?) steel plate to the bottom, partly as ballast and partly as protection, and he added the idea of also making the centreboard case out of steel, welded to the bottom plate. This seems like a good idea from a lot of angles I think. Get the "inside ballast" as far out as possible, without it becoming "outside ballast". Doesn't do anything to solve the issue of mud getting in but it should address Annie's concern somewhat about strength and leakage (as steel bends rather than cracks)?

    Just a thought: I assume most centerboard cases are enclosed at the top which is what creates the problem with mud clogging them up with mud. If you would make them "openable" at the top you could clean up any mud that gets there?

  • 18 Nov 2014 13:39
    Reply # 3153401 on 3144241
    Deleted user

    Ditto  design Jpeg please .

    Addressing Annie's concerns re Centre Board Plates.

    David the keel end plate is what I was about to suggest; I would also make the centre board box out of 3mm steel. I would weld a flange to the lower end of the box, all being inserted from under the hull; the flange would be faired into the hull and overlap the profile for 6" or so. It would relay all the loads into the hull for a good distance and provide easy fixing and sealing surfaces with the wooden hull. It would be a totally watertight and strong plate and box.

    The  plate on the keel end would match the box flange and make a lovely strong and closed aperture.

    Within the hull i would  obviously tie the supports for the sole to the CB box to lock it all together relaying loads into the hull fairly.

     All grit blasted and epoxy coated in and out before fitting to wooden hull.

    The  loads from the winch or hydraulics to lift the plate could then be relayed into the box so no part of the hull was being stressed by the loads of lifting or grounding. A bit like the "Southerly Yachts" do.

    A post / handhold could be extended vertically from one end of the box to the deckhead and comprise the lifting gear, easily removed  and stowed when not in use.

    The top of the box could have a 'lid' inserted in the top slot for when at sea, held with a couple of wing nuts.

    The  'lid' could have a length of steel attached and extending down to hold the keel plate down in event of being rolled.

    I made a similar set up for an old clinker hull i was renovating, when its CB box leaked like a sieve. It also stiffened the hull well. I  carried a 3' long x 6mm x 25mm piece of plate and a hammer, so from the top i could get rid of any stones or lumps; i hadn't fitted an end plate to the keel.

    At least with a steel plate and steel box you are not at risk of damaging the side box as is the case with a wooden  side.

    Of course most of this steelwork is low enough to act as ballast, so needn't add to total displacement if its weight is deducted from the intended additional ballast 

    As you know i like the Korora design a lot and have a few questions and will make another post when i have time.


    Last modified: 18 Nov 2014 14:11 | Deleted user
  • 18 Nov 2014 07:11
    Reply # 3153284 on 3144241

    Hi  Gary, yes I will email them to you. 


  • 18 Nov 2014 04:48
    Reply # 3153250 on 3144241

    Will do David. David do you have the design as a jpeg, if so could you email it to me please?

    Last modified: 18 Nov 2014 05:14 | Anonymous member
  • 17 Nov 2014 21:06
    Reply # 3152989 on 3144241

    Hi Gary, no problem, as with the nesting dinghy design I posted please post the link so that I can check on the comments. I tried to join the forum so that I could answer their comments but gave up after the third attempt failed, so if you could forward any comments that are relevant to this forum that would be great.

    Annie, valid comment, however I think that if they jammed they could be cleared quite quickly. Bilge boards could be an option but would have a noticeable effect on the interior layout as they would close off some of the lights into the main cabin and they reduce the space for the cabin seating and the galley and could make the present layout nonviable. The drop plate under the table has little effect on the layout and the forward centerboard sits under the forward bunk flat. Lee boards require a more vertical and flat side than Korora such as shown on my Barge Yacht design Rodark, she is also posted in my designs. She could be shortened by a couple of feet to get to your desired 26 feet, however this would probably mean that the separate head compartment would need to go. Lee boards are also less suitable for offshore work. Its all a compromise and you "pays your money and takes your choice".

     An additional thought that just occurred to me is that the center plate drops vertically and could have a narrow end plate that sits tight against the bottom of the boat when the center plate is lifted up. This would prevent mud from entering the slot and causing any problems. Cant think how to resolve the problem for the forward center board but that is higher, much closer to the waterline and may not even get buried in the mud at low tide.

    Last modified: 18 Nov 2014 07:09 | Anonymous member
  • 17 Nov 2014 19:09
    Reply # 3152900 on 3144241
    David, my greatest reservation is with the centre-boards.  Northland mud is thick and sticky and I can see them jamming up with great regularity.  The other thing I'm not happy about with centre-boards is that they are, in essence, openings inside the boat.  Life being what it is, if it can leak, it will.

    But your plans would seem to be ideal for bilge boards?  Any chance of those?  And they could be used to keep her upright.  I also like the idea of lee-boards.  Something to think about until you get your drawing table back!

  • 17 Nov 2014 01:31
    Reply # 3152413 on 3150202
    David Webb wrote:

    Hi Annie and Ash. Thanks for the comments, much appreciated. There is still a long way to go to finalize the design and any constructive comments are welcome. I am hoping to get my drawing board set up again some time after the Christmas/ New Year holidays and will continue with the design then.

    Thanks, David.

    David is it okay with you if I post your Korora design on the Wooden Boat forum?
  • 14 Nov 2014 05:46
    Reply # 3150202 on 3144241

    Hi Annie and Ash. Thanks for the comments, much appreciated. There is still a long way to go to finalize the design and any constructive comments are welcome. I am hoping to get my drawing board set up again some time after the Christmas/ New Year holidays and will continue with the design then.

    Thanks, David.

  • 14 Nov 2014 01:29
    Reply # 3150125 on 3144241
    Deleted user

    Annie and John,

    Its nearly 0130 here and Korora's  design is to blame.

    I think she looks great, very practical, very pretty, the lines remind me in a way of some of John Welsfords plans, but in a totally Junk way.

    Sail her into any harbour, anywhere -  she will turn many admiring heads.


    Last modified: 14 Nov 2014 01:31 | Deleted user
  • 13 Nov 2014 21:37
    Reply # 3150026 on 3148775
    David Webb wrote:


    I have just posted a design in JRA members files/drawings/David Webbs boat designs/ Korora 1 and 2 a design that I have been working on for the last few months. It seems to meet many of Annie's requirements. The design is a work in progress at the moment but I will be without a drawing board for the next few months so I have posted the design for comment and feedback.

    .../ ..

    There are some very clever ideas here, folks.  That's all I'm going to say for the moment :-)
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