Hello Everyone,

I recently purchased a 2002 Nacra 570 from an owner in Maryland and had it trailered here to TX (1500 miles) a couple months ago. I used to sail and race Hobie 16's for several years during and after college, and I decided it was finally time to get a boat of my own. I remember how the occasional Nacra would show up to various regattas, and they would run circles around our Hobie's. We all said one day "we" would be "that Nacra," and I decided the time was right for me.

So I bought this beautiful Nacra 570, and I had the boat professionally inspected by our local Nacra dealer. They replaced the forestay, which was partially frayed, did some minor fiberglass work, and other updates on pins and shackles. I then took the boat out for a test sail on a local lake, and the boat sailed perfectly.

Next, we trailered the boat to Corpus Christi for the weekend, and we rigged the boat as usual and sailed for a couple hours. The wind was blowing a steady 15-20 knots, and we had a full crew of 3-4 adults. We were having a great time double trapped and flying a hull upwind, when all of a sudden we heard a "pop," and the next thing I saw was the mast buckling about a foot above the spreader, dropping two of my crew in the drink, and proceeded to shred the mainsail. We floated out in the middle of the bay for an hour (last time I sail without a radio in bigger water), and fortunately a fishing boat saw us and towed us back to shore.

So my questions are:
- What do you think caused this failure, and more importantly, what can I do to prevent it from happening again?
- Should I replace the mast with a new factory mast or find a good used option? I am not convinced the mast itself was defective, but rather something wrong with the spreader assembly or bolts. But I'll probably get a new mast anyway...
- What about fatigue from trailering the mast? A 30 ft mast flexes a lot only being supported in two places, especially over bumps. I'm thinking of adding an extra support arm on the trailer but not sure if it's necessary.

After getting the boat back to shore, it appeared that the aluminum spreader bolts (screwed into the spreader bars) that attach to the fore-side of the mast had bent down, then fractured at the “U” cutout—definitely a weak point in the design.What could have caused the spreader to bend down and stress those connections to that degree? I looked closely at pictures of the boat just be before we went out on the water, and the spreaders were straight and diamond wires looked taut—so I don’t think we bumped the spreaders or diamond wires while stepping the mast. There were no obvious signs of corrosion on any of the components, but you never know if micro-fractures could be there somewhere. In addition to replacing the mast, spreader assembly, and mainsail, I will likely have custom adjustment bolts machined out of stainless steel to replace the aluminum bolts that failed.

Is there anything wrong with the sailing conditions that the boat should not be able to handle? Wind 15-20 knots, chop 1-2 ft, fully loaded on double trapeze with ~650 lb total crew weight on the boat, sailing close hauled and partially flying a hull, main sheeted in tightly, moderate downhaul. I thought these boats were designed for this—and the weight was well within the hull rating. I sailed Hobie 16’s for many years, have pitchpoled and capsized many times, and have probably done most things wrong at one time or another—and never lost a mast like this. Of course the 16’s are built like tanks… The worst I had was a snapped forestay that probably needed to be replaced anyway—and no mast or sail damage.

Kind of a bummer to wreck the boat on the second sail, but at least it's winter so I have some time to repair it right. I'll be happy to post before and after pics if there is a way to do that on this site. Anyway, thanks for your input and ideas on this!

Doug

--
Doug
2002 Nacra 570
Austin, TX
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Sorry to hear about your experience. That is an unusual failure. That mast extrusion is used on all kinds of boats without a problem so it probably wasn't a problem with the design.

1. From your description it sounds like it was a problem with the diamond wires. Those masts are very long and thin so the diamond wires and spreader provides most of the stiffness. Either the diamonds were too loose or the spreader deformed to such a degree that allowed the mast to bend in half and snap. Most likely one of the pins worked its way out or broke and allowed the spreader to rotate downward. That is why we most of us tape the crap out of the ring dings on those things.

To prevent such a failure from happening you need to inspect your spreaders every few months to make sure they are in good shape (no cracks or bends), tape up the ring dings and make sure the diamond wires are tensioned and in good shape. Many people ignore this because they don't really play a big role in every day sailing, but as described above they are super important to keep your mast straight and intact (hobie 16s have a beefier mast that doesn't need the diamond wires.).

2. Find a good used mast, any Nacra mast will do as long as it has the right length (I think a 5.7 or 5.8 will work fine). If you need castings reuse the ones from your old mast.

3. It likely wasn't trailoring that would have caused the mast to break. There is no load on the mast during trailering and it can literally take millions and millions of oscillations under it's own weight without ever being damaged. I'm nearly 100% convinced your diamonds or spreader let you down. Now that you know, it will likely never happen to you again.

4. 650 lbs crew, double trapped, AND flying a hull is a LOT of stress on a boat. It can handle that much weight in terms of bouyance but was designed as a 2 up boat (450 lbs max). That is a lot of stress to ask of a pretty light catamaran (well under 400 lbs fully rigged). A fellow I know in Aus had his 5.8 out with 3 people, 2 on the trap and blowing 30. He destroyed the shroud and mast (pulled the chainplate right out of the hull). You may have been out in higher winds than you thought.

Hope this helps. That is a truly great boat, I'm sure when you get it back up and running it will serve you well.

D.

--
Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
--

Without having the actual parts to inspect closely,(looking for fatigue failure etc) one can only speculate.
It does sound like a failure of the spreader system followed by mast failure.
Let's get some things out of the way.
In my opinion, trailering with two supports is not harmful, the mast is made to flex. If it sits on "edge" while trailered, it will flex less than if on its side, but I have never heard of this causing failure. People have been trailering cats for 30+ years this way, with no real history of failure attributed to metal fatigue.
Did the mast have a "ding" where it failed? Any dent will weaken the structure. Sort of like you can very carefully balance on an empty beer can. Introduce even a small deformity, & the strength, actually ability to resist deformation, decreases substantially.
Having diamond wires to loose can cause failure. The mast is pretty bendy, the diamond wires create a truss, limiting the bend, ie stiffening the stick so to speak. If 1 wire were to break it could result in mast failure. I think many of the guys who ocean sail change them every 3 years or so, & always as soon as they buy a used boat. The cutout in the spreader bars is not a weak point. They were never intended to accept any lateral force on those little ends. The force should be one of compression, trying to shorten the bar. As long as the bars stay perpendicular to the diamond wire, that is the case.
Your post seems to indicate a failure of the spreaders. Stainless fittings won't solve the problem. It sounds like the spreaders were either compromised, possibly from a previous crash,(maybe the PO bent them badly,then bent them back,severely weakening them) or the spreader end moved.
A couple of years ago I was at the home of a gentleman in Malibu who used to build parts for Nacra, & had sailed/worked with Tom Rolland during his early years. He showed me a photo of them sea trialling the Nacra 36.
We were discussing diamond tension & prebend( he was showing me a carbon fibre mast with double diamonds that went with his 20' carbon hulls). He made the remark that it was suicide to affix the diamonds to the spreaders using the method shown in the early Nacra manuals,(a couple of wraps of seizing wire).
The diamonds make a very strong structure out of a flimsy stik, but, ONLY IF THEY DON'T MOVE. As soon as they move out of perpendicular,(either up or down the wire), the force wants to move them further out of plumb, & integrity of the mast is lost. He was adamant about wrapping tape, enough that you didn't need those plastic end caps, very tightly in a figure 8 round the spreader ends & diamond wires to prevent any movement on the wire. As he put it, "if you can slam your hand down on the spreader end, & move it, you risk losing the mast. all the seizing wire does is keep the wire from popping out of the slot."
The fact that the inboard slotted ends of your spreaders were damaged leads me to believe the far end moved, either up or down on the wire.
The force placed on the mast is a function of how much mass you have preventing the boat from flipping. You can go out in a blow with 1 person on the wire, the boat will flip before a structural limit is reached. Put enough weight on the upwind hull,(even with no one on the wire) & you can break it before it flips. You say 3-4 adults...2 on the wire, 2 more on the upwind hull?...that is a pretty large moment holding the boat down, especially if they were larder adults, with corresponding large forces absorbed by the mast.

New mast are $$$, I would try to find a used one, even a bare stick, & transfer your fittings. I have an '84 5.7. I don't trailer it, but it does have 2 dings & we sail the crap out of it. I have had a buddy,(180lb) & my wife,(120lb) on the wire, with myself,(170lb) sitting on the upwind hull, driving as hard as she would go in 20mph winds, with no ill effects. Your 650+ is quite a bit more stress.
I'm no expert in the legalities of boat certification, but I don't believe that the max weight a cat is certified for means that you can use all that weight to pull more power. I think it has more to do with one hull flooding & staying just above water with that weight on board.



Edited by Edchris177 on Dec 08, 2013 - 09:28 PM.

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--

Hahahaha. Great minds think alike. And apparently simultaneously...

--
Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
--

That many people and that much wind is asking for trouble. Insurance is a great thing to have on your boat.

Quote

Is there anything wrong with the sailing conditions that the boat should not be able to handle? Wind 15-20 knots, chop 1-2 ft, fully loaded on double trapeze with ~650 lb total crew weight on the boat, sailing close hauled and partially

YES - your boat is designed for under 400lbs of crew weigh (what is a hull rating? )

15-20 knots is full on stress on your boat, double trapped pushes your boat to the limits and you have increased those loads by over 50% with that crew weight

I am sorry for your bad fortune but not surprised at all

PS i have seen a mystere 31' mast break due to 3 adults pushing a boat to hard in 20 - 25

Some really good tips in here. It was most likely diamond-wire/spreader failure. Did you flip the boat at any point during your sail?

That much weight on the boat can definitely overload it, as others have said. It's actually that kind of weight that Hobie used to test their products with. I say used to as none of the major manufacturers (Hobie, Nacra, AHPC to a much lesser extent) build their high end fiberglass products in-house anymore and the lack of quality control on the finished products basically makes any stress testing almost moot. Some boats come out of the factory great, others not so much, all can be made like new with enough TLC. Anyway, outside of mast failure, ripping a chain plate out of the hull was the likely result.

You didn't say how much diamond wire tension you set that day...if you didn't measure it there was some negligence on your part. When we race in the ocean, we replace diamonds every 2 years (thanks for the reminder, ours are due), and when sailing in those conditions I never leave the beach with the diamonds set lower than 40 on the loos pro gauge. Typically we'll go to 42 on the water. That applies to both the Nacra 20 carbon stick and the Infusion aluminum mast, so it's likely valid for the 570 mast but I haven't sailed that boat (refer to your manual/dealer).

Another pro-tip is to put beads of epoxy on the diamond wires themselves to prevent out of column spreaders.

Good luck.



Edited by samc99us on Dec 09, 2013 - 07:12 AM.

Check the classified ads on this forum. There is n5.7 mast for sale for $300.

--
Adam Bartos
Nacra 5.0
SolCat 18 (sold)
Lake Zurich, IL
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there is a guy in Houston that has a lot of used mast, Teddy Page, 281-610-1246, owns a business called Jet Ski Houston, check with him, and also in Destin FL area, Mike, that has a ton of used boat parts



Edited by Robbie on Dec 10, 2013 - 09:10 AM.

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Robbo
Wave#1181
Capricorn#86
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I had a similar experience on my Nacra Inter-18. Tough way to learn. I am sorry you have had the same lesson. Your spreader wires were too loose. I purchased a new mast from nacra all set up for $1400 just so you have a data point. I did have lots of trouble with Nacra/Yellow Freight and the ground shipping. First mast arrived scrapped/dinged as some bonehead moved it with a hilo.

The boat can take it, trust me. we sail in big stuff out on Lake Michigan frequently. Rudder castings are the thing you should stock up on and a spare blade. If you ever fall asleep at the wheel while surfing in and a rudder slips back and locks down, the back explodes off them or the casting breaks when you hit the beach. The rudders can be repaired, the castings cannot.

Need to edit this years footage, but here are some favs...

http://www.youtube.com/wa…UUQTUPCUyVJ34L7ILTFNt8Kg
http://www.youtube.com/wa…UUQTUPCUyVJ34L7ILTFNt8Kg
http://www.youtube.com/wa…UUQTUPCUyVJ34L7ILTFNt8Kg

Some motivation to get you back in the saddle.

BTW I have 2 halves of an F-18 mast behind my garage waiting for a project... I'm thinking a beach couch of some kind.

-- Norm

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nacra inter-18
CNBP
--

Thank you everyone for your feedback on this situation. I definitely think it had to do with a spreader or diamond wire failure--I just wish it could have been a more detectable problem ahead of time (i.e., no visible frayed diamond wires, no bend in the spreaders, etc) before going out. The spreader fittings were tightly taped at the mast (good I suppose, but bad that couldn't directly inspect the attachment points). After the mast collapsed, the spreader was clearly bent downwards AND the lateral spreader had clearly slipped about 6 inches down on the diamond wires--I just don't know if that was part of the cause, or if it shifted as a result of the mast coming down. The pictures that were taken of the boat show the spreaders very horizontal as they should be. The diamond wires were physically taut, but I would guess 50+ lb based on how stiff they were--with my non-calibrated hands of course... How much is too much tension? I'm wondering if something could have shifted during trailering, but still "appear" to be ok?

Maybe the answer is more strict preventive maintenance on the spreaders and diamond wires. I can't attest to how heavily the boat was sailed over the last eleven years, since I am at least the 3rd owner. The forestay was the only obviously worn component on the boat with about 30% of the strands broken, so I had that replaced before this trip.

On the boat loading, I know it was a lot of weight. I specifically bought the 570 because I wanted a larger boat to take friends out, but also sail with a lot of power 2-up. I researched the ratings and recommendations, which according to the Nacra 570 manual states "minimum recommended capacity 2 persons, max recommended capacity 4 persons," and max weight 749 lb. I thought I was well within these limits, and the boat sailed great, even upwind. It was not bogging down like a 16 would. The buoyancy of this boat was awesome (and not even close to pitch poling!). Should I really think of this as a 2-up boat in higher wind?? She has so much power, the extra weight really helped us...

I used to love sailing in the Gulf surf on a Hobie 16, but this experience has left me worried about doing the same in this boat (especially the idea of the chain plates ripping out of the hull while rising over a swell...). I definitely sail hard, and want my boat to be able to take whatever comes our way. If you have any other suggestions to help beef up the boat and rigging, please share! Also, thanks for the suggestions on finding some used masts!

I will also post some before and after pics in an album later this week that might help confirm the root cause of this failure.

Thanks for all your help!
Doug

--
Doug
2002 Nacra 570
Austin, TX
--

I will add that I do think the boat was sailed pretty hard for part of it's prior life because it has foot straps bolted on the side of both hulls close to the stern...is this really necessary for a Nacra?? It also has a very worn sticker with racing flags on the mast, so it's probably seen it's way around a racecourse a few times...

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Doug
2002 Nacra 570
Austin, TX
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The foot straps are normal and just help the crew stay in position, especially if they were running a spinnaker. When I read your first post, my thought was that there was too much weight on the boat and most here have agreed. 4 full-size adults is fine for dinking around the bay in light winds, but when you start to lift the hull all that weight is transferred to the mast. With that weight and that wind, something was going to break. It was just a matter of time to see what was the weakest link. In your case it appears the spreader/diamond wire was. Nacras are great boats and have great floatation. The hulls can float a heck of a lot more weight than the rigging can handle. That's why you can drive them so much harder than the H16s.
I hope you can find another mast quickly and economically. I think the lesson here is to drive like an old man when you have more than 500 pounds on board, or just put the extra weight on the leeward hull. It'll be a wet ride for them, but just give them the jib sheet and tell them to pretend they are on an AC72.

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Rob V.
Panama City, FL
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I did verify this data and i am shocked to see this. - http://www.nacrasailing.c…18-f-18-i-20-manuals.pdf.

I am really shocked to see they say 4 people at 661lbs for an I-17

the only thing i can think makes any sense of this is they offer a 1 year warranty and if you break your boat on day 357 ... you have to buy a new boat

I still feel these boats are designed for 2 adults and anything over that (in med to heavy air) is asking for problems

Quote

minimum recommended capacity 2 persons, max recommended capacity 4 persons," and max weight 749 lb. I thought I was well within these limits,

I believe that the data are for best case conditions, and parts in new condition. When I fly my planes they have a certain rating for say normal utility, and then a much lower rating if you want to do aerobatics. There is also something called maneuvering speed, which is the speed you can put the max input into the controls and not damage things. I'm sure the same transfers to boating. When you are heavy, in higher winds, and flying a hull that is a lot of stress. Throw some gusts, roll, and pitch in there and you increase the stresses greatly when things try to change direction.

--
Craig
Windrider Rave Hydrofoil
Nacra 5.2 Restored and heavily modified
Nacra 5.2 (one under restoration)
Nacra 5.7
Nacra 5.8NA
SoCal
--

Maybe the answer is more strict preventive maintenance on the spreaders and diamond wires. I can't attest to how heavily the boat was sailed over the last eleven years, since I am at least the 3rd owner. The forestay was the only obviously worn component on the boat with about 30% of the strands broken, so I had that replaced before this trip.


Doug[/quote

That was a screaming indication that all of the standing rigging needs replacement. I wouldn't be concerned about buying a race boat either. I would argue that you worked that boat more on that trip than it ever could have been worked in 2-up race mode.



Edited by bacho on Dec 11, 2013 - 10:49 AM.

--
Greenville SC

Offering sails and other go fast parts for A-class catamarans

That was a screaming indication that all of the standing rigging needs replacement. I wouldn't be concerned about buying a race boat either. I would argue that you worked that boat more on that trip than it ever could have been worked in 2-up race mode.



Edited by bacho on Dec 11, 2013 - 10:49 AM.

--
Greenville SC

Offering sails and other go fast parts for A-class catamarans
--

I agree with Bacho. Whenever I buy a boat the first thing I do is replace all the standing rigging (unless it is brand spanking new). You just never know how much stress it's seen (or how old it is). If one wire is frayed and the others are the same vintage, chances are that there are things you aren't seeing in the other wires.

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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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I think you just plain over loaded the boat. Beach cat capacity ratings are generally a bit of a joke and probably more based on getting sales or maybe meeting some irrelevant coast guard regulation. I think Hobie lists the Hobie 16 as having something like 800LBS capacity - yea right! In any case, as someone already mentioned, your NACRA can probably handle 4 adults in a light breeze and calm water with no problem. Start to get to hull flying conditions with that much crew and you're going to be putting some serious strain on the platform and rig. I wouldn't be surprized if you just flat out exceeded the the tensile rating for the diamond wire - i.e., not a failure due to wear or corrosion but simply a failure due to overloading. You would be much better off sticking to two or at the most three adults on board when the wind pipes up.

Best of luck getting back on the water.

sm

nacradoug

Thank you everyone for your feedback on this situation. I definitely think it had to do with a spreader or diamond wire failure--I just wish it could have been a more detectable problem ahead of time (i.e., no visible frayed diamond wires, no bend in the spreaders, etc) before going out. The spreader fittings were tightly taped at the mast (good I suppose, but bad that couldn't directly inspect the attachment points). After the mast collapsed, the spreader was clearly bent downwards AND the lateral spreader had clearly slipped about 6 inches down on the diamond wires--I just don't know if that was part of the cause, or if it shifted as a result of the mast coming down. The pictures that were taken of the boat show the spreaders very horizontal as they should be. The diamond wires were physically taut, but I would guess 50+ lb based on how stiff they were--with my non-calibrated hands of course... How much is too much tension? I'm wondering if something could have shifted during trailering, but still "appear" to be ok?

Maybe the answer is more strict preventive maintenance on the spreaders and diamond wires. I can't attest to how heavily the boat was sailed over the last eleven years, since I am at least the 3rd owner. The forestay was the only obviously worn component on the boat with about 30% of the strands broken, so I had that replaced before this trip.

On the boat loading, I know it was a lot of weight. I specifically bought the 570 because I wanted a larger boat to take friends out, but also sail with a lot of power 2-up. I researched the ratings and recommendations, which according to the Nacra 570 manual states "minimum recommended capacity 2 persons, max recommended capacity 4 persons," and max weight 749 lb. I thought I was well within these limits, and the boat sailed great, even upwind. It was not bogging down like a 16 would. The buoyancy of this boat was awesome (and not even close to pitch poling!). Should I really think of this as a 2-up boat in higher wind?? She has so much power, the extra weight really helped us...

I used to love sailing in the Gulf surf on a Hobie 16, but this experience has left me worried about doing the same in this boat (especially the idea of the chain plates ripping out of the hull while rising over a swell...). I definitely sail hard, and want my boat to be able to take whatever comes our way. If you have any other suggestions to help beef up the boat and rigging, please share! Also, thanks for the suggestions on finding some used masts!

I will also post some before and after pics in an album later this week that might help confirm the root cause of this failure.

Thanks for all your help!
Doug

I doubt anything changed while trailering, but your thought that there was only 50 lbs of tension applied is hopefully horribly off base. You need a loos professional PT-1 gauge (model shown here: http://www.westmarine.com/webapp/wcs/stores/servlet/Product_11151_10001_15195_-1?ci_src=14110944&ci_sku=15195&cid=sc_googlepla&device=c&network=g&matchtype=&gclid=CIXD8Yi6q7sCFQ7xOgodFF4AVw#). Diamonds are 5/32" stainless cable and base is typically 600 lbs of tension. If you could apply tension at all by hand to the wire they were too loose for sailing in 10+ kts of breeze.

NACRA's are decent boats but they are more fragile than the Hobie 16/18 in some regards. Rudders will break on any of the major platforms if you mess up a beach launch, and sometimes without expectation after a few years of use. It's simply fatigue life, and why you see racers buying new boats every 2 years.

420 on my cat (mystere 5.5)

Quote

Diamonds are 5/32" stainless cable and base is typically 600 lbs of tension.

You really don't need a professional tension gauge for your diamonds. Just follow the instruction in the Nacra manual (very difficult to pinch to the mast 12" above the bottom connection and make sure they are in good repair. As long as they are tight they will pick up the required tension. Boats are expensive enough to maintain without adding more complexity to it.

D.

--
Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
--

racers and people who are trying to squeeze every last drop of speed out of boat will adjust diamond and shroud tension for crew weight, wind and wave variables every day along with jib halyard tension

even non racers can better isolate variables by having a gauge handy so you know shroud tension every time you rig

Lastly, the nacra manual that quoted those weights gave terribly vague directions on how much tension is needed - "Diamond wire
tension should be tight initially."

Quote

You really don't need a professional tension gauge for your diamonds.

Edited by MN3 on Dec 12, 2013 - 07:44 PM.

Does the 570 have a wing mast?

--
Greenville SC

Offering sails and other go fast parts for A-class catamarans
--

I was actually mistaking the 570 for the 580, the latter is a little closer to the F-18 Infusion I do believe. You will need to refer to dealer specifications on the mast as it's not available online; it honestly wouldn't surprise me if it was a wing mast, since they use the same section on the F18, F16 and were using it on the Nacra 17 before the switch to carbon masts.

The tension I quoted was for a F18 Infusion mast and comes with no warranty or liability. Smaller boats will use less tension.

The days of leaving the beach without a wrench are over my friend, we adjust the diamond wire tension between races when it is blowing over 12 kts; if you think that is crazy, many teams carry heavy air battens in their boom and do a main sail batten swap between races.

Wolfman

You really don't need a professional tension gauge for your diamonds. Just follow the instruction in the Nacra manual (very difficult to pinch to the mast 12" above the bottom connection and make sure they are in good repair. As long as they are tight they will pick up the required tension. Boats are expensive enough to maintain without adding more complexity to it.

D.

Yes you can use the book but a cheap gauge is really the way to go and a local cat sailor will probably have one you can borrow for a few minutes. They do make a big difference in performance But like the man said,, if you race you want to own your own

--
2007 Nacra F18 Infusion
www.fleet250.org
Facebook: Sandy Hook Bay Catamaran Club
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probably wouldn't be to hard to build your own device
just need a real one 1 time to calibrate it

At last, I have posted some before and after pics of the mast collapse incident. I also did an additional inspection of the boat and rigging, and I confirmed that the diamond wires and attachment points are still intact. Only the fore-side spreader bolts failed, leading to the mast collapse. The aft-side spreaders are still attached to the mast, but the mounting bracket is bent downwards. Here are some pics:

• Before the fateful sail (does anything look wrong with the rigging?):




• Dead mast


• Broken spreader bolt


• Remnants of spreader bolts still attached to mast




• Remnants of spreader bolt attachments shown bent downwards next to fracture


• Aft side of spreaders still attached to mast, but are bent downwards


• Diamond wires are still intact and neither attachment point has been compromised




What I find most interesting is that the end failure mode was the spreader adjustment bolt breaking—not the diamond wires, or mounting hardware, or shroud lines, or forestay…. Instead, a bolt that should only be loaded in compression, primarily from the diamond wires, is what actually failed, leading to the mast collapse (I believe this is the “pop” we heard before the mast started to buckle). I would have thought one of these other items would have failed—or pulled the shroud anchors out of the hulls. I still think these aluminum bolts are under-designed for heavier sailing, and I would have much rather had a shroud line snap or disconnect to save the mast and sail. I will probably have custom stainless steel bolts made for the new rigging on this next round.

On a better note, my insurance finally came through on my claim after 2 long months of debating and negotiating. Let’s just say not all insurance policies are created equal—especially for boats. I would strongly advise anyone who has insurance to carefully read the fine print and exclusions to make sure you are ok with the limitations. I got very lucky with my claim, but a lot of things aren’t covered. As we all know, sailboats are not cars, and sometimes crazy s@?! just happens.

Anyway, I’m looking forward to getting the boat repaired to “like new” condition. Please let me know if there are any good upgrades you think I should consider, since I’m getting a new mast, spreader, diamond wires, and mainsail (probably mylar).

Thanks for everyone’s tips and ideas!

--
Doug
2002 Nacra 570
Austin, TX
--

looks like corrosion was not the issue, just age and metal fatigue

if your wires were not set correctly, they could add lots of stress (anywhere) on the system leading to the metal fatigue

the rust at the base of your wires is an indicator you should closely inspect or replace then

the rigging tape MAY have hidden a small crack that MAY or maynot have been viable and should be removed from time to time for inspection (my tape has been on my mast for years .. .maybe today a good day to remove it and inspect)

this is an expensive post - Thank you for posting and sharing all the pics

Thanks for posting the photos and the results of your investigation! I can't really say anything was at fault with your setup, looks like a bit of bad luck and finding the weak point in a design. It is possible you had some dynamic loading on the spreaders that could cause that sort of failure, but really your diamond wires would have to be loose and the spreaders at an angle, none of that seems to be the case.

Be warned however that moving to stainless steel on these bolts will be very expensive; you don't want a weld at the eye between the bolt and the attachment prong, rather a one piece bolt/prong fitting. I'd guesstimate that a competent shop would charge you $500 for those bolts, but maybe it can be done for less by simply cutting a slot in a threaded rod. You also have corrosion issues to contend with (two different metals), and a minor weight penalty.

I can't say any of the rust in the photos would cause me worry. I replaced the diamond wires on my last N20 from a reputable rigging company and within 2 weeks that level of rust was apparent. It's also pretty common on the staymasters we all use on the race boats. Simply surface rust that has no real effect on structural integrity. I will say my latest rigging from Rick Bliss at New England Catamarans has held up much better.