Dangerous designs?

Discussion in 'Sailboats' started by usa2, Nov 18, 2005.

  1. Vega
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    Vega Senior Member

    :p :p :p
     
  2. D'ARTOIS
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    D'ARTOIS Senior Member

    Doug, your claim is ridiculous. Earlier, I have asked you to come with the facts that (and not the principle) the canting keels excists for that particular span of time.
    I sail from my 19th, and the canting keel occurred to me only two years ago.

    If there was a track record of that long time - this what is happening now, specifically with POR and Movistar, shows - and if you don't see it I can't help it - that one, the designers, do not fully understand the pericles around the concept. Two, POR might not even finish, as her structural problems are that fundamental. The 2nd generation VOR will be quite different - that is for sure - and will be much better. The experiences of the crews are vital and will give sufficient information to make sure that such design-shortcomings as are shown in all the boats will not occur in the next future.
    Nevertheless the 2 ABN boats are superior and hopefully also Movistar will be able to repair the hydraulic system, otherwise we will land in a situation that a race w/o competition is not a race.

    Another thing Doug, I see a return of the metal boat. The composite boats are simply not strong enough. I do not say steel or alumnium - there are other metals.

    But don't try to sell us that those keels excist for such a long time and are failsafe - that is not the reality.
     
  3. Doug Lord

    Doug Lord Guest

    Canting keels

    D'artois you're prone to overstatement underlined with recklessness. I NEVER said canting keels were fail safe. I did say that they have been around a long time. Steve Clarks father used one on a boat that still exists starting around 1980-and there have been many others- MOST with excellent records. Dozens of CBTF boats(by Reichel-Pugh and and some others) world wide starting around 1990 with no failures due to design or construction that I'm aware of. And many others as well.There is an artile in Seahorse a couple of years ago by Dave Beck-I haven't found the issue- but it's here somewhere; something like "The History of Canting Keels". . You should get a copy of it.
     
  4. usa2
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    usa2 Senior Member

    I dont agree with the statement that we will return to metal boats. The problem here is people(designers, builders) are trying to save weight by making the structures as light as possible.

    The Volvo 70 rule sort of accidently encouraged fragile structures by not making a maximum bulb weight. So the genius designer and builders took as much weight out of the hull structure, therefore possibly weakening it, and then to compound the problem, they put this so called "saved weight" back into the bulb, so it can generate that much more stress onto the now lighter and weaker structure.

    That is a brilliant way to cause your boat to have structural failure.


    apologies for the rant..
     
  5. Vega
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    Vega Senior Member

  6. RCSail
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    RCSail Junior Member

    I see no basis for a claim that composite structures cannot be strong. It is true that carbon is stiff and cannot be made to gove, but that is of secondary importance. I believe that the fundemental issue is that the only place where the expense of carbon is justified is where weight is at a premium, and thus structures are not overbuilt. If we reverted to metal for racing boats, the incentive to reduce weight would be the same and we would still have strength problems.
    Additionally, even if carbon is eventually abandoned (which I doubt it will be) fiberglass, if not built too lightly, can be quite strong. My grandparents owned a 44' fiberglass cutter that they grounded on a reef and several shoals with no structural damage.
     
  7. D'ARTOIS
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    D'ARTOIS Senior Member

    Nice to hear (read) critical replies on my last post (not THE last post).

    I am trying to awake my idea of the late 90's : to construct a sailing yacht of considerable length - construction material: titanium.

    Do not ask which composition/alloy - that I will not disclose. In any case it is not available commercially.

    I will not come up as being lighter than a composite material - only 6 times as strong!!!
     
  8. zerogara
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    zerogara build it and sail it

    Strong? In which way? I don't have any data infront of me about metal properties and their elctrolysis compatibility and I will not dismiss your idea based on the cost alone because I can not assume you are among most of us with "limited" budgets and financing.
    I've only dealt with this material in bolts and nuts on racing motorcycles and it costs substantially for its weight savings.

    Doesn't this stuff corrode? Isn't it brittle (comparatively) and let's say you have the skin of the boat made out of this undisclosed alloy on the same weight as a well constructed composite panel. How does it compare on impact with an other solid object, or water at high speed!

    Don't they make a wire mesh out of some titanium alloy? Can you use something like this within a composite? How do titanium alloy fibers compare to carbon?
    And have you thought about Magnesium alloys? That gets really pretty when it is corroded and lasts for milleniums.
     
  9. Windvang
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    Windvang Yacht Designer

    Sounds pretty expensive. By the way composites can be pretty tough as well, they even make tank armour out of it nowadays.


    Plastic Tank Armoured Vehicle.

    The 'plastic tank' is a world first in military engineering. It's a groundbreaking new project, in conjunction with the UK Ministry of Defence and Vickers Defence Systems. The vehicle can withstand attack from a whole range of threats - including high performance cannon fire - while increasing the survivability of the crew against small arms fire, shaped charge anti-tank rounds and shrapnel from artillery shells, compared with conventional vehicles. In addition, the vehicle incorporates stealth technology to reduce its visibility to radar and infrared sensors.


    The Advanced Composite Armoured Vehicle Platform (ACAVP) is the first composite moncoque plastic AFV to have been made in the world. Vickers believe it could prove a tremendous asset; it's faster, lighter and therefore easier to transport by air than conventional vehicles, so it can be flown rapidly to war zones.
     

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  10. D'ARTOIS
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    D'ARTOIS Senior Member

    First of all Zerogara: titanium does not corrode, is not brittle and do not worry, it is stronger than anything else - the specifications can vary considerably and the lesser is published the better it serve my ideas.

    It reflects only how little peolple know about this metal and therefore I do not really appreciate the plastic tank as per proposition of Vickers.

    That tank is only resistant to handguns and light firearms and totally useless in serious battle environment. Easy to use in a rioting crowd, but there it's use stops. Furthermore, it is no item for this forum.

    I am not interested to wake furher ideas so I will have no further comments.

    Time will learn.

    Plastics will do, can do, but cannot do as much.....
     
  11. usa2
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    usa2 Senior Member

    give me a 16" naval cannon and we'll see how strong that plastic tank is...
     
  12. D'ARTOIS
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    D'ARTOIS Senior Member

    It is not the gun, but the ammo........A 76 cartridge will do nicely........
     
  13. Windvang
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    Windvang Yacht Designer

    Shaped charges and high performance cannons are not handguns! The tank is just an example of high impact resistand composites. Heavy tanks are also armoured with composites, although you may find metals in their composite layup. (Especially designed to withstand depleted uranium and tungsten rounds)

    I do not intend to flame Titanium as a boatbuilding material here, in fact if you have anything interesting to tell abouth it I am more than interested. Any numbers or test data will be more than apreciated.

    As for commercially available and affordable materials it will be very hard to beat composites whether you want strength, low weight or both.
     
  14. Paul B

    Paul B Previous Member


    In the 1980s there was a Nelson/Marek designed sled for a Japanese client that was built with a titanium hull. Named Marishitan? or something similar. Sadly the boat sank. It was 68 feet long, similar to the composite built sleds of the time.

    Ti has properties that make a nice spring. In bicycles it gives a nice ride as the frame soaks up the bumps. A carbon frame would be a much harsher ride, but would also transfer the pedal force better.

    Those same properties make it difficult to machine. Welding must be highly controlled without contamination. This may have been the downfall of the Nelson boat.

    I'm sure there are many alloys with different properties, but overall these issues must remain, at least in part.

    I have wondered about the ability to bond canting mechanisms into hulls appropriately. A fixed keel is bolted through solid laminate that includes both inner and outer skins. The loads are spread across a large area by the use of keel floors.

    The Canting Keel mechanisms are attached to the inner skins only via a secondary bond. Now you have to worry about core shear and tesnion/compression in addition to the bond itself. I am making an assumption here. Perhaps the builders remove the core in the area of the canting mechanism, making a solid ring frame. If so, the transition from the solid ring to the cores area might be the next weak link, since the flex in these areas would be so different.

    The next iteration of the VO70 rule should require the pivot to be normal to the outer skin. The whole notion of the bomber door/rotating drum arrangement has added far too much complexity to the program.

    That is if there is ever again a VO70 rule.

    By the way, the photos of the bottom of Moviestar shows a bump at the keel/hull intersection. If this boat has the bomber doors why would it have the bump? Normally the bump houses the pivot. If the pivot is inside the hull there should be no reason for the bump.
     

  15. D'ARTOIS
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    D'ARTOIS Senior Member

    Paul B, I do absolutely agree with you, I made the same observations as you did, and exactly the suspension of the canting keel in the composite boats creates a problem. But there is more. POR is out, doesnot have any winning chance.
    Doesnot and will not make anymore positive promotion next to be the general laughing stock. Bravo Micky Mouse team. (not funny at all; very good money down the drain);

    Typical that the two Dutch boats are doing so good, no? Build by Leen Schaap in Lelystad. Unknown builder, unknown designer (both not so unknown at all), still I think it's not the design (=shape) but the technical execution that makes the victims of Farr's calculations so minor.

    If all the boats were build in a healthy way, we would probably have witnessed a much more interesting race.

    So let's hope that for the next issue of the VOR that sponsors will use there brains instead of the part they sit on and turn their money to designers who has something to offer.

    Furthermore Paul, ti can be modified just alike composites. Basically if alloyed with other metals, it can made superstrong. Not only for springs in bra's or frames for bikes, or valve springs in the F1 cars, or artificial hipbones, it has many more applications.
     
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