[C320-list] Check your stem fitting - near catastrophic failure to C320

[Graeme Clark]

Just to correct my own post!

The perspective of the picture I posted made me wrongly state there was a backing plate, I can now see that it is in fact looking at the entire broken cross-section of the vertical bar to which the forestay (headstay?) connects.

You can see a tiny rusty part, which someone with better engineering knowledge may confirm to be crevice corrosion -  almost certainly starting from a tiny pit where the  triangular gussets are welded in place? 

Still very tricky to spot and worth a good look at your own boat to check for a similar issue maybe?

Graeme

On 4 Aug 2015, at 13:12, Graeme Clark <cg at skyflyer.co.uk> wrote:

> The C320 that I used to share before buying my own, suffered a near catastrophic failure of the stem fitting that attaches the forestay to the bow, last week;
> 
> How they didn't lose the mast I don't know
> 
> The boat is  serial no 303 built in 1996
> 
> This link, pasted into your browser, will show the failure, the red arrow is the fractured surface
> http://tinypic.com/r/t8lwz9/8
> (by the way, the halyard you see is the jury-rig to keep the mast up!)
> 
> For interest you may wish to see the current design of replacement offered by CD
> http://www.catalinadirect.com/index.cfm/product/2573_699/stem-fitting-c-320-c-34-c-36.cfm
> 
> Note that CD state they have removed the unnecessary and non structural triangular gussets that are clearly visible on the part that failed.
> 
> But you will also note that there is a ‘backing plate’ joining those two gussets that is located close to and to the rear of the part that failed.
> 
> My guess is that a small defect or other stress concentration was present on the rear of the vertical bar and over the years repeated flexing has caused a fatigue crack to develop and propagate.
> 
> The point is that it is very difficult to see this area, and I think any crack would be very unlikely to be spotted with a routine cursory inspection.
> 
> I have no idea if there’s any history of these parts failing, but If so I was not aware of it.
> 
> I would strongly recommend a careful  inspection of your own boat to make sure that no crack is developing in the same area.
> 
> I hope the above description is clear, but if I have confused you, please ask away and I will try and  explain further
> 
> Regards
> 
> Graeme
> #366, Jaskar