CNC Plans not Included

Discussion in 'Multihulls' started by jorgepease, Sep 19, 2016.

  1. groper
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    groper Senior Member

  2. jorgepease
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    jorgepease Senior Member

    Nice, I like that they run the lines under deck. Are unstayed masts not possible or do they not provide enough performance with this type of boat. The comments RobD made about all the savings of going with unstayed masts is burned into my mind. Also, probably a stupid question but do these boats carry anchors and where do they store the chain?
     
  3. waikikin
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    waikikin Senior Member

    Well, seeing as I have very little time to work on my 40'er... I'm not... but if I was to the choices would be either
    Cut & shut a molding from my 41' tooling at max beam & normal to/greatest molded depth from existing crown of deck & fill in the other 9'... twice;)(& not really a fan of the cut/shut)

    Or in a similar fashion to elements of Kelsal, Oram, Spirited, .. Groper would build the canoe body/shoe via some means either one/two off or contact molded in a female mold then set up/jig for the topsides with constant flare up until a little aft from the bow/s. most of this join would be under WL /boot top area except at transom. The jig could fit within approx 8' x 6' x 50' in the style of a box truss(could also be used for transport support to underwing for launch) & can be rolled for downhand/convenient internal tabbing of table molded components for inner & outer topsides and deck/deck edge moldings- these could be incorperating whatever lovely molded rolled edge & in plan view be to a very large radius to interface the nominal sheer- could also incorperate a rebate to accept/melamine sheet to minimise tooling cost.
    Wherever possible components would be contact molded with gelcoat finish with rebates/jambs etc molded in, the topsides stringer would be a molded roll edged bench top. Where appropriate moldings would be cored or come back to single skin for joining as apparent. Underwing formed/molded in situ between hulls set up in wind etc, bulkheads off the table as usual & similar for superstructure. Internal finishes could be whatever... I have no great aversion to frontrunner or similar being cheap, fast & easy... to replace when needed, some variance in hard and soft internals but to a consistent repeatable theme..
    Jeff
     
  4. waikikin
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    waikikin Senior Member

    It is nice, though I wouldn't get the lack of a lounge room past the boss...
    I've always felt that the usual bridgdeck cabin/accomodation/tranverse bulkheads does have the structural efficiency in creating a series of large box beams... with a lounge/shaded area within, maybe some extra windage but weight not sure on that... until it's filled with stuff of course.
    Jeff.
     
  5. jorgepease
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    jorgepease Senior Member

    I'd like to build a SIG 60 style Bimini on a 50'... Note It would not be enclosed with glass on front

    [​IMG]
     
  6. Jim Caldwell
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    Jim Caldwell Senior Member

    As we age your body is going to _require_ standing head room under that top.
     
  7. jorgepease
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    jorgepease Senior Member

    Im already at that age, I should have said, at same height as 60 so boom would have to be raised.
     
  8. Richard Woods
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    Richard Woods Woods Designs

    My test is always "Can I see all 4 corners from the wheel?"

    Most people want to have all round vision from the saloon or cockpit

    RW
     
  9. jorgepease
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    jorgepease Senior Member

    Richard, I'm liking eliminating stuff!! ))

    I've been playing with the design to see what can be eliminated ... I come up with 3 possible helm positions. The two aft would give you visibility 3 corners with some visibility on far corner. A center helm might give you visibility all 4 corners.

    IDon't know how SIG manages without the bulkheads I guess they have some heavy duty beams under the deck. This is a Raku design, leaving baths in place and slightly modding the rest. Where I pushed aft bunks in, that would be raised seating.

    I think the SIG 45 has doors in rear, I would put them in the center.

    [​IMG]
     
  10. rob denney
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    rob denney Senior Member

    Answers to posts since my last one.
    Jorge,
    The race proa iscoming along. Hulls are done, temporarily stopped the mast construction to check out a different rig concept and build method on my 25'ter.

    Unstayed masts work better on cats than stayed ones in terms of ease of use, maintenance and safety. Either a ballestron if you can't get the mast far enough forward, or a biplane with wishbone booms. Lowest cost would be a single mast in one hull.

    Your bulkhead landing drawing is pretty close. Works best with a box mould so you can line them up pre infusion, which is simpler than with a story pole. Almost impossible on curved hull sides sides or bottoms, dead simple on flats. Gluing area is increased if the edge of the bulkhead is glassed.

    Stack infusing works, but it means secondary laminating and extra prep, so overall takes longer. It is quicker and easier to add all the extra reinforcement, rebates, etc in the infusion. The object of Intelligent Infusion is to eliminate all secondary laminating. We are not quite there yet, but getting closer.

    Resale value is interesting. A 50' racer cruiser cat is for sale here. Well known designer and builder, sales quickly and well built with all the usual gear required to make it perform. Cost 1.3 mill a couple of years ago, asking 800K and no takers. So, at least a 500K loss. You could build a C60 for less than 500K, including your labour. Lighter and longer so probably quicker, certainly easier to sail. If you sank it instead of selling it, you would not have lost any more money than the expensive boat.

    Open deck or full cabin: Consider how the boat will be used. 8 permanent bunks is pretty pointless on a boat that 8 people cannot live on, and if there is nowhere for them to comfortably sit while sailing. Dining table and galley should be optimised for the number of guests that are likely. Flat deck space is great if you are standing, uncomfortable if you are sitting. Shade is important in the tropics, shelter is important wherever you are, but you have to be able to see the sails and as much horizon as possible.

    Eliminating stuff: Get serious about this and you end up with a harryproa.

    Groper,
    There is a larger variety of hull shapes possible with box moulds than with flat panel builds and more other shapes possible with core less areas than with solid panels. Have a look at the exploded drawing on http://harryproa.com/?page_id=1177 Each colour is a separate infusion, apart from the purple, which is 2, as are the beams. Furniture is another, Apart from a small amount of filleting and tabbing, all components are glued together, in male/female self aligning joins. Fairing is minimal. Tear off the peel ply and most of it is ready to paint.

    It is no problem to build things with plenty of compound curves, if you don't mind the time consuming wet laminating, tabbing and fairing.

    Round bottom hulls have less wetted surface than flat, but the work required to build them and install floors is huge. The added weight and windage to achieve headroom and give you something to stand on more than outweighs the wetted surface issue.

    Finished bulkheads should include doors, hatches, edge finishing, hard points for handles and hinges, additional laminate in stressed areas, landings for shelves and floors and rebates for fittings. Few of these are possible on a flat stack infusion, so have to be added after the shapes are cut out. Which is not a problem, but you are back to conventional, time consuming, sticky boat building.
    All these features are included with Intelligent Infusion along with rebates for cloth overlaps, so fairing is minimal. A caul plate can be added if you want it flat and shiny, as can veneer or finishes like formica or woven carbon. You spend a little more time laying out the infusion (dry materials, easy measurements) but no time with the wet sticky stuff.
    If you can infuse everything in one shot, cutting fibreglass panels and wet laminating make no sense.

    Adding flanges to the bulkhead is easy on one side, not worth the effort on the other. It is much easier to include the landings in the hull infusion, then glue the bulkheads in.
     
  11. groper
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    groper Senior Member

    Rob, I'm all for the box molded shape except for 1 thing. If the forefoot of a hull has a flat bottom it pounds in a seaway. The slamming gets pretty annoying and I wouldn't build another boat with a flat bottom forefoot again. It's not about the minimum wetted area thing, the modeling I did in michlet and with a wealth of information on the subject by professionals here- it's a given that virtually any shape with a reasonably fine entry and constant displacement to length ratio will have nearly identical resistance curves.
     
  12. jorgepease
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    jorgepease Senior Member

    Saw a video with bulkhead landings as part of the infusion. They stick out a good 6 inches I would say. It's just a couple of seconds as the video was a full tour of their boat. I will post it later.

    Here are a couple of pics of a Rapier 400 12 meter boat with cockpit under shade. Not sure if I like the galley up there but it's simpler than sticking it in the hull and leaves more room below.

    Also don't like the curves in the top, should just extend straight back with a good overhang aft. like the SIG60

    [​IMG]

    [​IMG]
     
  13. AusShipwright
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    AusShipwright Junior Member

    Jorge I have seen panels infused with flanges, obviously only on one side. Mdf was cut using CNC to the section shape required. The glass was layed onto the table up onto the flange, then foam and then glass over the top and up onto the flange again. The flange ended up being about 100mm wide
     
  14. jorgepease
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    jorgepease Senior Member

    On bulkheads that would eliminate the need to fillet and tape one side ... not sure how much time it would save.
     

  15. Richard Woods
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    Richard Woods Woods Designs

    I agree. Thats why my Skoota powercats all have Veed sections back almost to midships. And I don't have flat bottoms on my sailing boats either, even my Strike 18 trimaran has a V forward even though most of the hull is flat. My 28ft Gypsy similarly. Comfort always wins over a marginal speed increase on anything except an outright racer

    You can hear a Farrier sailing towards you because of the slamming mainhull. Much worse in my experience than most bridgedeck catamarans. (I have sailed F24, 27, 28, 31, 31R) The Crowther 38 I sailed last year also slammed the forefoot, because it had a bulb bow

    Security is always an issue with a layout like the Rapier 400. You cannot lock up the cabin so sensibly cannot leave anything in the galley when alongside, or even at anchor

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
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