Pod cat square rigger cold weather cruiser project

Discussion in 'Multihulls' started by Autodafe, Feb 4, 2012.

  1. basil
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    basil Senior Member

    G'day From Australia,

    Before I started to spend $200,000 I'd want to be contacting John Hitch who has a dead ringer of your design currently for sale. I'd be talking to him about displacement. This is a very clever design.

    http://www.thecoastalpassage.com/xit.html
     
  2. Autodafe
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    Autodafe Senior Member

    Not a bad suggestion Basil, thanks.
     
  3. ThomD
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    ThomD Senior Member

    I'm not sure that is true. The published reason was that their hydromat testing results came in at much more favourable numbers than they had estimated, and they were able to remove the 1/8" from the skin. Still 100 pounds or whatever it was, is still significant.

    The gougeon's 35 foot tris came in at 1000kg So maybe 1500 is possible in lumberyard materials at 40 feet, designed for cruising, and outfitted for racing. If not this boat.
     
  4. ThomD
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    ThomD Senior Member

    Keeping in mind that this design folds and is trailerable. That affects both the weight package - could have been lighter, and the design - could have had a lot simpler and cheaper beams. I'm not too sure how reassured one should be. I mean the structures are a known (geometry), but beyond that, I am not sure this example really says that much. Just imagine something heavy comes loose and flies around, or even a mast comes down. What kind of beam, made of what, do you really want to have.

    One has to admire Jan's courage were this design was concerned. He had previously had a minor nightmare with the complexity of the beams on Ollie, and this thing is way more nasty to build. Even a guy as formidable as Jan, had trouble keeping his interest up.

    I love the Gougeon boats and greatly regret that their business model did not allow them to keep designing for the public. But all that said, I am not too sure how open ocean tough they are (just because for the most part it wasn't in the brief).
     
  5. Autodafe
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    Autodafe Senior Member

    Thom,

    Regarding crossbeams, my concern was that in my inexperience I was missing something fundamental about load paths in a cat, and that crossbeams must have significant torsional stiffness or they wouldn't work. I was pretty sure that wasn't true, but there was that little seed of doubt.
    While Jan was no doubt motivated by foldability, and is using completely different materials, geometry and construction, it still provides some confidence in the basic concept.

    I agree that impact toughness is important, but on that score I think the typical aluminium pipe used on partial and open bridgedeck cats isn't very good either. It's hard to break, but fairly easy to dent and once dented has lost much of it's compressive and bending strength.
     
  6. Ilan Voyager
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    Ilan Voyager Senior Member

    I'm absolutely sure as I got the info from a member of the Adrenalin's team and confirmed later in Multihull Mag. I was making engineering for the Biscuit's Cantreau team, and I followed closely the F40 in 1987 (for Data General) and 1988. I've assisted about half of the races these 2 years. They had a small problem of weight that asked a lot of work (common fact in boat building)....

    The F40 rule specified a 1800 kg minimal weight as primitively the rulers wanted a ocean capable boat and it was a way to permit small teams to build boats without using too expensive methods.
    Adrenalin was a very interesting boat with the articulated amas. The team was top and fighted like lions. Unhappily the boat had not the power of Biscuits Cantreau but the races were absolutely beautiful.

    The Gougeon's 35 feet were in fact very "small" boats with submersible amas. The submersible amas (around 95 to 110 % of the displacement) conduct to rather "tender" tris with lots of heeling, and softer passage in the sea. It's impossible to push like with a 200% ama, and make fly the main hull, as the ama will sink in the sea.
    The righting moment is far lower, and softer (until 130 degrees) so the stresses are smaller. That permits a huge reduction of the scantlings as the whole structure can be made with stress dissipation flexing. The rig is also smaller and lighter.

    Let's compare the comparable; the stresses are grossly at the square of the speed in a dynamic analysis...Nothing to compare between a 15 knots cruiser and a 28 knots F40 racer pushed at the limit...The width is a very important factor and the torsional problems become huge. There a lot of difference between a 35 "small" tri and a 40 feet "big" tri.

    A tri involves a lot of surfaces and a big amount of work. The savings made by using inferior materials are a small part of the final cost. For example I have experienced that using a plywood with checking problems like the fir upsets all the price advantage. Too much time to finish it correctly. Better to start with a good plywood easy to sand and finish.
     
  7. redreuben
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    redreuben redreuben

    Ilan,
    Thanks for that post, you have illuminated for me in a practical way why a large displacement float is not necessarily an advantage on a cruising tri.
    Cheers,
    RR
     
  8. ThomD
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    ThomD Senior Member

    Or as Ted Hugger reported it in WB:

    "It was at this time the that the ongoing research really paid off for A. The test program produced new results during construction that led the Gs to decide that the main hull's .5" cedar-strip skin was probably stiffer than necessary for the anticipated loads. As a result, a decision was made to rout .125" of cedar from the entire surface of the center hull before the exterior layer of C fiber was vacuum bagged in place. This resulted in a saving of 200#, in a 4000# racing boat."

    "We made this radical modification in A's design with confidence, because we had the test machine and research data to back it up. We knew we were right; it was no longer guesswork" says Bertelsen."

    Agreed but they do win races against these more muscular boats in different conditions. We aren't building an F-40 here we are simply considering what is required at the thin end to get the job done. I don't disagree with your overall point that these numbers are optimistic, just that there are boats out there that a fairly light.

    In the 35s they use sea stays, so I don't know how soft and flexy they are. The articulated boats are different, though A had 175% amas, not 110%, she was designed to find not fight her way.


    I haven't had any checking with as little as 4 oz over. But I wouldn't choose it either. I think one should either go high or low with materials, there is a decent pay-off, probably impossible in any 40 foot boat, where very cheap materials are used so long as they are durable, and the overall price is so cheap that resale is irrelevant. Go above that point and it is an investment, and some significant costs are going to have to be born. But if you can build a boat for what most expensive boats loose leaving the lot, or did not account for in the first place (like 4000 hours of labour), then maybe it works.
     
  9. ThomD
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    ThomD Senior Member

    You might find this video interesting.

    http://www.youtube.com/watch?v=dDT0ijwXogs

    Bob was at one point considering a range of podcats, and had been very impressed with the cruising performance of one of them. He started building his own, but in the end went off on yet another two tangents, one this power boat he considered more family friendly. And another the water ballasted Slim range.
     
  10. Autodafe
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    Autodafe Senior Member

    Good video, I hadn't seen any pics of this boat on the water.
     
  11. bpw
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    bpw Senior Member

    How much cruising have you done?

    If not much I suggest buying something cheap and getting out there for a few years, your ideas of the ideal boat may change radically.

    Don't be discouraged by everyone telling you you need a big engine on a small sailboat, We have been cruising engine-less for the last couple years on our 28 ft Atkin double-ender and it adds another level of satifaction and challenge, as well as saving a pretty good chunk of money.

    Your budget sounds very low for a new build. I got a good hull and rig for basically free and spent about $20,000 getting the boat sorted for high latitude work. And that is a very simple boat (no engine, no fridge, no radar, 50w solar system for electrics) with almost all the gear being bought used. If we planned to stay in the tropics I probably could have cut the cost in half. just as an example, we have close to a thousand dollars worth of anchors on board, and all but one was used or given to me free, never mind the cost of all the rodes and windlass..If your going without an engine or just a small motor you need good sails, so thats another major cost, close to $5000 on our boat.

    Writing this from Valdivia Chile, Have not gone to the channels yet but on our way there in the spring. Happy to share my thoughts on being engine-less and what we are finding its like down here if you have any interest. I had a lot of trouble getting real info on sailing without a motor before we left since so few people are out there doing it.

    Ben
    s/v Inga
     
  12. Autodafe
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    Autodafe Senior Member

    Hi Ben,

    I'd love to hear about your views on engineless cruising, particularly as it relates to the Chilean channels.

    I haven't done a huge amount of cruising and I agree that what I want may change, but I enjoy the design and building so starting over wont worry me too much.

    George
     
  13. bpw
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    bpw Senior Member

    As long as you enjoy the build its all good, some people are builders, some are sailors, and some are a bit of both. Things are normally OK until a sailor decides to be a builder even though they don't really like building. Experimentation is fun and at least you should be able to strip most of the expensive gear if you decide you want something else.

    Haven't made it to the channels yet so not sure how it will go, likely interesting and difficult at times....

    But so far (San Francisco to Valdivia, cruised coastal from SF to Panama) we have yet to not go somewhere because we lack an engine, just takes us longer. Especially in central america where the winds are very light.

    I think outboards are a very good idea for small boats, lets you push your self around a marina or tight spot without the weight and complication of an inboard. You can leave it behind when you don't need it and buy a new one anywhere in the world pretty cheap. Also much easier to work on than an inboard.

    Small inboards (or electric propulsion) seem hardly worth the trouble, all the problems of an inboard and you still can't push the boat to weather in a blow. Modern engines are pretty light so if you go inboard may as well have some power on tap.

    Sailing engineless is sort of like going from top-rope to leading in rock climbing, a bit more dangerous, a lot more work, but once you switch you never want to go back because the added challenge is so much more interesting. Sailing in open water is pretty boring most of the time, the fu bits are sailing in tight areas and playing tides and wind shifts to best advantage.

    On the other hand, if where at home working and taking my boat out day sailing i would still have the engine, can make the difference between getting out on the boat for an afternoon or not. While cruising an extra day or so on passage is a non issue.

    Having a small pretty handy boat is good, I wish we had a more modern fin keel boat in tight spots, but you sail what you have and we just have to plan our approaches a bit better. (the dream is to build a Didi 34 when we return to the states). Having a boat small enough to manage anchor gear by hand is a big plus, you need to be able to kedge in tight spots and a 25 pound anchor is a lot easier than 50 pound anchor to deal with.

    Sculling ours work great, we have a 14 foot sweep that we skull with, think we might build a yuloh this winter and give that a try.

    Try it, you can always add an outboard or engine later.

    Ask questions if you want anything clarified.

    Ben
     
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  14. Autodafe
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    Autodafe Senior Member

    Thanks Ben.

    Because of multihull windage I think I need some power for docking.
    I'm an electrical engineer, so I'm planning to build myself a pair of small electric outboards out of professional curiosity.
    In general though I agree that no engine is cheaper and more fun.

    Do you use an all chain anchor rode?

    George
     

  15. Gary Baigent
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    Gary Baigent Senior Member

    For Ilan Voyager and Richard Woods, relating to 40 foot catamaran weights:
    Ron Given’s Split Enz predated the French Formula 40 multihull class by nearly two years and although lighter and carrying less sail area: 1550 kgs and 88m2 compared to F40 1800 kgs and 90m2, came uncannily close to the F40 Rule.
    Malcolm Tennant was churlishly unimpressed by F40 designs, which were running hot in Europe at the time; he was more involved in publicizing his recently commissioned Bladerunner 43 design, a racing catamaran that was lighter proportionately, (2500kgs) carried more sail, had full headroom in the hulls and was also cheaper - because it was built in strip planked cedar core and not high technology cores and laminates.
    By the way, Split Enz (see jpeg) basically of low technology, strip planked cedar and glass construction, has been raced hard for more than 25 years (held the Coastal Classic record for near two decades) and has crossed from Auckland to Noumea, or the reverse, numbers of times.
     

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