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Do aluminum booms break ??
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spennie



Joined: 13 Oct 1995
Posts: 829
Location: Thousand Oaks, CA

PostPosted: Wed Oct 17, 2012 10:07 am    Post subject: Reply with quote

6'4", 205 lbs., WS 22 years, have never broken the carbon part of a carbon boom. I'm told that carbon doesn't fatigue like metal, and I tend to believe that, since I have several ancient carbon booms (12-15 yrs.) that I use all the time. Bought a new Chinook a few years ago and love it. Bought a new Fiberspar before that, love it too. My oldest booms are Fiberspar, seem to last forever with minimal care.

The main advantage is stiffness. If you're dangling out on your harness lines and your boom flexes outward, it's getting shorter as a result. This throws your rigging out of whack, decreasing your outhaul. In a big gust, your boom flexes more, decreasing outhaul more, making your sail more powerful at the moment a gust hits, not good! The bigger the sail the more this happens, again not good.

So a carbon boom could be called an investment, since it lasts so long. Freshwater BAFing is very easy on them, so it would probably last 15-20 years or more if you don't crash on it too much, or drive over it with your car.

Buy as much carbon as your pocketbook can stand, it's worth every penny.

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swchandler



Joined: 08 Nov 1993
Posts: 5830

PostPosted: Wed Oct 17, 2012 12:58 pm    Post subject: Reply with quote

After breaking 6 Windsurfing Hawaii aluminum boom front ends in 1992, I was completely over with aluminum booms. After that I went with Gulftech carbon booms out of Corpus Christi, Texas, but unfortunately they incorporated an aluminum core in the front ends. As a result, I broke almost all those too because of internal corrosion. However, I still have one that I use, but only on my 4.2 and 4.6, which only see a handful of days a year.

When it comes to 100% carbon booms, I've only broken one, a Gulftech Glory, after 5 years of hard use. It didn't actually fail while in the water, but I discovered it seemed a bit wobbly. At that time, I had just bought a Maui Sails carbon monocoque boom, and found that Gulftech front end tubing was nearly entirely broken through once I removed the rear end extension to take off the harness lines. I also have a HPL 100% carbon boom that I bought new in 2004 that is still going strong.

The only aluminum component that I will use is a mast extension.
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LeeD



Joined: 12 Jun 2008
Posts: 1017

PostPosted: Wed Oct 17, 2012 1:10 pm    Post subject: Reply with quote

Spennie, you're told wrong.
Carbon fatiques like anything else, but does last longer. Car fairings, motocycle fairings, F-117 body parts, all break down from use and the stress's it faces.
Carbon is much stronger than aluminum, yes.
Look at bicycles. High end carbon bikes can last for more season's than the design is still valid. But it still wears down, get's fatiqued, get's softer, loses it's resilientcy, and is scrapped.
Tennis rackets last one season under top level players, and they rotate through at least 10 a year.
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spennie



Joined: 13 Oct 1995
Posts: 829
Location: Thousand Oaks, CA

PostPosted: Wed Oct 17, 2012 3:00 pm    Post subject: Reply with quote

From a composite manufacturer's website:

Excellent fatigue endurance concerning number of load cycles (many times higher than with metals) and residual fatigue strength (aramide and carbon epoxy laminates retain more than 60% of their residual static strength, which is far more higher than is possible with metals.)

So yes, it breaks down, but very very slowly, and only down to 60%. Also:

Higher specific strength (material strength/density material). Aramide and Carbon Fiber reinforced epoxies have approx. 4 to 6 times higher spec. tensile strength than steel or aluminum. Excellent weather/water resistance. Material has almost no corrosion, takes on little water which leads to low maintenance cost especially on the long run.

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zirtaeb



Joined: 03 Jul 2009
Posts: 2396

PostPosted: Wed Oct 17, 2012 3:48 pm    Post subject: Reply with quote

The LEAST trustworthy thing you can read is a manufacturer's marketing brochures, you must know that.
Toyota say their cares are the best, need the least maintainance. Heard the recall number's lately?
It's called MARKETING. They hire an engineer, for sure. They also hire 5 times as many AD men, who overide the engineer in the final draft anyways.
That is the basic structure of the free world.
If you believe everything you read, you would still be believing the earth is flat.
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spennie



Joined: 13 Oct 1995
Posts: 829
Location: Thousand Oaks, CA

PostPosted: Wed Oct 17, 2012 4:12 pm    Post subject: Reply with quote

So I can assume you have conflicting data from a better source? Don't see it here.
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jingebritsen



Joined: 21 Aug 2002
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PostPosted: Wed Oct 17, 2012 4:53 pm    Post subject: Reply with quote

i sail up to 20 times a month, year round. what i see most won't for a very long time. on top of that, i sail big stuff, and pump lots. i usually turn over my al. booms pretty frequently.

lots of boom brands have aeron as their OEM. aeron is now distributed in N.A. by aerotech sails.

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swchandler



Joined: 08 Nov 1993
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PostPosted: Wed Oct 17, 2012 6:45 pm    Post subject: Reply with quote

No doubt, aluminum booms are inexpensive in contrast with carbon booms. Maybe that could support an argument that you can afford to buy them and flip them frequently and still come out ahead. However, I'm of the mind with the idea mentioned earlier that carbon booms are an investment. You know, something that you would retain and comfortably use over a long period of time. Also, at least where I live where so many folks have moved to kitiing, there just aren't that many folks windsurfing that willing to buy used equipment, particularly used aluminum booms.
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feuser



Joined: 29 Oct 2002
Posts: 1395

PostPosted: Wed Oct 17, 2012 7:16 pm    Post subject: Reply with quote

zirtaeb wrote:
The LEAST trustworthy thing you can read is a manufacturer's marketing brochures, you must know that.
Toyota say their cares are the best, need the least maintainance. Heard the recall number's lately?
It's called MARKETING. They hire an engineer, for sure. They also hire 5 times as many AD men, who overide the engineer in the final draft anyways.
That is the basic structure of the free world.
If you believe everything you read, you would still be believing the earth is flat.


Unidirectional pre-preg carbon fibre with a good epoxy agent does survive many, many more flex cycles than aluminum. It shouldn't even be on the same chart.

I have a 6 year old carbon RDM made by Triana that is quite springy, still (subjectively more so than a brand new Ezzy). It has flexed in every gust, with every pump, going over every piece of chop since 2006.

You could say that, every time you bend aluminum, it breaks a little. Conversely, every time you bend composite too much, it breaks a little, too. Sometimes, it breaks a lot at once.

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DanWeiss



Joined: 24 Jun 2008
Posts: 1953
Location: Connecticut, USA

PostPosted: Wed Oct 17, 2012 8:26 pm    Post subject: Reply with quote

Here's the deal. Galvanic corrosion (also known as rust in iron and steel) affects aluminum by pitting and thinning its wall thickness, most often from the inside out. Salt water increases the speed of such corrosion.

Galvanic action occurs between dissimilar metals in direct contact when exposed to a conductor. Fresh water conducts, salt water often conducts better to my understanding. The mere penetration of a POP rivet increases galvanic corrosion potential due to the different metal in the mandrel as compared to the rivet and possibly compared to the material it fastens.

So it's not just the tendency of aluminum to fail with fewer cycles than carbon, but the way aluminum booms are assembled greatly reduces the material's normal life.

Carbon booms break, but they do not corrode and thus avoid the major reason alu booms and boom components fail.

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