Stuff I don't know: Why not use aluminium?

"Man, if I had the money, I think I'd get one of those Honda F6Bs," I'll sometimes tell myself.

Effectively Honda's Goldwing grand tourer sans top box, the F6B is, after all, a good-looking machine. And from everything I've read it's a hell of a lot of fun to ride, with handling that belies its massive weight and size. Ever since the bike was released a few years ago I've been daydreaming about owning one and riding it all over North America.

"But, actually," I'll say, continuing the thought. "If I had the money I can't imagine that I ever actually would spend it on an F6B. Because plastic."

Having seen one of these beasts in person I couldn't help but notice that it possesses quite a lot of plastic -- something that puts me off for a couple of reasons. Firstly, because it feels wrong to pay £20,000 (a) for a motorcycle with that much plastic. But more importantly because of what plastic does when stressed: it cracks.

Drop the F6B or accidentally whack it with a hard object and you'll be left with cracked bits of fairing that will fall off and cost you hundreds upon hundreds of whatever currency you use to get it fixed. Whereas if said damage were to occur to a metal part the result would be scratched paint and possibly a dent. Which might add a certain emotional value to the thing. Scars are cool, after all.

I'm picking on the F6B a little here simply because it has so much plastic, but the truth is that plastic is a feature of a great many bikes. I'm in stupid love with the Victory Cross Country, for example, but I know that if you fling that bike on its side the result will be quite similar as with the F6B: lots of cracked plastic (b).

My question is: why?

Not why does plastic crack, but why do modern motorcycle manufacturers use so much plastic? Or, rather, isn't there anything else they could use instead?

I understand that plastic has a fair few advantages: it's relatively cheap to make (and therefore less cost is passed onto the consumer) and it's light. Both very good things. But would it be possible to use some sort of other material, like aluminium? Why not make aluminium fairing? Is that possible?

It seems to me that aluminium would be more or less as light and as cheap as plastic, but with the advantage of being less likely to crack. Or, what about magnesium, which weighs a third less than aluminium?

Is plastic really the best solution? I feel, however, that if my aluminium or magnesium idea was valid somebody would be doing it by now. So, there must be a good reason; I just don't know what it is. Anyone have an answer?

I'd love to know.

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(a) I can't help noticing that it costs $20,000 in the United States, which is terribly unfair. Because $20,000 is £12,263. If offered here at that price it would be a damned reasonable machine. That price difference is so huge, I wonder if you'd ultimately come out ahead buying an F6B in the United States and importing it to the UK.

(b) Actually, no, I don't think that would necessarily happen, because I'm pretty sure the Cross Country comes with those kick-ass Victory floorboards that keep the bike from going all the way over.

Comments

  1. ABS plastic: 1.08 g/cc
    Aluminum: 2.7 g/cc
    Magnesium: 1.74 g/cc

    To be the same weight as plastic, the metals would have to be much thinner, and we all know how thin aluminum behaves. Magnesium also burns spectacularly. And metals are more expensive to form into the complex shapes that full fairings are often in. That said, the old dustbin fairings were usually made from aluminum.

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