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[chefslot]

Say i was to build a fishing boat, scaled it down from the original by 1:100, and say the original could take 100kg, would the scaled down version be able to take the scaled down weight load? .

[SailorGreg]

The simple answer is no.  Scale is a linear measurement while displacement (or carrying capacity) is a volume measurement (length x breadth x depth, although it is a little more complicated than that for a boat-shaped object).  If you take a 60' fishing vessel it might have a displacement of 60 tonnes.  At 1:100 your model will be 7.2" long.  If you scale the displacement linearly, you end up with a figure of over half a tonne.  i don't think there is a 7" model anywhere that could manage that!

Greg

[Pat Matthews]

The answer is Yes, you can scale the displacement (weight), but the scale factor goes with the VOLUME, not the length. This can be arrived at by CUBING the linear scale factor... which is just a compact way of saying "divide the original weight by the scale factor three times".

So that 60 tonne (60,000 kg) boat at 1:100 scale will be 60,000 /100 / 100 /100 =  0.060 kg = 60 g. (Not really a practical example for RC, but you get the drift).

[chefslot]

Cool i didn't think so, my thoughts was all to do with gravity and scaling that down which is impossible, but i guess thats all about displacement some where.

[malcolmfrary]

Any working scale model boat has to be the exact scale weight to float.  The lengths are to the actual scale, any areas are to the square of the scale, all volumes are to the cube of the scale, as is the power to move it at a scale speed. 
100Kg for the original would be about one crewman.

[chris_suffolk]

Scaling my tug weight down from the original, using the cubic factor, gives almost exactly the weight of the model to bring her to the correct waterline - so yes it does work accurately.

Things that don't scale are speed and pollard pull etc because the viscosity of water doesn't alter as the model in it gets smaller.

[chefslot]

So i've got a stand up paddle board, this is 3000mm long, and can hold my wait of 80000g easily. Say i was to scale it down to 300mm (30cm) it still would easily hold 8000g (8kg) Sorry for the brackets but to me it doesn't seem plausible, is it??

[chris_suffolk]

So i've got a stand up paddle board, this is 3000mm long, and can hold my wait of 80000g easily. Say i was to scale it down to 300mm (30cm) it still would easily hold 8000g (8kg) Sorry for the brackets but to me it doesn't seem plausible, is it??

You don't give a width or depth for your board - they will also reduce in the same proportions. If it goes from 3000mmm to 300mm, the other dimensions will also reduce by a factor of 10, and the overall load it can carry will reduce by a factor of 1000 (10x10x10), thus meaning it can carry 80000g (80kg), down to 80000/1000 = 80g, which is much more sensible

[chefslot]

You don't give a width or depth for your board - they will also reduce in the same proportions. If it goes from 3000mmm to 300mm, the other dimensions will also reduce by a factor of 10, and the overall load it can carry will reduce by a factor of 1000 (10x10x10), thus meaning it can carry 80000g (80kg), down to 80000/1000 = 80g, which is much more sensible

Well the length was just a figure to paint a picture, could give the width but that would also be scaled down to the same values.


So this 10x10x10 thing is accurate then? What is it called etc etc?

[malcolmfrary]

So this 10x10x10 thing is accurate then? What is it called etc etc?

10 = number        gives distance
10X10 = square of number    gives area
10X10X10 = cube of number   gives volume and weight


And yes, it is totally accurate.

[derekwarner]

Guys...lets get the terminology in the correct format first 
Weight of the boat......or displacement of the boat? ....the latter is relatively easy......... ....Derek
 
 
 
 

[essex2visuvesi]

Also bear in mind water is a constant and doesn't scale