Z Spar mast corrosion - how bad is it?

[PWS]

Hello

I am looking at a Dudley Dix Mini Cruise Mk2 which has a 10 year old Z Spar mast and boom. I have just been sent some photos by the owner, after we discussed the issue of corrosion/oxidisation of the mast below the forestay in two locations. I have never seen this before and it makes me feel its best to err on the side of caution.... I do not want the hassle or expense of having to consider a new mast if it is not possible to repair these problem areas, it would not be financially viable in any case. Any advice would be gratefully received.

Thank you.

[nuku34]

I'm not familiar with the model of boat you are looking at buying, but it looks like a trailer sailor with the mast down. That makes repairs easier and less costly. But I would be wondering what caused that corrosion; its pretty bad to actually have holes right through the mast. That looks like long-term corrosion...welding mast alloy (which is not the same as your stock alloy from the hardware store) is a special skill. I'd ask the seller to have it fixed professionally (and get the work documented) before buying. Or ask for a discount on the selling price.

[Sailmonkey]

I’ve seen corrosion like that. It comes from the mast cradles on the trailer with salty wet rags or other rag type padding creating a battery where the mast is in contact with the rags.


Looking closely at the halyard photo, I’d bet the knot on the halyard where all the white goo is fits perfectly into the hole.

I’m of the opinion that this isn’t really repairable on a smaller mast because the mast is so flexible.

[PWS]

Many thanks to nuku34 and Sailmonkey - your advice much appreciated.

[George_SD]

I have even older Z-spar mast and boom and none of it looks this bad. I would avoid as it's an expensive piece.

[PWS]

Thanks George for your reply and advice. I also have a Z Spar boom on my Rival 31 which is well over 10 years old and apart from the odd scratch is as good as the day it was put together, shows no signs of any corrosion. To give credit to Sparlight the maker of the existing mast on my yacht which is 50 years old next year, its made of a much thicker, stronger aluminium alloy and as we all know "they don't make them like that anymore....."

As Sailmonkey rightfully points out the damage is serious and could have been avoided easily if a little more preparation was given before the mast was stored away. It seems the first owner who was a boatbuilder lavished a great deal of care and attention on the build and fit out, so its sad to see this neglect take place.

I have been in touch with Z Spars technical department here in the UK and await their reply, I will post the content when I do receive it.

Fair winds and warm seas everyone!

[bil56]

on a pic, we see the traces of straps, mast stored tied with straps/ropes gorged with sea water... the disaster!

[Chotu]

Unless the corrosion has spread to a large area, does anyone else see how silly it is to be looking at a hole the size of the tip of your pinky finger when it is sitting right next to a planned hole 14 times larger?

[Jim Cate]

Originally Posted by Chotu

Unless the corrosion has spread to a large area, does anyone else see how silly it is to be looking at a hole the size of the tip of your pinky finger when it is sitting right next to a planned hole 14 times larger?

Exactly!

If those two holes are the only evidence of corrosion, I'd not be worrying about them. I'd likely clean them up to avoid stress risers on their peripheries and go sailing... and take better care of the mast whilst trailering!

Jim

[boatpoker]

Originally Posted by Jim Cate

Exactly!

If those two holes are the only evidence of corrosion, I'd not be worrying about them. I'd likely clean them up to avoid stress risers on their peripheries and go sailing... and take better care of the mast whilst trailering!

Jim

X-rays often show that corrosion has spread far beyond a visible hole.
This x-ray shows what lies below a single tiny pin hole in a stainless steel propeller shaft, the other photo is that shaft when it broke. The inside of the shaft looked like a Cadbury's Crunchy bar.

[Chotu]

Originally Posted by boatpoker

X-rays often show that corrosion has spread far beyond a visible hole.
This x-ray shows what lies below a single tiny pin hole in a stainless steel propeller shaft, the other photo is that shaft when it broke. The inside of the shaft looked like a Cadbury's Crunchy bar.

Yeah, but this thing is already eaten out on the inside. It’s hollow. It’s a mast. It’s not like a prop shaft. Things aren’t too hidden and can be whacked with a hammer to see if there are weak spots beyond the obvious hole. To see how far it spread.

[boatpoker]

Originally Posted by Chotu

Yeah, but this thing is already eaten out on the inside. It’s hollow. It’s a mast. It’s not like a prop shaft. Things aren’t too hidden and can be whacked with a hammer to see if there are weak spots beyond the obvious hole. To see how far it spread.

Forget the "hollow" it's irrelevant, You cannot see the inside of the aluminum without an x-ray. or maybe cutting a plug and a using a microscope on it. That is clearly not surface corrosion.

[Jim Cate]

Originally Posted by boatpoker

Forget the "hollow" it's irrelevant, You cannot see the inside of the aluminum without an x-ray. or maybe cutting a plug and a using a microscope on it. That is clearly not surface corrosion.

True, but are the mechanisms involved in the corrosion of the shaft and the mast not different? The metals surely are, the loads that are applied are different as well, leading to different failure modes to worry about. The shaft example is a red herring IMO and I'm kinda surprised that ypu, a professional, would use it.

If the conjecture about the origin of the holes (long term storage in contact with salt laden pads or ropes) is correct then poultice corrosion might well be a candidate for mechanism. If my non-expert understanding of that process is correct the effects are localized to the area under the "poultice" and would not tend to spread laterally through the mast wall without any surface indication of the spread.

Jim

[PWS]

Hello

I have heard back from Z Spars the maker of the mast and boom; they had their local agent inspect both, the mast was condemned outright as there was significant hidden corrosion within the mast, not just around the hole adjacent to the halyard slot but in several other areas, bit of an iceberg scenario where the full scale of the damage was not visible externally. The local riggers would not step the existing mast as a result of this assessment by Z Spars.

New mast cost from Z Spars is circa £6000.00 to include manufacture, all new standing rigging, stepping and tuning, electrical cabling only any ariels, lights or wind instrument fittings extra etc..

I will negotiate with the Seller and see where we go from here......

Thanks to everybody for your input and advice.

[boatpoker]

Originally Posted by Jim Cate

True, but are the mechanisms involved in the corrosion of the shaft and the mast not different? The metals surely are, the loads that are applied are different as well, leading to different failure modes to worry about. The shaft example is a red herring IMO and I'm kinda surprised that ypu, a professional, would use it.

If the conjecture about the origin of the holes (long term storage in contact with salt laden pads or ropes) is correct then poultice corrosion might well be a candidate for mechanism. If my non-expert understanding of that process is correct the effects are localized to the area under the "poultice" and would not tend to spread laterally through the mast wall without any surface indication of the spread.

Jim

OK, one more try... You cannot see inside the metal and have no idea how far that corrosion extends subsurface ... just like the ss.