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Staying Tight With Your Fabricator

6mm plate test 101 2

Dean Gunson, Operations Manager at Circa, is showing off a test section of rolled aluminum plate.That is a 250mm (10″) radius on a 16mm (5/8″) thick chunk  of aluminum!

6mm plate test 102

The ability to handle heavy plate in this manner allows us to work in high factors of safety without giving up hull shape efficiency due to shape control limitations.

Why do you need such heavy plate? 99.9931416% of the time you don’t. But if you ever find yourself sitting on a reef, with the hull pounding on a sharp piece of rock, or working through knife-like glacier ice, extra heavy bottom plate will afford a degree of mental comfort not to mention extremely high factors of safety.


Posted by Steve Dashew  (January 29, 2013)




12 Responses to “Staying Tight With Your Fabricator”

  1. Matt Marsh Says:
    99.99Pi. Nice touch. And your point is quite valid- if the overall design of the boat is such that the extra weight isn’t going to seriously compromise performance, and if the boat will be used in conditions where the extra beef might save the day, “overkill” starts to look very logical and very reasonable.

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  2. Kent Says:
    I wonder how thick the hull plate is for that 200′ mine sweeper that has been stuck on a reef for a week now.

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    James Masters Reply:

    http://www.militarytimes.com/news/2013/01/dn-trapped-minesweeper-to-be-broken-up-012913. Errors: 1) The USS Guardian minesweeper had a fiberglass-over-wood hull. 2) The National Geospatial-Intelligence Agency digital nav-chart had the reef mispositioned by 8 miles. (A review found another error near Chile.) Results: 1) 1000sq-mtrs of reef-damage @$300/mtr = $300,000 fine to be paid to the Philippine-govt. (also happened to a Greenpeace-ship) 2) “The Navy has safely transferred approximately 15,000 gallons of diesel fuel, 671 gallons of lubricating oil, dry food stores, paints and solvents contained in storage lockers, and the personal effects left behind by the crew from the ship,” the Seventh Fleet said…. 3) Vessel lost; plus, the dismantling will take more than a month. In all, a HUGELY EXPENSIVE pair of errors. Appears to me the US Navy designers and crews would benefit, as we have, from the Dashew principles of “OVERbuilding for safety” and “NOT-relying solely on the charts”. Imagine the savings of taxpayer-dollars if the Navy used the Dashew books as training-manuals + onboard-references….

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    James Masters Reply:

    the reference for the fine: http://www.militarytimes.com/news/2013/01/ap-minesweeper-guardian-runs-aground-philippines-011713/

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    ray Reply:

    So you propose all metal minesweepers? Mine sweepers were traditionally wood for a very obvious reason – old style mines which are still out there, were less likely to be detonated when contacting a wooden hull. I wonder if the Dashews would agree that the Navy would benefit from reading their books…seems to me as a fan of this site and an owner of their texts that they attempt to bring some of the behavior and thought process that the naval forces have distilled over the last thousand years or so to the masses. I always try to recall that as a group the armed forces are operating tens of thousands of vessels with a crew that must turn over with some regularity and that they do a damned good job of it – We wouldn’t be able to do any of the boating we do without them – I am a little protective so yes – you did notice a tone.

    Steve Dashew Reply:

    Perhaps there are some folks in the SetSail community who can shed light on why minesweepers are the way they are. Non magnetic is a requirement, but also the ability to absorb explosive impact and be repaired easily are part of the equation.

  3. Daryl Lippincott Says:
    Pretty stout version of an “English Wheel”. Would love to see a short video of that machine and operator in action…

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  4. Daryl Lippincott Says:
    This looks like a pretty tight curve for this thick a plate of this alloy. A little more than half way from the camera to the left side of the plate it looks like there may be some break down of the grain structure.

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    Daryl Lippincott Reply:

    After looking at the larger picture more closely it appears just at the center of the plate on the large radius end. It would be interesting to cut this piece cross ways in several places to see if this manifests it’s self only on the edge of the plate or if there are structural issues in the middle of the plate.

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    Steve Dashew Reply:

    The outer edges of the plates where they are clamped are always thrown away. But, now that you have raised the question, we’ll do a little forensic analysis to verify.

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  5. Rod Manser Says:
    Me wonders about how extensive the x-rays are and if there is any penetrant die inspection on tight radii. This may be a thicker material that usual on the 64/83. Of course, this specimen is an extreme case compared to one of your serial production articles… and I doubt that there are any structural integrity issues on the 97′s gentle curves. Definitely we are not into Cyclone class CPB territory here…

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  6. David M. Says:
    All of the services would like to build higher levels of safety into systems but they must balance any added safety with costs pressures since many among our news media feel every DoD system is an extravagant waste of tax money despite the face our brave service men and women lives and the security of the nation rely on them but any over budget weapons system is chum in the water!

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