Hey Dave,
Yes, many boats have experienced a failure of Harken block #308, especially when used as a 2:1 ratio first cascade on the backstay. I think our shock loading and static operating loading which is close the maximums for the block. I don't think we exceed, but maybe.
Anyway, I called a Harken rep on this, and the response was "Yea, that block has been a disappointment." He recommended either changing the loading or using a bigger block.
I changed the backstay configuration to one which replaced my first two 2:1 cascades with a single 4:1 cascade. This, of course, halve the operating and shock loading on the blocks in the first cascade. This was accomplished by making a double block out of two 308's and a big Ronstan non-captive pin shackle which had the width of the two 308's, a pin diameter which matched the 308 pin exactly, and a breaking strength of about 7000#. This double 308 block replaces the single which used to be attached to the fixed part of the backstay to turn the first cascade. It works great, and has not failed in 4 years of very hard racing (including a couple of SanFrancisco NOODs and a Santa Cruz Nats). I first saw a similar configuration on Olson 30 Wyewacket.
Hope this helps.
Regards,
Patrick Kershaw
s/v Surfer Girl
Seattle
-----Original Message-----
From: surfari [mailto:yhtlines@surfari.net]
Sent: Wednesday, June 30, 1999 10:19 PM
To: olson
Subject: backstay-Harken 308
While inspecting our backstay arrangement this weekend, it was noted that the Harken 308 wire block attached to the lower end of the backstay, (mwl 2000#, breaking 4000#) had what appear to be failed, or crushed bearings. (I haven't drilled it apart yet to see). There was no deformation of the case or bales(?).
Has anyone else had one of these begin to fail? Is there a recommended
replacement? Or are others considering this as a service item? Amazingly,
another boat, Eris carried a spare, which we happily appropriated. The Long
Beach West Marine had a number of these in stock, which makes me wonder...
thanks,
Dave Lampert
Received on Fri Jul 2 07:44:04 1999