ORC GP33 Class

Discussion in 'Boat Design' started by steve.b, Jul 30, 2009.

  1. steve.b
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    steve.b Junior Member

    Hi

    What is everybody's opinion of the GP33 class?
    http://www.orc.org/gp33.htm

    I am thinking about designing one of these for a university project.
    Any thoughts/opinions/comments or data would be greatly appreciated.

    Thanks
    Regards
    Steve
     
  2. joz
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    joz Senior Member

    Steve have you looked at the GP 26 and GP 42 as well?
     
  3. steve.b
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    steve.b Junior Member

    yes i have..
    I just like the size of the GP33 better. It is also a relatively new class which isn't already bombarded with a million designs/
     
  4. joz
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    joz Senior Member

    ah ok good luck with it.
     
  5. Crag Cay
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    Crag Cay Senior Member

    Incidentally, all these ORC GP classes are the same age.

    I don't know how much effort you want to put into this project, but I would do a lot more reading about these classes before deciding to devote much time to any work.

    These are the ORC's idea of level rating rules that would try to replicate the fun we all had back in the IOR days with the 'Ton Classes'. Essentially they have come up with a (IMS inspired) box rule at about the old Quarter Ton, Three-quarter Ton and Two Ton sizes as these (well two of them) enjoyed healthy support and the larger classes were used around the world for famous top flight race series such as the Admirals Cup, SORC, etc.

    But the world has moved on and there has never been such total support for an all encompassing rules since the demise of IOR. Most people want to race dual purpose cruiser/racers (especially in this size with a STIX >32) that will have some longevity and resale value or one-design classes. Therefore the 'grandprix' end of racing has struggled to find an outlet. The offshore boys have their own thing (Open 60s and Class 40s, Open 6,50) leaving the box rule for the TP52 being about the only thriving GP level rating measurement rule. The ORC thought a similar thing might work at the 26/33/43 foot size as well. But for them to do so, you need numbers to build classes, to have races, especially as these things don't rate particularly well under IRC.

    There's more to it than this, but essential the interest in the GP classes has been patchy at best with only the places that still have 'IMS racing' (as they measure more favourable under its current incarnation) showing much interest. (basically Italy / Med / South America).

    All the information you need to do a design is on the ORC website, but getting your head around this rule, whilst being an interesting exercise, might not lead to anyone else giving a ****!

    A design, to say the Class 40 rule, would be no more work, but there are plenty of other boats out there for comparison, including plenty in build at yards in SA. If you have an ambition to make a living as a designer, it's important to invest your energies in a part of the yacht market that has a discernible pulse.
     
  6. steve.b
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    steve.b Junior Member

    Crag, thanks for your opinion.

    I am actually a yacht design student studying in Southampton, UK.
    This design would be for my final year project. I, personally, want to steer clear of the very popular box rule classes (such as the class 40) due to there already being so many designs for these rules (same thing applies to TP52, STP65 etc).

    You have a very valid point about the dual-purpose needs of a design. The GP33 rig will rate relatively well under IRC, however, the weight will be the rating killer (ie - its not a brick with a pointy end which IRC heavily favours in this size-range)..

    So, if not a GP33..what other ideas are there out there? I am interested in a similar concept though..

    thanks
     
  7. Crag Cay
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    Crag Cay Senior Member

    Careful! Some of us can get touchy about our work!

    But it's not just IRC that drives the higher displacement. Such is the legacy of the '79 Fastnet, that most people (here) who buy a 33ft racer/cruiser would like to think of it as seaworthy, even if they never want to enter long races such as the Fastnet. Therefore RCD minimum displacement for Cat A is something that's very appealing in a commercially viable cruiser racer. (check what happened when the Figaro 1 became the version 2 and the SunFast 3200 appeared, etc).

    So what to design? Well, it depends what really fires you up. This is one of the opportunities in life to immerse yourself in something that is all you. Trying to design something that you're not passionate enough will be dull and you'll end up with all the another alumni from NA or Yacht design courses in life, doing stability calculations on sewage barges or even worse, being a surveyor. So what sort of boats and sailing arouses you?
     
  8. steve.b
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    steve.b Junior Member

    What to design - that still remains the question..

    the appeal of the GP33 class, dual purpose inshore, offshore boat..
    old mount gay 30 (whitbread 30) class

    I'd like to steer clear of the typical class 40/open 60/volvo 70 boxrules purely because they have had a lot of designs already.

    I'd like to stick in the 25-40ft size range..

    So, any suggestions anyone?

    thanks
     
  9. Crag Cay
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    Crag Cay Senior Member

    Here's an idea: There's a resurgence in double handed racing as many boat owners are increasingly sick of the cost, hassle and responsibility of getting a crew together. But I think that whilst many more may consider this, double-handed remains beyond the comfort zone of many.

    Therefore, I think a 'double-double handed' may have a lot of appeal! That's a race boat that is limited by class rules to be raced by four people, or specifically, two couples. There are boats that are sort of suitable (J105, JOD35WB, Sunfast 3200), but none encompass the whole package.

    The layout would have to be finely tuned to this end as well as incorporate the following:
    • A true performance class but not beyond the capability of weekend sailors in their 40 /50's. (Class 9,50 is not this!)

    • Cockpit / layout / loads to be specifically matched to the strengths of two couples.

    • Comfortably capable of achieving RCD Cat A with a STIX well over 32. That minimum displacement requires a boat of 9.5m LOA minimum but stretching it out over 10.5m might be better.

    • Doesn't get clobbered under IRC.

    • Sensible draught of 2m max with bulb keel (not T) with conservative hull attachment.

    • Adequate accommodation for two couples to live comfortably on board (as two couples!) during regattas.

    • Aft heads usable going to windward at sea (No1 requirement of women when out sailing! They object to suggestions they go 'over the rails!)

    • Fractional rigged with permanent backstay, full battens, swept spreaders, no runners, . .

    • Restricted sail wardrobe but suitable for a wide range of conditions (Solent chop, light airs in the Med, strong tidal areas, offshore, etc).

    • Conservative style that won't date quickly. But avoid 'retro' look.

    • Ability to carry water ballast for some events. Something around 500kg per side should be possible to incorporate without lowering STIX below 32. (IIRC the JOD35WB can only manage 350kg).

    Do some market research down at the double handed fleet at the Royal Southampton YC or via the Petite Bateau association. Prioritise your requirements or you'll end up trying to design a jack of all trades.

    The options for promoting this class could be one-design or alternatively try to evolve a class rule that might encompass suitable existing boats (J105 and JOD35WB for example).
     
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  10. fcfc
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    fcfc Senior Member

    fcfc

    GP 33 are very far from olders 3/4 tonners.

    Crew of 7, but only 3 berths required and 1.46m headroom. (4ft 9in), and OSR 3. (relatively protected or close to shoreline).

    That 's a 33ft day boat, no more.

    Perhaps you could look at classe 9.50 http://www.classe950.com/p/en/lemultimedia/
     
  11. steve.b
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    steve.b Junior Member

    hi

    thanks for your reply

    I have already finished and handed in my dissertation. I did a design of a GP33 in the end, with emphasis on the performance prediction. It was very interesting how the results turned out, i compared my design to that of Kanai with VPP software.

    Thanks everyone for your input
    Regards
    Steve
     
  12. fcfc
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    fcfc Senior Member

    Structural design of these things is a bit challenging :p

    When you look at GP 42 , certificate here : http://www.gp42.it/new/Boats/Roma_02/ITA 4202 - Roma 42_2 - 090515.pdf

    You see displacement 4225kg less keel weight 2298 kg mast and rig 200kg internal ballast 308 kg batteries 80kg engine 160 kg, you get 1180 kg 2600 lbs for a fully equiped decked 42 * 13 ft hull , able to resist the righting moment of a over 2000 kg 4500lbs bulb at 2.4m (8ft) draft .

    ORC class rules mandates ISO 12215 compliance, but do not state which design category. OSR 3 neither. Only OSR 0 1 2 mandate category A.
     
  13. steve.b
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    steve.b Junior Member

    indeed, that was a very interesting aspect.. My GP33 was designed to ISO cat B (offshore) requirements and ended up just over minimum class weight. The plus is that it is designed in Glass as opposed to designing a full carbon boat, with the obvious cost advantages..

    It is definitely possible with some careful thought into the structure.
     
  14. fcfc
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    fcfc Senior Member

    I am sorry to bother you,but may I ask a question about composite.

    I guess you specified epoxy resin for you boat.

    But what mechanical properties did you used for ISO 12215 ?

    in 12215 2008 annex C, you have 3 choices :
    ELa determination by full mechanical testing.
    ELb using tabulated data, with some measures.
    ELc only tabulated data with security coefficient.
    But the tabulated data is only given for polyester resin.

    Thanks.
     

  15. steve.b
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    steve.b Junior Member

    I designed the boat using EL-c, default data with 0.8 factor, ISO fibre content by mass.

    Although the boat should be built using epoxy, just the default values have been used. This just provides a conservative weight.

    As stated earlier, the main emphasis was a VPP analysis and the strucutre was done relatively conservatively, but really only to provide a weight and centre.

    However, if you are using pre-preg or even an infusion process, you can still do the material testing and use your own mechanic properties (which you also know the builder can achieve)
     
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