I lost the mast on Upgrade [M/hd rig] in Dec 2009 due to a chain-plate V-bolt failure. This was traced to an inconsistency in the metal of one bolt - it sheared under the deck in a strong wind. The insurance insisted I beef up the deck under the chain-plates. I now have new 'knees' now in place [scroll down to see picture] - one each side [plus new chain-plates]. There have been various comments in these forums about concerns over GK24 chain-plates. I think the design is basically sound and if you are concerned about the quality of the bolts - get them tested. or get new ones made up. There are also small non-destructive testing kits that can test your bolts in-situ. Mine looked OK from below, but were compromised as it turned out.

Post edited by: john tyler, at: 2010/03/02 21:07

Post edited by: john tyler, at: 2010/03/09 18:53

Post edited by: john tyler, at: 2010/03/09 18:56

John and me are both at Poole YC so we have discussed this for sometime. I reckon his insurer was a bit over the top with the knees specially as the lowers can't be that tight as it inverts the mast on a masthead. I've bitten the bullet and changed the deck fittings to 6mm plate with 8mm uprights which when combined with the rigging strop to the bottom of the main bulkhead for the lowers beefs the whole area up. The bolts are separate from the fittings so they can be changed as will. I also increased them to M10 instead of the M8 threaded 'U' bolts. I have some CAD drawings if anybody wants.

Pic of Upgrades Knees.

CAD drg of the chainplates

Tried uploading file, they are TurboCAD or pdf, anybody got suggestions on how best to upload as they get rejected as is.

Post edited by: Chris Hawkes, at: 2010/03/08 22:38

Its been a while since I was on the GK24 site...



on Forethought (fractional rig) I decided that as the hull was dimpling and the chainplates were leaking as they pulled up from a cracking deck, I would insert new tie wires to the bulkhead -





They are described more in full here - http://www.hamble.demon.co.uk/gk_standing_rigging.html

Scroll down to the pictures

So far so good.... They have withstood all that the rest of the rig has taken for 5 years now. Now to deal with the rotting bulkhead.


Mike

Post edited by: mikejames, at: 2010/04/25 07:26

I did the internal rigging to the main bulkhead some years ago on Minx in a similar way to Leeway in the PBO article 1997? They work just nicely and you can watch the deck wind back down to its correct position. Of course its pretty useless if the 'U' bolt through the deck goes which it did on Upgrade. As I said early I think the insurer for Upgrade went OTT with the knees so I just got rid of the U bolts altogether. I was never particularly a fan of the longshroud fixing plates on the deck as the fractional that have now been proposed for M/Hd so hence my beefed up new deck fittings. Hopefully never to be an issue again!