Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Rope ladder -- How to be able to cast it long distances?

  1. Dec 24, 2017 #1
    So here's a question for ya boyscouts"

    You know those rope ladders? the kind with the wooden dowels that are used as stairs? Well, my question is, how could a grappling hook be affixed to a rope ladder so that the hook and its rope are thrown, but when you go to pull on the rope connected to the hook the slack between the two are synched together so that the ladder climbs up to the top of the hook?

    This way, the hook can be thrown great distances, affix itself to a roof, and the rope ladder would be pulled to the top of the building?

    I'm having trouble conceptualizing how this would work, its not exactly intuitive, nor is it something I've thought about a great deal (much like how I was bogged when trying to solve a rubicks cube based on written instructions)

    Advice would be tremendously appreciated.
  2. jcsd
  3. Dec 24, 2017 #2


    Staff: Mentor

    Ancient mariners invented the solution to your query. They call it messenger lines.

    A messenger line is a very thin rope or a string. It can be thrown over a yardarm or it could have a grapple on the end an a pulley (mariners call it a block). I used to put a weight on the end to make it easier to throw, but a grapple hook is its own weight.

    The key points are a) The messenger line and/or hook are light enough to throw a long way. b) The messenger line must be doubled, so that it reaches from the ground to the top and down again. b) The messenger line is strong enough to lift the ladder, including any friction (reducing friction is where the block comes in.)

    Here's a picture of people using messenger lines.
  4. Dec 24, 2017 #3
    Not quite sure what you said about the messenger line needing to be long enough to go down, and back up again?

    I'm not quite sure how it could be done with a grappling hook. I Imagine a grappling hook tied to a rope ladder, the grappling hook goes onto the edge of a building, how does the ladder get hoisted up the rope?

    You mentioned a grapple with a pulley on the end -- I'm a little confused conceptually about how this would work
    Could someone please draw this out

    If I had some rope or string, it might be easier to visualize.

    Those are fantastic pictures
  5. Dec 24, 2017 #4


    User Avatar
    Science Advisor

    Up and back down again. Your grappling hook likely has an eye. Instead of tying the rope to the eye you tie one end to the top of the rope ladder and pass the other end through the eye. You slide the grappling hook halfway down the rope. So if you have a 60 foot rope, the grappling hook is 30 feet in. The grappling hook is now at one end of a 30 foot doubled rope. You hold onto the free end and toss the hook. When it catches and holds, you pull on the free end of the rope and the rope ladder is hoisted up. You now have to fasten the free end securely before you can climb the ladder.
  6. Dec 24, 2017 #5
    Like you I have a difficult time visualizing such a device in action.

    My suggestion is for you to purchase the different available models of rope ladders and hooks a lots of line and rope and heavy fishing weights. And experiment, see what you can make work.

    Also sports training would to develop the muscles and visual coordination you will need.

    If you are close to a harbor or boatyard, you might hire someone with experience to train you.

    I bet, even if too inland, you could find someone to teach you lariat or bolo?
  7. Dec 24, 2017 #6


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    etc. would make an excellent basis for achieving what's needed but . . .
    Sending what is effectively a loop of line through an eye on the grapple could be problematic unless the loop is kept from tangling - which would spoil the whole thing. One way to solve that problem would be to have the loop inside a light sleeve, to keep the two lengths together - side by side but not twisting or tangling together. When the grapple is firm, you pull back the sleeve and you have your loop of light line. You can use this to pull out a heavier loop which could support your weight.
    BTW Merry Christmas for tomorrow folks.
  8. Dec 25, 2017 #7


    Staff: Mentor

    In case anyone is interested, the rifle in the 3rd picture of post #2 is an M-14, apparently outfitted to fire blanks. When I was in Army basic training in '67, that's the weapon we used for marksmanship training. It was superseded by the M-16.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted