[RESOLVED] Scale

[Pantier]

A rather embarrassing (and stupid) question that nevertheless has managed totally stump me.

I build models, mainly aircraft but the odd ship too. As a kid I built a model of the Titanic at a scale of 1/350. The real thing was 269m (882ft) long and sure enough the model 77cm long (296/350). Fine.

However the real thing weighed in at 46,000 tons. So, 46,000/350 = 131 tons for the 77cm model, clearly something is amiss. Is it because the first calculation “works” effectively in 2D while the weight takes account of the 3rd dimension? i.e. I should be square rooting to the power of 3 and then dividing by the scale factor (1/350).

Any help is thoroughly appreciated (Ah the beauty of the internet, I can stay anonymous and not look like a prize muppet in front of colleagues…)

[si_the_geek]

Welcome to VBForums!

Your assumption of the third dimension sounds right to me, but I'm not sure if it works in quite the way you are thinking (square root), it may be a cube root, or some other calculation.

[zaza]

Just because you scaled the lengths by 350 doesn't mean you kept the mass the same, does it? If you built your model out of exactly the same materials, but everything was scaled in all 3 dimensions by 1/350, then you'd expect each piece to weigh 1/(350^3) as much, and hence you'd expect the model to weigh the same when compared to the total mass of the Titanic, namely 0.001 tons or about 1kg.

To put it another way, your model was 77cm long, but it wasn't as wide or as high as the real Titanic, was it?

Actually, I suspect that you didn't use exact scale replicas at 1/350 of everything and in the correct materials, but that you built it out of plastic and wood, so the weight scaling becomes a bit irrelevant.

zaza

[Pantier]

Thanks for the replies everyone. I have a cunning plan how to find out with a practical method. I'll let you know.

[autoactuary]

I can't believe you want the weight of your model to scale. As said above the material would have to be the same to get the same density and also you would need every peice of the titanic in your model! I think some of the washers would be microscopic. Why dont you just calculate the weight of the model, the weight to scale, subtract the weight of the model from the weight to scale, and add a peace of lead inside your model to compensate for the difference.

Really though, most people don't pick up their models and play with them so I'm not sure it will impress anyone.

[Pantier]

Guys, its so much easier than this. The weight of the titanic in model scale (ie if the real thing, made out of steel etc, was shrunk to 75cm), is equal to the weight of water it displaces, just like the real thing. All I did was calculate the volume of the submerged area.

Can't remember what it was but it was sensible and I liked.

Clever ehh?

Ciao, all.

[zaza]

Guys, its so much easier than this. The weight of the titanic in model scale (ie if the real thing, made out of steel etc, was shrunk to 75cm), is equal to the weight of water it displaces, just like the real thing. All I did was calculate the volume of the submerged area.

Can't remember what it was but it was sensible and I liked.

Clever ehh?

Ciao, all.

I don't really understand what's going on. I thought your problem seemed to be that you didn't understand how scaling the dimensions by 350 gave you 131 tonnes for the weight of your model. Were you actually after finding out the weight? Of the model? Or the scale?

Still, at least you're happy. Don't forget to mark the thread as Resolved.

zaza

[Pantier]

how'd I do that?

[zaza]

Top of the page, there's a menu called Thread Tools. It's in there.

zaza