[C320-list] Backstay blocks... question for you engineering types

[Jon Vez]

Hi Tony,

Still a lurker here...the SWL for the ratchet is for the cam portion and is
more than enough to handle any load you can put on it. If it were anywhere
near the 300 lb breaking strength there is no way you would be able to
release it. I use the same SWL on the ratchet/cam for my jib furler on my
355.

-----Original Message-----
From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf
Of Tony Murphy
Sent: Monday, May 19, 2014 12:11 PM
To: C320-List at Catalina320.com
Subject: [C320-list] Backstay blocks... question for you engineering types

I'm working on pulling together the parts to assemble the backstay adjuster
as described on the C320 website.  Thanks to Jon Vez for the wonderful
writeup and illustrations.

I am wondering about one thing. the triple blocks that Jon described on the
starboard side all seem to be rated for a SWL of at least 1800 lbs.
Likewise, the single wire blocks (3 of them) are all rated for SWL of about
2000 lbs.  The 5/16" lines all seem to have well over 3000 avg tensile
strength.  However, when I'm looking for a single racketing block with cam
for the port side, all I seem to be able to find online are ones with a SWL
in the 300-600lb range (if I stick with the matching 57mm Harken carbo
blocks). I realize this block isn't absolutely necessary if you don't want
"coarse" adjustment as Jon mentioned in his writeup.

Am I missing something? Maybe I'm making it too complicated.  Does anyone
know the typical loads that will be placed on these components?  If I could
reduce the SWL requirement for the triple blocks, I could definitely shave
off a hundred or more of the total cost, but I'm afraid to do that without a
better working knowledge of what loads I should expect to see.

Tony Murphy
Bella Sol #886