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Carbon Boom Breakage.
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GURGLETROUSERS



Joined: 30 Dec 2009
Posts: 1354

PostPosted: Sat Sep 07, 2013 4:08 am    Post subject: Reply with quote

Thank you Bamer for your expert opinion.

Quote; 'From what I have seen there are a lot more engineers in the bike industry than in the windsurfing industry .....an engineering degree is generally more profitable in solving different problems than impirically derived expertise in one area.'

You suggest what most have long suspected, with windsurfing being a 'suck it and see' industry, with the paying customer as the guinea pig. Does the heat problem you state also apply to carbon booms left baking on the beach (ground, parking lot etc) when picked up to carry rig and board, (or suddenly loaded with body weight in harness), or are they saved by their comparative rigidity and lack of intentional flex, as compared with mast problems?
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lucashurt



Joined: 06 Oct 2010
Posts: 9

PostPosted: Mon Sep 09, 2013 2:37 pm    Post subject: Reply with quote

Hi GT
I'm not Bamer, but I would suspect the heat failure would be much less common in booms because the diameter to wall thickness ratio is so much lower. The same applies to skinny masts.
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keycocker



Joined: 10 Jul 2005
Posts: 3386

PostPosted: Mon Sep 09, 2013 3:16 pm    Post subject: Reply with quote

I don't think bamer means that heating a carbon boom in the sun causes permanent damage. The boom arms may have been autoclaved when they were made to cure them at higher temp.
It hardens epoxy to heat it up to a certain temp, but can soften it enough so that you need to cool off before placing a load.
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GURGLETROUSERS



Joined: 30 Dec 2009
Posts: 1354

PostPosted: Mon Sep 09, 2013 4:21 pm    Post subject: Reply with quote

I don't know if anyone recalls that multi-million pound all carbon fibre large ocean going catamaran, which the designers felt certain had been correctly stressed to withstand any seas it could encounter, but which broke up and was lost on its first venture? Was it ever ascertained where they had gone wrong?

Let's hope the Airbus design team who rely on carbon fibre better know what they are doing, with regard to long term durability and safety.

Also, I cringe when watching F 1 carbon braking systems glowing red hot under extreme loadings. How on earth do they not break up?
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keycocker



Joined: 10 Jul 2005
Posts: 3386

PostPosted: Mon Sep 09, 2013 5:26 pm    Post subject: Reply with quote

Not to worry. The carbon parts should have been on those planes a long time ago but the draconian testing takes so long that some tech gets old fashioned before it ever gets approved.
Ever notice most planes are still built with rivets like in WW1?
They are of a nearly hundred year old design, but once it got the airworthness certificate that is nearly impossible to get, they will make them like that forever.
Greene has trouble getting those certificates for the epoxy parts he makes in his board shop for helicopters. They are plastic ducts for the air cond.
I built a composite plane called a Varieze forty years ago. It wasn't even a kit plane, just a book of instructions.Still flying after forty years.
Construction just like modern board. The positioning of the UNI, and orientation of all the fibers was a big deal.
Looks like a UFO.
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GURGLETROUSERS



Joined: 30 Dec 2009
Posts: 1354

PostPosted: Mon Sep 09, 2013 5:35 pm    Post subject: Reply with quote

Nice one K.C.

My father started to build one of those Flying Fleas in the 1930's, the plans of which were in the pre war Popular Mechanics magazine. (I think.) It was a flying death trap which, once inverted, couldn't be righted.

Luckily for my mother (and for my existence, I suppose) he was sent off to fight in the war, and forgot all about it.

'Them' were the days! Rolling Eyes
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bamer



Joined: 30 Sep 2014
Posts: 58

PostPosted: Mon Sep 09, 2013 10:51 pm    Post subject: Reply with quote

GURGLETROUSERS, to be fair about the engineers in our sport, most sail designers I can think of are engineers. StarBoard has an engineer in charge of board development. Many fin designers are engineers. I would argue that shaping and building boards is more of an art than a science, but the really excellent shapers seem to work in both areas.

There could be a long discussion about the technological soundness of the windsurf industry versus other sporting goods industries. I think on the aggregate the windsurfing industry is pretty solid in comparison with surfing, kayaking, bicycling, etc. Given how many components are involved in making a rig versus the number of participants I think the gear is excellent and there are a lot of talented people moving things along.

On the booms, your scenario could happen but it is less likely than with a high carbon content mast for exactly the reason lucashurt said and because boom grip does an okay job of insulating, even though it is thin and black.

Below are pictures of a temperature readings from a bare mast and the back side of a sheet of boom grip put in the sun. The surface temperature on the mast measured out to 136.7 F. The EVA grip 119.3 F. Both were taken after 10 minutes in the sun with ambient temperature at 92 degrees. This was after 4pm so I don't think the sun angle was ideal for really heating things up.

The heat deflection point depends on the properties of the epoxy used. As keycocker said some epoxies are cured at an elevated temperature and elevated cure resins generally have higher heat deflection points. It depends on the resin whether things start getting weaker at 125 F, which is easy to reach, or 250+ F, which would never happen for anything we use or most anything just heated from the sun. The higher temperature resins are generally more expensive to buy and use because you have to have the heat source and provide fuel for it (gas, electricity).

The 136.7 degrees observed on the mast is ~10 degrees above the highest heat deflection onset for anything West System makes. So if the mast was made with a resin with similar properties to West System, the sun angle was more overhead, there was some extra heat generated from a luff sleeve, and the was mast under load (as all rigged masts are), we could be headed towards a failure.

Reaching the heat deflection point does not at all mean there is any permanent damage just as keycocker said. It just means the epoxy matrix is not as strong as it is below this point, how much weaker again depends on the resin properties, but with some cooling and time (this depends as well) the part will return to 100% as strong as original (keycocker hit this as well).

I have faith in the aerospace carbon products like the new Dreamliner and A380. There are similarities to what we use, but the materials, technology, and controls they employ are pretty different.



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