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

[aronella at gmail.com]

Oops! Just saw it on the Defender site....

Sent from my iPad

> On May 22, 2014, at 6:41 PM, Tony Murphy <tony at midwestphysics.com> wrote:
> 
> Lou,
> 
> I have not used one of the backstay adjuster’s you’re referring to (I believe you’re talking about the one made by CS Johnson… here… http://www.defender.com/product.jsp?path=-1%7C118%7C2358491%7C2358500&id=76471)
> 
> The notes say that there should be a 1.5:1 ratio between the backstay base width and car height.  But I believe it should say something along  the lines of “The car won’t release if it’s higher than 1.5 times the width of the base (distance between two backstay turnbuckles).
> 
> Because of this, I decided to go with the 3 Harken wire blocks… which Jon Vez indicated in his writeup.  I am modifying Jon’s installation a bit and will post comments in a couple weeks after I have it installed. 
> 
> Tony
> Bella Sol #886
> 
> 
>> On May 22, 2014, at 8:18 AM, aronella at gmail.com wrote:
>> 
>> 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
>