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

[aronella at gmail.com]

I recently installed a four sheave adjuster; it tightens very well, but does not go back up when released. It has to be forced up (with a LOT of force by the boathook).  Any suggestions greatly appreciated.
Thanks,
Lou Spitz

Sent from my iPad

> On May 19, 2014, at 2:46 PM, Jon Vez <jonvez at comcast.net> wrote:
> 
> 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
>