Saw-resistant composite?

Discussion in 'Fiberglass and Composite Boat Building' started by Markusik, May 3, 2021 at 5:14 PM.

  1. Markusik
    Joined: Jun 2017
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    Markusik Junior Member

    Can anyone think of a lightweight way to increase a foam-cored fiberglass-epoxy composite’s resistance to a saw (circular, reciprocating, or chain)? Not looking to make it impossible to cut, just more difficult, time consuming, or blade-specific. I have an unfashionable interest in security. Thanks in advance.
     
  2. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    Eh, I read about this recently for bicycle locks. Technically it's foam core - it's just that it's aluminium foam with embedded ceramic spheres. But practically it can't be cut or drilled!

    Maybe you'll find better ways in the references to the accompanying paper.
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    Kevlar is devilishly difficult to cut, but if someone comes along with a diamond cutting disc, all bets are off.
     
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  4. DogCavalry
    Joined: Sep 2019
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    DogCavalry I aim to misbehave.

    Mr E beat me to it. Thick kevlar.
     
  5. comfisherman
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    comfisherman Junior Member

    Worked on a commercial fish boat that had stainless wire mesh in the laminate coating the fish hold liner. Not sure why.... all I know is it made me incredibly unhappy to cut out. Went through at least a hundred cutoff wheels.
     
  6. DogCavalry
    Joined: Sep 2019
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    DogCavalry I aim to misbehave.

    Actually, the way to do it is a combination of widely varying materials. The tool for cutting the steel wire is unsuitable for the kevlar and vice versa.
     
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  7. gonzo
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    gonzo Senior Member

    You need to get rid of the fiberglass and use different fibers. Whether the laminate will satisfy the structural requirements is another story. Look at the fibers used in cut-resistant gloves. They use a combination of Kevlar and stainless steel.
     
  8. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    After thinking this through awhile ago, the top of the transom is the only place I considered making uncuttable. All those components are buried under the laminate, but they become part of the structural core, and so I went away from it. The problem with the concept is a cordless recip can cut in anywhere around the perimeter of the mounting, so making it uncuttable would require the aramid and stainless covering the entire transom. Then a determined thief could still cut the hull, etc. And so the concept quickly became undesirable. And so, I ultimately decided against doing anything, but the top edge of the transom could fool a dumb thief. A heavy aramid plate on the inside and a stainless 1/2" thick top edge would be just as good, stop, slow, or confuse them and not involve the laminates.

    I was of a mind like Gonzo, but making it structural was just too painful to attempt.
     
  9. comfisherman
    Joined: Apr 2009
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    comfisherman Junior Member

    Concrete saw and some carbide blades..... had a friend who did fishing boat salvage. Would pickup an odd job here and there with him when young. I've cut 2 inch stainless shafts in minutes with one. A determined thief is going to get in.

    We pulled a 3412 out of a steel boat a few years back. Welder marked the area, I ground a thin line with a cordless grinder, he hit it with his mobile plasma. In about 15 minutes 2 guys in a pickup truck had a hole in a steel boat that's built to survive a life in the bearing sea big enough to pull a c32 cat out of. So no material is fool prof.
     
    Last edited: May 4, 2021 at 11:13 PM
  10. rxcomposite
    Joined: Jan 2005
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    rxcomposite Senior Member

    Kevlar loaded with carborondum powder.
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    I know that sand sprinkled on wet paint on wooden step treads gives a nice safe non-skid, but if you later go to sand it smooth, not easy !
     

  12. comfisherman
    Joined: Apr 2009
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    comfisherman Junior Member

    I have a pretty good relationship with an abrasives maker, we met at a trade show and he was a bit surprised how we used some of his stuff.....

    He sends me random stuff for feedback, I destroy or use it and write up some detailed thoughts. Last week he sent me thin cutoff wheels setup for a 7 1/4 saw. It was immediately stuffed on the end of a 10 amp angle grinder to see how it could hold up to some real abuse. My neighbor boat needed the top of the aluminum stack cutoff. It was 3/8 aluminum with a supporting lattice. It cut as fast or faster than a metal cutting tooth blade. Man size hole faster than you can down a cup of coffee.

    Volunteered to cut a keel cooler recess in a boat down the line in the yard. Thick solid glass close to 1 inch and it was through in alarmingly fast time, albeit the glass did erode the wheel fairly quick the project only needed one blade.


    Now I'd not reccomend strapping circular saw blades to angle grinders, it's very unsafe. But thief's dont have osha they just want results. The new thin high speed carbide blades could cut the transom off an aluminum or glass boat with a 9 ah battery and a cordless angle grinder fast....


    Security takes all kinds of forms, right now the tools trump the armor fairly substantially.
     
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