Nyloc nots loosening?

[Glenn Ashmore]

Has anyone ever had any experience with or heard of a Nyloc nylon lined
nut backing off a bolt?

Here is the situation: I import a very good anchor called a Spade from
Tunisia. They come in two pieces a shank and a fluke which mate
together in a tapered socket that locks the shank in position when any
load is placed on it. When there is no load the two pieces are held
together with a 1/2" stainless bolt and stainless Nyloc nut tightened
snug to the sides of the socket. About 1" of bolt extends beyond the
nut. The nut is not torqued down because the shank must be loose enough
to slip forward into the taper to lock. All the load on the bolt is in
shear. There is no force in tension or torque. Overall it is a very
solid arangement.

Now the problem. A New Zealand sailor is claiming that his anchor
(which thankfully I did not sell) failed because the nut backed
completely off the bolt which allowed the bolt to fall out. There is
very little vibration and no torque on the bolt. The nut was in good
condition, new when installed and had never been removed. Is there any
way that a Nyloc nut in good condition could possibly make more than 20
turns on a loose bolt on its own?

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

 

[Rheilly Phoull]

Aren't the Nyloc nuts for a one time use. I know the similar type in
aircraft are that way. One solution would be to double nut it with a
standard nut and then a nyloc on top of it. Myself, I would drill the bolt
and use a cottor pin so the nut could not run off the end of the bolt.

Leanne
s/v Fundy

Sounds far fetched to me, probably someone having a go !!

 

[Peter W. Meek]

Has anyone ever had any experience with or heard of a Nyloc nylon lined
nut backing off a bolt?

Now the problem. A New Zealand sailor is claiming that his anchor
(which thankfully I did not sell) failed because the nut backed
completely off the bolt which allowed the bolt to fall out. There is
very little vibration and no torque on the bolt. The nut was in good
condition, new when installed and had never been removed. Is there any
way that a Nyloc nut in good condition could possibly make more than 20
turns on a loose bolt on its own?

Was the anchor set, or was the anchor in the boat?
If there was some sort of repetitive motion where
the shank continually rotated the bolt, it might
have backed the bolt out of the nut. Nylock (or
nylock type) nuts don't have a tremendous amount
of torque resistance -- just enough that they
don't turn easily. I can't quite turn one with
my fingers, but can turn them easily with any
kind of driver including a bare socket (no
drive). There is a reason why moused or safety-
wired pins are traditional in ground tackle.

 

[BruceM]

Her is my experience with a swivel on a mooring in Australia. (I realize
you're talking on an anchor)
I had a boat "head off" after the nut came off a 7/8" ground tackle swivel.
I must admit it wasn't brand new but what happened was that in the
manufacturing process, after assembly (screwing on the nut), it had been hit
with an arc welder to prevent it from coming unsrewed. There wasn't a lot of
weld on it.
Over some time the corrosion or electrolisis etc "ate" off the weld.
In Australia or anywhere else in the Southern Hemisphere, the weather cycles
almost without fail, always go in a anti-clockwise direction. You folk in
the Northern Hemisphere will notice that your weather will always go in a
clockwise direction??
I'll explain a little...........
After a North wind you will get a Westerly, then a Southerly. Before you get
your next Northerly you will get an Easterly. This is in the South.
The opposite is applicable in the North??

Now as you know.... most threads are clockwise? Guess what happens in the
Southern Hemisphere??
I honestly feel that this problen should be addressed with the utmost
urgency. There have been many examples of valuable fishing boats on a
mooring taking off with only half of the swivel hanging on the end of the
mooring rope.
If anyone doubts what I'm saying, I still have in my possession the two
halves of the swivell, as well as the almost complete net which I dived for
& recovered. I suspected sabotage as I had a check of the tackle only a few
weeks prior to this happening. If this is an insurance claim & it was on
ground tackle & it was in the Southern Hemisphere, Then I suggest the claim
be paid!!!

In summary, I bekieve that the manufacturer of these swivell's needs to
produce a run of "left hand threads" for the South.
Regards.... BruceM