Carbon Fibre cabinets

Seeing and hearing is believing

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Firestar
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Post by Firestar »

I'm not arguing about it, even though there's no such thing as a lightweight hand layup, only one thats light in comparison to other hand layups. CF density is about 2, glass fibre about 2.5, so on a box the size of a cab the weight saving wouldn't be worth bothering with.
Done by hand, the resin would be 60% of the weight anyway, which is where the press or autoclave comes in, as the fibre to resin ratio is much higher, saving a load of the weight.

If someone wants to spend a fortune on a box that stays shiny for 5 mins and charges up like a capacitor every time it's shoved across a carpet just so they can say it's got carbon fibres in it, it's fine by me.

I'm simply saying that personally I wouldn't bother, I'd prefer to have one that attracted hippie birds rather than static, that way all the shocking stuff would happen backstage rather than on it.
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Post by Cknopp »

I think that if you do a bit of research on Carbon Fibre in motorsport, the conductivity issues have been figured out since the early 80's. Also, if there are no wires directly attached to the cabinet, and there are no fibres exposed, it would be rather inert as well.

Also, Carbon Fibre is only expensive if you don't know where to look. I have done some research on purchasing, and layup, and I don't think that a good CF cabinet would cost much more than a Tolex shrouded, finger/dovetail jointed birch plywood cabinet. Actually, once you do the original mold, you could actually produce them for significantly less labor than wood ones.

The real key is finding speakers that are light enough to make it worthwhile... If you lighten the cabinet by 20 pounds, but still use heavy speakers, you aren't really accomplishing much.

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Spongebob
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Post by Spongebob »

An internet customer of mine tells me he is (has) built a carbon fibre cab of a "futuristic" design 18 Watt amp. Well actually, from what I understand, it's a combination of wood & CF. Also that CF is part of his trade. I've asked for a photo but not received one yet.

It seems that a problem he is having is that each time he touches the cabinet he gets a very big static shock! 8O

I've suggested he join this group, so if he has and is reading this, perhaps he will give us all some more detail?
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krx
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Post by krx »

Spongebob wrote:It seems that a problem he is having is that each time he touches the cabinet he gets a very big static shock! 8O
Ouch! Gotta ground that cabinet, I'd think. Carbon fiber is conductive.
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zaphod_phil
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Post by zaphod_phil »

Even with all that resin holding the fibres together....?
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rjgtr
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Post by rjgtr »

Maybe a ground wire from the cabinet to the amp chassis will solve that.
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Plexi
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Post by Plexi »

back in the old days we had community sound.. fiberglass enclosers.
Alice cooper used a huge setup of PA stuff like that. I think alot of the moniters,and studio moniters, and outdoor speakers are carbon fiber.

another one of old were the Heil speakers..

http://www.communitypro.com/files/liter ... OCHURE.pdf
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krx
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Post by krx »

zaphod_phil wrote:Even with all that resin holding the fibres together....?
It's not that much resin. As long as two fibers are touching, they'll conduct from one to the next.
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LeeMo
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Post by LeeMo »

If the fibers didn't touch, they would make a capacitor. 8O

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Spongebob
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Post by Spongebob »

rjgtr wrote:Maybe a ground wire from the cabinet to the amp chassis will solve that.
From what I understand, he gets the static shock when it's NOT connected to a main supply. Here's what he told me about it.....

"I did toy with the idea of a full cab, but a major problem, apart from it scratches easily, is that you have a conductive carbon mat surrounded by an insulating epoxy resin, and I know from making it that the bloody stuff can sometimes charge itself up like a big capacitor if it’s squashed too hard, and probably if it’s dragged across a carpet as well. Don’t mind people saying my amp is shocking, but it’s a bit of a swine getting one every time you pick it up."
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Post by rjgtr »

Songebob,

Well that would be a drag! Waybe if you put tolex or a thin material on the outside that would help. Hey I wonder if the olde Stienbergers or the parker flys have that issues too! :wink:
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Cknopp
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Post by Cknopp »

What I don't understand is what kind of resin is he using that is conducting the shock to his hand? The resins that I have looked at are inert, and electrically insulating. Maybe he needs to spray a continuous skin coat over the entire thing (especially any trimmed edges).

After that, it would have to be inductive to gain any type of charge.

PS: If you look at the BMW F1-09 during preseason testing with their battery KERS system, they had a mechanic touch the car, and get jolted pretty hard. The press release that they sent out after they solved the problem stated that they found out what was happening (wire scraping the CF under full lock), and that their solution was to encapsulate the entire tub in a resin coat to prevent it happening again.

I understand what these guys are saying, but I must say that pre-preg would be VERY suceptible to this, due to the very close mat/resin ratio, but I cannot see how a good topcoat would not fix the issue? That is like saying a wire is not safe even though it has dialetric insulation around it.....

I will take the builders word for it however. I may disagree with speculation with what I have learned, but I will not disagree with experience. Unless he doesn't know what he did in the first place! :-P
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Post by zaphod_phil »

Because it's a very good dielectric it's probably good at accumulating charge on it's surface. Similar to when you rub a ruler with cloth during the cold winter months. If the surface were coated with a conductive film that might help, especially if it could be grounded.
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