Demasting - Broken Shroud Anchor Pin

Wives don't usually see the humor in a demasting - especially when a bear cub gets hurt. Good luck with that one.

In an odd twist of fate, my wife and I were on the FL Keys back in April and had a mast come down on a rented O'day 22. The wind was heavy, but not insane. That is two masts in two years. My wife has not wanted to be on a sail boat since.....

Granted the O'Day was a poorly maintained rental boat, but still..........

So we had the boat out yesterday in the first real wind since getting her all back together again. Had a nice steady building wind out of the south of 15 - 25 MPH. We were on a 1 hour plus tac, tight reach, double trapped with the windward hull skimming the waves, when something popped loud. We brough everything to a stop and poined into the wind to check things out. It turns out, one of the rear cross bar bolts that holds the crossbar to the hull snapped. We beached the boat and lashed it all othether as best we could with some spare line and limped home, taking it as easy as we could in near 30 MPH winds.

So I am getting tired of broken parts. I am going to replace all 8 crossbar bolts, but what's next? Is this 30 year old boat just to old to sail this hard? Total crew wait comes in at 340 lbs, so it's not like were overdoing it on creaw weight. Any recomendations on what else I need to change? I have been visually looking for things that look worn or cracked, but there always seems to be something odd that one would not expect to fail, well failing...... All rigging is new, shroud anchoring hardware is new, shackles are probably a mix of 10 - 30 year old hardware, but anything that had a lot of wear we tossed.

What about the mast tang? That seems like what could go wrong next? Is there anything I should do there? Do they ever come off the mast when sailing hard? There is a fair amount of wear on the tang from the shackles wearing in. How much wear should a guy let happen there before replacing that?

Never heard of a mast tang breaking but as for other parts that break, I have seen several broken mast rotation arm bolts (the one at the bottom of the diamond wires). I also just broke a diamond wire a few weeks ago. Aluminum rudder pins break. Halyard rings break. Frayed lines break (particularly interesting when its your trap line and you are out on it or it is your tramp lacing).

need help on which nut is actually right.
Hobie catalog says 8050321 but RushMan confirms this is not the right part.
MMiller says 8050311 but that this is a thinner nut than the "old" heavy hex nut (i would prefer the extra threads given all this talk of demasting), but the "old" number is obviously not 8050321.

On the pins... if both new and old are 5/16-18, then the threads must have the same major diameter, which means the shank diameter of the "new and improved" rolled threads is actually less than the shank on old machined threads (seems like more cross section would be better). What is the new grade of stainless? It must have a low yeild in order to be roll formed. Low yield strength and smaller shank = easier to bend..??

hardenable stainless? higher strength? shorter nuts? what am i missing here? (aside from the cheaper cost for roll formed fasteners and shorter nuts)

Thanks

Those changes were not cost driven. The new pins are far stronger. Rolled threads are better by not chipping the stainless which creates a crack.

There has never been an issue with the nut end of the connection, so no reason to think a standard nut is not going to be fine.

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

I believe the key to the newer roll formed thread shroud anchor pins is that there is no "cut" left in the neck of the shroud anchor pin from the old style thread cutting process, which would tend to be the weakest spot and develop cracks / or fail from that point. If I remember my engineering correctly, most of the stresses on the pin will be carried around the outside circumferance of the pin, with very little being carried by the center material when there is any sort of side loading or torque being applied as well (there usually inadvertantly is). So the important thing is that there is a "clean" transition from the threads / nut that is holding the pin in position to the rigging attachment point (hole)...free of machining nicks, such as those caused be a thread cutter.

So i shelled out my $60 for two bolts (and ordered some other stuff)... they didn't ship the eyebolts, so after telling my girlfriend about how anchor bolts fail and cubs get layed open by falling rigging, i didn't have the new parts for the weekend (makes for a relaxing 3rd ride ever eh?).

So monday I take them out of the box.


http://www.flickr.com/photos/52330871@N04/4821986797/

what's wrong with this picture?


http://www.flickr.com/photos/52330871@N04/4821986803/
a little closer.


http://www.flickr.com/photos/52330871@N04/4821986805/


Tiny little cracks all around the "eye" of the bolt. So i stand by my statement that Hobie (or some shop in China) is making cheap anchor bolts with no quality control... But, of all the places to scrimp, this is NOT the place to do it.

This is a high stress, dynamically loaded (cantilevered even) eyebolt. These cracks act as stress risers. Under cyclic loading this is the perfect recipe for crack propagation (this is the failure mode of the old "weak" bolts, right?... stress concentration at the top of the thread and cyclic loading?) Throw in some salt water and crevice corrosion and I'm riding a time bomb.

This improperly designed under-built connection is "the #1 reason masts come down" and the solution is to replace them? more often? with this? (i'm not trying to be cheap, I'd gladly pay $120 for a heavy duty bolt if i knew it would keep the damn rig from slicing up my girlfriend... maybe not every year). I guess as long as i sail a hobie, they have a lock on my business, so a de-masting is good for somebody.

so i want to sail this weekend, it's gonna blow hard. what is your vote? bent bolts or cracked bolts?

This new style pin is much stronger than the older ones. No reports of failures. Use them. I suspect you are seeing a surface fragmentation from the pressing process.

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

looks to me like like they were left in the electropolisher waaay to long. material is missing where the electrode is attached to the bolt, it's a mini-canyon.

The good news is that that's not where the bolts usually fail. They tend to fail at the threads, at least that's what I've seen.

But I understand your frustration. I really wish that Hobie would just bite the bullet and make a beefier anchor bolt. Increase the diameter one size and beef up the pin a little and there would never be an issue. In my opinion, this is a component that should never have to be replace on the boat - just like bow tangs, crossbar bolts, gudgeon screws and all the other major structrual fittings.

sm

I kind of doubt that a larger diameter is needed...think of how many thousands of 18's were built, and how few and far between the failures are...the dealers know this for sure, since they sold the replacement pin for the ones that broke.

The new pins really are of a better material, as Matt M says...most "ordinary" grades of marine stainless steel are only slightly magnetic, if at all...such as the old style shroud anchor pins:



The magnet will pick up the new pins, package and and all...in fact, it will "jump" off the countertop to the magnet from about 3/4" away. This is also a good way to see if your boat has the correct ones, if you are unsure...they will feel solidly magnetic.

Matt, is there a new part number for the new style anchor pins? I requested new style pins from my dealer but apparently received old style pins based on the previous post magnetic test.