Sailing yacht designed for self build

Discussion in 'Boat Design' started by Unik, Apr 27, 2016.

  1. Unik
    Joined: Dec 2015
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    Location: Ukraine

    Unik Senior Member

    Lion 600, sailing yacht designed for self build

    Draft sailing yacht Lion 600 designed for self build out of plywood. Frames, bulkheads details of internal and external cladding designs prepared for cutting on CNC lathe

    LOA, 6.00 m
    LWL, 5.9m
    Beam, 2.5 m
    Draft, 1.5 m
    Main square sails, 22 m2
    Full-load displacement 1.15 tonnes.
    Capacity 4 person
    Outboard engine, rated at 4-15 HP

    Attached Files:

  2. John Perry
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    John Perry Senior Member

    I felt I would comment since no one else has. To my non-professional eye it is a promising design well presented. Having said that, its not the kind of boat I would want to build for myself - I dont like the boxy high windage near flat bottom style myself, but that's not to say that others might not like it. Dont like the shape of the cabin windows either but they do follow the contemporary styling idiom - did you consider a reverse rake to the stem? (only joking).

    Assuming that your reason for posting was to attract comment, here are a few minor, perhaps insignificant points:

    Everything appears to be from plywood but the shading of your picture sugests compound curvature in the cabin roof - perhaps make that area as three pieces each with single curvature.

    I am in the process of building a small boat with cnc cut plywood myself. I have cut the ply joints as tapered fingers (similar to the finger joints seen in structural house timbers these days) rather than jigsaw type joints thinking that tapered fingers may be a bit stronger, although perhaps the epoxy jointing is good enough that it makes no odds in practice. Jigsaw type joints will make the panels lock loosely together but I would not rely on that for accurate alignment of the panels over a 6m length - for that I have small holes at the ends of each panel so that I can line the holes up with a tight string. Incidentally, I have had my plywood cut by waterjet and I am very pleased with the results from that.

    Once you go to cnc cutting of the plywood its good to get absolutly everything cut that way all in one go, I am glad that I did that. I suspect that there are small parts, say in the internal fit out, that could be included in the cnc cutting to fill in the gaps between the larger parts without actually using any more sheets of plywood. Just as one example, you seem to have drawn bunk bases cut with removable panels presumably for storage underneath, so you will need to double the thickness of ply around the edge of the openings to make retaining rebates for the removable parts - the extra ply parts needed for this could certainly be included in the cutting.

    The details of the design are a large part of what makes a good boat. I think you still have some detailed design to do - for example the details of the lifting keel system are critical and are not shown in your drawings. You need the keel to lift without too much effort and without excessive wear. Good to have access to the sliding arrangements and good to be able to lock the keel down. No way shown to mount the outboard - presumably this will be a fold down bracket bolted on the back. No detail of mainsheet. I wondered whether the jib sheeting angle is a bit large, but perhaps it is OK for a boat that probably isnt intended to point really close.

    The ballast ratio is probably quite low. I think boats of this genre are now quite often designed with water ballast since that can give similar stability to low ballast ratio permanent ballast while being possible to jetison for light wind or road trailing. Your keel bulb may be a problem for living on board when the boat is dried out unless 'legs' are provided or small suplementary bilge keels.

    At first sight I thought the underbody looked too shallow for the likely displacement and payload but I expect you have done your weight and bouyancy calculations with a computer so if you have done that correctly I am sure it will float as drawn.

    AFAIK the gas bottle must be in a separate ventilated compartment.

    ps. I like the way you have included the sea on your drawings - is there something I can download to do that on my Solidworks drawings (just for fun - no practical necessity!)
  3. Stumble
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    Stumble Senior Member

    Just a few thoughts...

    1) the small headsail and pin head main are going to result in a boat that is short on horsepower. with a non-overlapping jib there is no reason not to make the switch to swept back spreaders, no backstay, and a carbon rig. Allowing for a square top main with a lot more power.

    2) the rudder cut out is fine, but I would want it open on top. Being able to swing the tiller out of the way is a huge space saver. But I would probably try to open the entire transom.

    3) it's a very small cockpit I assume to gain more room down below. But I would be concerned it is too small for more than two people. It may be ok for a couple, who doesn't have any friends to daysail with.

    There are a lot of usability issues I see. It reminds me of a boat designed to be camped on comfortably, but will make a poor sailer. In this size range I don't the market is really there. It doesn't look to have the speed to capture the performance market, the ease of use of a trailer-camper market, and would be difficult to daysail. Honestly I am not enthusiastic.
  4. philSweet
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    I like the boat and don't see anything to fault in the hull. But the rig and deck hardware clash a bit with what I would expect to see. As a pocket cruiser with fairly modest performance potential, I'd want no more than one winch on the boat, and an option for no winches. The one winch would be positioned for anchor breakout, kedging, and handling other mishaps in addition to its use in normal sailing. The jib track and low cut jib is a fussiness I think few would want. On a pocket cruiser, I like to be able to adjust the height of the jib, so a hoist about 3' shorter than the forestay would be about right for me. With this, I can use a fixed turning block and get any sail set I might need. Set low gives lots of twist for gusty air and set high gives low twist for steady moderate air. And I agree with Stumble that tricycle stays and a bigger main would be my preference for a boat this size. As would end of boom sheeting and simple roller reefing main with a boom that slides on the mast's sail track.

    The life lines don't work at that size. They basically become tripping hazards. They need to be about twice as tall to be functional. Some small ocean racers get by with 24" lifelines, but generally that is too low in the recreational market. Yours appear to be about 18". Personally, I despise lifelines on boats under about 33'. I want to be able to move around quickly on a small boat.
  5. gonzo
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    gonzo Senior Member

    I agree about the lifelines in small boats. They are a cosmetic feature to make the look like "little ships".
  6. Skyak
    Joined: Jul 2012
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    Skyak Senior Member

    I don't like them anywhere. All they provide is false confidence -stabbers and trippers. Jack lines show you mean business.

    The Clipper Race lost a woman recently. She wasn't clipped in and simply washed out the back ,a terrible way to lose a great person.
  7. Stumble
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    Stumble Senior Member

    On the boom I would probably go with a Farrier roller bool style. Where the main wraps around the boom, and the boom has a handle attached on the front of the mast to roll it up.
  8. rwatson
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    rwatson Senior Member

    Yes, I agree.

    I guy I knew bought a small sail boat with SS lifelines, and his girlfiriend got her leg caught up in them on the bow - and snapped her shins. I still get the heebies thinking about it.

    The good news was that they were on a Mac 26, so he could power fast to get help.
  9. rwatson
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    rwatson Senior Member

    And the price is ??? :)
  10. Unik
    Joined: Dec 2015
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    Unik Senior Member

    you're right, the Roof of the wheelhouse has a complex curvature so it consists of 4 parts

    I've been using to connect pieces of plywood jigsaw puzzle, unlike the wedge-shaped connection, the puzzle gives a more accurate connection and does not require to compress between the joined sheets. error connection puzzle +- 1 mm to 1m long, is permitted.

    Cards cutting parts included all parts including small parts finishing, the kit also includes cutting of parts for drift boats of the well , lifting keel, rudder and cutting the portholes of the deckhouse

    In the drawing of the sail plan is submitted to the racing version was developed at the request of my friend, in the standard version lifting keel has no bulb and is not in favour of gabarite the bottom of the boat. Ballast is 250 kg and is attached to the bottom of the boat for easier operation with a lifting keel. Water ballast in such a small boat built out of plywood I believe extravagance.

    Displacement and load distribution are calculated carefully taking into account different variants of the load.

    Gas Balon as you rightly said is located in an isolated compartment

    PS. happy will help you draw a sea to your drawings )))
  11. Unik
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    Unik Senior Member

    Designing a small boat is always a struggle of compromises. I have the option of an open transom for this boat which allows you to raise the tiller. The cockpit of the boat is designed to accommodate four people, its size dictated by the desire to increase the space in the cabin. It is possible to install a more modern sailing equipment and a grotto with a square top but the boat will be more expensive, besides increasing the area of a sail requires an experienced crew.
  12. Unik
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    Unik Senior Member

    To change the square sails on the boat provided a twist jib, mainsail scribers I suggest using lazy jacks.

    With regard to the lifelines of its height is 450 mm, its installation is dictated by the rules.
  13. TANSL
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    TANSL Senior Member

    Indeed, in many countries the lifelines are not an option for the designer, they are mandatory and their structure and minimum height is regulated.
  14. Stumble
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    Stumble Senior Member


    1) on the transom at least cut away the bridge over the tiller. Just this would make the boat far more usable at rest. A full on open transom maybe a nice option, but as a sock I would get this cut out.

    2) for sail area, you list 22m^2 at a weight of 1.15 tons. Compare this to a J-22 with 21m^2 of sail area and a weight of 1800lbs. I am concerned that your boat is going to be seriously underpowered, particularly if you expect to have four campers onboard.

    Take a look at the Seascape 24 rig as a comparison. It uses a non-tapered carbon tube, no spreaders, and a very square top sail. The cost compared to an aluminium rig was something in the $500 range, but lighter, easier to step, simple, and with its tripod stays very stable.


    The additional cost of the farrier boom system is probably around $150 or so once you buy the boom extrusion. It's a very simple furling system that works quite well on small boats.

  15. Alik
    Joined: Jul 2003
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    Alik Senior Member

    The design looks nice and quite packed with everything. But I would look at performance rather than beds and headroom on this size.

    I don't see the point for amateur construction of boat that duplicates mainstream production models. Such boat can be bought on secondary market for the fraction of price one would spend building boat on his own (including working time and buying parts).

    Amateurs build boats for one or few of reasons:

    1. Cost; this means that building boat should be muck cheaper than buying similar size craft; say Wharram catamarans. Simple designs!

    2. Passion to build boats by their own hands. They want such boats be visible and they want take pride of their work' not likely they want the boat look like a production one. Beautiful designs!

    3. Specific/unique features and customization, not available on existing production boats. Unique/special designs!

    What features are behind this design?...
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