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Chinook mechanical joint failure
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rtz



Joined: 31 Oct 2010
Posts: 256
Location: Oklahoma City

PostPosted: Mon Oct 14, 2019 12:08 am    Post subject: Reply with quote

I just took mine apart to check it. While the amount of locktite used or not used is questionable; that upper bolt connection is concerning. Not much thread and totally reliant on the locktite to keep it together.

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manuel



Joined: 08 Oct 2007
Posts: 991

PostPosted: Mon Oct 14, 2019 12:41 am    Post subject: Reply with quote

The hourglass glue fails when oxidation eats away the bottom metal part. I've had one fail on me and rescued someone else with the same issue. Hard to rinse underneath.
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GURGLETROUSERS



Joined: 30 Dec 2009
Posts: 2330

PostPosted: Mon Oct 14, 2019 2:48 am    Post subject: Reply with quote

The old 'rubber' UJ's we used were NOT all one piece. They were three seperate parts bonded together with a thinner rubber shell bonded around the outside.

The top and bottom sections were moulded around the top and bottom flat metal discs (for stud attachments), each of which had a n inner convex surface which were then bonded top and bottom with a central (the hour glass) solid piece. The continuous outer skin was then bonded around the assembly.

It was not possible to check the security of the inner bonded (glued) sections for seperation. It was only possible to check the central hourglass section for tears or splits.

In the late 90's we had a batch of these rubber hourglass UJ's which were faulty. (Farmed out to a new cheaper factory somewhere with poor quality control) They were all recalled. I had one pull apart in the surf, and the construction fault was obvious. The upper disc section had ripped off the central hourglass because there was next to no glue on the convex inner surface. just the thinner outer skin had been taking the strain!

Some of us have changed to the newer North tendon joints which have a hollowed tendon with a secure non stretch Dyneema cord through the middle which totally prevents the tendon from stretching, while allowing it to bend. So far they are holding up well, and one of mine is now into its third year with no apparent damage to the tendon, which North claim is of a superior high tech material. (Whether or not who knows, but they work!)
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GURGLETROUSERS



Joined: 30 Dec 2009
Posts: 2330

PostPosted: Mon Oct 14, 2019 2:51 am    Post subject: Reply with quote

P.S. Second Manuels point about inner corrosion of the metal plates which cannot be seen or checked. I laid a used one up for a year and the corrosion couldn't be mistaken. The top section developed a marked bulge, and masses of green stuff had spewed out! Very pretty, if you like that sort of thing! Laughing
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dvCali



Joined: 23 Aug 2007
Posts: 1072

PostPosted: Mon Oct 14, 2019 10:17 am    Post subject: Re: Chinook mechanical joint failure Reply with quote

NOVAAN wrote:
We have had several of these separate where the cup and clip connect to the joint. No thread lock was used from the factory. Mine came loose the first day but I got it before it failed. I never thought about the pin that connects to the plate. This one failed on the far side of the reach. Leaving me with my sail in the water and my foil board heading down wind fast. Luckily I foil with a life vest that I attached to my sail and swam like heck to catch my board. It was an hour long struggle to get my gear and myself back to shore.
Again there was no thread lock on the part. I would suggest checking these joints before using. A drop or two of red could save you a long swim or a lost rig. The only thing that saved mine was the vest

Thanks for the heads up, I have been using tendons for ages, but I did get a mechanical for foiling and now it is foiling season Shocked I'll check it, although I have the Euro version that is different with a stainless steal unit seating on top of the joint. From the photos on the chinook site it looks like the connection might be a bit longer and threaded from the top without any plastic washer.

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cgoudie1



Joined: 10 Apr 2006
Posts: 2275
Location: Killer Sturgeon Cove

PostPosted: Mon Oct 14, 2019 11:30 am    Post subject: Reply with quote

It may be a small point, but I can really feel high frequency mast shock
through the mechanical and even the tendon units. The rubber puts a little
dampening on abrupt board movement thought the rig. I like the feel
better, it's just smoother. Especially with epoxy boards. Glass boards, not
so much, probably because they damp out those shocks in the board.
I've never had a rubber hourglass break, but I do replace them when they
start to crack, which is usually about the end of the 2nd year of hard use.
If you bend the thing, and it's go cracks in it, you should replace it.

Really glad Chinook has found a replacement, because I've got a couple that
need replacing.

-Craig

rtz wrote:
On the 12th of last month; Chinook sent out an email announcing the hourglass was back:

https://chinooksailing.com/collections/mast-bases-us-basecup/products/1-bolt-rubber-mast-base-us-cup

I've only used the Tendon and Mechanical. Always heard the hourglass ones break?

Those who use them; what do you like about them or why do you prefer them?
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coachg



Joined: 10 Sep 2000
Posts: 2777

PostPosted: Mon Oct 14, 2019 1:35 pm    Post subject: Reply with quote

Zero frequency shock when foiling. That plus the fact that the mechanical is much easier to attach a sail to on the water is why I use it for foiling.

Coachg
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cgoudie1



Joined: 10 Apr 2006
Posts: 2275
Location: Killer Sturgeon Cove

PostPosted: Mon Oct 14, 2019 4:00 pm    Post subject: Reply with quote

Well, that's nice and all, but what I really want is the rubber uni with 2 Bolt quick disconnect. They don't have that yet, but I'm hoping.

-Craig

rtz wrote:
On the 12th of last month; Chinook sent out an email announcing the hourglass was back:

https://chinooksailing.com/collections/mast-bases-us-basecup/products/1-bolt-rubber-mast-base-us-cup

I've only used the Tendon and Mechanical. Always heard the hourglass ones break?

Those who use them; what do you like about them or why do you prefer them?
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akrausz



Joined: 19 Sep 2008
Posts: 130
Location: Sarasota, FL

PostPosted: Fri Oct 18, 2019 7:18 am    Post subject: Reply with quote

cgoudie1 wrote:
Well, that's nice and all, but what I really want is the rubber uni with 2 Bolt quick disconnect. They don't have that yet, but I'm hoping

Like this?
https://www.worldwinds.net/chinook-2-bolt-upper-rubber-joint-us
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akrausz



Joined: 19 Sep 2008
Posts: 130
Location: Sarasota, FL

PostPosted: Fri Oct 18, 2019 7:26 am    Post subject: Reply with quote

I tried a couple of mechanical one-bolt units. Unfortunately, I just couldn't stop them from twisting themselves loose while sailing. Chinook handled the situation perfectly...took the mechanical units back and replaced them with whatever I wanted. Went back to the hourglass and all is good again.
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