I have contacted several swivel sources to send me test samples. The
manufacturers have been fairly cooperative but the importers and
distributors have been less interested so I will probably not be able to
test every model.
I did get a chance to pull an $80 Anchorlift stainless swivel and a length
of ACCO and Campbell 3/8" HT (Grade 43 galvanized) over the weekend. The
Anchorlift swivel fits the Spade S140 well and is rated for a working load
of 12,500 pounds. We pulled it to the working load because I didn't want to
destroy it and it deformed only a little. Overall length before the test
was 3.782" and after it was 3.787". The pins were still straight. I hope
to get in at least 3 or 4 more swivels in the next week or so and will test
them when they get here. Anchorlift swivels are available he
http://www.rivermarinesupply.com/xca...r_Swivels.html
3/8" Grade 43 chain is rated 5,400 lb working load and 16,200 minimum
breaking strength. Both stress/strain curves were almost identical straight
lines to about 11,000 pounds then they yielded and eventually broke at
16,800 for the Campbell and 17,200 for the ACCO.
The interesting part was that there were 2 yield points and that the curve
was "almost straight.". The first yield point was at about 6,500 lb. We saw
a small blip and stopped to check if our mounting slipped. What had
happened was that the zinc between the links collapsed. After resuming the
test the line curved upwards. This was caused by the round links flattening
out against each other. I did not try to measure the links but I suspect
that the chain may have trouble fitting the notches in a chain wheel
smoothly before it reaches the actual yield point. Once past the yield
point you will need to buy new chain. However, if I were in a blow that put
10,000 pounds of load on my rode, retrieving the chain would be the last of
my worries. :-)
One interesting thing to note: While ACCO seems to be the recreational
marine standard, the Campbell Grade 43 hot dip galvanized is virtually the
same product. The ACCO galvanizing MAY be a little thicker but I could
measure no difference. Campbell chain is carried by many more industrial
supply houses than ACCO so it is easier to find locally without having to
pay truck shipping and it is usually 15 to 20% less expensive.
--
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
"Wayne.B" wrote in message
...
On Tue, 6 Dec 2005 17:23:24 -0500, "Skip Gundlach" skipgundlach at
gmail dotcom wrote:
So, has Glenn succeeded in destroying any of these to see about their
strength relative to the chain itself? I read of many boats surviving
hurricanes whose chains are so distorted they'll no longer fit in the
gypsy,
so I expect these swivels would cause serious deformation, or even
failure,
of the chain before breaking, themselves. It also seems that putting a
serious load on, and then inducing twist, would be needed to do a
"true-life" test...
=================================
I guess we'll have to wait and here from Glenn on the testing. The
European stainless steel unit that someone recommended cost around
$300 so it's not likely we'll see much "testing to destruction" on
that one. I'd have some concerns about mixing a stainless swivel with
galvanized chain and anchor in any case.
If the chain distorts but you and the boat survive the hurricane,
that's a small price to pay in my opinion. With 3/8 HT chain the
difference between SWL (no permanent distortion), and ultimate
breaking strength is about 10,000 lbs so it is easy to see how that
could happen.