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  1. #1

    hang from concrete ceiling - angle question?

    Hi - quick question about hanging angles for a hammock.
    My hammock is about 2.8m long but the ceiling I can hang it from only has a space 3m apart.
    I can hang from 10M diameter anchor bolts in the ceiling but won't this put a lot of strain on the suspension line and the anchor bolts as the angle wil be very tight?
    I've uploaded a rough diagram here:


    There is a side wall that I might be able to use instead and then a ceiling anchor further away. I could very possibly extend the anchors to 3.8m apart but would prefer if they were closer.
    Last edited by Dr1Gonzo; 12-29-2013 at 12:16.

  2. #2
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    Welcome to HF.

    That straight down of an angle on the hammock suspension will create way too much sag to be comfortable.

    With anchoring points that close together and high up, I would use them to suspend a ridgepole (as used in the turtledog stands) and hang the hammock from the ridgepole. Ignoring dynamic loads, this will only put approximately half your weight on each anchor.

    Use anchors with a pullout rating providing an adequate safety margin and be sure they are correctly installed.

  3. #3
    Quote Originally Posted by gmcttr View Post
    Welcome to HF.

    That straight down of an angle on the hammock suspension will create way too much sag to be comfortable.

    With anchoring points that close together and high up, I would use them to suspend a ridgepole (as used in the turtledog stands) and hang the hammock from the ridgepole. Ignoring dynamic loads, this will only put approximately half your weight on each anchor.

    Use anchors with a pullout rating providing an adequate safety margin and be sure they are correctly installed.
    So, you mean just a cicular ridgepole without the triangular stand?
    How far below the ceiling should the ridgepole be?
    Floor to ceiling is about 3metres.
    Also,
    1/ how does the ridgepole reduce the load on the anchor points?
    2/ Isn't the angle on the suspension ropes the same as they are tied onto the ridgepole instead of the anchors?
    3/ If the ridgepole is 3metres long, then won't that make the sag the same as just hagning from the anchor bolts?
    Last edited by Dr1Gonzo; 12-29-2013 at 13:13.

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    Quote Originally Posted by dr1gonzo View Post
    so, you mean just a cicular ridgepole without the triangular stand?

    yes

    how far below the ceiling should the ridgepole be?

    about 5', you will need to experiment a bit.

    floor to ceiling is about 3metres.
    Also,
    1/ how does the ridgepole reduce the load on the anchor points?

    the angle changes the force, although in this case it is probably negligible. You can play with this simulator to see the effect the angle has on applied force.

    2/ isn't the angle on the suspension ropes the same as they are tied onto the ridgepole instead of the anchors?
    3/ if the ridgepole is 3metres long, then won't that make the sag the same as just hagning from the anchor bolts?

    the hammock won't hang as you have it drawn...see my sketch.
    Ceiling Suspension.png..........

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    Senior Member gargoyle's Avatar
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    Excellent description gmcttr!
    Ambulo tua ambulo.

  6. #6
    Thanks!
    So, what is the best length for the ridgepole if the hammock is 2.8m long?
    Presumably, the anchor bolts in the ceiling can be 3m apart but the ridgepole can be longer?

  7. #7
    Senior Member kayak karl's Avatar
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    make sure you use the right type of anchor bolts. most are for stress to be at right angle. check with concrete supply house for proper ones. i would not trust a lowes/hd employee for this.
    "Tenting is equivalent to a bum crawling into a cardboard box, hammocking is an art" KK

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    Quote Originally Posted by Dr1Gonzo View Post
    ...So, what is the best length for the ridgepole if the hammock is 2.8m long?...
    I'd use 3.25m-4m depending on how much room you need for the hammock suspension.

    ridgepole to ceiling suspension.png

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    Quote Originally Posted by kayak karl View Post
    make sure you use the right type of anchor bolts. most are for stress to be at right angle...
    Yep...it is the pull out rating you're looking for and not the sheer force rating.

  10. #10
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    If I were faced with mounting a support for a hammock in a concrete ceiling I would find out what type of concrete I had to work with, it's PSI rating, whether it was poured in place or precast. Armed with that information I'd find the nearest Hilti dealer to ask for the best anchor for my application. Fastening is what those guys do.

    I would also decline to hang from one anchor point. I would install unistrut and hang from a couple of unistrut channels anchored with multiple anchors. I would consider mounting 2 pieces of unistrut perpendicular to the direction of the hammock ridgeline with an eyebolt in the middle of each piece of unistrut.



    I know that's not concrete but I wanted to give you a visual of what unistrut looks like, and what the strut nut looks like and how you would install the eyebolt to it. Also I would purchase slotted strut to eliminate drilling holes thru the unistrut.



    Notice the square steel washer on the outside of the unistrut channel, I highly recommend them when dealing with heavy loads. I have had crews install tanks of fire suppression agent above ceiling in data centers and miles of heavy steel pipe using the Hilti HDI anchors, they do not fall out.

    Good luck. Use sound engineering judgement and plan for your supports to hold far more loads than you calculate.
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