Van de Stadt Caribbian 40

Discussion in 'Boat Design' started by edik, Mar 9, 2013.

  1. Ilan Voyager
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    Ilan Voyager Senior Member

    Thanks Michael for the wise words. I'll add that all the Van de Stadt boats have an excellent reputation of seaworthiness and strength. I never heard of a bad boat by them, and when you see the quality of the plans...

    Many European shipyards made (and make) excellent boats in polyester, strong and durable. Units 30 years old are found in very good shape at low prices, and the investment to put them in pristine estate is rather low.

    An Franch acquaintance of mine is now at Panama on a Centurion 40 1990 by Wauquiez
    bought for 95000 Euros (after hard bargaining, but he had the cash in hand the best argument...) in excellent shape, very well equipped with a 43 HP diesel engine. He put 20000 Euros for refitting all the details and he is a making now a circumnavigation with his wife. 115000 Euros all taxes included (sales taxes in France more than 18 %...) is around 155000 USD...No further comment...

    An example of Centurion 1989 for sale in France at 110000 Euros all taxes included
    http://www.monbateau.com/monbateau-.../18373/Lunit/M/Punit/E/NOMBATEAU/Centurion 40
    Read the rich inventory...even in French you'll understand!
    with some pics...

    The Alubat 39 (a well known boat for circumnavigation in aluminum with excellent reputation) of 1988-1990 complete, equipped and ready to sail are around 95 to 110000 Euros...
     

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  2. pdwiley
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    pdwiley Senior Member

    The *keel assembly* is 8m long. It's a full length shoal draft keel.

    The entire vessel is 11.995m LOA and displaces 7.5 tonnes - in theory. I know the length is correct because I've finished it.

    The plate is 4mm for the hull and 6mm for the keel sides, 200 x 40mm for the keel shoe.

    A strip plank hull without insulation is not going to be as comfortable as a steel hull with 60mm of insulation. It will be a lot less hassle doing the interior however.

    I agree that one has to be very careful in claiming anything WRT strength of materials.

    PDW
     
  3. Landlubber
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    Landlubber Senior Member

    The entire vessel is 11.995m LOA ....clever move mate.

    12M is another world of expenses. (here in Australia anyhow).
     
  4. pdwiley
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    pdwiley Senior Member

    Yeah - that measurement was *not* an accident :)

    The bowsprit is in a tabernacle so it can swivel vertical and therefore isn't a fixed part of the hull, therefore doesn't count for LOA.

    PDW
     
  5. Ilan Voyager
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    Ilan Voyager Senior Member

    My mistake about the keel shoe because of too fast reading. That shows also you have a good building as shop with strong beams so you can -cleverly- move all the pieces. Not all have this advantage, and sometimes moving the plates can be hard and even dangerous. A 2.44*1.22 4 mm steel plate weights about 93 kg and can crush fingers or feet.
    What means WRT? About strength of materials, most have their pros and cons and the decision depends on a lot of factors, including the availability of the material and shipyards experienced (or home builder feeling) for working it.
    But in most of the cases, building a hull in metal is not for the home builder with no previous knowledge of the material.
    About insulation that depends of where you navigate...In the tropics a metal boat is a pain if the decks are not covered by an insulating deck material like wood (and that becomes very heavy...). The metal can become very hot even painted in white and accumulates heat. In temperated waters is so-so. In very cold waters insulation is imperative and asks for a lot of precautions because of condensation problems (and possible corrosion).
     
  6. edik
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    edik Junior Member

    Why is everybody talking steel? If one is not obsessed with the notion of building a very light boat - and why, pray say, would one want a very light cruising boat - one can have an Alu boat with thicker plating, say, 8-9 mm bottom, 7-8mm sides, 6mm deck, and still have a boat that is lighter than steel. A boat with a plating like this would be incredably strongld, thicker plating would make welding easier and plates would be less prone to deforming. No?
     
  7. Ilan Voyager
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    Ilan Voyager Senior Member

    We were just discussing about steel like about the weather...Light cruising boat? Yes me, but a multihull, a very simple catamaran, plywood/glass epoxy, as long as possible.

    About aluminum thickness you can even go further with the "strongall" system used by the shipyard "Meta" (sorry no documentation in English). Thickness on a 12 meters 12mm...No internal structure in the hard chine boat. it's a lot of metal.

    That gives rather ugly boats as you can imagine it's very hard to ploy a plate of such a thickness unless you have the very big tooling. The design options in hard chine look rather limited specially at the bows, which are too full.

    The shipyard makes many claims of strength, etc...The results seem a bit more mitigated. None of these boats is beautiful, none is a "good runner", I mean not a racer but a boat able to make 150 miles a day in normal conditions. And all are very expensive. Some have problems of fissures. I do smell that the lack of elasticity of such thick plates may concentrate stresses in some points and causes fatigue. Just a wild supposition.

    Aluminum must be maintained with attention and great care, and built without flaws, specially in the electrical system. I do not exaggerate, I mean simply that aluminum asks attention of the problems of electrolysis at the conception, building and maintenance. I have seen a bunch of bad cases of corrosion, but I saw also aluminum boats in pristine condition after 30 years on sea, with meticulous owners.

    As engineer I do not see the advantage to put more metal than necessary to achieve the necessary resistance for a normal use, with a easily feasible frame. More metal, except for an exceptional program like pushing growlers somewhere in the Arctic, is just a waste of material and thus money.
    A certified welder is not worried by the ordinary thickness of the alu plates used in common boatbuilding, and knows how to minimize deformations. He's paid for that, he has been trained for that and he has already burnt and deformed his quota of plates while learning.

    More hull weight means more sail surface, more ballast, bigger hardware, bigger and heavier mast if you want to keep some ability to sail at a decent speed. It's a vicious spiral. You may obtain a dog, slow, pounding in the sea because of his weight compare to its volumes, making suffer its structure which may be paradoxically less robust, and often less stable in hard sea by the change of metacenter . One sure thing: it will be more expensive.

    If you buy plans from a reputed architect like Van de Stadt, resist to the temptation to modify anything, at least in the structure. These guys have the experience of hundreds of built boats, and the use of classification societies has a good purpose; safe boats. Generally you pay the architect for plans I do hope were carefully calculated there is no need to modify it unless by a very qualified NA.

    A LLoyds A100 yacht in alu is already built like a tank, with lots of margin.
     
  8. edik
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    edik Junior Member

    Yes, I'm familiar with "strongall" system and no, I would not go that route. All I was considering was adding, say, a mm of thickness to make the hull "even stronger."
     
  9. Ilan Voyager
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    Ilan Voyager Senior Member

    The hull won't be specially more stronger as you normally have to reconsider all the framing. No need specially with designs in LLoyds A100 or DNV qualifications.
     
  10. edik
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    edik Junior Member

    What do you mean by reconsidering all the framing? Do you mean one would have to subtract that one mm of additional plate thickness from the ribs?
     
  11. Ilan Voyager
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    Ilan Voyager Senior Member

    Absolutely not! You must have a frame in relation with the skin, so the frame must go thicker. It's a global system; when you touch one element all the others must go in the same ratio of mechanical inertia, or there won't result enough gain in strength in relation with the increase of weight. In clair you have to re-define all the structure...

    There is also a parasitic effect. For example you have a boat deck 4mm, topsides 5 mm, under water 6mm.
    Put a mm more everywhere. Increase of weight of the skins;
    Deck +25%, topsides +20%, underwater (oeuvres vives in French) + 16.66%.
    Morality the center of gravity is going up and probably aft so more ballast will needed to get the initial stability. The boat won't be in its designed waterlines and the wetted surface increased, thus less mean speed. Trying to get again the speed will add further problems.
    I do not talk of all the other adverse affects.
    And probably if you want to get more "strength" in marina maneuvers it would be simpler to add just a good defense of an absorbing material like rubber. In case of grounding on a reef, one mm more won't change the situation. And if a 100,000 tons cargo crush you, nope the boat will be badly knocked whatever the hull thickness. A anti-collision radar would be more effective and less expensive...
    In fact active systems like radar (even a small anti collision one) and sonar, GPS and charts for careful conservative navigation (stay away of the reefs....), careful meteo evaluation, and seaworthiness (that means an equilibrated boat and that's the result of a good design) in bad weather are far more efficient than a thick hull for the security.

    In fact you need just enough strength to withstand bad weather without disintegrating the boat, no more. The remaining is affair of the skipper.
     
  12. edik
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    edik Junior Member

    Why all the drama? The same boat is offered in steel or Alu with the only difference being less lead in the keel of a steel boat and a little more overal displacement. I'm not aware of any other changes in the design.
     
  13. michael pierzga
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    michael pierzga Senior Member


    For a cruising boat You want the lightest construction possible.

    Every kilo you save during construction can be added latter as a kilo of anchor chain, kilo of tender, kilo of beer.

    The finished yacht, fully fit out and ready for action, must float on her designed waterline.

    Removing lead ballast to compensate for overweight condition is not acceptable for a cruising yacht
     
  14. pdwiley
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    pdwiley Senior Member

    Steel is cheap, easily worked and much, much more forgiving than working with aluminium, that's why.

    It makes absolutely *no* sense to upsize the scantlings in excess of what the designer specified.

    Thick aluminium is not easier to weld, it merely is less likely to distort due to poor technique. Against that is a greatly increased cost in material, welding equipment, consumables etc etc.

    I venture to guess that you have no experience in metalworking, welding or heavy materials handling. That's fine, everyone has to start somewhere, but playing with scantlings is not a good place to start out.

    FWIW I think building one of these hulls is well within the capability of an amateur, in steel. In aluminium, maybe, but I wouldn't do it and I've the shed (so no worries about loss of shielding gas), the materials handling equipment & experience in metal fabrication.

    However as I said before, if you can buy one, you're better off buying one. It's going to take 3 years of solid effort, *minimum*, and a lot of money to build your own. You will never, ever get back what it costs you as an investigation of the used boat market will show.

    PDW
     

  15. erik818
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    erik818 Senior Member

    edik,
    I fully understand the problems with following instructions without trying to improve. I need to remind myself constantly to follow the plans, and if I slip and start to "improve" I'm lucky to have my wife there to ask me the sobering question "why?".

    If you go along to build the boat you want, I assume you will buy components like engine, mast, sails, rope etc. Your'e probably not going to start with metal ore or trees and then refine that into the building material you need. You will use processed material or ready parts and assemble them to a boat. How much ready-made material are you allowed to use and still feel that you have built the boat yourself?

    You have not stated that you insist on making the hull yourself, and I don't see why you couldn't have a shipyard build the hull according to your plans. It would make the project more manageable. Personnally, I would buy any service I don't find satisfaction in doing with my own hands.

    That said, I actually would find satisfaction in starting with trees from my family's forests, saw the planks myself and build the hull myself. The size of the boat is less important. I buy the epoxy and glass fiber though...

    Erik
     
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