SibLim update

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  • 13 Jul 2017 20:27
    Reply # 4975117 on 4315719

    Annie, thank you for the efforts on the blog - they make great/interesting reading (no surprise really given your previous record as an author of fascinating books!)

    The tabernacle discussion is interesting too. We went for a forward opening tabernacle, but given the layout of things the mast actually steps about a metre below cabin height, with the pivot about 300mm above the roof line (swinging thru a slot in the cabin roof). 

    The original design from the designer called for building a wooden case dividing the cabin in two with the mast stepped onto the keel and pivoted at cabin roof height (wherry-style) - but this "mast version of a centreboard case" so wrecked the usability of the cabin we started again, and constructed the tabernacle and step in steel (yes, very infra-dig I know). So, the structure is now a piece of box section secured to the "keel", with the open sided box for the lower part of the tabernacle welded to the top, and four steel box-section braces securing this between the deck clamps, port and starboard and a substantial laminated beam forward. This is then bolted (thru the cabin roof line) to the upper part of the box (with the (yet to be finalised) pivot.) The obvious problem with this design is the opportunity for leakage! I think the best current plan is to make a large fabric "boot" that is seized to the mast above the pivot and secured around the edges of the opening in the cabin roof. A bit like a gearstick boot in a car. Time will tell if this works.

    We are using an alloy-lamp-post mast and planning for only 16-18sqM of sail so hopefully this will be strong enough!

    As a picture is quicker than all these words, these two pages in Befur's Blog might help add some clarity... one  two and following pages.

    Annie, I still think you are going to beat us into the water with a "fully finished" boat, our current plans are to install the steam plant and try to "see if it floats" before the winter, and then aim to fit the sailing rig in the following season :-/

    Last modified: 13 Jul 2017 20:42 | Anonymous member
  • 13 Jul 2017 06:07
    Reply # 4972005 on 4315719

    No, please don't add an extra shelf on the port side. As I said, what you have is fine.

  • 12 Jul 2017 22:13
    Reply # 4971500 on 4969399
    David Tyler wrote:You're both right, of course. The load when sailing is taken by the bottom of what I think of as the fender locker, but I understand is now the woodshed (Tys tie's fender lockers totally fill with water when hard on the wind in fresh conditions, and I was under the impression that wet wood doesn't burn as well as dry wood...) I was thinking of the times when I was short tacking with both boards down, and when the windward board was inadvertantly dropped. There was definitely some discernible movement, though of course Tystie has pivoted boards, which transmit forces through the pin, and Siblim doesn't.

    Your port side shelves will be fine.  Put something similar on the other side, and all will be well.

    The wood lockers are intended for wood that has just been brought aboard.  Quite apart from the fact that there is heaps of room under the foredeck for fenders (which will probably only be used at junkets, when someone wants to come alongside), I know from harsh experience that not very much wood takes up a lot of space until sawn into stove-sized lengths.  I shall have a box below for the sawn-up wood which can dry out nicely there (not that I have any intention of sailing hard on the wind in fresh conditions if I can avoid it!)  But putting newly-gathered wood in the deck lockers, will avoid bringing insects on board, and if any wood happens to have rot spores, they won't be finding their way below.


    I shouldn't have thought that even with both boards down, the windward one would put any serious loading on the inside of the box, but I shall certainly assume that you are correct.  I have an enormous capacity to worry and am now thoroughly discomforted with respect to the bilgeboards, so I am fitting an extra 12mm, shelf, at the same height as the stringer the deck lockers are attached to.  (From what I can gather from drawings showing the bilgeboard down, this is where the top will be.)  Well filletted to the bulkheads and board casing, I trust this will do the job, although the shelf below it will be somewhat less useful.  On the starboard side, as I said, I am fitting a fore-and aft counter, which is about 800 mm long and, fortuitously, at exactly the correct height.  With the bulkhead cut, coated and framed up, it would have been more than vexatious to have to start again on that side.  I can't put a similar set of shelves that side, because the passageway is already well to starboard of the centre line.  The amount of strutting and bulkheading in the heads compartment will put HMS Erebus to shame, when completed!

  • 12 Jul 2017 03:49
    Reply # 4969399 on 4969273
    Annie Hill wrote:
    ueli lüthi wrote: as the leeward board will take the big part of the forces. it's the outward side of the case that needs to be strong on bilgeboard top level – and there the hull should provide sufficient strength…

    utnik


    Well, I have to admit that this was my thinking, but I'm the first to admit to being totally ignorant about engineering stresses and very challenged when it comes to thinking about them.
    You're both right, of course. The load when sailing is taken by the bottom of what I think of as the fender locker, but I understand is now the woodshed (Tys tie's fender lockers totally fill with water when hard on the wind in fresh conditions, and I was under the impression that wet wood doesn't burn as well as dry wood...) I was thinking of the times when I was short tacking with both boards down, and when the windward board was inadvertantly dropped. There was definitely some discernible movement, though of course Tystie has pivoted boards, which transmit forces through the pin, and Siblim doesn't.

    Your port side shelves will be fine.  Put something similar on the other side, and all will be well.

    Last modified: 12 Jul 2017 07:36 | David
  • 12 Jul 2017 01:16
    Reply # 4969273 on 4969252
    ueli lüthi wrote: as the leeward board will take the big part of the forces. it's the outward side of the case that needs to be strong on bilgeboard top level – and there the hull should provide sufficient strength…

    utnik


    Well, I have to admit that this was my thinking, but I'm the first to admit to being totally ignorant about engineering stresses and very challenged when it comes to thinking about them.
  • 12 Jul 2017 01:13
    Reply # 4969271 on 4969200
    Graeme Kenyon wrote:

    A good answer; I was just wondering, that’s all. I’m going for the high fulcrum myself anyway, for other reasons, and as you already know, that will work just fine. But one thing I do know – you won’t need 8 men to help you with the mast, although I can’t imagine any shortage of willing helpers. If you rig things right, you will be able to do it yourself. If you can pull up an anchor, you can raise a mast.

    Go for it Annie – don’t let anyone change your mind, only you should do that. I do enjoy and admire that faintly defiant tone of self determination in your posts – and what a great job you are doing.



    Well, as I say, I can still change my mind.  I could be wrong about the fulcrum height making any difference.  I would need to put a wedge at the foot of the mast in the tabernacle to ensure the water drains, but that's not exactly difficult.
  • 12 Jul 2017 00:27
    Reply # 4969252 on 4967090
    David Tyler wrote:

    Remember that the inner side of the bilgeboard case needs plenty of support at the level where the top of the board is going to rest against it.

    as the leeward board will take the big part of the forces. it's the outward side of the case that needs to be strong on bilgeboard top level – and there the hull should provide sufficient strength…

    utnik

  • 11 Jul 2017 23:50
    Reply # 4969200 on 4315719

    A good answer; I was just wondering, that’s all. I’m going for the high fulcrum myself anyway, for other reasons, and as you already know, that will work just fine. But one thing I do know – you won’t need 8 men to help you with the mast, although I can’t imagine any shortage of willing helpers. If you rig things right, you will be able to do it yourself. If you can pull up an anchor, you can raise a mast.

    Go for it Annie – don’t let anyone change your mind, only you should do that. I do enjoy and admire that faintly defiant tone of self determination in your posts – and what a great job you are doing.


  • 11 Jul 2017 22:46
    Reply # 4969113 on 4967087
    David Tyler wrote:

    Graeme and Ron,

    I tried, and failed, to persuade Annie set the tabernacle in the boat with the open side aft, and then to put the pin through the heel plug, where it can do no harm. Easy to do, and a no brainer where there is no coachroof to clear, as is the case with SibLim. And as you say, for occasional use there need be no pin. This arrangement has been used for centuries in the Yorkshire and Northumberland cobles, and would work well here, too.

    To me it wasn't a no brainer.  The SibLim mast isn't a short, stout stick like on a coble, and I'm unlikely to have half a dozen stalwart men to help me get it down. And Pete preferred the arrangement that we went for.  By having the fulcrum a little further up I think you have a little more control.  I prefer, in this instance, to go with what I know and with what I have used in the past.

    But as Graeme says, should I (or the rest of you) change my mind, I can always reverse the tabernacle!  It's not installed yet.

    Last modified: 11 Jul 2017 22:53 | Annie
  • 11 Jul 2017 22:43
    Reply # 4969109 on 4967090
    David Tyler wrote:

    Annie, 

    Lots of good thought going into the heads compartment, this is looking very fine.

    Remember that the inner side of the bilgeboard case needs plenty of support at the level where the top of the board is going to rest against it. On the port side, the shelves are going to do that, so make 'em strong.

    I can't figure out where the battery is going to go now?


    Er, your drawings don't show this and I don't recall you ever mentioning it.  There is a C-head to port with an athwartships counter and your original drawings showed a heater on the other side.  The newer drawings show a C-head going right out to the bilgeboard case, with a small counter forward.  Nothing on the other side.  As it happens, I intend to put a decent counter on the starboard side and have a fore-and-aft bulkhead inboard of it.  It so happens that the counter has ended up at the same height as the stringer on which the bottom of the 'fender locker' rests.  But the shelves on the other side - which also have a fore-and-aft bulkhead inboard of them, have been fitted for heights according to what is going to be stowed on them.  I can, I suppose, remove the top one, put a small, but thicker one higher up and fillet it all in.  Perhaps you would like to tell me what you had in mind before I go ahead and fit what I've already made.

    The battery is going under the cabin sole on the starboard side.


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