mast step JSO32

[roman74]

Good day to all! Faced with such a problem. Crack and corrosion of the mast base. Boat 2002. I have owned it for 6 months. According to the former owner, he did not pay attention to it. I recently made a crossing of about 500 miles. The crack has not changed. There is no such detail in the new Sparcraft catalog. I wrote to Sparcraft dealers, they told me that this part is not being produced. I wrote a letter to Sparcraft, they haven't responded yet. How to deal with this?

[roman74]

more photos

[Charlie-Bravo]

Just the one crack, or is there a matching one on the other side?

Still a lot of metal bolted to the deck, so I wouldn’t think the mast will walk. 

Keep pestering Sparcraft, they might have a slightly larger collar, perhaps not a perfect fit, but could be packed out.

To my mind the collar assists mast base location and is handy for attaching various blocks, once rigged, a mast base is surprisingly difficult to move even without a collar.

Did your surveyor not mention it?

CB

[roman74]

The crack is only on the right side. There is no crack on the left. But on the left there is a slight corrosion in the initial stage. I wonder if the corrosion itself is the cause of the crack. Corrosion products are very hard crystals. Can they, when formed, create such a stress upward leading to this crack. The base of the mast from below is free of defects. The rigging are covered.

[Charlie-Bravo]

I think the casting would be anodised , and the corrosion set in after the crack appeared, by exposure of non anodised material to about the most hostile of environments, corrosion can lead to stresses but more likely it is the result of the crack and not the cause.
Castings can have weaknesses, voids etc , and are generally brittle in nature , it might just have been a casting with a fault, or abused (dropped) at an earlier time,  and as you say, it doesn’t appear to be getting worse.

Perhaps live with it, flushing it and or a squirt of WD just to slow the corrosion, and think about a remedy when the mast needs to come down for other maintenance .
You could have the crack welded up, sand blasted and re anodised whilst the mast is down, should you want to.

CB

[mikebz]

Thanks for the heads up, I'll check mine (2003 SO32) next time I'm on board.  I wonder if this is the sort of thing which could be 3D printed fairly easily?

[roman74]

Thanks for the answers. I will think.

[rene460]

Hi Roman, That crack looks worrying at first sight, but I also think it is probably not very important. It looks like a bending failure of the casting, perhaps involving a casting weakness as already suggested, aided by corrosion on the underside due perhaps to damage to the anodising. Perhaps filing to make it sit better on the fibreglass for example. Corrosion products tend to expand as oxygen is taken into the metal structure, eventually bending the centre of the casting upwards until a crack appears. Then pitting of the crack becomes the main mechanism. Though attempts to explain are really conjecture without detailed examination. (Do I see a faint sign of the fibreglass cracking in one photo?)

As already mentioned, the mast base is mostly loaded in compression by the end of the mast extrusion and spreads the load over a larger area, so as not to damage the fibreglass. It also acts as described to keep the foot of the mast in place.

Even with that crack, the casting is quite securely bolted to the SS plate inside the cabin, so the remaining parts are quite securely anchored and I don’t see any reduction in ability to hold the mast foot in place or to spread the compression load. The block anchor points still appear sound, so I don’t see any big problem.

I would probably keep following up with the mast manufacturer, in the hope that a replacement suitable base can be obtained for eventual fitting when you need to lower the mast for other reasons.

In the mean time I would try and keep the area clean by flushing with fresh water followed by a squirt of some sort of corrosion inhibitor. WD 40 is a water displacer and tends to evaporate away so does not give a long protection. A corrosion resistant compound such as CRC or Innox or similar product might help slow any further corrosion (perhaps after WD to remove the wash water). The aim being to achieve a measure of piece of mind and minimise further corrosion.

The compression load under the thin metal of the mast extrusion is quite high, so any 3-D printed solution would require metal printing, not the normal plastic material. Even if the original part is no longer available, an alternative pattern suitable for the extrusion may be available, unless the extrusion itself has been discontinued. However it would not be too hard to manufacture a replacement out of aluminium by 3-D machining, which is reasonably well available these days.

In summary I tend to think the main requirement is to keep an eye on it until you get some resolution from the mast maker.

I hope that makes sense and is helpful.

Rene460