Let´s be practical. Are we in the right way?

Discussion in 'Stability' started by Antonio Alcalá, Nov 6, 2007.

  1. DanishBagger
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    DanishBagger Never Again

    I say keep your boat if you like her and she gives you pleasure. Why change a good thing? Unless, of course, you really aren't satisfied, and are looking for a suitable replacement.

    If it's some small(er) issues, say a crappola designed back stay or something in that line, you could upgrade that instead – provided you want to, of course.
     
  2. Vega
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    Vega Senior Member

    I thought that your manners had improved. But it seems that your fathers never had time to teach you and it is obvious that you don't have the ability to learn for yourself how be polite. You are very rude, to say the least.:(
     
  3. Antonio Alcalá
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    Antonio Alcalá Ocean Yachtmaster

    Vega and Guillermo:

    I should be mots grateful if you could answer me about if you´d change my 473 for those boats I put in my post.

    Forget your problems, both are brilliant

    A.
     
  4. Vega
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    Vega Senior Member

    António, thank you for your kind words. :) I am just an Architect and an old salt (a capitán de yate, like you) that has taken an interest in sailing boat’s stability. I have learned a lot and there is always a lot more to learn. Anyway, I know something about it and I try to make that knowledge available to the ones that know less than me.

    As you can see on post 32 of this thread, I have said that probably your boat has been certified (some years ago) as having a 119 AVS and a 48 STIX



    But on post 39 I have wrongly referred the certified numbers as 51 STIX and 119º AVS instead of the correct numbers, posted by me on post 32, that were : 48 and 119.
    (red for mistaken number, blue for the intended one)



    On post 54, when trying to explain to you why Guillermo had obtained a significantly higher STIX, when using the curve you provided (the one with a bump) I have persisted in the mistake and I have used 119ºAVS and a 51 STIX, referring to the certified stability numbers, instead of the correct figures, I mean 119 and 48.

    I was trying to say that the curve that you have posted (with an AVS of 126º) and that Guillermo used to calculate a 51 STIX, without that bump (not considering the cockpit influence on the stability), would give 119º AVS and a smaller STIX, probably the certified 48 (and mislead by the previous mistake, I have posted 51).



    I am sorry for the confusion, that is, if you did not understand what I mean;) .

    I will edit posts 38 and 54 to correct those mistaken numbers.
     
  5. Antonio Alcalá
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    Antonio Alcalá Ocean Yachtmaster

    Now I bring your attention please:

    Somebody has offered me 3 posibilities for changing my 473.

    1.- First option: 1984 Hallberg-Rassy 49. No comments Everybody knows it

    2.- Second options: 1989 Formosa 51 Ketch. I´d like comments about her. Excellent MCR but not a great sailing performance

    3.- Third option :1989 Diana 60 ( Tayana) sloop rigged. Displacament 30.000 kg.Excelent condition ( I saw her)

    4.- Fourth: Grand Soleil 53 , 1992 model GS 52. German Frers Design. Great sailing performance.


    My intention is getting a boat with total security for crossing oceans in any weather condition, but attention: sometimes "solo" andsometimes with my family, I´ll choose depending on the forecast the adequate course avoiding bad conditions.

    Waiting your responses

    A.
     
  6. Vega
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    Vega Senior Member

    There is no total security on the sea, especially in a small yacht (all of them are small compared with the sea).

    If security is your only concern, buy the heavier and bigger boat, get a crew and get bored:D .

    The Grand Soleil 53 is a nice and fast boat, but with a 15 year old standing rig you would better substitute all the cables and see if the reefing system permits you to operate it from the cockpit (I don’t think so). You would have to change that too.
     
  7. Vega
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    Vega Senior Member

    Of course, take a look at post 54 (edited accordingly with explanation on post 64).

    Of course, it is what I was saying, I mean that you used the curve provided by Antonio, the only one that was posted, the one with the Bump.

    What I was saying was, that some years back, the curves that were used to calculate STIX had no Bump (they did not take into account the cockpit influence). These curves were the same ones that were provided to customers (when they asked nicely) and to the press when they tested the boats (as stated in the magazines).

    Well, boat manufacturers could all be stupid and were just providing people and magazines stability information with worse stability values than the ones they could obtain, with curves that would take into consideration the volume of cockpits, curves that (in your opinion) were allowed but that they chose not to use.

    It is possible, although not likely. Anyway, some years back the stability curves had not that Bump, due to the cockpit influence.

    Take a look at some of the old ones (1999/2003) -I can post a lot more if you want:
    (Etap 37; Arcona 40-Deck Saloon; Feeling 36;

    Going up and coming down, no bump on these ones, and a deck saloon would have a big one, if the cockpit were considered.
     

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  8. Vega
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    Vega Senior Member

    Let’s now look at two from the same manufacturer, one new, other some years old:

    The brand new Elan 41 has one with a bump. The 37, one of the oldest models still in production, has one without a bump.
     

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  9. Vega
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    Vega Senior Member

    Take a look at the one from the new J 120, and the ones from the new Jeanneau 36i and new Jeanneau 42i.

    They all have a bump.
     

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  10. Vega
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    Vega Senior Member

    Let’s look at the Oceanis 373, a model that is about the same age as his big sister, The 473:

    And we will see that the boat has a stability curve without a bump (not considering cockpit influence).

    Let’s look again at the curve that was provided to Antonio (473). It has a very clear bump on it.

    Both boats have about the same cockpit configuration and are boats with similar characteristics (with different sizes).

    Both GZ curves would have a similar Bump if they were made taking into consideration the cockpit influence.

    As it was not the case, It seems to me that the curve that was provided recently (two years António?) was a corrected curve, similar to the ones that are made now to calculate STIX and AVS (with a Bump).

    That would explain why Antonio’s curve has a bigger AVS and provides a bigger STIX, compared to the one that was used, (some years back) to certify the boat. That one was like the one from the 373, I mean a curve that had no Bump and that had not taken into consideration the cockpit influence on stability. That curve had provided a 119AVS and a 48 STIX and the one given to Antonio would provide a 126 AVS and a bigger STIX and in that case, a 51 STIX makes sense.

    That was what I was trying to say on post 54, the one that deserved from Guillermo the following comment:

     

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  11. Guillermo
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    Guillermo Ingeniero Naval

  12. Vega
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    Vega Senior Member

    That is no answer, and that is harassment.
    If you do not understand, I can try to explain better.
     
  13. DanishBagger
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    DanishBagger Never Again

    Ouch, the harassment card has been played.
     
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  14. Vega
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    Vega Senior Member

    Mike, as you can see on the posted page, (part of the certifying dossier) there are lots of items that count to the Maximum Load Condition. You can see that full tankage (water and fuel) are considered as well as basic equipment stores and a lots of other things.

    The difference between lightship (MLCC) and Maximum Load Displacement (LDM) gives the Maximum Load (ML). Maximum load is in this case 2160kg.

    Contrary to what Guillermo says, on that Tag (Builders Plate) what is there is not the Max Load (including all items – 2600kg), but the max load, except fuel and water (see small picture). The value that is on the Builders plate is in this case 1500kg (and not the Maximum Load – 2600kg).
     

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  15. MikeJohns
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    MikeJohns Senior Member

    Paulo
    I must admit I am totally ignorant wrt European requirements and base my comments on some of the data we have been forwarded in the past when dealing with both Australian and overseas manufactured vessels.

    If this information is freely available for all CE vessels then it is clearly well considered for consumer protection .
     
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