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The "Sib-Lim" Challenge

  • 02 Jan 2015 19:53
    Quote
    Reply # 3179746 on 3179718
    Anonymous member
    Annie Hill wrote:

    I very much like the ideal of a steel bottom plate and was going to suggest to David that this could be done on his Sib-Lim.

    I've been drawing a slab of external ballast on my later sketches (coloured red). If there's going to be some external steel, with the associated maintenance, it might as well add an appreciable amount of weight, and keep the hull clearer of the pebbles and oyster shells. If there's a slab of cast iron, 6in thick, it will weigh a ton and fulfil most, if not all, of the ballast requirement. If there's a slab of cast lead, of course, it can be thinner. If there's a steel box, 6in deep, filled with steel scrap and cement or resin, the density will be lower and some internal ballast will be needed.
  • 02 Jan 2015 19:21
    Quote
    Reply # 3179718 on 3179154
    Anonymous member
    Robert Biegler wrote:

    Have you considered a Harry proa (http://www.harryproa.com)?  You will see that aesthetics are not normally Rob Denney's highest priority, but you could move that up the list.  Keep the concept, but make the lee hull a narrow dory hull with Wharram-like sheer and overhangs.  Likewise the weather hull.  Or you could keep the vertical stems and give the weather hull a deeper draft and a small water plane area, to slow response to waves.  The proa is one of only two sailing boat designs I know where that concept can make sense...

    No, I haven't and I wouldn't.  I agree with you 100% about the aesthetics.  I don't like the idea of carting a spare hull around, I like to be able to tack instantly when I'm headed in a confined area and there is no way I want to play with a balance jib.  I can see the appeal of a proa, but not for me.

    A plywood version of Bolger's design #635, Col. Hasler, might tick all the boxes, if you like the looks.  Not many people do, but I am one of them.  You can see renderings here: http://www.flickr.com/photos/hallman/tags/colhassler/. 


    (Shame they couldn't spell his name correctly!)  Had a look at the photos - centreboard again     and again, I'm afraid the aesthetics don't appeal.  Nor the big windows.  I hate curtains and I live on board, so would prefer not to be in a goldfish bowl.  Yes, of course I could change that, but it's designed as 20ft, and the idea is to start with something that is supposed to be 26ft, rather than re-drawing something else.  However, I very much like the ideal of a steel bottom plate and was going to suggest to David that this could be done on his Sib-Lim.

    If you are willing to entertain a totally untried concept for shallow draft and weatherliness, which you would have to test at model and sailing canoe scale first, I can also make a suggestion of my own.

    Well of course, make a suggestion of your own: this is what the Sib-Lim Challenge is all about!!
  • 02 Jan 2015 19:09
    Quote
    Reply # 3179711 on 3144241
    Anonymous member
    I've not had reliable Internet access (and there are few things worse than trying to post while constantly losing the signal), but I will post some of the comments I made to David about Plan A.

    You didn't send me a sketch of the 32in berth, but I feel I might actually prefer that option - it's quite a good sprawling berth for someone of my stature and two could fit in if sufficiently motivated! But looking at your layout, you could have a berth wider than that at the shoulders and then tapering at the feet, couldn't you? Between stations 1 and 3?  I see two issues with the big double berth option: one is that if you are going to use it as a seat, you need to strip at least the head of it every day, and I don't like that idea.  The second is that there is no fore and aft settee, and I like one because it means I can sit with my feetup and look out of the window; and a U-shaped seating area, like Fantail's, is much more conducive to socialising than both people sitting staring at one another across a table.  So if you went with the smaller berth, could you have a more Fantail-type saloon? 


    I just love the boat in profile - cute as.  I'd like an athwartships cooker, but I don't see it being a real option in your plan, because the galley is a straight bench, isn't it?  Loads of stowage - I don't think I have that many clothes, but it looks like a good place for sewing machine and beer.  One does need a dedicated beer locker, don't you think?

    Actually, if one were to move the berth forward a station, it might make sense to swop stowage and heads so that the latter is not 'in your face' so to speak. 

    I like sticking with the forward raked mast.  The drawback of its being more difficult to ascend is more than compensated for by the ability to sail ludicrously by the lee, the fact that regardless of the swell or wash, the sail never swings into the centreline and the good behaviour of the boat at anchor.  To say nothing of having a bit more foredeck space.  When we come to design the rig, I think I'd like a longer yard, please.  This one does occasionally get the wrong side of the lazyjacks!

    I'm hard to please, aren't I?  But then, a man likes a challenge!

    I haven't had chance to look at David's latest - just got on line now, and felt I ought to contribute to this debate.
  • 02 Jan 2015 17:05
    Quote
    Reply # 3179615 on 3144241
    Anonymous member

    The general concept, the appearance and the use of space are ticking many of the boxes in Annie's specification and list of requirements. I've gone about as far as I can with sketching the design in 2D CAD, and the next step is to acquire and learn to use a 3D boat design program such as Delftship. The first problem there is that there are no programs that are native to Mac (except jSDN, which I can't make any headway with, and I can't find a manual), and so I will have to run a PC program in Crossover. I'd be grateful for recommendations.

    There are the hydrostatic calculations to do, and the bow needs to be modelled, virtually or as a hard model, as I can't be sure of exactly how the shape should be, on the basis of the 2D drawing.
  • 02 Jan 2015 09:32
    Quote
    Reply # 3179439 on 3144241
    Anonymous member

    David

    This is starting to look very promising.  Are there any plans to make a model... virtual or otherwise?

    Peter S 
  • 01 Jan 2015 20:55
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    Reply # 3179279 on 3144241
    Anonymous member

    True, I'd forgotten the heater. It will need to go forward of the galley, between stn 3 and stn 4.

    However the double berth arrangement didn't find complete favour with the Owner, so I've been back to the drawing board and worked out a single berth arrangement. They're now both in the Technical Illustrations photogallery.
  • 01 Jan 2015 18:59
    Quote
    Reply # 3179216 on 3178628
    Anonymous member
    David Tyler wrote:

    I believe I’m beginning to get a feel for the accommodation layout.

     


    David

     

    That sounds good. 

     

    But would there be a place for a heater and if so of what sort?

     

    Jonathan 
  • 01 Jan 2015 16:25
    Quote
    Reply # 3179154 on 3144241
    Anonymous member

    Have you considered a Harry proa (http://www.harryproa.com)?  You will see that aesthetics are not normally Rob Denney's highest priority, but you could move that up the list.  Keep the concept, but make the lee hull a narrow dory hull with Wharram-like sheer and overhangs.  Likewise the weather hull.  Or you could keep the vertical stems and give the weather hull a deeper draft and a small water plane area, to slow response to waves.  The proa is one of only two sailing boat designs I know where that concept can make sense.

    You'd have acommodation all in one hull, the hatch always faces away from wind and spray, the concept is intended for a single, unstayed mast.  If you are worried about the balance of CE and CLR, my preliminary experiments with a balance jib on a stay to the windward hull look promising.  I haven't quite managed to steer my model with sails alone, but I have two more modifications I can test this year.  But I am already confident that the windward jib improves the steering balance of a proa.

    A plywood version of Bolger's design #635, Col. Hasler, might tick all the boxes, if you like the looks.  Not many people do, but I am one of them.  You can see renderings here: http://www.flickr.com/photos/hallman/tags/colhassler/.  Susanne Altenburger had this to say about the boat: https://groups.yahoo.com/neo/groups/bolger/conversations/topics/63979.  Remove the mizzen, move the main mast back, replace the off-centreboard by bilge keels.  Alternatively, leave the mast right in the bow, use a split junk, and a bow centreboard, like Sven Yrvind (see also http://sofiaboat.se/).  Possibly lengthen the hull by a metre.  Bolger wrote in his original description that this would likely improve the boat.  

    If you are willing to entertain a totally untried concept for shallow draft and weatherliness, which you would have to test at model and sailing canoe scale first, I can also make a suggestion of my own.
  • 31 Dec 2014 04:24
    Quote
    Reply # 3178628 on 3144241
    Anonymous member

    I believe I’m beginning to get a feel for the accommodation layout. I think this kind of boat should be built on its bulkheads, at the station positions, to save labour. The stations are 950mm apart, about 3ft 1 1/2in. That means you can get a 6ft 2in berth between two stations. I need to put the heel of the mast at stn 2, raked forward. I need to put the bilge/dagger/boards between stn 3 and stn 4. 

    Port side: 

    Between stn 2 and stn 4 I can fit a double berth that is 4ft wide for more than half its length, tapering to 3ft forward, extending out to the centreline. This is similar to the positioning of the double berth in the Sunbird 32.

    Between stn 4 and stn 5, a table, 3ft square. You sit on the head of the double berth and the quarter berth.

    Between stn 5 and stn 7, a quarter berth for a guest - because the stern is high, this is not the kind of tunnel that you wriggle into, there is generous height, and half of it is out in the cabin. 

    Starboard side:

    Between stn 2 and stn 3, composting heads.

    Between stn 3 and stn 4, clothes stowage.

    Between stn 4 and stn 6, galley.

    Forward of stn 2, light stowage, accessed via foot of double berth and past the heads.

    Between stn 5 and stn 6, on centreline, platform under the hatch, with water stowage under.

    Aft of stn 7, wet lockers for warps, fenders and buckets. Slide for outboard on aft face of watertight bulkhead at stn 7.

    Forward of watertight bulkhead at stn 1, wet locker for anchors, chain and warps.
  • 30 Dec 2014 21:51
    Quote
    Reply # 3178484 on 3178434
    Anonymous member
    John Hess wrote:
    David Tyler wrote:

    I've found a little time to make a sketch of the five panel hull that I talked of. You'll find it in the illustrations photogallery...


    David,

    Did you find Tystie's open transom as useful as hoped when ocean cruising? Would you recommend an open transom for your Sim-Lim design?


    Yes, I like it very much. Not so much for ocean cruising, when it's just a very large cockpit drain (though I don't get a serious amount of water in the cockpit, even in the roughest conditions), as for coastal cruising, when it combines with davits to make dinghy work very much more convenient. Annie now uses a 5'1" dinghy, and since the transom width I've drawn is greater than this, I'll recommend to Annie a similar setup to mine.
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