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Sportfish bow explodes; too much flare?

Discussion in 'General Yachting Discussion' started by 993RSR, Jun 10, 2020.

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  1. Liam

    Liam Senior Member

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    Also much larger length for length. People say a Viking 60 is the same as an Azimut 60 when they compare.
    But the reality the Viking 60 has 64 of LOA without a bathing platfrom, the Azimut will be 60 with pulpit and BP, and the Viking will have a 20 to 35% of more beam.
    Result an Azimut 60 will need two 1000hp engines and will do 35 knots, and the Viking will neeed to 1500hp to do the same.
    Yes sportfish are constructed heavier, stronger and run very good, no doubt about that but it is good to compare apples to apples.

    As for the above Carlo Riva remark, he was influenced by Chris Craft but in reality he started more or less with them, his family boating business is even older.
    And in the Lake area of Italy, there is other pioneers as Baglietto, and the Abbate family.
    His Chris Craft influence had nothing to do on the designs, but was more about how to make his wooden runabouts produced in a commercial sense, it is there that he copied Chris Craft the most.
    There was a two dozen builders doing wooden runabouts in Italy alone.
    As for modified hulls, I mean those are nothing new. Be careful at the entry because most traditional hull shape used convex hull, which is why a hull like this would dive to much in a following sea.
    As Sonny Levi once explained to Don Aronow you have to go always with concave above 40 mph.
    I think it was a Cigarette 38 which stuffed in Italy and basically finished in two parts because of its convex hull shape.
    Convex works well in head seas, though buoyancy needs to be given a lot of importance, but concave is the way to go above a certain speed and in following sea is king.
  2. mapism

    mapism Senior Member

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    Haha, good thing that I saw the crucifixion coming - Q.E.D.! :)

    I am not going to argue with all the heritage and cultural stuff.
    From a technical standpoint, highly flared hulls were long surpassed by other designs - that's just a fact of life, which doesn't leave much room for debate.
    But by saying so I don't mean to disrespect the remarkable work of some Carolina builders, as much as I didn't mean to disrespect the wooden Rivas of old - far from that.

    I'm even less going to argue with muscle cars being part of US culture, btw.
    Also because if we should debate automotive heritage, as an Italian I would feel like taking candies from babies: we were building the GTO and the Spider California when the Mustang wasn't yet on the drawing board, and when your (lovely, no doubt about it!) pony car eventually hit the road, we were building the Miura, go figure. ;)

    There's another point I don't agree with, though:
    Now, having said that we are now doing a bit of guesswork, based on pics alone, I think it's just by coincidence that the deck cracked along the bulkhead.
    Which in this instance, certainly did NOT act as a collision bulkhead anyway - that's what it's supposed to do in the event of a frontal collision, while the dynamic of this accident is completely different.
    As I said in my previous post, the forces at play here compressed (or squeezed, as I previously said - just pick your preferred wording, I'm sure you see what I mean anyway) the hull topsides, right in the area where the hull goes more convex/flared.
    And THAT is the major structural damage. The deck cracking is just due to the fact that it had to let go at some point - a collateral damage, so to speak.
    But if the larger point of impact with the water when the bow stuffed would have been just a couple of feet more astern, the hull delamination and breaking of the topsides could have just as easily been behind the bulkhead, rather than in front of it.
    And imho (though now I'm just speculating, of course), the same boat, built in the same way and in the same conditions, would have been better off with much LESS bow flare.
    The whole boat might have stuffed deeper in the water, of course.
    With more green water over the deck, surely.
    But the load on the topsides created by the impact with the water could have dissipated much better and faster, if it weren't for the flared shape.
    And in turn, this could avoid such impressive structural damages.

    Talking of which, I'm not sure of how anyone can suggest that the repair is an easy and quick job without seeing the hull inside - which is what I would want to check carefully, and also behind the bulkhead, by the way.
    I guess it's always possible to find a yard willing to re-attach the deck, patch the topside (including the part gone AWOL), and call it a day.
    Better on anyone else's boat than on mine! :eek:
    Last edited: Jun 13, 2020
  3. PacBlue

    PacBlue Senior Member

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    Some History of the famous Riva:

    "In November 1962 the myth was born: it was named Aquarama. Since its presentation, at the third Milan International Boat Show, the Aquarama became the symbol of Riva par excellence, almost "a brand within the brand”. The prototype was the mythical Lipicar no. 1, the evolution of the Tritone. 8.02 meters in length, 2.62 meters wide, capable of sleeping up to eight people, two berths at the bow, two 185 hp Chris-Craft petrol engines, a speed of 73 km/h. "

    These were the next generation of his Tritone line which was done in the 50's, those also powered by Chris-Craft engines.
    But note the famous Christ-Craft wooden runabouts were built as early as 1927. It would be hard for any boat builder not to be influenced in part by them. Interesting to note that both Chris-Craft and Sea Ray were companies located and founded near Detroit that went on to become big Industry names from the same region, the manufacturing capability in that area was just unbelievable.

    My favorite Carlo Riva story was his relentless search for some engine related failures that were being built by Chrysler in the US and causing him warranty headaches. He personally went to the Chrysler engine factory and went down to the production line and witnessed the casting of the engine blocks were they had a manual process of using a sledge hammer to free the casting and this was causing a small fracture that was his warranty problem. He took the time to find the root cause when nobody else could, now that is a passionate and driven boatbuilder!

    As far as the Concave/Convex hull shape something does not seem right in your post. Here is a link to a Michael Peter's article on the topic with a reference to Sonny Levi as well, and the Concave sections disperse the load while the Convex sections create higher impacts:

    https://www.proboat.com/wp-content/uploads/2011/04/hispeedpowerboats126low.pdf

    If anything, those early Cigarette's had straight sections similar to their Formula 23 and Magnum origins.
  4. PacBlue

    PacBlue Senior Member

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    We do not have to have arguments on the topic my friend but open discussions usually arrive closer to the truth than not.

    The forward Bulkhead did its job correctly as the bow fell into the trough of a 3m sea, which means the "hole" left in that trough could have been up to 5m. Ultimately, the boat left on its own power and went to the Boat Yard and will play another day with that regional Carolina flare reinforced for a second life. They flare is a local design attribute for a good reason and while some are more extreme than others, it comes with the territory. The Buddy Davis boats were the first major boat builder to produce what was once only available to a custom project. It is part of Americana and here is a nice book on the topic:

    https://www.amazon.com/Carolina-Flare-Boatbuilding-Sportfishing-Heritage/dp/B0026OW6F0

    As far as cars go, the muscle car era was a fantastic time of large V8's with high horsepower in what were at the time unrefined production cars. That is the influence we experienced in the US.

    To compare Ferrari's to a US production builder is a usual but wayward response. Building 50 specialty cars when Ford is building 50 an hour is a far different animal meant to be enjoyed by the masses, not the elite. And when they wanted to , we all know what they really could do with a Ford GT and the history behind that program. But those are discussions meant for relaxing ocean view bars with drinks to go around for all :)
  5. mapism

    mapism Senior Member

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    Well spotted, J. I think that Liam simply swapped the terms, in his post.
    As I also did when I mentioned ..."more convex/flared" - my bad.
    Actually, calling a curve concave or convex is only a matter of viewpoint... :)
    But by logical extension of the naming commonly used for the bottom of a V boat also to the whole hull, the shape of highly flared topsides should be called concave, not convex.

    That said, you are also swapping the terms, in the conclusion of the sentence I quoted.
    It's in fact the convex bottom that disperses the load, while the concave concentrates it (as it happens in flared bows, when the whole hull gets stuffed in the water, up to the topsides).
    That's also mentioned in the article you quoted:
    "for softer running sections, we always draw convex sections forward"
    Whereas convex means the opposite of flared, just to avoid any further confusion.
  6. PacBlue

    PacBlue Senior Member

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    Let’s keep the discussion of convex/concave from the chine and below.

    Topsides (above the chine) introduces a complete new language with old fashioned Naval Architecture terms terms like flim or flam to describe bow flare.
  7. mapism

    mapism Senior Member

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    'salright, I'm not so interested in semantic, particularly in a language which ain't my own.
    My point is simply that as much as a concave bottom concentrates the load upon wave impact, the physic reasons are exactly the same which were at work against the flared bow of this boat, and eventually destroyed it.

    After all, just think of the most convex shape that you can find on a hull, i.e. the bulbous bow of displacement vessels.
    I'm not aware of any bulb bent, let alone broken, by a wave impact.
    Bent flared gunwales on the other hand, rare as they can be, are not totally unheard of - even in steel boats!