How many layers to bullet proofness?

Discussion in 'Boat Design' started by ScottK, Feb 1, 2010.

  1. Obsession
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    Obsession Junior Member

    A ferro cement boat? Or what? I can't imagine your "sand" built boat being light enough to match the speed/characteristics of a planing boat like http://oceanmaster.net/articles/article-bullet-proof.htm ...
     
  2. Boston

    Boston Previous Member

    I just turned down a 'free" ferro cement boat

    um not sure if you read the thread but Im not the one looking for a bulletproof hull
    nor do I think there is much practical use for one
     
  3. gonzo
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    gonzo Senior Member

    The question is whether that particular boat is bullet proof or not. If you don't know, why do you post unrelated data?
     
  4. troy2000
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    troy2000 Senior Member

    OK, let's not be hijacking this thread to complain about hijackers...:p
     
  5. gonzo
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    gonzo Senior Member

    The boat manufacturer claims it stops a 9mm, but doesn't give the bullet type or the load. I believe it will stop a lead bullet with a standard load
     
  6. Marco1
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    Marco1 Senior Member

    It is true that 9mm is a bit vague. Commercial 9mm projectiles vary from 70gr to 150gr and propellant load has even more variations but they are all handguns and perhaps the biggest variable would be length of barrel and distance. If fired from 100 meters they can be stopped by a 200 pages book.

    It may be possible to build a "bullet proof" hull within reason and excluding solid copper projectiles from long barrel guns and it is possible to make it light enough to still be a normal boat, yet such can not be achieved by a solid mass of resin and fibres. It will have to be a series of thin layers of different materials that can give way a little and act as a shock absorber and do not present a solid front for the bullet to brake through. The idea is that the first layer will absorb part of the energy and brakes yet brakes without damaging the next layer that stays intact to repeat the process protected by a softer layer between the two. The more layers the more energy it can absorb and the thicker the part of the wall that stays in one piece to keep on sailing. Ideally a softer layer between the two allows for the two layers to slide over each other as they brake much the same way the leaf springs on a car.
    I have no idea why anyone would want to spend a truck load of cash to build such boat if at all possible but that is beside the point.
    A solid hull will probably withstand a rim fire .22, a 38 short and may even stop a 9mm of low weight, say not more than 115gr and with a standard load and from a short barrel. Anything more, will be a problem. Forget any rifle bigger than a 222, forget all magnum and even 45 ACP. A 223 would probably go in one side and out the other and keep on going a few hundred meters afterwards. A 308 may not even deviate from it's course providing it does not encounter a thick bottomed frying pan in its way.
     
  7. PsychicWarrior
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    PsychicWarrior Junior Member

    I am very intrigued by this subject as I am planning a 30 mtr Exploration yacht to go around the world. The hull design is one I have been pondering for a while.

    THe new space age materials are nice, light etc yet one bozo/pirate/rogue patrol office can sink you with one shot from a medium rifle? or AK47.. which makes me wonder.

    Would a Steel hull be better off ? I would think so.. but curious who knows what here.

    Thank you.
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    I'd be more worried about the crew stopping a bullet than a boat hull, a decent bilge pump will handle the hole in the hull, that would be the least of your worries coming under fire. And to the point about thickness of fibreglass laminate, the composition as regards reinforcment type and percentage of laminate is more relevant to ultimate strength. As for literal bullet proof boats, leave that to the military, it is outside of the scope of recreational boat design.
     
  9. PsychicWarrior
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    PsychicWarrior Junior Member

    Thx for your reply. Well, if the bullet penetrates the fuel tank, a bilge pump wont help you.

    The point is.. these things have to be designed to where some punk pirate with a gun can't stop the whole show.

    A steel hull would afford you that I would think yet thats heavy and slow. There must be some answers.
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    The best answer would have to be keep away from known trouble areas, carriage of weapons would likely be illegal in a lot of countries if going the armed defence route. It is pretty hard to see how you can prevent being boarded by people with criminal intent other than avoiding areas they are known to infest. Outgunning them seems impractical.
     
  11. PsychicWarrior
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    PsychicWarrior Junior Member

    Well, back to the original point.. as any punk with a gun and small motor boat shouldn't be a show stopper.
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    Any punk can shoot you driving down the road, but few people have bullet-proof cars, if yachties won't be deterred from entering waters known for piracy, they will just have to wear it if the worst happens.
     
  13. cthippo
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    cthippo Senior Member

    Here are the standards used by the US National Institutes of Justice, and is recognized as an international standard. These are performance standards rather than materials standards, but it's data.

    http://en.wikipedia.org/wiki/Ballistic_vest#Performance_standards

    Something else to remember is that most armored fighting vehicles are only proof up to 7.62 NATO ball (if that). Larger caliber rifle fire or armor piercing bullets will penetrate. Only Main Battle Tanks can really be considered "bulletproof".

    A Browning .50 AP round will punch through 1-2 inches of steel, and that's a lot of fiberglass :D
     
  14. srimes
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    srimes Senior Member

    sounds like you need a concrete sub.
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    Best bet would be a naval escort through pirate-infested waters, but they may want to stay at a discreet distance using your boat as "bait" to lure the bandits out of their lairs.
     
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