Carbon Mast Down -Poor Build.

[Graham W]

According to my engineer husband, the failed shackle wasn’t a stamped one. He kept it because it was interesting! I don't know whether it was yard supplied or not as we bought the boat second hand.

That looks just like the shackles on my boat.  I think I got mine from Seascrew or Baseline Marine (probably the latter, who specialise in this sort of thing).  I’d be suspicious of cheap ones on Amazon or eBay and hopefully yours was a freak failure.  Do you know what gauge the shackle was?  Mine are 6mm.

I’ve had what looks like brown corrosion on the surface of more than one 316 fitting from Wichard.  To misquote from Startrek, it’s stainless Jim, but not as we know it.

[Llafurio]

... I’ve also alerted the yard to this thread so that they can respond.

Thank you, Graham W, that is very good of you. Anything vital on a sailing boat like a mast that fails catastrophically in less than catastrophic conditions is simply "not good enough" and needs to be rectified. There will be more masts out there of the same design and build as Paul's. I would put out a warning to them at this stage, do not trust your main mast without inspecting and reinforcing your mast top!!

As I had been the person who originally led SwB to using carbon masts for mizzen, gaff yard, and main mast, and as I have built my own carbon masts and spars since 2003, without ever having a fail, even in tough conditions, they are very welcome to ask my advice how to build better or remedy what's out there already.
Claus

[PYoung]

Last weekend, in a Drascombe Rally, in brisk but not unusual conditions, I saw a BR20 carbon mast fall. I attach a photo (Credit: Paul M.). Have a guess what likely caused it.

Or, better, what would have prevented it.

How would one check their mast for possible weakness? I own a 2011 BC23, was there a specific date when the masts were better engineered?

[Llafurio]

This particular problem probably does not apply to BCs. Only to cylindrical carbon masts with wooden end plugs.

[Richard Walkerley]

Just a little more evidence of problems with carbon masts...

Shortly after buying my BR20 I noticed splits in the carbon mast both at the top and bottom (see attached picture). Previously the boat had been over wintered in a large greenhouse so I guess the wooden plugs would have dried out so when I took her home and left her outside the plugs would have expanded as they adjusted to the ambient humidity thus causing the split.

As advised by SB I repaired the area with epoxy and fibre glass tape wound in a spiral around the mast.  That was 5 years ago and so far no further problems. More recently I have used an epoxy clear varnish to provide at least some UV protection.

[PYoung]

This particular problem probably does not apply to BCs. Only to cylindrical carbon masts with wooden end plugs.

Here is a photo of my BC23 mast. It looks a lot like what you describe above!

[Peter Cockerton]

Whitecaps

The issue being reported with the mast and fittings is relevant to the gaff rigged boats BR20 and BR17 with carbon fibre main masts, you probably do not recognise from the original image posted the top mast stainless steel fitting which secures the shrouds to the top of the mast and also a connection point for the jib luff wire. Your carbon fibre mast along with my BR20 Bermudan rigged BR20 does not have the end tube wooden bungs and the shroud, jib luff wire and forestay attachment points are riveted to the mast on the front and side of the mast. The open ends of the mast are sealed with some sort of synthetic composite material which will not expand with moisture changes.

So rest assured on this point at least and I’m sure all will become clear when an official report is posted on this forum with appropriate actions if required to prevent this potentially serious failure from happening again.

Peter C

[Matt Newland]

Dear All,
Sorry for the silence these last few days. We are in the middle of Southampton boat show prep and we have a new boat coming out there, so lots to do.

We are in touch with the owner about this issue. He recounts that winds were 15km/h gusting 20, so not severe. He bought the boat new from us 12 years ago.

As Claus says, the problem affects only gunter rigged carbon mast boats (ie boats with a "gaff" though it is technically a yard, or topmast). The issue is with the main mast, not the topmast.

We are doing our best to trace all owners of these with the following information:
The top of the mast, where the wooden end bung enters the carbon tube, is potentially prone to splitting. This could happen because of water ingress and bung swelling, and/or because of insufficient wound reinforcement on early masts at their ends.
The important thing is to check for any signs of splitting at both ends of the mast, but particularly the top.
Do NOT use your boat if you see any!
You are looking particularly for splits in the length wise direction of the mast - ie up and down.

The good news is that the repair is straightforward and relatively simple to effect. We are preparing a document to send out to any owners affected but they should not use their boat if there is any splitting in the mast ends. It is easy to repair now, but not if the whole mast comes down.

I am afraid we cannot say for certain when the additional reinforcing, that is now always specified, was first used. We had several suppliers of carbon in the early days and our record keeping was not up to it. The main thing is check, and take early action (CONTACT US) if you see any signs of splitting.

If you can see that your mast does not have any extra reinforcement, you should also get in touch with us and consider applying this as corrective action. The extra reinforcement looks like a slight swelling (about 1mm extra diameter), over the end 300mm or so of mast length. It often shows up in sunlight as having a different reflective pattern. If you do not have this, we advise wrapping the ends with glass fibre plain weave tape set in epoxy resin, but more details will be in the document, so don't hesitate to get in touch.

On another note, the carbon does get damaged by the sun, with age, and it is worth considering painting it (ideally with 2 pack Epifanes, International or similar yacht paint). Cream or white is a nice colour that keeps the temperature down in the sun.

We would like to apologise for any inconvenience this may cause owners, and once again, sorry for the late response.

Matt

[Llafurio]

The good news is that the repair is straightforward and relatively simple to effect. ...

I disagree. If it's a simple strengthening collar around the upper end of the mast, it won't do. Once the rim of the wooden mast top plug has already been softened and worn over the years, the old
plug can still be pulled down into the hollow mast, and wedge and burst that open, as described above by Ape Ears.
IMO an entirely new and modified mast top plug must be set in to surely prevent this.

I attach a photo from 2008. Notice it's teakwood to avoid swelling, the rim is wider than the mast diameter, and there is a longer stem inside the mast to reduce the prising open force on the mast profile end.

This photo was shared with SwB at the time.

C.

[Llafurio]

Since 2010 I am using an even better design for the masttop plug.
The shrouds are no longer attached to a mastband on the protruding end of the plug but are attached to the sides of the mast to a bolt through mast and internal stem of the masttop plug, and there is a sheave for the main halyard set into the mast riding on that bolt. The plug is again made of teakwood, and the rim is about 2 mm wider than the outer diameter of the carbon mast, for safety.