Chainplate bolt failure

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Chainplate bolt failure

Postby 151 » Tue May 20, 2008 7:57 pm

Whilst competing at Felpham last weekend the aft bolt on the port shroud chainplate failed. Fortunately the mast stayed in the right place! I cant say upright....another story! The bolt sheared at deck level and on removing the forward bolt that too sheared at deck level with little effort. It looks like both had been over tightened based on the dents in the fitting. I have a replacement plate comming from Ovi but the receiver under the gunwale now has 2 broken bolts hanging out of it. I can't find the part on the spares website. Has anyone any suggestions without destroying the threads. the pliers and turn trick did not work.
Russ
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Russ

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Re: Chainplate bolt failure

Postby Rick » Tue May 20, 2008 8:04 pm

I think the old shrouds used to go into a alloy cylinder, is that what you have?

The stainless & alloy used to react...

I think now the boats come with just big washers so it's an all stainless set up.

Have a look at a newer boat; if you are replacing I'd go for the new set up as it's all the same material.

Double check the above as I may be wrong ...

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Re: Chainplate bolt failure

Postby 151 » Tue May 20, 2008 8:11 pm

Yes, it is a black alloy tube that is so beautifully fused together a science teacher would be proud. I will check a newer boat at the club and take it from there.
Thanks
Russ

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Re: Chainplate bolt failure

Postby Rick » Tue May 20, 2008 8:49 pm

I'm pretty sure the current standard fitting is all stainless using large washers to spread the load.

Perhaps Ovis should do an upgrade notice to get rid of the ally cylinders because as a class we don't want a spate of rig failures bumping up our insurance.

I don't know if this is a real issue or if we may see more as older boats reach a certain age and the corrosion starts to cause the bolts to fail.

Perhapes Chris T or Paul can comment on this ...

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Re: Chainplate bolt failure

Postby Chris T » Wed May 21, 2008 8:21 am

Morning All,
I decided to drop the alloy bar under the gunwhale not long after I started at Ovi's.
The bolts used to be A2 stainless and tapped in to the solid bar, whilst the bar does spread the load and the bolts are originaly fitted using duralac as a seal, I had often seen the bolts snap due to the corrosion (on other boats)
All the other boats we fit out here simply have a penny washer bent to fit the underside of the gunwhale (apart from the 49er), I decided to do the same for the MPS and also upgrade to A4 stainless.
There should also be washers on top of the chainplate under the head of the bolts.
I do not think it is a great issue, I only know of one other failure in the three years I have been here, if a boat is well looked after and washed after use there should be no reason why they should not last.
These alloy bars are still used today on all the 49er's with failure being uncommon.

Chris.

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Re: Chainplate bolt failure

Postby 151 » Wed May 21, 2008 8:50 am

Chris,
from your description the fitting is in its original state as the duralac is still visible on the underside, would you recommend changining the other side to washers rather than the bar fitting at the same time?
Russ
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Re: Chainplate bolt failure

Postby Rick » Wed May 21, 2008 8:54 am

Chris T wrote:Morning All,
I decided to drop the alloy bar under the gunwhale not long after I started at Ovi's.
The bolts used to be A2 stainless and tapped in to the solid bar, whilst the bar does spread the load and the bolts are originaly fitted using duralac as a seal, I had often seen the bolts snap due to the corrosion (on other boats)
All the other boats we fit out here simply have a penny washer bent to fit the underside of the gunwhale (apart from the 49er), I decided to do the same for the MPS and also upgrade to A4 stainless.
There should also be washers on top of the chainplate under the head of the bolts.
I do not think it is a great issue, I only know of one other failure in the three years I have been here, if a boat is well looked after and washed after use there should be no reason why they should not last.
These alloy bars are still used today on all the 49er's with failure being uncommon.

Chris.


Thanks for the detail Chris, I guess if I had an old boat I would re-duralac the bolt each winter.

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Re: Chainplate bolt failure

Postby Chris T » Wed May 21, 2008 8:58 am

If I had a boat, I would change to the washers and do away with the potential issue.

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Re: Chainplate bolt failure

Postby Rick » Wed May 21, 2008 9:10 am

Chris T wrote:If I had a boat, I would change to the washers and do away with the potential issue.


Probably the best idea; can people buy a kit on-line to do that?

Should we put an article on the website explaining the issues detailed above and the recommended solution?

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Re: Chainplate bolt failure

Postby russ » Mon Jun 02, 2008 5:38 am

Rick wrote:Should we put an article on the website explaining the issues detailed above and the recommended solution?

Yes please. I am quite keen to make sure my rig doesn't fail in front of a container ship (being run over) or ferry (people pointing and laughing).
I'm 100% sure my boat has the old set up, sail number is 210, might be useful to publish where the changeover was.
Russ nzl210

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Re: Chainplate bolt failure

Postby Chris T » Tue Jun 03, 2008 2:55 pm

I am on the case, part number number available online shortly, I will post the link here.

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Re: Chainplate bolt failure

Postby griff_323 » Mon Jan 18, 2010 10:06 am

A slightly disturbing variation on this; I have the washer arrangement on my boat (#323) yet at the weekend one of the bolts sheared off (about mid way up the bolt) with no warning. Luckily it held on the other bolt so I was able to get home with the mast still up.

There are no obvious signs of any corrosion - I'm guessing it's just a defective bolt and there would have been nothing I could have done to see it coming.

- Griff.

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Re: Chainplate bolt failure

Postby Tom Offer » Mon Jan 18, 2010 2:26 pm

Hi Griff,

This happened to me last year and I think Ovi's have now upped the spec of the bolts. Paul Clements got some boffins at Rolls Royce where he works to take a look and they put it down to "dynamic loading"; the fact that the load on the rig is constantly fluctuating rather than the amount of load. I can't find the thread or mail trail now but someone else might have it and I think it may have been discussed at the natianals last year on one of the days that were blown off.

My boat was pretty new at the time and the rig tension had dropped after everything had bedded in a bit which may also have been a contributing factor to the range of laod being applied.

Re preventative action it's important to tighten but not overtighten and someone cleverer than might be able to tell you how to get the torque right although common sense will get you in the right ball park I'm sure. I checked all my other bolts afterwards and found that a couple were a bit too loose.

Cheers, Tom

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Re: Chainplate bolt failure

Postby paul manning » Fri Jan 22, 2010 10:46 am

Dear all

Just to clarify this, Ovington Boats have now changed the bolt spec. used on the chainplates.

If anyone wants to change, please drop them a line, and I'm sure they can provide you with some more.

Following the survey there are a few details like this, and once I've got the information sorted, we'll publish on the website.
Paul Manning
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Phone 0044 (0)7843 269353
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Re: Chainplate bolt failure

Postby Rick » Sun Jan 24, 2010 9:32 pm

paul manning wrote:Dear all

Just to clarify this, Ovington Boats have now changed the bolt spec. used on the chainplates.

If anyone wants to change, please drop them a line, and I'm sure they can provide you with some more.

Following the survey there are a few details like this, and once I've got the information sorted, we'll publish on the website.



Paul,

Please can we have a short article on this with the part numbers for the bolts we need to order ...


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