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J Burns

On 11/2/14, 4:55 PM, wrote:
On Sun, 02 Nov 2014 16:16:36 -0500, J Burns
wrote:

On 11/2/14, 3:21 PM, Oren wrote:
On Sun, 02 Nov 2014 15:09:12 -0500, J Burns
wrote:

Seeing nylon stretch made me very nervous.

Flying steel cable makes me more nervous. Same as with tow chains.
Stuff breaks. Nylon strap is the best; if you happen to need a
"mountain winch". Both can kill you or upset your day.

I tried a nylon tow strap once. The tow required a fraction of the
strength listed on the package, but it broke immediately.

Energy is force times distance. The barrel of an M101 is 231cm. If
somebody were to shorten to barrel to 1cm, it wouldn't impart much
energy to the projectile.

One day the tractor sank to its axle, down in a gully. I got the 4WD
pickup and nylon rope. The rope was supposed to have a lot more
strength than the traction of the truck, but as it stretched and
stretched, I thought, "Uh-oh!"

It seemed like looking down the barrel of a loaded howitzer, or at a
slingshot. With enough stretching, perhaps the broken rope itself could
go fast enough to injure me or the tractor driver. If somehow it
carried the metal it was fastened to, that would cause destruction and
maybe death.

I got a chain and it worked like a charm. With no discernible
stretching, I knew there would be little slingshot effect. Besides,
applications with a lot of stretching put a lot of wear on a rope.
When wirking with a rope, throw a heavy blanket over it - or rie an
old tire in the middle. Not enough energy in the rope to move the tire
more than a few feet - or the blanket.

The empty 4WD pickup probably weighed 2 tons. There may have been a ton
or more on the rope, and it seemed to stretch a long way. If it was 50
feet and stretched 10%, that would be 5 feet. It seemed like a lot of
energy to me.

I think it was 1/2" nylon, with a minimum strength of 5670 pounds.
Ropes aren't required to spend 12 years sitting in classrooms, so a rope
may not know its breaking strength. I guess that's why the safe load
for 1/2" nylon is only 473 pounds.

In 1971 I worked on Alaskan purse seiners. Aft, on the starboard
gunwale was an L-shaped pipe weighing about 40 pounds. At a certain
point in making a set, it was supposed to be removed and laid on the
deck. The deckhand who did it had decades of experience, but once he
forgot. We saw the line catch it. A second later it was gone like a
shot. It splashed 100 yards away. I was glad it didn't hit the skiff
man. That showed me the awesome energy in stretched nylon.

After that, I served on a 900-ton ship. Depending on how the tide was
running, mooring at the pier could be a special challenge. One
technique was to come in fast and catch a bollard with the forward
spring line. The nylon would absorb the shock, swing the bow to the
pier, arrest the ship's motion, and start it backwards, where the aft
spring line could catch it. The energy in nylon was awesome, but if it
parted, the snapback could be fatal. I've just read that for that
reason, manila is preferred for mooring lines.