T20 -- New development class

Discussion in 'Multihulls' started by idkfa, Sep 26, 2011.

  1. P Flados
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    P Flados Senior Member

    The club setting with a safety crew is the low risk case.

    The more limiting settings are the open water settings. Just imagine you are in breaking waves 14 miles west of Ft Meyers with the sun about to set and it happens. Randy had made good choices with his design such that he did not need to call the Coast Guard.

    http://watertribe.org/forums/topic/sewsew-ec2013-saga
     
  2. Doug Lord
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    Doug Lord Flight Ready

    T 20

    There is a lot that can be done, design wise, to make a high performance 20' tri self-righting(definition: automatic righting with no crew effort) from a capsize or pitchpole.
     
  3. waynemarlow
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    waynemarlow Senior Member

    At 20 feet long I would consider any boat of this size, an inshore or protected waters boat, not an offshore channel hopping size of boat. I know 20ft cats have almost been around the world but that's an exception to the rule, not the norm.

    So do we need to have them built to survive offshore style conditions, do we need them to be able to self right, can we back off a bit on durability ?

    Nice to see the very starter of this thread, actually put his money and time into building a T20 boat that pretty much fits the very configuration that evolved within probably the first page or two of this thread. Kudos and I wish more of the posters would become more active in the doing rather than the talking.
     
  4. waynemarlow
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    waynemarlow Senior Member

    T20 Class

    I do thing there is merit in this T20 Trimaran class, enough to want to continue to develop the ideas. With a number of designs and design plans at 20ft about to come to the market in 2015 then we should perhaps want to establish a few playing rules before a manufacturer decides to want to impose their rules. The F18 and F16 cats have done this exceedingly well and have well established racing fleets due to the manufacturers not having the means to manipulate the rules to favour their designs. It works well and could easily be copied.

    My ultimate aim would be to set up a working website etc that everyone could gather information and where other boats are establishing fleets and where similar boats could meet up, perhaps using the internet, for social and fun racing.

    So to establish the playing rules. I would suggest the following.

    Two divisions based on the same minimal box rule of 3 hull Trimaran hull configuration, 6m x 6m x max height of 9.15m mast x 3 soft sails configuration.

    Division 1

    20sqm main, 8sqm jib, 21sqm spinny or screacher. Lifting foils allowed, min 220kgs

    Division 2

    17.5sqm main, 8sqm jib, 21sqm spinny or screacher, at all times 1 hull must touch the water, a small cabin with min 1.25m head height, min 250kgs.

    To encourage the building of low cost boats, Division 2 boats fits nicely into using F18 hulls and rig and include existing boats such as the Pulse 600.

    max. mast height: 9.15 m (F18)
    max. mainsail + mast area: 17 m² (F18)
    max. spinnaker area: 21 m² (F18)
    Rudders (F18), no T rudders.
    Tiny cabin, min height 1.25m. Sitting height for coffee/tea or potty!

    From experiance a semi develpment class such as this works best with the least number of rules. We could take a class document such as the F16 class associations and modify it to suit. The F16 class worked hard to minimise the rules and it has payed off with almost no rule changes since the first formation of the class.

    I have been a bit limiting on mast height to try and encourage low cost boats based on existing well developed rigs and sails. The F18 is highly competative and a huge amount of R & D has already taken place. With the Div 1 boats I have opted for a 20sqm main to try and spice up a relatively heavy boat at 220kgs. Again with the F18 at 180kgs all up, then a F18 on a diet and 80kgs central hull should be about that figure of 250kgs. Div 1 boats would want to build their own Ama's and could easily achieve this figure ( a F16 hull is only 24kgs where as the F18 is 40kgs ). Sail area should limit the need to go over square on width and I would suspect most boats will opt for that sweet spot of 4.5 - 5m over all.

    Comments please.
     
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  5. Richard Woods
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    Richard Woods Woods Designs

    Sounds a good idea. I'll think about it over the next few days. But I'd give the cabin a minimum floor area under that headroom, or else everyone will have A frame cabin tops or even pyramids to keep weight/windage down

    I'll talk to the Multi23 owner on Sunday when I sail with him to hear his views.

    RW
     
  6. waynemarlow
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    waynemarlow Senior Member

    Cabin size

    Thought of the cabin size already and we could use a " box " rule in the detail, say a box of 1m x 1m x 0.9m should be able to be fitted without obstruction inside the cabin. I think the cabin on the Pulse would limit that size.
     
  7. Doug Lord
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    Doug Lord Flight Ready

    T20

    I like it Wayne-maybe a bit less weight than 220kgs(484lb) ?
     
  8. waynemarlow
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    waynemarlow Senior Member

    The problem with having to large a spread of weight on the Div1 boats would mean they would be too fast against the Div2 boats and would need different markers.

    Also at only 30kgs lighter it would mean a Div2 boat could simply fit new Amas and mainsail and enter Div 1 with existing masts and central hull.
     
  9. Richard Woods
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    Richard Woods Woods Designs

    Way too big. Sorry. 1.2m height over 600mm square minimum is more what I was thinking for a dayboat. Assuming the cabin is under/in front of the mast a 900 width implies 900 at WL forward, and thus much more aft.

    Boats are always heavier then you hope. So if too low a min weight no one will meet it. And since weight = displ a lower weight means a smaller, narrower hull that cannot, for example, sensibly take 4 people day sailing. Even if it works for 2 people racing

    I said before, whats the point in the class if it offers nothing that you can get with a much cheaper/easier to handle ashore beach cat? Taking more people out (maybe young children) is one benefit, another is keeping drier when sailing, requires less athleticism, more comfortable seating...dry space for a porta potti,

    RW
     
  10. Doug Lord
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    Doug Lord Flight Ready

    T20

    Div 1 has lifting foils and ,therefore, much greater speed potential already. Why not make minimum weight 450lb( 204.5kg) for Div 1?
     
  11. waynemarlow
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    waynemarlow Senior Member

    Box rule

    Yup just using that box as an example, my guess the small cuddy on the Pulse will dictate what actual size is needed, but make it simple and people will respond with good design.

    I agree on the weight that Div2 should be heavy to cater for the designs that can handle 4 people or two, but if we go too heavy then the 17.5sqm main starts getting a bit wee.

    At this stage open to good suggestions and between us we should be able to put together a pretty good class rule.
     
  12. Doug Lord
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    Doug Lord Flight Ready

    T20

    Great idea-some things to resolve:
    1) 6m is 19.68, do you want to go to 20'(6.1m)-I think it would be the best way to go.
    --
    2) Does a transom hung rudder get counted in length? I hope not as long as it is a "normal" type rudder? What is "normal"?
    --
    3) Do we want to legislate whether or not the boat can be righted by it's crew?
    I think we should...
    --
    I think Div 1 and 2 are good to go with these questions resolved... I'll keep thinking about it. My Fire Arrow fits except for beam and SA-but not too far off.
    Mast is ok as is.
     
  13. Richard Woods
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    Richard Woods Woods Designs

    When deciding on the minimum weight you also need to consider the safety gear that needs to be carried on board. Do you want boats to be reasonably self sufficient for day racing, or only race with escort boats? Another difference between beach cats and this class.

    Safety gear is heavy. I once weighed ours for our Strider, the absolute minimum necessary under the Round the Island race rules. For example a single burner stove with an empty gas bottle ( the rules didn't say the stove had to work, just that there had to be one). That saved 1lb, 500g. Despite that, it all weighed 90kgs. A huge amount considering that we only used 60kgs of glass to build the whole boat

    So what should you carry? anchor (5kg min), chain, warp, flares, handheld vhf, it's under 7m so no need for nav lights. Lifejackets for all, throwing line, lifebuoy? Sensibly fenders, porta potti. what else? then add up all that weight, what do you get?

    The Pulse "cuddy" appears to be open backed, so is it a cuddy - as in a cabin - or just a large storage locker? You'll need to define that carefully

    RW
     
  14. waynemarlow
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    waynemarlow Senior Member

    The dimensions are in the title.

    Yup elementary school boy error on the overall dimesions, 6m is not 20 ft. As the boats we have been talking about have always been 20ft then I should have had 20ft x 20ft.

    Rudders have always in the cat classes been excluded from over all length.

    I can't see how we can legislate for self righting as I'm not sure until we start building and sailing boats and tip one over, whether we actually can. I would doubt it somehow, yes we can fill one Ama with water and then stand on it like the Weta system, but this boat is whole lot bigger than the Weta and I would suspect that the flotation of beams and such like is going to have an effect on any righting system. Lets leave that one up to each manufacturer as a " bonus " to their clients if it can be self righted.

    Safety gear should be up to local sailing rules, when you enter a race, there's normally local rules such as carrying safety gear and anchors. Lets make the rules specifically to cater only for the bare boat and leave the rest up to local organisers. What is needed at one area is maybe not needed at others.

    Perhaps a few years down the line there maybe a movement by the paid up members of the class with official T20 sail numbers to vote in such items. Again if we deal specifically with the bare boat and follow the F16 method of setting up a class, minor ammendments can be instigated down the line with a majority of voting class members. One thing the F16 class did though was to limit the changing of the rules to years rather than months, to try and get stable rules. By the time you try and change a rule, technology has moved on and we ended up with a very low number of changes.

    Is a cuddy a cabin or a sail locker. In the real world the overall size is probably not that important. Its the height that will effect windage mostly. If we put in a sufficiently big enough " box" rule that will fit an average cuddy then to aerodynamically fair that in, you will get a pretty standard looking boat. To build a one off with a triangle as the cuddy is not doing anybody any favours and I would hope peer pressure would be enough to prevent this.

    I advocate that we should be able to get all rules of this class on one A4 sheet of paper, perhaps drawings and such like on another, but all pertinent basic class rules should be on that first page. The more complicated you make it the more open to abuse. Interestingly in motor racing theres a number of classes now which have really simple rules but use peer pressure to enforce those rules, one such rule is that anyone can buy at xxxx price, the engine of a competitor and fit it to their own car. It stopped over night the blueprinting and secret moding of engines.

    Lets be blunt here though, this is not a OD class but a semi development class, there will be oddities at times and we will have to accept them. Some of those oddities will benefit the class, others won't. We will just have to deal with those along the way. For the moment keep things simple with basic class rules and we should be OK.

    I really advocate this class as a fun amatuer class that is not bogged down by fine detail and that 50% of the class fun, is out of the boats, at the bar or at meetings. The racing is just a means to get boats together and the apres fun is the deal clincher.
     

  15. Doug Lord
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    Doug Lord Flight Ready

    T20

    I agree, Wayne.
     
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