|Topic Review (Newest First)|
|08-19-2008 04:23 PM|
Originally Posted by sailingdog View Post
Point is is didnt break did it....
|08-19-2008 03:46 PM|
With the forces distributed properly across a harness, rather than on a make shift restraint, like a 1/2" wide hem of your shorts or the cuff of a cotton glove, you would be surprised at how much force and how violent a fall you can survive, provided the anchor points hold you. I’ve been out rock climbing and fallen 20-30' only to be caught up by my harness and gotten out of it with little more that some sore muscles and some bruising where the harness was.
Most harnesses will spread the force out over a fairly large area of your body. Be aware that some harness/PFD combinations are not meant for all people to use. The ones commonly found at West Marine, like their 4000 series aren't for use by people shorter than 5' 8" or so.
Originally Posted by Stillraining View Post
|08-19-2008 03:11 PM|
While water skiing this past June I slipped into my ski while sitting in on the gunnel..spun around and bailed off...The 1/2 hem of my nylon shorts hung up on the recessed cleat of my boat...so there I was face down in the water all 200 lbs of me and a ski and a wet vest...The shock load was only about 8" but three strong guys could not free it or finish ripping it without really putting a bind on my leg...it had to eventually be cut destroying my shorts...we wount talk about my pride...I still have a hint of whats left of the bruising to the inside of my thigh almost two months later..
Every once in a while I will jump out of one of my excavators with a cotton gloved hand getting hooked on the vandalism prevention package clips welded to the door frame...I look like and feel like a side of beef hanging in a locker..Hurts like heck and wrenches my whole body at arms length..
If I survived the forces necessary to break even the poorest made tether system out of 1" double/tube webbing I wont be in any shape to assist myself let alone any other and most likely will be dead.
I use to climb and teach climbing...Other then the actual harness we never bought any other gear we sewed all our own...including aid sturrips..The ebay one or home made ones will suit me and the ones I care for most in the world just fine.
|08-19-2008 11:31 AM|
|arbarnhart||I used to belong to the Small Boats forum on Yahoo, but was kicked out for having an opinion contrary to his self (Don Elliot runs the group with a tight fist). Ayway, he has a drawing of a DIY harness that is two ropes - one around the waist and oneover the shoulders like a long necklace. Both ropes have loops on both ends and all loops meet at the naval where they are clipped together then that clip is clipped with a quick release to a line on the boat. You would really need to know how to braid properly to make the loops, Knots could work but would be bulky with 4 loops.|
|08-19-2008 11:31 AM|
The other factor, stretch, will spread the decelleration over a longer time lowering the peak force.
Of course if you stretch to far, you might go half way over.
|08-19-2008 08:59 AM|
Originally Posted by montenido View Post
|08-19-2008 07:50 AM|
If you did a bit of research, you'd realize that the breaking strength of tethers and jacklines needs to be far higher than what you might expect. The momentary shock loads on a jackline can be very, very high. A person falling across the boat and getting stopped by the tether may generate upwards of 20 G's of force on the tether. If they weigh 180 lbs., which isn't all that heavy, that means the shock loading is 3600+ lbs. Then add in the mechanical advantage caused by pulling at a near-perpendicular angle to the jackline... and you've got some really serious forces involved.
Also, on a typical small sailboat, where the halyards are 3/8" polyester double braid, the breaking load of the line is about 4400 lbs. If tying a bowline only has at best 60% of the breaking strength of the line, you're now looking at 2600 lbs... Which isn't much more than 10:1 for a lot of the sailors I know—and that assumes the line is in perfect condition, without chafe or UV damage—not generally the case.
Also, consider that the shock loading caused by falling may be an order of magnitude more than what you actually weigh, the safety margins aren't all that large.
BTW, this is one reason I upgraded my halyards to spectra cored lines of the same diameter...to get a greater safety margin even with some wear and tear on the lines.
Originally Posted by montenido View Post
|08-19-2008 12:33 AM|
Alright, great thread, but I have to weigh in also. Yes, I am fairly new to sailing, but I am not new to using webbing, ropes and carabiners in lifesaving conditions. I also bought a pair of 40' jacklines on ebay. Very well stitched with good quality hardware and top-quality webbing. People, these materials are so strong that they will never feel your weight if/when you fall and are restrained by them. The 1" webbing is rated for well over 1000 lbs breaking strength. The same holds for well-tied knots in quality rope. When you go up the mast using your good condition halyard (tied with a bowline), it is so much stronger than the load that you are applying that the safety factor is probaly more than 10:1.
Check the knots and stitching of any sewn loops in any safety gear, no matter the brand name or the amount of $ spent. That is just prudent.
Keep up the great threads. I am learning so much from you all.
|08-19-2008 12:19 AM|
I find this thread funny.
On one end, there are people that will buy the best and sue if it fails.
On the other end, there are ones that hook it up and use it.
I lean more towards the latter. You hook a line up to pull your 20,000 lb sailboat upwind without worrying about it, so what’s the big deal about hooking a line to your body. Sure I’d test it, at the dock. Do a couple of falls, see how it feels. adjust the lengths.
I do admit, I’m an engineer, so I take this stuff for granted, but if you want to buy or build a tether, go for it. It’s better than not using one.
BTW: This is my next project, so let’s keep talking about it.
|08-18-2008 07:36 PM|
|Allanbc||I have been a caver for almost 30 years. I've made my own harnesses and gear and trusted my life to it many, many times. I have no problem with making my own jacklines and tethers. As already pointed out, just use the proper gear for attachments.|
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