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Carbon Boom Snap- Repairable?
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d0uglass



Joined: 28 May 2004
Posts: 1084
Location: Bonita Springs, Florida

PostPosted: Sat Aug 17, 2013 4:07 pm    Post subject: Carbon Boom Snap- Repairable? Reply with quote

Aww, dang.

I've just dialed in my 11.0 formula setup to where it works nice, and now my Chinook Carbon boom has given up. I was upwind of the launch when it happened so I managed to sail back to shore ok, but the boom is definitely not usable- broken clean through just a bit behind the harness lines.

Does anyone ever repair a break like this, or is this a "scrap the whole thing and pay a huge amount of money for a new boom" kind of thing?

Thanks,
James



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zirtaeb



Joined: 03 Jul 2009
Posts: 2402

PostPosted: Sat Aug 17, 2013 4:25 pm    Post subject: Reply with quote

It can be repaired, but how much effort are you willing to spend?
Make a carbon wrapped aluminum core tube that fits inside, underlapping about 4".
Wrap over the outer tube with 4 layers of carbon, go sailing.
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joew



Joined: 18 Jul 1999
Posts: 152

PostPosted: Sat Aug 17, 2013 4:29 pm    Post subject: Reply with quote

I had a similar break in a North carbon boom years ago, however it was wave size. I repaired it by epoxying an 8" piece of alu. boom extension inside the broken area, it added a little weight but held up well enough till I moved on. Big boom , huge load, don't know if this will work for you but maybe worth a try, better than scrapping the whole thing.
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MrFish



Joined: 04 Sep 2009
Posts: 238

PostPosted: Sat Aug 17, 2013 6:58 pm    Post subject: Reply with quote

How close does the boom tail get to that when fully inside the boom?
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d0uglass



Joined: 28 May 2004
Posts: 1084
Location: Bonita Springs, Florida

PostPosted: Sat Aug 17, 2013 8:58 pm    Post subject: Reply with quote

Thanks for the ideas! The boom tail doesn't get close to that area so it shouldn't interfere with an aluminum endoskeleton. I'll try it. Smile
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bred2shred



Joined: 02 May 2000
Posts: 660
Location: Jersey Shore

PostPosted: Sat Aug 17, 2013 10:29 pm    Post subject: Reply with quote

I had virtually the identical thing happen to two of my Chinook triple clamp booms last year (both booms broke within a month of each other). Chinook sells replacement arms. My booms were mid-size and the arms were $150 each. I ended up replacing all the arms on the reasoning that if one side broke, the other side is likely to be not too far behind.

Anyway, the point is you can fix the boom for less than cost of new, but I would not mess around with trying to fix the broken arm. Inspect the head and tail pieces and if they're in decent shape, get new arms.

By the way, the guys that are recommending splicing the broken arm together by using an aluminum tube inside the carbon tube need to take into consideration the effects of galvanic corrosion. Aluminum is about the worst material you could ever pick to use with carbon/graphite- they are at opposite ends of the chart when it comes to galvanic similarity. The aluminum in contact with graphite will be severely corroded in a salt water environment.

sm
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boardsurfr



Joined: 23 Aug 2001
Posts: 566

PostPosted: Sun Aug 18, 2013 9:22 am    Post subject: Reply with quote

bred2shred wrote:
By the way, the guys that are recommending splicing the broken arm together by using an aluminum tube inside the carbon tube need to take into consideration the effects of galvanic corrosion.

Very good point. We have a few hybrid booms (aluminum front, carbon tail). They perform well and are a lot cheaper than carbon booms, but the amount of corrosion is amazing. No problem if you sail every day, but let the boom stand around for a few weeks without taking the tail end out, and it's almost impossible to take apart. Pure aluminum or carbon booms don't have that issue (if they are stuck, it's usually due to sand).
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dvCali



Joined: 23 Aug 2007
Posts: 454

PostPosted: Sun Aug 18, 2013 8:49 pm    Post subject: Reply with quote

d0uglass wrote:
Thanks for the ideas! The boom tail doesn't get close to that area so it shouldn't interfere with an aluminum endoskeleton. I'll try it. Smile

As somebody else has mentioned: don't use aluminum. You could use a pre-made carbon tube, but I doubt you can get close enough tolerances to guarantee a good bonding between the broken part and the fix.

I'd suggest to use carbon tape (look toward the bottom of http://www.fiberglasssupply.com/Product_Catalog/Reinforcements/Carbon_and_Kevlar/carbon_and_kevlar.html )

Take off the grip and sand the tubes for a good 6", do multiple carbon wraps with wet (epoxied) tape, and wrap the whole thing very tightly with electrician tape that you have "prepared" by putting some pin-holes in it. The excess epoxy will be squeezed out: it is a poor man vacuum bagging. For how many wraps, in what order do a little research. I am not sure if it is better to do separate wrappings and cures, but I suspect it is since the thickness of your repair should be at least as much as the thickness of the original tube. Would it work ... no so sure Embarassed Embarassed I personally would buy a new one or give the job to somebody that has quite a lot of experience with composites.


Last edited by dvCali on Tue Aug 20, 2013 10:45 am; edited 1 time in total
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outcast



Joined: 04 May 2004
Posts: 2404

PostPosted: Mon Aug 19, 2013 10:20 am    Post subject: Reply with quote

I have saved the ends of the sup paddle shafts when I cut them for size.
If they fit, they would be the right stuff for a ferrule splice. Maybe check in at a local shop as they cut a bunch for their sales.....The kailoa shafts seem suited

You will prob find the inside tube of the boom is not smooth enough for a good bond....no need for a inside smooth surface for the maker and sanding it would be a bitch.....plus alot probably splintered...what dvcali said

IF you could find the right splice tube and it's smooth, yeah, i would give it a go with alot of epoxy filler......the wraps will de-sleeve when you stuff unless you do an external sideways wrap on top

BUt....I would not load it with an 11-0 anymore, and you've got to be able to trust your safety to it

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Sailboarder



Joined: 10 Apr 2011
Posts: 443

PostPosted: Mon Aug 19, 2013 8:03 pm    Post subject: Reply with quote

If I was to do it, I wouldn't really care for carbon fiber. I would use glass fiber.

To do the endoskeleton, I would use an aluminum tube, beefed up with fiber glass to electrically isolate the aluminium from the carbon fiber. I would also weaken the ends of the tube, maybe with slots or sanding, to distribute the stress buildup that will occur at the "sharp" edge of the tube.

Once epoxied and solid in place, I would then sand the outer and do what dvCali suggested with fiber glass. You need as much continuous material as there used to be in that area. Original carbon fiber at the broken spot simply butted and held by epoxy doesn't count.
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