Colligo Titanium Tangs Fractured in Two Separate Dismasting Incidents

[svaletheia]

Both I and a friend have now had titanium mast tangs from Colligo Marine fracture in nearly identical manners as part of individual dismasting incidents.

It is our belief, though not legally proven (yet) that the fracture of these tangs represent a defect in design or material which caused or were a significant component relating to the cause of the dismasting. Both sets of tangs were recommended by the manufacturer as being suitable for the application in which they were installed, and installed under the instruction and inspection of well regarded professional riggers.

I have more detail on my blog if you are curious as to the specifics, rather than just cut and paste here.

http://oddasea.com/archives/142-A-bi...asting....html

In my correspondence, the manufacturer has disclaimed all liability or responsibility and won't even refund the rigging purchase. I will post his email reply if you wish, and over on SSCA you can see his official response and the email he sent me, if you're an SSCA member:

http://www.ssca.org/forum/viewtopic.php?f=4&t=16557

So, if you're considering or have already installed titanium mast tangs, especially from Colligo Marine, beware. Two boats have already lost their rigs where this part was the only noted significant failure subsequent to the dismasting. Pass it on to your friends.

[Brion Toss]

Hello,
First, would you tell us a bit more about the rig? On your site, the pictures show a junk-rigged ketch; has that changed? I'd just like a clear idea of what the rig looked like.
Next, everyone be sure to read John Franta's reply in the second link you posted.
Next, while you say that the tangs were the only significant failure in the dismasting, I would have to count the folded mast as significant, too...
Finally, what was the other boat's rig?
Fair leads,
Brion Toss

[knuterikt]

The junk rig give you a rather long section of unsupported mast..

Are you sure that your lamp post sections have (had) sufficient strength?

http://www.oddasea.com/archives/P3.html

tangs ?


Lamp posts

[svaletheia]

The junk rig is what I turned to after the ketch rig came crashing down 250 miles offshore. It is brand new and was designed by a naval architect. It is not under question and, as it is fully unstayed, has zero tangs or shrouds.

I'm on an iPad now and will respond in more detail when I return from this trip.

The original allied ketch rig was fully serviced before the dismasting and nearly everything was dismantled and all hardware was replaced. The mast crumpled after the tangs let go. I saw/heard that much. Spreaders were intact in the water.

The other boat was a sloop rig also fully serviced with new Colligo tangs.

[jfranta]

If anyone knows anything about any Colligo titanium bracket failures out in the field please let us know. This is the second forum posting that Daniel Collins has made that specifically stated another boat, besides his own, has had fractured Colligo brackets on it. Aside from Dan's boat, we have not heard of any other issues with these brackets. We are very concerned and would like to investigate this alleged incident but we contacted Dan and he refuses to give us any information on the boat mentioned, or its owner. Time could be of the essence here as these are critical components. If you have any information please email customerservice@colligomarine.com or call 480 703 3675.

John Franta, Colligo Mariine

[quote=svaletheia;6872]Both I and a friend have now had titanium mast tangs from Colligo Marine fracture in nearly identical manners as part of individual dismasting incidents.

[jfranta]

Originally Posted by svaletheia

Spreaders were intact in the water.

Dan, with all due respect, this is what I received from you by email on Dec 4.

"Hi John,

Looking underwater, which is where I got the best look at the situation after the reflex of "what just happened" - it appeared that the spreader I could see (the starboard one) was not bent or broken, and as best I could tell (which, sadly, is not for sure, with the ripple effect and the murkyness and the general motion of everything) it appeared that the masthead bent off to starboard pretty much sideways. That's what it looked like coming down and after the fact. But I can't say for sure if there was any fore-aft component to that as I was sitting well aft and in the water everything was all wonky.

I can tell you for sure the entire rig fell down nearly straight on the beam, it did not come down forwards nor aft but pretty much straight perpendicular to the centreline.

--
Daniel"

Again, based on the information you provided of the incident on your boat, including the brackets that we analyzed, there is no conclusive evidence that the brackets were the primary failure mode. In fact, considering the strain rate sensitivity of titanium, a rapid application of a high load, as would be present in a spreader buckling or breaking or possibly some other rig failure modes, would be more in line with the damage shown on the brackets presented. If you have any other information we would certainly like to see it.

We are sorry that our analysis does not concur with yours. Dismastings are difficult as usually most of the data goes overboard, not giving us many opportunities to learn from.

John Franta, Colligo Marine.

[Cayo Quemado]

The Allied Princess 36 would seem to have a transverse rigging load of about 12,000 lbs. I would hope to find 9/32" or even 5/16" wire lowers, but even 1/4" lowers will have a combined break of 15,000 lbs. Daniel says he was verbally assured that the tangs were "massively over-engineered". The e-mail that he posted as coming from John reads

"The first thing that we did was to pull test another set of brackets from the same lot as the brackets you sent. As you know, they tested to over 13,000 lbs break strength."

Does "set" mean a pair? If so they actually seem a bit light to me. Or I've simply misunderstood the issue.

Daniel also referred to taking pictures of the rig in the water before he "let it go". The only pictures I've seen are the broken plates themselves but I can't imagine much of anything would be visible of a mast trailing behind the boat, fouling the mizzen, pounding on the hull while wire cutters were employed in very difficult conditions where time is critical and leverage is difficult to find, plus the constant movement of wires and mast all whipping about in 2 meter seas. "Let it go" indeed.

[Jim Fulton]

I've been following this thread with interest, and have followed all of the links, but something remains unclear. From the account on the Odda Sea website (nice site, BTW):

"One of the first things I did was to pull on each of the shrouds to see if any had failed and to see if I could reposition the rig underwater to better see what had happened. Pulling on the lower starboard shrouds (the ones under tension on the upwind tack I had previously been on) revealed two cleanly fractured titanium tangs, the metal pieces which bolted the shrouds to the mast. ... I was able to reposition the rig underwater enough to see that the mast had folded in half at the spreaders, that the cap shrouds were definitely still attached all the way up, and that further recovery of the rig would be impossible by a single person. So after taking what photographs I could, I let the whole lot go."

When and how were you able to remove the parts of the broken tangs that were still attached to the mast? In my limited experience, removing rigging tangs is a non-trivial task, even when the mast is firmly supported on sawhorses on the hard. I can't imagine how you were able to retrieve the pieces under the conditions you describe.

Jim Fulton

[svaletheia]

Cayo,

See this thread: http://briontoss.com/spartalk/showthread.php?t=2094 for some discussion on my rigging notes, and consider it was the lower (not cap shroud) tang plate which broke, which under Toss's equations, if I read them right, puts a design load of 6648 lbs at 2.5 safety factor on the lowers, in total. This, with its attendant safety factor, is still about half of the breaking strength of Colligo's tangs, as advertised. Therefore I stand by the "massively overengineered" statement as John and I had discussed on the phone. Per the tested breaking strength of the tangs, they should have been massively overengineered and I don't fault John's math in his design work. Which is why I believe that the tangs had a defect in manufacturing or that the bend line, where they fractured, excessively weakens under day to day loading and that this was either not taken into account, or, to believe John that it was, that something in his manufacturing process causes it to be weaker over time than his calculations assumed.

Jim, the tangs fractured cleanly in half, as shown in the photographs. Thus retrieval was as simple as picking them up by the shrouds. I was not able to remove the parts left on the mast. I'm not sure how I gave the impression that I did from your pull quote, unless you are assuming that having two pieces means the tang was originally a single piece, which it was not - it was a double plate tang assembly.

John,

Precisely - the spreader was intact. Given that I could see the starboard spreader, and that under starboard tack upwind the port spreader had effectively no load on it, it is not conceivable that a catastrophic failure of the port spreader would be either possible nor contribute significantly to such an intense shock load as you speculate. So in fact my statements are consistent and continue to point to the fact that there was no observable cause or indication of shock loading from another failure, particularly the regions under high stress at the time which, particularly according to your suspicions, would include the spreader. I continue to respectfully disagree with you that some hypothetical catastrophic failure of another part, the evidence for which does not exist and supporting evidence against which does, caused such an intense shock loading on the lower shrouds as to fracture a titanium tang cleanly along an area which was not a weak spot and was in fact as you say engineered to be four times the strength of a weak spot - all without leaving any indication of stress on any of the six bolt holes which you state were the designed weak spots and you agreed on your own inspection show zero evidence of overloading. It just doesn't make sense.

The other boat, who has, according to my phone conversation, visible witness of the chain of events of their situation, will be contacting you independently and I will feature their story or encourage them to do so once they have had some time to recover from the shock and deal with their damaged boat. I do not wish to press them too hard at this time, but suffice it to say their story will be more conclusive than mine if our initial conversation is any indication. I'm sure you will hear from them in reasonably short order.