Discussion: Pocket Cruising Power Catamaran Design for Recession Times...

Discussion in 'Powerboats' started by Seagem, Jan 11, 2009.

  1. Manie B
    Joined: Sep 2006
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    Location: Cape Town South Africa

    Manie B Senior Member

    The cat that i posted pics of was built by one of our "local" boatyards Coplan Boats. The boat is hand laid GRP polyester with balsa core stiffening. Essentially it is a one off design, semi-dispplacement with relatively large flat planning areas at the sterns which gives extra flotation. The corrected top speed for the boat is more like 20 knots WOT. My friend owns the moulds and is busy modifying them. The next build will be longer and wider.

    However at under 10 knots the boat is a absolute gem and the 50 E-tec's are superb.

    I am going to the boat for the weekend of 30 Jan 09 and will take lots of pics and post them with decriptions, and i will get more technical info and figures then :D
     
  2. Seagem
    Joined: Jan 2009
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    Location: Cayman Islands

    Seagem Junior Member

    Thanks Manie....

    Thanks Manie....

    Yeah, 20 knots is more like it: Schionning designed the Prowler 9 meter with very narrow displacement hulls (15.5 to 1 ratio) that does about 23 knots with twin 50's, according to one user...

    http://www.schionningmarine.com.au/login/pages/images/Completedesigncomparison.pdf

    Make sure to find out about the designer and all the main specs, including bridge deck clearance and underwater pics of bow and stern hull lines. Also, please ask the owner of the mould if he is interested to build one for a 3rd party...

    Well, I guess he would be, since Coplan Boats already builds the Elf 26, Ocean Spirit 34 and Ocean Spirit 42, according to Google.
     
  3. Manie B
    Joined: Sep 2006
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    Location: Cape Town South Africa

    Manie B Senior Member

    Seagem i am sure that they can build it, the problem is that the mould has been widened to 4 meters and i think the lenght is now 11m?
    Transport costs would be prohibitave.
    However i will post more after the end of the month weekend - which is our "Around the Island" race which is the biggest inland race in the world :D
     
  4. sabahcat
    Joined: Dec 2008
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    Location: australia

    sabahcat Senior Member

    So does that mean you don't have a design yourself or need a builder for the Cayman's like you implied in your opening post?
     
  5. Seagem
    Joined: Jan 2009
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    Location: Cayman Islands

    Seagem Junior Member

    Likely not a problem, as he probably has a mold split in the middle longitudinally to which he's adding a spacer piece for additional width and with the hull lines aft of the middle of the boat flowing essentially parallel, a transom can be put in several feet short of the actual back end of the hull...

    The advantage of the Schionning 950VT design is that it's semi-planning and will go faster when adding more power - thereby appealing to a wider range of potential customers - while your friends displacement cat has a maximum design speed of about 25 knots but will be more efficient up to about 20/22 knots...

    Ocean freight has gone down a great deal in the last few months, as the Baltic Index that reflect Ocean freight rates, has virtually collapsed due to the Depression starting to bite...

    [​IMG]
     
  6. Seagem
    Joined: Jan 2009
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    Location: Cayman Islands

    Seagem Junior Member

    A reminder...

    Hello Manie,

    You promised us more information and photos on your friend's cat and we're all ears and eyes, waiting for it...
     
  7. Nick Muller
    Joined: Mar 2009
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    Location: Mauritius

    Nick Muller New Member

    Hi Manie when do you expect the longer mould to be completed? Will Copland be using/renting these moulds? I am looking at a Cat, but would prefer a little bigger that 34'. Regards Nick
     
  8. plankton
    Joined: Jul 2008
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    Location: Jupiter, FL

    plankton Hang on, beeg wave !

    Interesting post, now the arrows have stopped flying, :D

    Can I ask a simple question of Seagem - what is your budget ? If you're trying to do all this on a shoestring then I'm of the opinion that you'll end up with a hull that won't last, especially a catamaran hull. But if your budget is open-ended as far as the prototype goes (with a view to producing a decently-priced market option) then I might have some suggestions. If you can stretch to 29', then Shultz's Super Sliver thing might be a possibility, if a bit narrow in hull form for a live-aboard.

    There's also this : a 25' hull that could easily be adapted with some judicious re-location of consoles and stuff. This thing runs well with 60hp motors. It might look ugly but it's from a yard that has over 15 years experience of building cats and it's built like a tank.

    [​IMG]

    [​IMG]

    I also find it interesting that no one has mentioned the 2600 series Glacier Bay yet. I've owned two of them and cannot fault the hull for what it is, a mid-20 knot top-speed displacement hull that works well at slower speeds with moderate power - say twin 90's for example. You also get a decent berth in some of the cabin models, notably the 2680 and 2690. But having said that, I've some other ideas that may be of interest once you've given us an idea of budgetary constraints.

    Having run a small catamaran in the Caribbean for two years I have some understanding of what you want, and why. I'm interested in how you're going to cope with heat and humidity issues on a live-aboard that size, too. It's bad enough living on a 38' foot boat with AC in the islands, let alone a wee "cabin-cruiser" ! You're not planning to run AC with that 2KW generator, are you ?

    I concur heartedly with Manie about the E-Tecs. I've just come back from New Zealand and I had two boats there with them. Never a beat missed, good torque in the mid-range and extremely pleasant fuel economy - once you get used to the noise of them. Not quite as quite as a 4-stroke but definitely smoother than a 2 pot.

    As a end-note, I might add that I've been on an awful lot of the cats in this size-range; in SA, the US, the UK, Australia and NZ. One thing stands out - you'll really have to do your homework if you want a fuel efficient hull with all the gubbins you plan to put into it. Some of the ones that you might find desirable from a seaworthiness point of view may be real fuel guzzlers, and those that don't guzzle fuel may well be lightly built. The Sharkcat, as previously mentioned, was a great sea-boat, but required some serious horsepower to get it moving.

    More later.
     
  9. Seagem
    Joined: Jan 2009
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    Location: Cayman Islands

    Seagem Junior Member

    Open Budget for the Proof of Concept Boat...

    Open Budget for the Proof of Concept Boat: in today's recessionary climate, unless you have sufficient discretionary funds of your own that you're willing to write off, if necessary, then there is no point to even discuss the matter...

    Lately, I have been in contact with South African boat designers and builders who have extensive experience with rough seas, where their tuna fishing cats do 120 miles round trips and come back loaded with several thousand pounds of fish using relatively modest outboard power...

    The 2600 Glacier Bay series is one of their best, but the beam is still only 8'6'', while I want to go to 10' with a much higher bridge deck, which is the way the former owner of Glacier Bay is going with his Aspen series, which has all the features I want in a very compact package, except that it's a single diesel engine PROA!!!!!...

    http://www.aspenpowercatamarans.com/pages/26AspenC-80.html

    The length is not set in stone and it may well end up being 28' or 29' overall...

    There are boat A/C's that will put out 9000 Btu's and work off a 2kW generator: http://www.wrightmarine.net/4994.html

    ... and 6500 Btu's off a 1kW portable generator: http://www.wrightmarine.net/4973.html

    If putting everything I want together was easy, I would not be posting here: I was hoping to get some worthwhile input, but so far genuinely helpful posts like yours have been rather scarce and not even Mannie has fulfilled his promise to come back with more info and pics...

     
  10. ThomD
    Joined: Mar 2009
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    Location: TO

    ThomD Senior Member

  11. plankton
    Joined: Jul 2008
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    Location: Jupiter, FL

    plankton Hang on, beeg wave !

    Hi Seagem,

    Thanx for the answer. As your budget seems to be of a beneficial nature, may I point you in the direction of Noah Thompson from NZ. He could be of great benefit to you in both design and construction parameters. He builds in aluminium (a good way to build a first hull and a possible material for your Caribbean vessel that could offer many advantages) and DuFlex panel. I am uncertain whether he has any designs that would fit your current requirements but he could well have something up his sleeve that would suit you straight off the shelf.

    He visits this forum and may be reading this as we speak, but otherwise drop him a line at info@eastcapemarine.com

    He did a wonderful rendering for me a couple of years ago for a project that I have put on hold, and he might well be able to give you some of the advice you are seeking.

    Hope this helps, and good luck with your project.
     
  12. eastcape
    Joined: Jul 2003
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    Location: NZ

    eastcape Senior Member

    Stock Plans

    Thank you for the kind recommendation Plankton,

    My apologies for not responding to this post earlier Seagem, I have been very busy with deadlines with a 100' power catamaran kitset boat design . Most of my design work is all custom to suit the clients exact specifications. Custom design work is not usually associated with recessionary budgets. Therefore I was reluctant to respond when part of the threads title was "recession times"

    I do have some "Pocket Cruiser" stock plans available, and as we speak, my website is being upgraded with more content. I think the new content for the website will be available on the 1st April 09, but don't hold me to that. The stock plans that will be advertised are close, but not quite, to your specification list. Check my site around that time and let me know if I can be of further assistance. I'm more than happy to discuss how we can alter one of my stock plans to suit your requirements.

    Kind Regards,

    Noah Thompson
    East Cape Marine Ltd.
    PO Box 705 Te Puke, NZ 3153
    Fax +64 7 573 4099
    Mobile +64 21 11 00984
    info@eastcapemarine.com
    www.eastcapemarine.com
     
  13. Seagem
    Joined: Jan 2009
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    Location: Cayman Islands

    Seagem Junior Member

    Thanks for making contact....

    Thanks for making contact: I did e-mail you early on but never got a reply, so I thought you must have been too busy to bother with such a small project, even though it may eventually go into production if the proof of concept is successful and discretionary spending hasn't completely died out...

    The 26' Aspen design referred to in previous posts clearly shows that what I want to do is feasible in a small package - with a little ingenuity and I'm willing to extend the length to 28', if necessary to provide a larger cockpit. The main difference is the amount of fuel and water which is much larger in my concept (100 gallons fuel + 80 gallons water) and a lot closer to what's needed in reality: even though there is no need to fill up all the tanks for short cruises to keep weight down, there is plenty of volume available near the centre of gravity of the boat to put them in, rather than have to struggle later with a bunch of cans...

    As mentioned earlier on another thread, I'm impressed by the performance of the Chilkat 30, a result of its high length/beam ratio of +/- 18...

    http://www.boatdesign.net/forums/bo...hape-fast-efficient-catamaran-hull-25745.html

    ...and by the asymmetric hull design of the Morelli 21' foiler that promotes banking in turns...

    However, I'm not convinced that a pure planing hull is the answer and a displacement hull a la Schionning will end up being too long to fit the bill: but, I really like the way he has freed the swim platform from the outboard engine in his latest 'Vapour Trail' designs, which, unfortunately are fuel hogs due to the large wetted surface and low beam to length ratio...

    I get the feeling that a compromise design between displacement and planing will be needed to carry the weight efficiently in order to obtain a fuel consumption of 3 to 4 miles to the gallon at 23/25 knots cruising speed with hopefully no more than 115 hp twin 4-stroke engines. I envision a sharp entry blending into a half round section for the first 2/3 of the waterline, then flattening out, while the very wide bow chines - to effectively knock the spray down and provide a rapid increase in buoyancy - would turn down below the flat bottom to prevent the lifting stream of water from escaping to the sides...

    But, I'm wide open to any other ideas, as long as they do the job at hand...

     
  14. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Hi Seagem,

    Sounds a bit like a variation on the Atkins tunnel-stern sea bright skiff shape. Such a hull form, compressed in beam to the dimensions of one hull of a cat, could have some interesting- and possibly quite desirable- behaviour. Curious to see if anyone here with experience in such hulls could chime in?
    The "ChiliKat" you mention appears to use some similar hydrodynamic concepts, although in a rather different form. I think it might be a good avenue to explore for what you're trying to do, if you really must have high-20s on the speedo.
    There is a very big difference between a 25' and a 30' powercat, given identical beam and similar performance. I've never built one, but I've been doing a lot of sketches lately and have been very hard pressed to find any way to fit more than the most basic accommodations into anything under 28 to 30 feet, and when you do manage to cram an interior in, the boat invariably ends up looking pretty chunky. Given the kind of interior features you seem to be looking at, I'd be thinking more towards 30' than 25' if you want to maintain decent short-passage capability.
     

  15. eastcape
    Joined: Jul 2003
    Posts: 50
    Likes: 5, Points: 8, Legacy Rep: 62
    Location: NZ

    eastcape Senior Member

    Contact

    Thank you Seagem,
    I have responded via e-mail to your questions.




    Regards,

    Noah Thompson
    East Cape Marine Ltd.
    PO Box 705 Te Puke, NZ 3153
    Phone +64 7 573 8101
    Fax +64 7 573 4099
    Mobile +64 21 11 00984
    info@eastcapemarine.com
    www.eastcapemarine.com
     
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