5-1 ratio rule

[Treeaddict]

Do you all follow 5-1 ratio for rigging? How I understand it: the rope mbs or abs is 1000 lbs, you have a wll of 200 lbs. I think some people use the 10-1 (like for life safety) to rig with I’ve heard.

Regarding shock load rule of thumb as I understand it: a 100 lb limb dropped 1 ft will exert 300 lbs of force. Doubled just for the fact it’s dropped and then 100lbs for each foot dropped. Is this how you see it? Obviously this force can be lessened when it’s allowed to run and braked slowly.

Just trying to confirm if my approach/thinking is correct or needs modification. Thank you much!

 

[friedrich]

the lower your safety ratio the less cycles to failure. i‘ve used 1:1,5 safery factor but you will only get a couple of cycles and risk snapping your line. with my good ropes over high value targets i try my best to stay within 1:10. with my „burn lines“ and just for moving brush/convenience i work with a lower safety factor.

 

[Altissimus]

Five is a low number , Ten is kinda standard ... (for me anyways)

 

[Treeaddict]

Thanks for the advice! I’ll keep it closer to the 10’s. I don’t want to spend $400 on a new rope for a long time.
Searching rigging suppliers and material types I came across where one site was recommending a 3-1 ratio. Can’t remember the exact rope manufacturer though. Good way to sell more rope I suppose.

 

[SeanKroll]

Maple Leaf ropes sound to be economical, and some like them.

I've had the same bigger Stable Braids for a long time since they are rarely used.

 

[pete mctree]

I use 10 to 1 as a rule - your ropes last much longer as you get an increased cycles to failur.e. I buy 2 grades of rope theses days - 3 strand or something similar as burner ropes - usually have 14mm and 16mm kicking about. Then I have 16mm and 21mm double braid - expensive ropes that get looked after. So far the system is working

 

[CurSedVoyce]

Since I rig for my mini, about 8:1. But I will go 10:1 as needed. I try not to bugger my kit. No one rope for the job. Spread the love.

 

[theTreeSpyder]

i went about 10x, but then some manufactures report conservative or boastful than what test average at i think.
As a CYA, legal headroom in more established, conservative of long scope range; vs. other of more sale$ view company tilting table a bit?
.
Double Edged Sword: greater/safer swl ratio, is less elastic against Load.
In a softer impact, hang or lift not much significance.
But in more dynamic use can cause higher loading to all connected points as takes hit with less elasticity.
Classically is if have a 5k rope and a 10k.
500# Load enroaches more on 5k tensile strength; but is more elastic against the dynamic loading than the 10k.
>> to point of if take the 5k and put as pulley support on load to overhead 'drop-eye' pulley(functions as end to ground control
>> even like this reports more rigid against the 500# dynamics more than a single support leg of the 5k line w/o pulley on the Load.

Does wear harder cycles; and i think the more delicate elasticity is first to fade from rope.

 

[SeanKroll]

Double whip tackling increases the capacity of what you can rig with your rope to roughly double.

 

[Bart]

For hard snubbing the load, the tension spike is about 0.2 seconds long and is controlled largely by the rest of your set up besides the rope size. IIR the quantity of energy absorbed in the rope is on the smaller proportion size. FWIW