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Carbon Boom Breakage.
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GURGLETROUSERS



Joined: 30 Dec 2009
Posts: 1335

PostPosted: Thu Aug 29, 2013 4:12 pm    Post subject: Carbon Boom Breakage. Reply with quote

One of the arms of my longish (7 to 8 metre sail size) 7 year old carbon boom cracked next to the head (all one piece continuous) today, and just got me back in by hastily hopping out of the harness, feathering as much as possible while keeping some drive, and holding the mast with front hand.

Am I right in thinking that inertia loadings (body weight and leverage with bigger sails) are greater on bigger booms and bigger heavier boards, and that carbon may not be such a good idea, unless made much stronger, for physically active riders who are always energetically pumping to plane?

Just wondering how long others make biggish carbon booms last? Is 7 years of energetic usage good, bad, or just normal? The racing boys (win at all costs) seem to change their booms every season, but only as a precaution, they say. On the other hand, everybody keeps repeating that if they don't break in the first few times used, they'll last for ever! I can't believe that, and my failure seems to me to have been a FATIGUE failure, from usage.

Just wondering what's real, with carbon when used under stress?
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mac



Joined: 07 Mar 1999
Posts: 5143

PostPosted: Thu Aug 29, 2013 4:22 pm    Post subject: Reply with quote

GT--I have 5 carbon booms in current use, all at least 3 years old. Three of those cover sail sizes 9-12 meters, one is for a 6.8 and 7.8, and one for my small sails. Racers tend to reinforce their front ends, and replace the front end pieces, but other than that, 5-8 years is not an unreasonable period of time for loaded up (20 mph and more) sailing on pretty big sails.
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GURGLETROUSERS



Joined: 30 Dec 2009
Posts: 1335

PostPosted: Thu Aug 29, 2013 4:46 pm    Post subject: Reply with quote

Ah! Thanks Mac.

It may then be a case of buying the perceived best quality carbon booms, perhaps with detachable front pieces which can be replaced.

What makes would you say have the best reputation? I like Chinook (broken boom NOT Chinook) booms and have an old much used large alloy one which still seems to be 'the works.'

Since I don't believe in heaven... is gear free there?... and I won't be windsurfing once I'm 'deaded', I'd better start spending now. ( Wink )
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slinky



Joined: 24 Aug 2007
Posts: 412
Location: Old Saybrook Ct.

PostPosted: Thu Aug 29, 2013 4:58 pm    Post subject: Reply with quote

So what's the alternative to carbon, if in fact it might not be such a good idea? The only other material I am aware of is aluminum, and from past experience, carbon if far more durable. I have a set of fiberspar wave booms that are at least20 years old and are still going strong. Never broken a carbon boom, but I broke 3 sets of aluminum over a span of 5 years.I'm a lightweight at 150.
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GURGLETROUSERS



Joined: 30 Dec 2009
Posts: 1335

PostPosted: Thu Aug 29, 2013 6:13 pm    Post subject: Reply with quote

I meant long booms Slinky. My carbon wave boom is also 7 years old, but given my constant weight and strength, the strain on its shorter arms when overpowered with a small sail in high winds, won't be as great as that on a longer boom when overpowered (or pumping vigorously in lighter winds) with a much bigger sail.

What I meant by present use of carbon perhaps not being a good idea (my fault for not being clear) was that big booms need to be proportionally thicker, heavier, and beefed up for durability. That's what I want for safe cruising out at sea alone.

Unfortunately (from my point of view) carbon is seen as a means of making lighter, ( which racers want of course, and they are still breaking things), rather than durability. Durability no longer seems to be a market goal nowadays.
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stevenbard



Joined: 11 Nov 1993
Posts: 4058

PostPosted: Thu Aug 29, 2013 7:06 pm    Post subject: Reply with quote

Chinook is the best brand IMO. Most durable and I've only broken one on a mast high wave on Maui. Since I was hooked in, I was happy it broke...

They are expensive, but mine last 5 or more years.
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whitevan01



Joined: 29 Jun 2007
Posts: 473

PostPosted: Thu Aug 29, 2013 7:49 pm    Post subject: Reply with quote

gurgle, the deal with carbon is that is soooo much stronger then metals that less of it can be used to get the same strength so the product ends up being lighter.

carbon booms don't use that much less material than aluminum booms so they are way stronger. also, I believe (although I didn't look it up) that carbon has much better fatigue properties than aluminum. the drawback to carbon (as you found out) is that it is brittle and only fails catastrophically. also, carbon does not have good impact resistance.

booms are subject to high torque loads.

carbon booms, esp. in larger sizes, are far superior to aluminum because of the increased stiffness and the substantially lighter weight so both stronger and lighter than aluminum.
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GURGLETROUSERS



Joined: 30 Dec 2009
Posts: 1335

PostPosted: Fri Aug 30, 2013 3:43 am    Post subject: Reply with quote

Thanks for the answers. I'll check with our Chinook importer.

In the Mountain Bike world there were many carbon component failures a few years back when everyone jumped on the 'build as light as possible' band wagon. Experience (at customers expense) showed that they crossed the line towards unfit for purpose. There are fewer failures now but there are still areas where alloy seems to be the more reliable choice. (Chain stays, for example.) It seems some board models are also straying into flimsy territory. (Thread on a certain Exocet boards cracks, and Patrices reply as to what should be avoided.)

In windsurfing, we seem to expect things to break at regular intervals, while yachtsmen, dinghy sailors, and kayakers would find that unacceptable.
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slinky



Joined: 24 Aug 2007
Posts: 412
Location: Old Saybrook Ct.

PostPosted: Fri Aug 30, 2013 6:45 am    Post subject: Reply with quote

GT, check out Maui Sail carbon booms. Many pros think they are the best. I have a friend who sails formula and uses their booms. Compared to my fiberspars, which I always thought were great, they are much stiffer, with larger diameter carbon tube in key areas to increase stiffness and strength. Overall an awesome product, but heavier, and more expensive than others. I guess you get what you pay for.
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whitevan01



Joined: 29 Jun 2007
Posts: 473

PostPosted: Fri Aug 30, 2013 7:48 am    Post subject: Reply with quote

GT,
If you are interested in a Maui Sails carbon boom, I have a barely used 170 cm one for sale. Also, check out Chinook Pro 1 carbon. IMO, the best carbon boom out there and made in USA.

carbon bikes, I have a carbon road bike, and two carbon mountain bikes, carbon handlebars on all of them, carbon rims on the road bike and old spinergy rev x roks carbon wheels on my dual suspension K2 Oz carbon mountain bike. never had a problem, except I did crack a carbon (Zipp) road bike rim once when going 30 mph where they were doing road work and part of the road had been "gouged" away for new pavement and hit about a 3" high "ledge" in the pavement. all these bike are more than 10 years old and have lots of mileage and crashes (not the road bike thank goodness) on them and no problems with the carbon. I even bashed the K2 into some rocks one time (it is monocoque carbon) and it didn't even get scratched.

boats: I raced sailboats for 42 years, and the last boat I sailed (helmed) was a custom Farr 41. It was actually made of Kevlar, but had carbon rig and carbon North 3DL sails, carbon spinnaker pole, never an issue with strength or durability. that boat even had a carbon tiller.

as you can tell, I am a carbon fanatic.

carbon cars: Formula 1 cars have been pretty much all carbon for quite some time, and hardly anybody gets hurt in them any more. compare that to the days of aluminum chassis and fiberglass bodies when guys were dying all the time. (60's to early 70's).


anyway, the point of this rant is that you can't go wrong with a carbon boom IMO, unless maybe you go with an off brand.

have a good day.
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