Swain BS_36 Stability curve

Discussion in 'Stability' started by junk2lee, Mar 9, 2011.

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  1. welder/fitter
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    welder/fitter Senior Member

    Recap, or fanciful spin? Evan isn't a home-builder, he's a professional builder who has done much more fabrication, fitting & welding than Brent, of much higher quality, but, the aft quarter shows damage from an external source, so, more likely a design than construction fault. I'd suggest that the hull was dented more than "slightly, but I'd certainly agree that - without adequate framing - that is a weak spot(design fault). Interesting that the owner chose to repaint the hull black.
     
  2. junk2lee
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    junk2lee Junior Member

    no "routinely",no "if"...not many "boats".I get that far wiring up a plywood dinghy and just jigsaw it away.otherwise,ya gotta love matt+resin ...
     
  3. junk2lee
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    junk2lee Junior Member

    ...then Evan should know better than to change the plan,or ignore the designer's specific advice....How can it be a "design fault" when your "professional builder" didn't build to the designer's specific direction in this hull?
    and per your cross examination style per: "I'd suggest that the hull was dented more than "slightly,etc."...I think the jury can see through this.

    The whole "is this boat stable?" is pretty tenuous too.It's a pretty normal-looking cruising boat.There's one sailing off Chile right now,experimenting with sea anchors...but I didn't hear 'em mention that they lie in the bilges trying to keep her upright...
     
  4. troy2000
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    troy2000 Senior Member

    Let's see.... first you deny there's any damage, and claim its just an unfair hull due to poorly fitted panels.

    Then you admit there are dents, but shrug them off as though they're so trivial as to not be worth mentioning.

    Finally you get all wound up, and indignantly blame the builder for ignoring what the designer supposedly 'advised' him to do (as opposed to what he drew in the plans).

    Need I say that your credibility and objectivity are somewhat in doubt here?:)
     
  5. junk2lee
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    junk2lee Junior Member

    well,yes,Troy,it's obvious YOU do "need say it".

    as to "deny damage" that's from the owner's webpage that welder insisted I read aloud to his own befuddlement apparently.and now Evan's a "professional builder" allowed to take liberties with the plans?or is it"supposedly"?I am finding it awfully hard to strain to the logical whirlygigs here....
     
  6. welder/fitter
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    welder/fitter Senior Member

    I suppose I shouldn't expect more than this from someone with no experience in the construction of metal marine vessels; one who is obviously a follower of the swainie mantra. But you're defending the indefensible, whether you get that, or not.

    As many contributors to, & followers of, these threads do not know who Evan Shaler is, I offer a few posts from the oriamiboats site, in chronological order:

    http://groups.yahoo.com/group/origamiboats/message/131

    http://groups.yahoo.com/group/origamiboats/message/419

    http://groups.yahoo.com/group/origamiboats/message/913

    http://groups.yahoo.com/group/origamiboats/message/2207
    http://groups.yahoo.com/group/origamiboats/message/8905

    http://groups.yahoo.com/group/origamiboats/message/14188

    http://groups.yahoo.com/group/origamiboats/message/15568

    http://groups.yahoo.com/group/origamiboats/message/18591

    http://groups.yahoo.com/group/origamiboats/message/18908

    http://groups.yahoo.com/group/origamiboats/message/22401

    http://groups.yahoo.com/group/origamiboats/message/22413

    http://groups.yahoo.com/group/origamiboats/message/23020

    http://groups.yahoo.com/group/origamiboats/message/23074

    What one will find fascinating is that, prior to 2006, Brent encourages people to see Evan about having a hull constructed(post#913?). However, because one owner decided to buy a hull from Evan, rather than have Brent build one for him, Brent suddenly views Evan in a negative light.

    Am I suggesting that Evan is the perfect boatbuilder? No. he has built far more completely welded hull/deck units than Brent, and his welding & fitting is superior to Brent's. As well, Brent takes much credit for work done by Evan and denies Evan his due credit, such as the building of Winston Bushnell's NorthWest Passage boat & Winston's daughter's boat.

    Obviously, my question regarding the damage on Carl's hull has nothing to do with the stability discussion &, as I stated in that post, I didn't want to hijack the thread. I was concerned that raising the issue would give Brent & junk2lee the opportunity to take this thread further off topic, and my concerns are validated by the last several posts, many of them being my own. So, to Tad and other contributors who have done so much good work, here, I apologize most profusely. Once, again, I suggest that Jeff keeps that which he considers of value & tosses the rest. If junk2lee wants my answers to his silliness, he'll have to start another thread.
    Mike
     
    Last edited: May 22, 2011
  7. Jack Hickson
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    Jack Hickson New Member

    The backs of those keels have a 1/2 inch by 4 inch ( 12mm by 100mm) on edge, inside, from centerline to chine , supporting the trailing edges. That's a lot more transverse support than I see on Wileys boat. How thick and wide are the transverse supports you guys use? More than 100mm by 12mm?
    As this flatbar was obviously not adequate , the plans call for 3x3x1/2 inch angle, which is far stronger, connected to the aft end of the centerline tank and tank top, which is even stronger, and unlikely to go anywhere in a collision.
    The collision in the photos would have torn the bottom out of Wynand's plywood boat.
    I don't recall anyone advocating 10,000 lbs of chain.
    When someone makes the centerline of the hull totally useless as tankage, as you have advocated, then the tanks have to go somewhere else. The only " somewhere else" available, is higher up, drastically reducing stability, by several thousand ft lbs. Evan refuses to put the tankage on the centerline, leaving owners of his boats no option but to put the tanks much higher up in the hull, as was the case with MOM. This is typical of people who build and redesign boats, with almost zero cruising experience. Evan is a very meticulous and skilled metal worker. His knowledge of boats is absolutely minimal, and someone with so little boating experience, or comprehension, should never be allowed to make design decisions. .
    Wynand, the impact on Gringo has absolutely nothing to do with transverse frames, as only one or two would have been in the impact area, and their strength would have been tiny when opposing the momentum of a freighter. The deck ,being a steel plate on edge, appears to offer far more resistance, the bottom , slightly less, but far more than any transverse frames would. .
    No one claimed you could spend money so foolishly as to spend $500 to $700 on fixed ports, and still have a cheap boat. One can assume that other cost over runs were the result of such foolishness.
    In today's depressed boat market, assuming one can spend that way, and not lose a pile of money in the resale price, is totally wishful thinking. The only way to come out ahead is to keep the initial costs down.
     
  8. welder/fitter
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    welder/fitter Senior Member

    This is what I referred to. My eyes must be getting old, because I wondered about that enormous amount of chain. My apologies.
     
  9. pdwiley
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    pdwiley Senior Member

    Absolutely correct. Also totally irrelevant seeing as mine is a shoal draft full keel design so the chances of hitting anything on a close to vertical leading edge are zero.

    BTW the bottom plate of my keel is a 200x40 flat bar, the keel sides are 6mm plate and there are 200x6 full depth floors at every frame location.

    2 people with Witch hulls have documented doing pretty much exactly what happened to MOM. In both cases the damage was scraping paint off the keel.

    Brent, it looks like those keels *did* rotate and buckle the plate. I'm no expert but it's possible that this is a good thing in this case as one of the alternatives I can think of is tearing the keels *down* at their leading edges and rupturing the hull plate. That would be a lot worse.

    PDW
     
  10. troy2000
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    troy2000 Senior Member

    You're making no sense. I repeat: first you denied there was any damage, and insisted we were just looking at the equivalent of sloppy work in stitch and glue. Then you acknowledged it was damage because even Brent said so, but belittled it as trivial. Then you blamed the builder, and said the damage was the direct result of not following Brent's 'advice.' Make up your mind.

    As already mentioned, this really has nothing to do with the topic of the thread. But it's a clear window into your debating tactics.

    I do know that back when I was contracting or when I was a tract superintendent, an architect or engineer wouldn't have gotten half an inch with me by giving me 'advice' on how to change his approved plans. I'd have told him, "take responsibility for what you're saying. Hand me an additional or amended, signed and stamped drawing."
     
  11. Jack Hickson
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    Jack Hickson New Member

    There is very little chance of the leading edges tearing loose, all the impact is at the trailing edges. In any impacts I've seen, including hull speed impacts, the leading edges have never moved.
    Had the tank been there, and fully tied in to the angel supports, the trailing edges would have never moved. Scraping paint would have been the only damage.
     
  12. pdwiley
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    pdwiley Senior Member

    I can't agree that all the impact is at the trailing edges (unless you're running in reverse). The initial impact is at the leading edge, obviously. If the force vector is horizontal then the load will be taken equally by the keel to hull weld line and transferred to the web floors. We know this doesn't happen because of the plate buckling. The force is obviously being transferred backwards & upwards from the impact area. There has to be a pivot point about which this force is applied and there has to be a corresponding downward force on the leading edge unless the pivot point is the attachment point of the leading edge of the keel. It may be that the force vector is small enough that the structure is adequate to handle it, but it has to be there.

    Yes, quite possibly. Perhaps you can get Haiden to crash his hull into a rock so we can see if you're right....

    PDW

    PDW
     
  13. Jack Hickson
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    Jack Hickson New Member


    Haidan did crash his boat into a rock. No serious damage. No dents behind the keels. One with much lighter webs across the front (3/16th) than the back ( Half inch)hit rocks several times at hull speed, the back web bent but the front one never moved. That was before people started putting center line tanks in.
    Fiberglass boats with high aspect fin keels have major problems with the keel bing driven up at their trailing edges into the hull, in any impact. The leading edge never has this problem. The "C&C smile", a crack that regularly appears at this point is an example.
     
  14. Jack Hickson
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    Jack Hickson New Member

    What is being suggested here is that the Romans were wrong to make their bridges in the shape of arcs,and they would have been just as strong if they had piled the blocks horizontally, in a straight line.
    What is being suggested here is that propane tanks , submarine hulls , oxygen bottles, scuba tanks , etc gain little or no strength from their shape, and would have to be no more than 15% thicker if they were built square. Given how much space and convenience the designers of nuclear subs give up by making them round , it is being suggested that the designers of nuclear subs have it all wrong, by making them round.

    Back to stability.
    Super glue a doubloon to the bottom of a beach ball, then throw it in the water.
    AVS? 180 degrees. Center of Gravity ? Almost in the middle , very high, far above the waterline.
    This clearly demonstrates how deck shapes have far more effect on AVS than ballast ratio or VCG
     

  15. troy2000
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    troy2000 Senior Member

    OK, I'm lost. Spell it out for me. How does gluing a coin to the bottom of a beach ball demonstrate that "deck shapes have far more effect on AVS than ballast ration or VCG"? :confused: :confused: :confused:

    Seems to me it proves instead that ballast is more important than deck shape -- because a football would end up coin side down, also. So would a hemisphere with a perfectly flat deck. In fact, just about any inflatable this side of an air mattress would do the same thing, if you attached a weight to its bottom....
     
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