SibLim 3.5m x 1.48m (11ft 6in x 4ft 10in) cruising dinghy

  • 23 Apr 2021 10:15
    Reply # 10341891 on 10332447

    Will bilge keels simplify the build much?

    Not much. I'm thinking of an 'egg crate' construction of backbone and partial bulkheads, slotted together and built up onto the inverted cockpit sole. The bilge keels in their simplest form would be made of 12mm plywood and slotted onto these partial bulkheads at angle perpendicular to the sloping hull panels, 22˚ to the vertical. Their upper edges would be filleted to the cockpit sole.

    I would like to see the relationship between these bilge keels and any proposed skegs/rudders. One thing, which is essential in my view, is the ability to drag the boat and/or pull it up and run it along rollers. For this it is better to have any appendage start with a gentle entry and run through clear to the stern. This does not quite seem what David has in mind here.

    This is for hauling the boat up a beach for camping? If the roller were to go under both bilge keels, they would need to be pretty long, more than the beam of the boat. Since the bottom hull panel is horizontal in the athwartships direction, I would be thinking in terms of two or three standard cylindrical fenders to go under just this part of the hull. Putting skegs on would prevent the rollers from holding the hull upright, so I wouldn't add them. Directional stability under sail shouldn't be a problem with such long bilge keels.

  • 22 Apr 2021 22:02
    Reply # 10340056 on 10332447

    The rig, of course, would be the extended Halibut model.

    So ... is anyone else interested in building one, I wonder? 

    I think you are onto something very good, David, and I sincerely hope you will have some takers and develop this concept to its completion. I think it could be the basis of a near-perfect junket boat and explorer/camper. I would like to build one, but have too many projects already on the go, and committed to the Golden Bay now. (I’ll make a confession – I’ve now got two of them, and a small bunch of grandkids.) Maybe one day.

    In the meantime I am seriously considering (with permission and hopefully further advice from you and Arne) to try the extended Halibut rig on my current Golden Bay conversion (which is coming along well.)

    (I have nearly competed the structural changes to the Golden Bay and thinking now about appendages, rudders, rigs, ballast – I would like to bounce some ideas as the Sibim 3.5 evolves, but it would be better to leave this thread clear for development of the Siblim 3.5. I’ll use the “Junket Boat” thread for that, and hope for some critical response).

    Yup. Shallow bilge keels might work.

    The Siblim hull, with its deep body and deadrise does allow a relatively efficient use of water ballast -and that midship section allows a decent pair of bilge keels without any increase in draft. Will bilge keels simplify the build much? (there are some minor structural details we have yet to see). There is no doubt they will simplify the sailing – one less thing to have to adjust and attend to when you only have one pair of hands. They sit the boat upright too. I have no doubt they will take the boat to windward. (To my mind, the only other option worth considering  would have been an off-set swinging board - but the Siblim hull rather calls for two of them, which seems like a bit of extra work both in the building and in the operating).

    I would like to see the relationship between these bilge keels and any proposed skegs/rudders. One thing, which is essential in my view, is the ability to drag the boat and/or pull it up and run it along rollers. For this it is better to have any appendage start with a gentle entry and run through clear to the stern. This does not quite seem what David has in mind here.


    Last modified: 22 Apr 2021 22:24 | Anonymous member
  • 22 Apr 2021 20:31
    Reply # 10339801 on 10332447

    If I ever find myself in believing I could have the patience needed to build a boat, this would probably be the first on the list. It’s just perfect for small big adventures in the archipelago and the million lakes of this country.

  • 22 Apr 2021 11:21
    Reply # 10338211 on 10332447

    Yup. Shallow bilge keels might work. They are horrible on a ballasted cruiser, when it comes to scrubbing and antifouling time, but on a water ballasted dinghy that can be tipped on its side for cleaning, that's not an issue.

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    Last modified: 22 Apr 2021 11:22 | Anonymous member
  • 20 Apr 2021 20:38
    Message # 10332447

    I really would like a SibLim of my own; and the only way I'm going to get one is to build one of a size that I can fit comfortably (not pushing the limits too far) in my front room, and that I can manage to take down to the harbour on a launching trolley and pull back up to the house again - but not every time it's used, if it's self draining it could spend short periods between uses on a mooring.

    So I spent this afternoon getting the Freeship model as good as I can, and exporting the panel developments and linesplan to DXF format. If I take my laptop cruising this summer, I can use the rainy days to work on drawing the components and nesting them onto sheets of plywood.

    The figures work out well. 233kg displacement at 0.188m draught, with a lot more loading easily possible. 60kg of that can be water ballast. Dry weight around 90kg fully rigged. The cockpit is a cuboid 2m x 1.22m x 0.35m, with its floor 0.112m above the 0.188m waterline, so sleeping aboard is possible. There is room outboard of the sides of the cockpit for board cases, either straight-lift or hinged; but I'm coming around to the idea of shallow bilge keels. My main use would be in Ravenglass estuary, possibly Duddon Mouth, or even Morecambe Bay and the Solway Firth, at a stretch. In all of these, the ability to sail on a heavy dew is a distinct advantage. Deep boards and rudders would be a liability. So I'm also wondering whether twin rudders with endplates at the same draught as the bottom of the boat and keels would provide enough steering.

    The side decks are gently angled outwards, for some gentle sitting out, nothing too athletic - this is a boat for gentlemen of a certain age who are not as strong and flexible as they used to be. In the cockpit, I'm thinking of a very free-form arrangement, with tethered closed cell cushions 10cm thick for seating that can be moved around, probably with two stacked together for a rowing position.

    The rig, of course, would be the extended Halibut model.

    So ... is anyone else interested in building one, I wonder? 


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    Last modified: 21 Apr 2021 07:44 | Anonymous member
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