# Fall arrest systems



## Calidecks (Nov 19, 2011)

KennMacMoragh said:


> I use DBI-Sala harnesses with a DBI rope grab. A decent set cost about $500 for the harness, rope, lanyard, and anchor. If you get the cheap kind in a bucket, they will be uncomfortable and people won't want to use them. They are also hard to adjust around the legs, so if they are not right and you fall, you will be half the man you used to be.
> 
> What exactly are you building? Are you trying to tie off rolling joists for a deck?


I've got a 1000 s.f. deck I'm demoing that's about 15 feet up. I really like the idea of having a retractable, because removing old decking will go rather quickly, it doesn't make since to keep adjusting the slack as I'm moving back. The other issue is the retractables are, I believe designed to tie high. I have my eye on a tree, but OSHA wouldn't go for that. Lol However, I'm more concerned about the saftey then I am about OSHA. that huge tree isn't going nowhere.


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## KennMacMoragh (Sep 16, 2008)

Wouldn't you swing and smash against the tree? You can try attaching multiple anchors to the deck but the hard part when tying off on a floor is being in a position where you can't free fall more than 6 feet. Even with the retractable I can see it as being a problem when you're standing in the corner and the anchor is in the middle of the building. 

I don't know if harnesses will make you any more safe in that case. You might want to consider skipping the harnesses and using a safety monitoring system which is legal. Have an initial safety meeting with your guys, have 4x8 sheets of osb ready to flop down as soon as the decking comes up. Teach them to tack the sheets down, pound the nails out of the decking when they rip the boards up. If you're constantly talking about safety with your guys, it will keep them more alert. As soon as all the old decking is off you can spread the new decking on the joists and nail up a temporary rail pretty quick and you would be good to go.


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## Dan_Watson (Mar 1, 2008)

Guardian cyclone for the harnesses. I attached a set of bags right to it and its great. Almost like wearing a big set of bags with padded suspenders and belt.









Why not attach a 2x across some of the joists and just attach something like this - 

https://www.bigrocksupply.com/store/p/8750-FallTech-7414-Bolt-On-D-Ring-Anchor.aspx4

Or this - https://www.bigrocksupply.com/store...fety-1015-Moveable-ARS-2x12-Truss-Anchor.aspx

A speader bar only works on properly braced trusses and the other anchors need to be attached to sheathed lumber (according to all the systems I have looked at)


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## Calidecks (Nov 19, 2011)

Everyone I'm out of thanks, but I appreciate your advice


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## Tinstaafl (Jan 6, 2008)

All this fuss over 15'? Spread out a bunch of beanbag chairs on the ground. :laughing:

Kidding aside, they actually use a system like that over in ...Ireland, if I remember rightly. Someone posted pics of it here a few years ago.


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## Calidecks (Nov 19, 2011)

Isn't there a certain height that if you fall it's the same as jumping from an airplane? I heard it's 32'. We used to get these little saftey tips in our check, I think it said something to that effect. 

At what height do you reach maximum speed? Or do you constantly keep picking up speed infinitely?


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## Dan_Watson (Mar 1, 2008)

Californiadecks said:


> Isn't there a certain height that if you fall it's the same as jumping from an airplane? I heard it's 32'. We used to get these little saftey tips in our check, I think it said something to that effect.
> 
> At what height do you reach maximum speed? Or do you constantly keep picking up speed infinitely?


Wasnt there a movie about this? Mid 90's....

Terminal velocity.


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## Calidecks (Nov 19, 2011)

Dan_Watson said:


> Wasnt there a movie about this? Mid 90's....
> 
> Terminal velocity.


Where's all the super geniuses when we need them?


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## Dan_Watson (Mar 1, 2008)

The 32 your thinking of is probably 32' per second which is the acceleration of gravity. If I remember correctly the average person would have to fall just over 1000 feet before reaching the average speed of a skydiver in a prone freefall.


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## JR Shepstone (Jul 14, 2011)

Near the surface of the Earth, an object in free fall in a vacuum will accelerate at approximately 9.8 m/s², independent of its mass. With air resistance acting on an object that has been dropped, the object will eventually reach a terminal velocity, which is around 56 m/s (200 km/h or 120 mph) for a human body. The terminal velocity depends on many factors including mass, drag coefficient, and relative surface area and will only be achieved if the fall is from sufficient altitude. A typical skydiver in a spread-eagle position will reach terminal velocity after about 12 seconds, during which time he will have fallen around 450 m (approx 1,500 ft).[1]

-Wikipedia


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## CarpenterSFO (Dec 12, 2012)

Just a couple general thoughts (not necessarily directed at Mike or his situation):

1) You have to accept that in some situations safety will slow you down. Demolition generally, and demoing an old deck specifically - are those types of situations. It's a cost.

2) Once you've agreed that you're going to slow down, you can rethink how things can or should be done. Ladders, scaffolds, whatever. I'm reluctant to walk open joists any more - I'm older, my sense of balance isn't what it once was, and if I fall I'm going to take a beating, even if I catch myself going through. I don't mind walking around on the joists to get from point A to point B, but it's not a working platform for me any more. Well, you can roll joists from ladders, without fall protection. It's a little slower, but not that much, and once you get a system in place (helpers moving ladders around) it's pretty efficient.

I don't know if there's an alternate way to demo Mike's deck, other than doing it the traditional way (deck demo tool from above) tied off to some higher point, but it's a question to think about.


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## Calidecks (Nov 19, 2011)

Looks like I got my Thanks button back


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## KennMacMoragh (Sep 16, 2008)

Californiadecks said:


> Isn't there a certain height that if you fall it's the same as jumping from an airplane? I heard it's 32'. We used to get these little saftey tips in our check, I think it said something to that effect.
> 
> At what height do you reach maximum speed? Or do you constantly keep picking up speed infinitely?


You would only constantly pick up speed if you were in a vacuum. When you jump from a plane you keep picking up speed until the wind drag equals the force of gravity which is 9.8m/s^2. Terminal velocity is about 120 mph if you were in a position as if you were lying down. I don't know how long it takes to reach that speed though.


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## Inner10 (Mar 12, 2009)

KennMacMoragh said:


> You would only constantly pick up speed if you were in a vacuum. When you jump from a plane you keep picking up speed until the wind drag equals the force of gravity which is 9.8m/s^2. Terminal velocity is about 120 mph if you were in a position as if you were lying down. I don't know how long it takes to reach that speed though.


Terminal velocity relationship is asymptotic, you never truly reach 0 acceleration. Not to mention air density and body position would largely determine your speed of falling.

Either way it's not 15 Feet. :laughing:


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## KennMacMoragh (Sep 16, 2008)

Yeah I know, you can roll over and it will change


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## Chad McDade (Oct 14, 2012)

I think you would use sqrt(2gh) with h being the height fell and g being the gravitational acceleration of 32 feet a second per second. Using that formula if you fell 15 feet you would be traveling about 31 mph when you hit the ground.


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## Calidecks (Nov 19, 2011)

Chad McDade said:


> I think you would use sqrt(2gh) with h being the height fell and g being the gravitational acceleration of 32 feet a second per second. Using that formula if you fell 15 feet you would be traveling about 31 mph when you hit the ground.


Which is plenty to kill you


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## Chad McDade (Oct 14, 2012)

Californiadecks said:


> Which is plenty to kill you


Without a doubt.


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## Calidecks (Nov 19, 2011)

Californiadecks said:


> Isn't there a certain height that if you fall it's the same as jumping from an airplane? I heard it's 32'. We used to get these little saftey tips in our check, I think it said something to that effect.
> 
> At what height do you reach maximum speed? Or do you constantly keep picking up speed infinitely?





Inner10 said:


> Terminal velocity relationship is asymptotic, you never truly reach 0 acceleration. Not to mention air density and body position would largely determine your speed of falling.
> 
> Either way it's not 15 Feet. :laughing:


It was 32' that I was referring to when questioning terminal velocity. Not 15'


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## CarpenterSFO (Dec 12, 2012)

...


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## Inner10 (Mar 12, 2009)

Californiadecks said:


> It was 32' that I was referring to when questioning terminal velocity. Not 15'


Terminal velocity isn't static, and you never actually achieve it, it's all how your body catches the air. If you were wearing a chute you may be able to get real close in 32 feet....but not going ass over tea kettle off a deck holding a hammer.


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## Calidecks (Nov 19, 2011)

Inner10 said:


> Terminal velocity isn't static, and you never actually achieve it, it's all how your body catches the air. If you were wearing a chute you may be able to get real close in 32 feet....but not going ass over tea kettle off a deck holding a hammer.


Hence why it was a question because I didn't know


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## Calidecks (Nov 19, 2011)

Well guys, I hired a saftey guy just for this project. There's enough money in it to do this. I'm not going to guess at this chit. 

Thanks for all the help!


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