I would like to know if this has happened to any other 6.0 sailors? The particular failure that is of interest is the spreader bracket that is rivited to the mast. As can be seen in he photo attached, the tangs that are attached at the back of the mast are welded on the sailtrack side of the web. they are at an angle due to the shape of the mast, this creates a moment arm that combined with the force on the rear strut caused the sail track to collapse. this has the result of increased spreader sweep. increased sweep results in more force on the rear strut, and you get the rest.

The first time this happened the failure did not go catastrophic (sp) the sail track collapsed and I had trouble getting the sail down. I bent the mast back into shape and had an improved bracket made. never had any problem after that. The improved bracket is shown in the second attachment. The tangs were moved forward about 1cm to get them on the correct side of the web and the shape was changed to spread the bending load. Jack Young was made aware of the problem and these two solutions were given at the 2001 nationals. Jack's reply was that "it never happens"

Well, recently I had to replace my mast for other reasons. I took delivery of the mast at a regatta, and so was unable to install the modified bracket from the old mast. I was disapointed that I had to even think about changing a bracket on a brand new mast, but was ready to do so as soon as I had a chance. I was busy and forgot about the bracket and two weeks later was sailing in the Sail for Hope in Newport with 400lbs on the wire, lots of wind and the mast failed. It was very disappointing to know that a $15 part could have been changed and the failure most probably would not have happened. So what I would like to know is, Does this ever happen??

Here is a photo of the modified bracket. works great!

What kind of prebend / diamond wire tension were you running. It's hard to tell because the whole thing was probably twisted but in your first photo, it doesn't appear that the center tang (leading edge of mast) was centered on the mast.

Wow, what year mast is it?

Maybe you saw MY posts, about the 'inverting mast', on my 6.0na. It's a NA, but it was bought and sailed in #93, sail #111, I think it's #11 production model.

Anyway, my mast went, or inverted, and after taking the diamond wire tension off, it was about 18", when measuring from a straight line ene to end, to the greatest point of bend, bent forward, away form the sail track.

Some of my friends and I 'bent' it back, on some pylings at a parking area on the TX city Dike.

After I posted about this type of failure, many others posted about the same failure.

Well, I figured since it was trash anyway, wouldn't hurt to try and bend it back, which we did, then added more rake, and more diamond tension, and guess what?

Sails better, sail shape is better than ever!
Spin and all!

Never heard of this type of failure, maybe too MUCH spreader rake?

Jake,
The outer diamonds were set at about 35 on the loose gage, inners at about 10-15(just tight) The sweep was at about 1 1/4" if my memory serves me. I intentionally set the sweep on the low side when I set the mast up because I knew that I had to switch the bracket. I normally run about 1 3/8". unfortunately as the tangs bend in the sweep increases and all goes to hell. As I said this is not the first time this has happened to me, and I did point it out to Performance. Very disappointing. the mast was two weeks old and is not being warranteed!

Todd,
Brand new mast, two weeks old. 1 1/4" sweep. No bending this baby back, it is indeed trashed. Performance not going to warrantee. Spinnaker voids the warrantee. The failure was not due to spinnaker loads, but it was rigged.
Dave N6.0NA 322

Hi -
Prindle 19 owners may want to check the spreader configuation out because briefly looking at the photo it looks like my P-19 configuration.

Paul Nardone, Jr.

Thats enough to make me sick. And I'm not the one out $3000 either! I feel bad for you.

What does 35 on the loos gauge relate to in lbs? How much prebend was in the mast (displacement at the spreaders from a string running from mast tip to foot). I ask to hopefully avoid the same.

Thinking about the spreader rake, less rake (i.e. closer to straight out at 90 degrees from the mast) would apply more direct pressure to the luff groove as the loads increase. More rake would apply more of a local shear load to the mast and tang rivets and might be easier on the luff groove. I wonder if maybe having more spreader rake might have reduced the loading in that area? Just a wild thought.

Jake,
I do not have the conversion table with me. But rest assured that it is not an exesive amount of tension. he prebend was very slight, probably less than .5inches. The prebend is trivial when compared to the bend induced from downhaul and sheeting.
The problem is with the design of the bracket pure and simple. I suggest that you change yours to avoid any problems. I sailed with the modified bracket with no problems. it is a minor mod. you just have to find a stailess welder/fabricator. Or better yet complain to the factory. it is a desin flaw that should be changed. enough said. It is time to go ice boating!

I work for a machine manufacturer making machines mostly from stainless steel = fabrication easy!

Ice boating....Cooool! One of you guys are going to have to take me out on the hard water sometime.

Don't throw it out! Home builders can use the pieces for crossbeams. I know a guy trying to get a Inter 20 mast for his N6.0. If you don't want to try that too, maybe he will sell his old mast. Unfortunately, you live on opposite coasts.

TheoA,

The Nacra 6.0NA mast fully rigged is not $3,000...it's $895 according to Performance Cat's online 2001 pricing guide! Not too bad IMHO!



Crack,

I had some of my fellow engineers double check me and they agree that having less spreader rake actually significantly increased the compression force directly inward on the luff track of the mast. I hate to say it but this lack of rake likely caused more direct compression at the luff groove of the mast which led to the failure. The compression forces on the luff actually decrease greatly (up to a certain point) with additional sweep in the spreaders. I'll be glad to put together some drawings to further the discussion if you like.

What was the reason you had to replace the previous mast?

I had some very scary experiences with 6.0NA mast inversion that only happened occasionally but took me quite a while to figure out. I dropped out of one Down the Bay race because this was happening and I couldn't make it stop without slowing way down.

Once I discussed it with some really good sailors and they suggested looking for a couple of things I could suddenly see what was making it happen.

Scenario:

1. I ran very little spreader rake.

2. I ran a lot of diamond tension, about 850 lbs on the outers.

3. I had a 1994 sail #141.

4. My mast would start to pump and invert in meadium to heavy air and heavy chop headed upwind. Typically I had the main sheeted very hard, yet I hadn't started to apply downhaul past the power position.

5. The mast would start to pump, invert, and make some very scary noises as I crashed into waves. When it would pop through the spreaders in mid-inversion cycle the compression loads would have momentarily been much higher and could have contributed to the type of failure you describe.


Understanding and solving the problem.

It turned out that there were a couple of other factors involved.

1. That series sail forced you (me) to run the traveler car fairly far back even when sailing upwind in a decent breeze or the bottom of the sail would invert

2. It liked a really tight mainsheet.

3. What was happening was when the boat would slow down crashing into a wave, the momentum of the sail and rig itself would keep the rig going. The mast would rotate very briefly past 90 degrees (although it was very hard to notice if you weren't queued up to look for it). Once the mast goes past 90 degrees, with the main sheeted hard, you are actually pulling forward (from the mast's perspective) on the top of the mast with the highly loaded mainsheet. The top of the mast pulling forward would act as a lever with the shrouds and forstays attaching at the fulcrum, forcing the middle of the mast backwards, inverting the mast through the diamonds.

As the mast recoiled from the "bounce" induced by crashing the chop, it would swing back to a more appropriate orientation, all systems would return to pulling the "right" way on things and it would bounce back through the spreaders into it's normal pre-bend shape with a loud metallic "boing".

A complete cycle of normal to inverted back to normal would take less than a second and would normally only happen every 3 to 10 seconds depending on the sea state. Backing of the throttle would fix the problem but didn't help me understand the problem.

The answer is 2 fold:

1. Apply backside mast rotation control at the front beam to prevent the mast from over-rotating in these conditions.

2. Add a little more downhaul to give the mast more support down the back preventing inversion.

While I am not a 6.0 owner, the fact that they will not warranty a new mast because of a Spin is a serious situation that all owners, especially those with Spinakers should be fumeing about! Spinakers are in now and I imagine very few 6.0's don't use them. To not warranty a mast because it was rigged is a copout. You Dealer should also be pushing them hard to settle. Performance Cat surely doesn't need the bad press.

I sure won't buy a NACRA if they won't warranty the mast because of the spinaker being rigged. On the other hand I was out the day that CrackX mast broke, and it was some serious conditions. Enough that I was concerned on the our F31R. How much is a new Mast anyhow? Will your insurance cover it?

jdaf31r,

you are saying two different and conflicting things: A) performance should warantee the mast even though it was never designed to have a spinnaker (whether or not most of us have them) and B) the conditions led to the failure of the mast. Certainly you wouldn't hold Performance responsible for the failure considering the conditions that day - right? Who can rule out operator error? We assume a good deal of personal responsibility with how we tune and rig out boats. We also assume a lot of responsibility deciding to sail our boats in heavy weather.

At what modification stage should a manufacturer be responsible for failure? If you attach a nitrous bottle to your car engine and it dies (whether or not the nitrous was on at the time), should the manufacturer warrantee it? There has to be a line somewhere.

For the record, I have no affiliation with Performance other than owning one of their boats. However, I work for a machine manufacturer as a Customer Service Manager and deal graciously with warrantees all the time.

I think they SHOULD warrantee the mast. It's just like a similar situation. A buddy of mine is fighting with Ford as his new cobra motor with 4300 some miles on it grenaded. Ford says that he "drove it hard".... umm, or what the heck is it for then? Are you supposed to own an SVT (special vehicle team) car and drive it like someone in a crown vic?

Likewise, are you supposed to own a Racing cat and sail it like it was a sunfish? You buy something that is 2 years old and it fails...ok, perhaps it was worn out or went through to many stress cycles....you buy something that is 2 weeks old and it fails.... start asking questions....

The more I look into class rules, and stuff like dealers not taking care of customers, the more I just want to piece a taipan together and not even think about the non exsistant but make you feel warm and fuzzy warrantee

end of rant

First, I agree - it sucks that the two week old mast failed and if a similar situation was presented to me at work, I would certainly pony up a discount on a replacement. However, a warranty covers defective parts or designs. They do not cover using an item for other than what it was intended or for any failures relative to the user modifying that design or using it outside of the specifications.

In your buddy's Mustang Cobra incident (that sucks too!) he would have to find a way to prove that something in the engine was defective since Ford has already determined that it was something outside of their control. From Ford's perspective, perhaps they suspect that he constantly ran the engine 2000 rpm over red line - they do have data logs in the ECM to record such things. If that were the case do you still expect them to warranty the engine? We know nothing about that situation but I'm trying to show that as owners we have a certain responsibility to use our equipment as it were intended. It's so typically American to not want that responsibility after something breaks. I do agree with you that the Cobra is a car that should be driven hard – but it can be driven TOO hard. It certainly would be nice if Ford were a bit more detailed in their explanation (maybe we only got half of the story too).

Even ignoring that a spinnaker was rigged, I think it's pretty clear that the mast in question was not defective - the question on the table is whether or not the design of the spreader bracket is adequate. There are a LOT of Nacra 6.0s out there and I'm sure Performance would have enough data to determine if it's a design problem. While I don't have any raw data supporting it, I've never heard of this kind of failure unless it was associated with having less than the specified amount of spreader rake - which this case clearly had. Again, I think a discount on a replacement would be the right thing to do simply because the whole situation sucks...especially for CrackX. But I don't think anyone can show that the Performance Catamaran supplied parts were defective or the designs faulty.

Jamie Wrote:

The answer is 2 fold:

1. Apply backside mast rotation control at the front beam to prevent the mast from over-rotating in these conditions.

2. Add a little more downhaul to give the mast more support down the back preventing inversion.

Hi Jamie, we've met before, when I was over Forida's way for some regatta's so time ago.

I never analyzed the forces in my masts inversion, always chocked it up to alot of double trap, in conditions like you state, and alot of chute flying, metal fatigue, (my sail used alot was #111), etc.

Interesting your statement about the backside, or leeward rotation on to prevent over max rotations. The double trap scenario also acts as a rotary force, further overrotating the mast. As stated, I increased spreader rake, and wire tensions, after manually bending the bast back from inversion-(waht a chore that was!), and even with the chute, etc, sails great again.

I agree totally with your analysis, and measures to prevent it's occurrence. I now always use some degree of downhaul, even when it's light, and always keep the main sheeting tight with the chute up, using traveler if needed. I'll definitely be trying the leeward side rotation prevention as well.

Todd Bouton
N6.0na, +
#111

I thought it was necessary to clarify a few points.

The Nacra 6.0 was 'flying' the spinnaker when it flipped, not just rigged for one. The factory offered a new mast at a greatly reduced price (at the urging of the dealer - me) even though the mast was being used with a spinnaker. Dave commented to others on site that he was not using any downhaul while flying the spinnaker which is asking for problems. Did he let the mainsheet go to save them from going over which is a common mistake when someone has limited spinnaker experience, who knows? That often will cause a mast to snap. If he was using a Model 'A' Loos Gauge then 35 is only about 365 lbs and 15 is only about 150 lbs. which is way too little tension. His previous mast didn't fail while in use it was rolled into power lines and got zapped.

I agree with Jake's assessment about the spreader rake. I caused my mast track to squeeze slightly at the spreaders in the same race. Before the race I moved my spreader rake forward to 1 1/4" (same as Dave's) which I have never done before. I've always had it at factory specs. 1 3'4" and never had a problem. It was a windy, rough and wild race. I downhauled the daylights out of the sail like never before and the combination of that and too little spreader rake caused the mast to arc like a banana. I noticed the excessive downhaul too late. My fault, no one else's.

Te 6.0 mast hula was pretty much resolved several years ago. I haven't had it happen more than once or twice in recent years and only in extreme conditions. It used to happen all the time. Wide lower battens, move the jib cars outboard and most critical, don't bring the clew traveler car too far forward. As the wind would pick up I would usually move the traveler car way forward. I eventually realized the different angle of pull on the sail from the mainsheet system was inducing the hula. I found this out from experimenting in light conditions a few times with the car all the way forward and sheeting in hard.