Hayn stem ball vs z spars socket...

[Tim-JS]

Hi, any riggers out there who can comment on some local advice we received today in Grenada?

We want to change the diamonds and martingales on our lagoon 400 z spars mast.
The old fittings are z spars, but the local rigging company only have access to hayn hardware, and the hayn stem ball is bigger than the z spars socket fitting in the mast.

The local rigger says it's standard practice to "just grind the hayn stem ball" until it's small enough to sit in the z spars socket and everything will be fine, but it feels like it'll be impossible to get a perfect fit and we worry that if we try to do this, we'll introduce a risk of point loading within the stem ball / socket mating.

Is there anyone with rigging experience who can advise whether this would be an acceptable option ?

Thanks, Tim

 

[vyv_cox]

It sounds dodgy to me. I carried out a failure diagnosis on a stemball eye a few years ago. It had failed in fatigue due to excessive slackness in the forestay, resulting in the stem contacting the socket, loading it excessively. High friction between the ball and socket due to uneven grinding could result in the same failure.

 

[Tim-JS]

Hi Vyv, thanks for the speedy feedback.

Are you saying that the risk is that if we grind the ball badly (I think it's fair to say there's no chance of getting a perfect mating shape), it might sit so badly that the stem doesn't exit in the centre of the hole in the fitting, and because of this the stem touches one of the sides of the hole, causing excessive loading/wear on that point of the stem, which ultimately leads to failure?

If so, could we mitigate this risk by simply taking great care that the install has the stem exiting in the centre of the hole?
My thoughts being that if it starts off in the correct orientation, it's not going to move to an incorrect orientation later on?

Apologies for asking, but i forgot to mention that this only cropped up after we received the made up cables, and found that they dont fit correctly, and i can see a big arguement occurring if we have to have a conversation with them about rejecting what they've already made up for us.

Thanks again, Tim

 

[vyv_cox]

Hi Vyv, thanks for the speedy feedback.

Are you saying that the risk is that if we grind the ball badly (I think it's fair to say there's no chance of getting a perfect mating shape), it might sit so badly that the stem doesn't exit in the centre of the hole in the fitting, and because of this the stem touches one of the sides of the hole, causing excessive loading/wear on that point of the stem, which ultimately leads to failure?

If so, could we mitigate this risk by simply taking great care that the install has the stem exiting in the centre of the hole?
My thoughts being that if it starts off in the correct orientation, it's not going to move to an incorrect orientation later on?

Apologies for asking, but i forgot to mention that this only cropped up after we received the made up cables, and found that they dont fit correctly, and i can see a big arguement occurring if we have to have a conversation with them about rejecting what they've already made up for us.

Thanks again, Tim

Yes, if the ball was not perfectly aligned with the socket the stem would be off to one side. I could see the same happening if the ball was not perfectly round, plus it might lead to point loading which it is not designed for.

Is it not possible to replace the socket as well? When I replaced my shroud T-bars due to a known misalignment problem I replaced the sockets as well

 

[Tim-JS]

Hi, thanks again.

Replacing the sockets is certainly an option to explore, but we've already been surprised that the rigging company have had sourcing issues and the "pin to pin" replacement cables we asked for didn't actually include a replacement "pin" at the non swaged end when they arrived, meaning we have to either reject the order they delivered or re-use the non swaged stem balls from the old rig, so I expect either they'll be unable to source the sockets, or when they do, we'll find they won't fit.

After already removing the old rigging, we've currently got a mast with no diamonds and martingales fit, and the wives and kids are due to arrive for their holiday in less than 2 weeks...

Thanks again, Tim