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

[Tony Murphy]

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