Losing Confidence

I'm beginning to lose confidence in the Mirage Drives again. This morning, while slowly cruising around 3 mph, no load, no surfing, no hard pace, the mirage drive started acting like it broke. I pulled it up and found the mast rod broke. If I had slammed into something, that I could understand, but this happened in deep water at an easy pace. How can this be? Is Hobie using an alloy instead of solid stainless steel? The steel looked rusted at the snap point.

All stainless is a alloy or more correctly a mixture of components mix it one way more strength its less resistent to rust and corrosion less strength more resistant, so more steel and less chromium = more strength and more rust and the opposite would be true as well.

In that pic it looked like it had that fracture there for some amount of time as those rust marks typically don't happen overnite.

On the topic of masts I'd like to see a graphite mast something that would allow some more flex so the big turbo fins can get alittle more shape to them or a even bigger set of fins, but graphite masts would definitely be a great way to get alittle more out of this system.

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Fastfish/Geoff
Kayaks Owned>Outback/Mine & Revolution/Wife

That first photo seems to show a weld at the point of failure? Looks odd.

How old is the mast?

Stainless is just that... Stains "Less", but as described by Fastfish it is a combination of materials to get the strength, but not be to the point of being brittle... less stain, but not soft and bendable.

Material for masts is a high grade... PH 17-4.

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Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

I agree with Matt. It looks like the mast was damaged at some point and welded. Did you buy the boat used?

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Southwest Hobie Island Club
http://www.facebook.com/southwesthic

I am not an expert but I have sent a lot of broken stuff to the materials lab for failure analysis during my career. The dull part pf the mast was cracked prior to the ultimate failure. The crack surfaces rub against each other which is why they are dull. The shiney part is the only part of the mast that was carrying the load just prior to failure.

Without great expense, there is no way to tell what caused the crack to start in the first place. My bet is Stress Corrosion Cracking which frequently starts at some surface imperfection. It could be a manufaturing flaw but it also could be a tool mark (where pliars used to install the mast?).

The good news is that this did not occur quickly and the crack should be readily visible. I just looked at all three of my drives and found no evidence of cracking. Personally, I will take a look at the masts before any long usage.

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Mark N
Outfitter
Revo 13

As I understand "Stainless" Steel is only stainless in an oxygenated environment - i.e. when air or water is able to circulate around the metal - and that in situations where the steel is enclosed or oxygen is in some other way shut out it, will corrode like any other metal. This is why on yachts s/s chainplates that have been fibreglassed-in are subject to corrosion and failure. When you pull the snapped-off stub out of a drive you will usually find that it is covered in corrosion but I would have thought that there was enough circulation around the bit that sticks out of the drive since it always seems nice and shiny - however it is hard to see exactly what is going on in and around that part of the mast.

I have had a number of fin mast failures over the years since Turbo fins came out. I haven't counted them but I would say at least 6 - only on turbo fin masts though.

From my experience the photos show a typical break - there's usually a sharp lip on one side of the break and often a bit of tarnishing around the area and in my experience the masts always fail at exactly the same place i.e. at the point where the mast sticks out of the drive. If I am right about the properties of the metal, corrosion inside the drive might be playing a part.

What I have found is that a break can happen at more or less any time - I am guessing, as have others, that the damage builds up over time (repetitive stress or metal fatigue) and that the break can therefore occur without warning and under even relatively light loads. I have certainly had this happen to me - one minute pedalling along gently, then in one moment the drive goes all squishy, and in the next it is all over red rover !

It has happenend to me when only metres from shore going in and coming back, and at the very apex of an all day trip (that one turned into all day an most of the evening) so it can be hard to predict.

It might be possible to detect damage by examining the masts but I have never tried. My approach has been to hope that it doesn't happen too far from shore and carry spares and the wherewithall to install them at sea. Also to be fit and resourceful enough to be able to get back home or to safety under some other power than pedal power if I should find myself without my drive for whatever reason. If I was really going a long way from a safe shore in a remote area I would think seroiusly about carrying a spare drive AND my spares (just in case something else should break - you never know and if you have no hope of rescue, better be prepared)

One thing I would say is that I feel (i.e. no real hard evidence) that knocking a mast on something hard can encourage a break - e.g. I once dropped a drive in my garage. It landed on the end of the mast without doing any apparent damage. Next time out the very same mast snapped. A similar thump happenedimmediately before another breakage. I suspect that the damage was already done but that the bash brought on the actual break.

The drive unit is 15 months old and has never had any problems with the masts. There was no weld that I was aware of - bought the unit brand new and have never replaced anything. Have never hit any submerged object with this unit. What may look like a weld is where what was holding the rod together rod finally gave up the ghost and peeled away.

The other mast on the drive unit shows rust discoloration and some pitting on the mast rod at the point where it meets the rubber fin. I took it by the dealer today and learned someone else in this area had recently had a rod break in two. Thankfully the dealer replaced the broken rod and I'm good to go - no down time, but, solid steel breaking in two does lower confidence levels. Things like this make me worry about entering a race like the Phatwater Challenge (42 miles down the Mississippi).

Interesting. Thanks for confirming I'm not the only one stobbo. Usually when there are parts breaking it goes back to a design flaw or a manufacturing issue, which Hobie deals with appropriately.

These turbo fins put a lot more stress on the entire drive and I'm thrilled to see that other things that used to break (cables) are holding up well. It may well be that Hobie needs to make the rod diameter a little larger down near the screw in point where all the stress accumulates or maybe the manufacturer needs to treat the steel rods to strengthen them? Dunno. That is meeting room discussion material for Hobie.

Thanks for listening Hobie.

Thanks for posting, Rnykster. I'm thinking about getting a Hobie in a couple of years, when I retire and I'll have storage space for one. This is just the sort of thing I need to be clued up on, i.e. what can go wrong and what spares should be carried.

It reinforces my inclination to choose the Adventure, because that would be the easiest of the Hobie kayaks to paddle, in the event of drive failure.

Mary

Bicyclists usually carry a spare tube or a tube patch kit. For a while, I carried spare replacement parts for the pedal drive unit but eventually decided it was much easier to swap drive units than to do drive unit surgery in bouncy waters while the sun goes down, so I now carry a spare drive unit on every trip and a few tools to tighten parts that may come loose, like nuts and set screws. The Adventure is a good choice because if the worst happens and you can't use the drive unit, the Adventure is easy to paddle as compared to something like the Outback that paddles like a bathtub.

I went out yesterday after work and had the same exact thing happen and it broke in the same place. I'm not upset because mine was at least two years old and I have bent and straightened it at least once and they have take alot of abuse.

I had to paddle like heck to get back in so I could go to the dealer and buy the new mast. (That was good incentive to get back to shore in time so I can try again today.)

Rnykster, I'm a great admirer of your racing prowess. With your success, you obviously put a huge strain on your equipment and, not surprisingly, break a number of Drive parts as well as boats. Hobie keeps replacing all these parts for you under warranty -- it's almost like having a sponsor for your events. You can't beat a deal like that!

Obviously there are very few users who have the power and endurance to beat surfskis with an Adventure. Considering the highly unusual stress you put on your equipment, I am a little surprised to see you make a comment like this, as if you expect the equipment to take that kind of punishment without wear and tear.

Your break pattern is typical and shows no defect. Here's a pair that had been bent then broke a few hundred miles later:


The mast breakage is caused by 1) being bent several times, 2) over-flexing from extended heavy use or 3) any combination thereof. This is almost exclusively a Turbofin phenomenon. Even so, most folks wouldn't break one over the course of a lifetime of use, unless it's been bent and straightened several times.

Heavy flexing accelerates wear. Just like an airplane wing spar, the flexed area becomes brittle and eventually develops hairline cracks. With your level of use you should probably replace the masts every 800 to 1000 miles to minimize the chance of accidental breakage. With the current Drives, most Turbofin users should get a mast life of at least 2000 to 4000 pedaling miles safely, except that each good bend and straightening probably cuts the remaining life in half. So if you're planning an important race, you should replace both masts since the other one has probably developed stress cracks as well.

When I bicycle, I've never had anyone say they were surprised by the amount of strain I put on the chain when climbing a hill whether it was recreational or during a race. Fact is, I've never had a chain break and the power my legs have is small compared to actual bicycle racers. If chains broke regularly for the daily bicycle rider, there would be design changes.

The only reason I beat the surfskis is they kept capsizing. I'm a retired senior citizen and appreciate you uplifting me to being one of the few who put unusual stress on the Hobie. I didn't know seniors could be that strong.

I'm aware this is a Turbofin phenomena and I have begged Hobie for years to strengthen their design so it would hold up to regular use (daily). The rod didn't break during the race when it was supposedly under the most stress. The rod shouldn't break period, especially if it has never been bent.

In the past the additional turbo related stress was breaking the composite sprocket material regularly. Hobie inserted a brass fitting into the sprocket to strengthen the sprocket and now the sprockets are not breaking anymore. Thank you Hobie! Unfortunately, the next weakest part is now breaking - the rods. It is not a problem related to elite group of super athletes. I'm just a regular kayaker who enters one to two recreational races a year.

Yes, I expect that when I spend $500 on a brand new drive unit that it should last for the warranty period. I'm sorry if that surprises you. The rod break pattern you show may be typical, but, it should not be happening. Either the metal rod needs to be strengthened (tempered) or increased in diameter to accommodate the NORMAL stress put on by the ST Turbo fins which is a NORMAL product. I have done nothing to supercharge the Adventure what would put unusual stress on the parts.

I'd gladly pay more money for a drive unit that is designed to last and stand up to a higher level of daily use, one with waterproof sealed bearings, petal clips, and solid steel designed not to break.

My goodness, such modesty! I'm just wondering how many of the 19000+ forum members have done anything vaguely resembling your "normal" activities:
Obviously small snippets of a brilliant racing career that has spanned over 6 years with lots of disciplined training. Pray tell, did this same person write the following with a straight face?

Yeah, right! Fortunately for you and me, Hobie doesn't exclude racing activities from their warranty, unlike many manufacturers.

Exactly! Likewise, most normal Mirage Drive users will never see a mast break. But since you brought it up, lets make an appropriate comparison. What IS the life expectancy of a bicycle chain used in racing? Here's an example:

"Then one day I rode the Fleche-Opperman trial, 425km in one day, and most of it in rain and wet roads of course. Before the ride, I couldn't detect chain 'stretch'. After the ride, the chain was completely worn! ONE long wet ride!!"So do you think the manufacturer should build a stronger chain for all of us?

If these NOT-so-durable bicycle components had to to operate in a marine environment like your Hobie equipment, those advanced alloys wouldn't last a month!

Now if you have a suggestion for a better mast material than 17-4 PH stainless, I'm sure Hobie will be all ears! Perhaps you'd like to review the specs first: http://www.aksteel.com/pdf/markets_prod ... _Sheet.pdf

The bottom line is, when you train and race, you put a hugely abnormal load on your equipment. That makes you about one in a thousand. So when you wear parts out or break them prematurely, I don't think it's correct to pretend to be average user and blame it on design defects or substandard materials. That's just my opinion and I may be wrong. I'm still a great admirer of your racing skill and wish you every continued success in your upcoming races!

BTW, when you become eligible to collect Social Security, like my friend who who just won the 28th annual San Diego Bay 2 Bay five mile race with his Hobie Adventure against competitors half his age, then you'll be a "senior citizen" You still have quite a long wait -- enjoy it!

Rynkster:

Absolutely your awesome and a inspiration for some of us less active members keep it up and keep us posted as to ur exploits.

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Fastfish/Geoff
Kayaks Owned>Outback/Mine & Revolution/Wife