Chainplates

Many owners have replaced the 6mm shroud U bolts with 8mm dia versions. Marinestore sell an even better A-bolt, which has a flange welded across the legs making it very strong – the web address for this part is http://marinestore.co.uk/page/mrst/PROD/u-bolts/PBBW-408518/. The flange also helps to ensure a good watertight seal as there is a large area on which to apply a bed of Sikkaflex.

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If you have a Corribee which has been built as a kit boat you may be less than happy with the way the bolts have been fitted. It is fairly easy to strengthen this part of the structure using stainless steel backing plates to spread the load over a wider area. The photo below shows the A bolts fitted through holes in the full length plate. The plate itself is bedded onto the underside of the deck with a generous layer of thickened epoxy resin (to ensure the load is spread evenly). Reinforcing straps are bonded to the hull side – these have been drilled pepper-pot fashion so the epoxy has a good mechanical bond.

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The strap has to pass through the bulkhead (one of the A-bolts actually straddles the bulkhead). The straps themselves will be covered with lining material eventually (probably polypropylene carpet material, which many owners have fitted in preference to the original foam-backed vinyl). Some finishing work is needed – the original ply backing pads had been glassed in so the whole area needs a good rub down followed by a coat of thin epoxy resin to smooth it out. The A-bolts also need trimming to length.

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Source: corribee.org

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4 Responses to “Chainplates”

  1. Simone Says:

    Hello everybody. I am Simone from Italy and I am the happy owner of a Corribee here in Tuscany. On my boat I have replaced the old U-bolt with new 8mm A-bolt. The overall looks very sturdy. I would like to know from any Corribee owner which rigging screw diameter (model) I should use with the new chainplates. The old ones seems too small and when I tried to screw it they slightly bend and I am afraid that under pression the two flange will deform and break. Do you have any suggestions? Many thanks from Italy.

  2. Charles Riley Says:

    Hi George,

    I have two of these fine boats – one is a fin keeler built in 1975, built and finished by Newbridge for the boatshow (its sail number 242 and is the one on the Newbridge brochure – see the website history section) and one is a bilge keeler from about 1980.

    I assume Newbridge wanted the boat show example to be as good as it could be and as intended – and here the chainplates are 6mm U bolts fastened through the deck only. In fact, they have been completely glassed over – Newbridge glassed the deck to hull join completely – so its difficult to tell if there is any form of backing spreading the U bolt loading. Im assuming there is – but during this boats refit over the next year, I will be grinding back to find out.
    The Bilge keeler is probably home finished – as the finished equipment count and quality is certainly much less than the boat show version (which had absolutely everything you can think of) – but on this version, there are also 6mm U bolts, this time backed with marine ply spreaders. The bilge keeler deck to hull join was obviously done before the U bolt chainplates were fitted as its not glassed over. However, on this version, the deck to hull join glassing is a bit thin – looks like a single layer of roving.

    I’m replacing the U Bolts with 8mm versions on the bilge keeler complete with 25mm wide stainless steel straps as per the article on this site. However, I remain concerned about the integrity of the deck to hull join on both boats – and am adding glassed in vertical straps in a number of places along the join for peace of mind on the bilge keeler. I have yet to decide what to do with the fin keeler.

    By the way, its nearly relevant as it involves the deck to hull join, but Ive stripped the old Iroko rubbing strake off the bilge keeler. It virtually fell off – it was only riveted on and there was virtually nothing left of the rivets. Useful to do this job as well – Robbins in Bristol have made me great replacements.

    Best,
    Charles
    “Dream On” and “Polly Anna”

  3. George Wallis Says:

    Hi,

    I’m wondering what the original chainplate fitting was for these boats? Was the default fitting a plate bonded through the deck only, or was there a strap bonded to the hull? In kit boats, was the fitting of the chainplates left to the discretion of the owner/builder? I’m looking at an example in which the chainplates are bonded through the deck only, and I’m trying to figure out whether this is the standard way of securing the shouds.

    GJW

    • scorribee Says:

      Before doing the work detailed above, my chainplates were exactly as Charles describes, ie a small ply backing pad, and glassed over after the U-bolts were fitted. The problem with the 6mm U bolts is that the depth of the thread results in a smaller core diameter – around 5mm. This is why so many owners have increased them to 8mm dia. If you are concerned with the hull/deck join then it makes sense to reinforce the join locally at each U bolt (and maybe at the stem and stern fixings as well). I would always use epoxy and woven glass cloth for this rather than polyester resin.

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