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Chinook Carbon Triple Clamp Mod to two-pin
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bred2shred



Joined: 02 May 2000
Posts: 658
Location: Jersey Shore

PostPosted: Wed Apr 25, 2012 11:21 am    Post subject: Chinook Carbon Triple Clamp Mod to two-pin Reply with quote

Several weeks ago, I broke a boom arm on a Chinook carbon triple clamp boom. This boom's at least 5 years old and has had a lot of use and Chinook was real good about getting out a set of replacement arms. Anyway, later when I was inspecting the boom arm and tail piece on my other triple clamp boom, I noticed that the pin holes for the adjustment collars had heavily ovalized due to repeated wear of the stainless pins against the carbon tubes, and that concerend me because eventually, the pins would wear completely through. It also allowed a lot of slop between the tail piece and the boom arm.

In order to correct this problem, I realized that with some minor modifications, it would be possible to add a second adjustment collar to each boom arm. Doing this would effectively double the amount of contact area between the pins and the boom tubes and therefore reduce the amount of wear.

The process is as simple as drilling a second 11/32" diameter hole in the boom tube at 6cm inboard from the existing hole (notice the elongation of the original hole, the hole in the tail piece was even worse).



Then, using a rotatary tool, grind out the ends of the second set of adjustment collars so that they'll slide completely onto the boom arm (note that there's a small "nub" inside the collar that must be ground down as well).



Once the holes are drilled and the collars modified, remove the existing collars, slide on the modified collars, then re-install the original collars, and you're good to go.



Anyone with a Chinook carbon triple clamp boom should probably inspect the adjustment holes. If you use your boom a lot, then the holes have probably ovalized and you may want to consider doing this mod.

sm


Last edited by bred2shred on Wed Apr 25, 2012 4:23 pm; edited 2 times in total
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bonner



Joined: 17 May 2000
Posts: 15

PostPosted: Wed Apr 25, 2012 2:36 pm    Post subject: Reply with quote

Same problem, but I just use velcro strips and secure them directly over the adjustment pin on each arm so the adjustment pin can't pop out while sailing. They don't come off at all, problem solved.
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swchandler



Joined: 08 Nov 1993
Posts: 5820

PostPosted: Wed Apr 25, 2012 2:53 pm    Post subject: Reply with quote

Not really, sm is right. In my experience, the problem with increasingly oblong holes is the fact that the rear extension will begin telescoping back and forth, and you'll feel it at every jibe. As a result, it lessens the stability and performance of the sail. The bigger the sail, the more problematic it becomes.
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bred2shred



Joined: 02 May 2000
Posts: 658
Location: Jersey Shore

PostPosted: Wed Apr 25, 2012 4:14 pm    Post subject: Reply with quote

bonner wrote:
Same problem, but I just use velcro strips and secure them directly over the adjustment pin on each arm so the adjustment pin can't pop out while sailing. They don't come off at all, problem solved.


This mod has nothing to do with the pins coming undone (although that would be another benefit due to the redundancy of having two pins per side).

This mod reduces (or hopefully eliminates) the elongation of the adjustment pin holes by adding a second set of pins. On my most used boom at my most used setting, the adjustment hole in the tail piece is elongated by AT LEAST 50%. Eventually the pin would wear the hole so much that it breaks through to the adjacent hole which would make that boom setting totally useless.

Finally got the pics to post in the thread.

sm


Last edited by bred2shred on Thu Apr 26, 2012 11:28 am; edited 1 time in total
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loonie2



Joined: 18 Jun 2004
Posts: 126

PostPosted: Thu Apr 26, 2012 9:05 am    Post subject: Reply with quote

I've had the same issue on a well used Chinnook carbon. I noticed it 1st when the clips opened up when sailing. I cut the boom arm shorter & re-drilled the hole. This also allowed the pin to go through a different hole in the extension which was also wearing. The problem is my boom is getting shorter & I may have to do this again soon. I like the two pin solution shown in the photos.
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bred2shred



Joined: 02 May 2000
Posts: 658
Location: Jersey Shore

PostPosted: Thu Apr 26, 2012 11:33 am    Post subject: Reply with quote

loonie2 wrote:
The problem is my boom is getting shorter & I may have to do this again soon. I like the two pin solution shown in the photos.


I had originally considered doing the same thing, just cut the end of the main body tube off and drill a new hole so I could use a different hole in the tail piece. The problem with this is that not only does your boom keep getting shorter, but also, the length markings on the tail piece are no longer accurate, so your boom settings get all screwed up.

sm
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bonner



Joined: 17 May 2000
Posts: 15

PostPosted: Thu Apr 26, 2012 1:33 pm    Post subject: Reply with quote

Oh I'm sorry "born2shred", if you did more than go back and forth, you would have known about the pin popping out while sailing. Happy drilling and cutting...
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bred2shred



Joined: 02 May 2000
Posts: 658
Location: Jersey Shore

PostPosted: Thu Apr 26, 2012 4:10 pm    Post subject: Reply with quote

bonner wrote:
Happy drilling and cutting...


Actually, boner, there is no cutting involved with this mod...obviously you still haven't read the post.

The reason I did this mod is SO THE PINS WON'T WEAR OUT THE HOLES IN THE BOOM ARMS. I've sailed chinook booms for close to 15 years and in that time I've NEVER had an adjustment pin pop open.

But anyway since this concept seems a little too complex for you, the next time you're in NJ, give me a shout and I'll explain it to you. Then we can share a sesh, I could use some company...or a laugh.



sm
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SwellRipper



Joined: 21 Apr 2009
Posts: 135
Location: Channel Marker 8A

PostPosted: Thu Jun 14, 2012 11:01 am    Post subject: 2012 Chinook Pro Carbon Reply with quote

I just got a new 2012 Chinook Pro Carbon boom 135-185 size. On the first session I noticed "telescoping" action of the rear piece into the front piece when pumping the sail. It's mostly happening on one side. The front of the boom is super stiff and responds well with power to every bit of wind, front hand pull, or mast base pressuring, so that's good. But when pumping or flapping the sail with the rear hand that sloppy oscillation happens, not good. I'll take it back to the dealer to see what they say, but any comments from the forum are appreciated. Obviously, I won't be modding a brand new boom though.
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swchandler



Joined: 08 Nov 1993
Posts: 5820

PostPosted: Thu Jun 14, 2012 1:18 pm    Post subject: Reply with quote

You should remove the clip assemblies and check for oblong holes on the boom arms. Since it's a new boom, any oblong characteristics wouldn't be based on long use, but instead based on a manufacturing error. If you find oblong holes, I would recommend pursuing a warranty replacement.
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