24ft Bluewater cat sketch

Discussion in 'Multihulls' started by dsigned, Dec 18, 2018.

  1. guzzis3
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    guzzis3 Senior Member

    The G32 was designed to capsize and be righted like a beach cat. It also has extremely narrow hulls to minimise the problems associated with long narrow cats.

    At 8'ish you won't get more than 20 sqm of sail on that boat and even that will be marginal.

    Those hulls will push up a big bow wave early and the slot will be full of turbulence even at 6 knots.

    The lack of rocker will make it a pig to tack.

    Take a look at Mr Woods Saylon, Ross Turner's Jarcat 6, Mick Wallers TC670 (and other mini bridgedecks). These are boats designed with tremendous experience and thought. You can't replicate that in 5 minutes with no understanding of the problems. Everything about your sketch screams a lack of understanding of the issues.

    However you probably don't want to listen, so by all means build it and let us know how you go.
     
  2. Gary Baigent
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    Gary Baigent Senior Member

    Original sketch (cross between schooner and ketch - and not a drawing) rig on Jim Young's 40 foot trimaran Bladon Racer launched in the 1970s.
     

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  3. redreuben
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    redreuben redreuben

    What is your blue water experience?
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    He did say "blue water", I was thinking it would be more "white knuckle".
     
  5. guzzis3
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    guzzis3 Senior Member

    or certain death.

    Every time I look at that sketch it scares me, even before you utter those magic words "blue water". I reckon you could trip that up with no rig at all if you were a tad careless in a seaway.

    As I've mentioned I'm working on a trailer. I know it's along time coming. I've done the engineering but stuff keeps cropping up to delay my finishing the drawings. When I do I'll post here. It will make assembling up to 30' cat easy singlehanded and facilitate launching in minimal water. It will make most demountable cats including those with cuddy cabins about as trailerable as a farrier tri. And the "folding mechanism" stays on the trailer, so it's cheap and easy.
     
    ALL AT SEA and Niclas Vestman like this.
  6. Niclas Vestman
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    Niclas Vestman Junior Member

    That was a seriously funny post! :D :D

    On another note.
    I do get the lure of the idea of the OP. Only that size concept screams not sea worthy in so many ways.
    It should be noted what Mike Waller writes in the description of his TC 670 design. Quote -"Note that its intended use is sheltered and semi sheltered waters, and not open water."

    This one seems like a copy of the Waller TC670, only with uppdated design. andamanboatyard(dot)com/torr-679/
    And it looks way better than the sketch on a bar napkin in post #1. I'm quite sure the OP will agree. If dreaming up a concept, why not making it look good at least, even if not very sea worthy (that is while sinking)? ;)
     
  7. dsigned
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    dsigned O.R.C. Hunter

    I'm happy to listen to suggestions that don't ignore the basic constraints of the design.
     
  8. dsigned
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    dsigned O.R.C. Hunter

    Is there a minimum beam/righting moment you would consider suitable? And is the worry about getting blown over or broadsided by a wave (of both)?

    A quick Googling seems to indicate that Tiki 21s and 26s have done passages, and a Heavenly Twins 26 has circumnavigated. That seems like it would put the minimum at something like 12 feet of beam.
     
  9. dsigned
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    dsigned O.R.C. Hunter

    It does look better. The reason for the bar napkin is time and ability. I have the time and ability to do sketches, and neither the time nor the ability to do 3d renders. I do like the design you linked. I think the big difference (besides increasing the LOA) would be adding the enclosed bridge.

    EDIT: It's probably not strictly true that I don't have the ability. I can do 3d drawing, but it's significantly more time consuming for me than simply sketching. I also find sketching therapeutic, as I don't need to be staring at a screen to do it.
     
  10. guzzis3
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    guzzis3 Senior Member

    Fantastic. So my understanding is you want trailerability, the ability to occupy a single berth in a marina and to go bluewater cruising.

    The obvious choice is a folding trimaran.

    Option 1: There are a set of plans to an F32 on ebay us atm but he wants $2900 US for them which is too much. That set is the X which is oversize. The new farrier organisation should be able to supply the narrower hull lines possibly at some cost.

    Option 2: Join the yahoo farrier group. Plans come up there from time to time. Ian Farriers plans are the best in the business by a country mile. More like a complete boat building course. The boats are not easy to build but the result is superb.

    Option 3: Ray Kendrick has his Avalon 9. If it were me I'd ask for some of the details of the new 32' boat. You could avoid the aluminium ring frame and have 8' trailering and width in port. Ply or foam. $150AU for plans so even if you bought both sets...

    Option 4: Sango. You can't fold on water but it such a superb boat. Easier than a farrier to build and accommodation for days. 15'. I don't know where marinas draw the line on beam but years ago it was 16'.

    Form stability is almost all about beam, the distance from the mast to the bit that floats, or occasionally the heavy bit that weighs it down. Length doesn't really come into it. In theory shorter boats may pitchpole earlier but it doesn't seem to matter much. Have a look at John Shuttleworth's Cheetah. It is the opposite of what you have drawn. 8 meters long it is 6 meters wide. _IF_ you are incredibly careful and never break concentration you can carry all the sail you want. As soon as it gusts you reef or drop altogether, then all you have is the eight of the spar and rigging aloft but in the real world even the super sailors who race tornadoes occasionally stuff up in round the bouys racing. What chance do you think you have making a passage for days/week/months of NEVER making a mistake, NEVER missing an approaching gust or squall ? And as they say about terrorists, they only have to get it right once you have to get it right every time.

    Wharram does design relatively narrow boats. He also puts very small low rigs on them. And his boats are a LOT wider than that. Remember wharrams have massive overhangs so a tiki26 is really a 23' boat with baggage. A t26 is 15' wide and carries 26.5 sqm sail. A t30 is 25.5' on the water, 16'4" wide and carries 35.8 sqm of sail, which is more than I would have expected actually...although his center of area is low so...Hinemoa is 11'4" and carries 16 sqm.

    Cooking fat (T21) sailed round the world. 21' long 18'on the water. It's not about size as such it's about a balanced considered design taking all the factors into account.

    Hope that helps. If not let me know where I've gone wrong.
     
  11. guzzis3
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    guzzis3 Senior Member

    The tor679 has an empty weight of 860 kg and a design displacement of 1000 kg, ie no gear and maybe 2 crew. It is unsuitable for open ocean sailing. There are plenty of mini bridgedecks like that one. I started drawing one a while back based on the belief I could trailer a 9'6" wide boat in every state in australia. As it is it only applies to queensland so I abandoned it. Search hirondelle catamaran for a similar boat. Hirondelles are 10' wide. 20% wider.
     
  12. guzzis3
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    guzzis3 Senior Member

    I know it's a joke but technically that's a schooner isn't it ? Schooners have either a shorter front mast or both the same length. Ketches specifically carry a shorter mast aft ?
     
  13. Niclas Vestman
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    Niclas Vestman Junior Member

    Well, to be fair, I think it is all about expectations. Most might think "dsigned" has some kind of daysailor in mind. But the mention of Ming ming II implies an almost survivalist approach to boat design. And well. In some cases it is almost easier to make small boats structurally strong. Much like the wacky Sven Yrvind Bris boats. The last ones looking more like an escape pod, or cross between egg and submarine. With its shape, kevlar sandwich build and short, hard to break spar with gaff rigg. Designed to be able to be tossed around for a while without sustaining structural or rigg damage. I quess the biggest problem would be keeping the occupant of the escape pod from braking all the bones in his body while being tossed around. But I guess there is a quite simple solution to that problem too. So I wouldn't say it's an impossible venture to make such a concept work. I believe guzzis3 points out one of the major problems. The need for non stop concentration while sailing a narrow boat. And that makes those boats that slide or fold out seam like a good idea. To me it seems possible to come up with a layout that works both extended while sailing, as well as "folded" or slid together while in the marina. On such a small boat, one way would be having those fold out seat "benches" to gain righting moment, but with additional floatation. Almost like small amas (quadmaran with mini auter amas). Those would be easy to fold in. But probably more complicated and making less sense than a trimaran to begin with. Quite contradictory to the KISS principle :) Also might be vulnurable to structural failure. Also some sort or self righting system would be a must. Probably involving some form of balasted centerboard and or inflatable "airbag" on the cabin roof. I guess often those ideas don't come from a need to get a boat built fast, but more from a desire to investigare feasability and the joy of entertaining ideas of invetion or personal learnign about different subjects.
     
  14. jamez
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    jamez Senior Member

    Last edited: Dec 21, 2018

  15. Gary Baigent
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    Gary Baigent Senior Member

    I think the original US schooners have the shorter foremast - but then again, there are a couple of plans/drawings in Chapelle of equal height mast versions too. Young's Bladon Racer had equal rigs in height and sail area - and the after rig overhung the stern by a number of feet; also originally had float water ballast - which was automatically dumped from the leeward one but retained in the windward.
    Seemed to have veered radically off-subject? No apologies though.
     

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