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Chinook mast base failure in the waves
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GURGLETROUSERS



Joined: 30 Dec 2009
Posts: 1344

PostPosted: Thu Jan 16, 2014 1:28 pm    Post subject: Reply with quote

Most rubber U.J.'s appear to be built of three separate parts glued together (base moulded around alloy plate at bottom, top ditto, and central bobbin) with a thin continuous rubber sheath around the whole thing.

It is impossible to see if the glued joints are about to give way, or to know how well they have been glued together during manufacture.

There was a batch of faulty ones (short of glue) some years back. A new one I bought failed on its third outing when the bottom separated from the bobbin at the joint. Examination showed only part of the join had been glued, and all that was holding it together was the partly glued joint, and the thin rubber sheath around the outside. No check could have shown that fault before it failed..
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isobars



Joined: 12 Dec 1999
Posts: 14157

PostPosted: Thu Jan 16, 2014 1:34 pm    Post subject: Reply with quote

I used the mechanical bases for over a decade of very heavy year-round sailing, during which my mast crashed onto my decks literally many thousands of times. Nary a deck dent, but one mech base did blow up after years of use due to operator error: I wasn't checking the screws, and one or more loosened. I advise checking them WITHOUT ACTUALLY TURNING THEM occasionally.

I also use only two-bolt bases, to spread the load on the box.

I also ENVY THE HELL OUT OF SAILING IN JUST BOARD SHORTS. Smile
But for a day or a week in the peak summertime heat, I gotta have at least a little insulation on the western mainland U.S.
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manuel



Joined: 08 Oct 2007
Posts: 137

PostPosted: Thu Jan 16, 2014 4:32 pm    Post subject: Reply with quote

I have the old version of this one.
Maybe it's easier to trust this one instead because tendons can be expected and the rope hold better than the weak strap.

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U2U2U2



Joined: 06 Jul 2001
Posts: 3056
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Thu Jan 16, 2014 7:09 pm    Post subject: Reply with quote

its a Streamlined 2 bolt with a tendon
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U2U2U2



Joined: 06 Jul 2001
Posts: 3056
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Thu Jan 16, 2014 7:11 pm    Post subject: Reply with quote

isobars wrote:
I used the mechanical bases for over a decade of very heavy year-round sailing, during which my mast crashed onto my decks literally many thousands of times. Nary a deck dent, but one mech base did blow up after years of use due to operator error: I wasn't checking the screws, and one or more loosened. I advise checking them WITHOUT ACTUALLY TURNING THEM occasionally.

I also use only two-bolt bases, to spread the load on the box.

I also ENVY THE HELL OUT OF SAILING IN JUST BOARD SHORTS. Smile
But for a day or a week in the peak summertime heat, I gotta have at least a little insulation on the western mainland U.S.


DURING WHICH MY MAST CRASHED ONTO MY DECKS LITERALLY MANY THOUSANDS OF TIMES....... MANY THOUSAND OF TIMES. REALLY ?

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isobars



Joined: 12 Dec 1999
Posts: 14157

PostPosted: Thu Jan 16, 2014 8:14 pm    Post subject: Reply with quote

Inspecting an hourglass takes seconds; I bend 'em and inspect them every time I rig. Tendon inspections, though, require disassembly (it's the screw holes that fail). Or is there some other way to inspect tendon screw holes?
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manuel



Joined: 08 Oct 2007
Posts: 137

PostPosted: Thu Jan 16, 2014 11:55 pm    Post subject: Reply with quote

In my case, the internal metal part shows signs of corrosion which means that water was getting in from underneath where the bolt goes through. Without pulling it apart one couldn't tell anything was wrong.

A tendon is quite easy to inspect while the hourglass rubber requires a wise grip?

Some have a wider strap, why use such a narrow one, grrrr...
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isobars



Joined: 12 Dec 1999
Posts: 14157

PostPosted: Fri Jan 17, 2014 8:46 am    Post subject: Reply with quote

The hourglass normally fractures at its readily viewable midsection; no disassembly required. I think your failure mode is much less common.
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dennis_c



Joined: 05 May 1998
Posts: 650
Location: Rio

PostPosted: Fri Jan 17, 2014 12:25 pm    Post subject: Reply with quote

manuel wrote:
Must have swam for a good 1h 1h1/2.

And all the time thinking at least my failure mode is much less common no doubt.
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manuel



Joined: 08 Oct 2007
Posts: 137

PostPosted: Fri Jan 17, 2014 10:21 pm    Post subject: Reply with quote

Must be the time of year... this is my old streamlined.
At least this one didn't break completely through, although impossible to detect without pulling apart.

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