How's my math/reasoning (canoes)?

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ChrisGreaves
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How's my math/reasoning (canoes)?

Post by ChrisGreaves »

Consider a canoe; one builds a 1:8 scale model, then a half-size model, then the full thing.
But how does it scale up?
Assuming that the models maintain their proportions, doubling the length (height, width) should raise the volume by a factor of 2^3, or 8 times.
Assuming the same material (density) is used, raising the volume by a specific factor should raise the displaced volume by the same factor; so the bearable load should rise by the same factor, right?
Doubling the model length should increase the available load by a factor of eight.
(And yes, one would have to include the weight of the canoe shell, and the weight of fittings and accessories in the available-weight calculations).
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Rudi
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Re: How's my math/reasoning (canoes)?

Post by Rudi »

The maths is beyond me, but I'm curious as to where you plan to row to. The Atlantic is a vast span of water...
If you are fit enough you can come for some tea and scones?
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Re: How's my math/reasoning (canoes)?

Post by HansV »

Chris is probably expecting a flood, and preparing Noah's canoe to transport the animals, two by two...
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ChrisGreaves
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Re: How's my math/reasoning (canoes)?

Post by ChrisGreaves »

Rudi wrote:The maths is beyond me, but I'm curious as to where you plan to row to. The Atlantic is a vast span of water...
If you are fit enough you can come for some tea and scones?
Well doh! You don't ROW a canoe, you PADDLE it.
And anyway, I'm actually thinking of a kayak (which AFAICS) is a canoe with a waterproof canopy, also one paddle with two ends, if you see what I mean.

Take a sheet of regular paper; cut a strip two-inches wide off the bottom; fold this strip in half; staple both ends.
Open it out a tad and you have a canoe, right?
OK. So not paper, but I suspect that real simple pliable boat can be made out of a flexible sheet of something sealed, with a suspended seat/harness (to lower the COG).

Short enough to wrestle onto, and off, public transit.

And definitely NOT lake Ontario, let alone the St Lawrence River.

Maybe the mouth of the Rouge River.
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Rudi
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Re: How's my math/reasoning (canoes)?

Post by Rudi »

ChrisGreaves wrote:...I suspect that real simple pliable boat can be made out of a flexible sheet of something sealed...
Remember that wood warps, so you might end up with a weird shaped canoe or a canoe that goes warp speed. :hairout:
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Rudi
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Re: How's my math/reasoning (canoes)?

Post by Rudi »

HansV wrote:Chris is probably expecting a flood, and preparing Noah's canoe to transport the animals, two by two...
:laugh: I'd like to see Chris "paddle" his ark...that will take a bigger miracle than the collecting of the animals.......
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Re: How's my math/reasoning (canoes)?

Post by Rudi »

BTW Chris....
This IS NOT allowed.

If you're gonna kayak....you gotta paddle....no cheating!
Jet Kayak.jpg
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Re: How's my math/reasoning (canoes)?

Post by Rudi »

Regards,
Rudi

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DaveA
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Re: How's my math/reasoning (canoes)?

Post by DaveA »

Chris,
You are not doing things right. In most cases you are talking about area 1:8, but your conclusion is wanting Volume.
A 1:8 scale model will contain 1/64 the of the area of a full scale item, at any scaled cross section.
Sorry I really messed this one up :blush

When finding the VOLUME of a scaled item and comparing to a full scaled item the numbers really go wild.
As an example a 1/2 scale view of an item would have 1/4 of the area of the full sized item.
Likewise a 1/8th scale would have 1/64th of the area of the full scale item.

Trying to do area and volume from a scaled down model is very tricky. It has been many years (BC, Before Computers), but we had to do this when we working on a new plane design and had to provide the volume of the cargo compartments to the possible customers as most of them were under a "Snail Mail" contract to provide x number of cubic feet for snail mail shipment.
Last edited by DaveA on 12 Aug 2014, 16:49, edited 1 time in total.
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Leif
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Re: How's my math/reasoning (canoes)?

Post by Leif »

DaveA wrote:Chris,
You are not doing thing right. In most cases your ate talking about area 1:8, but your conclusion is wanting Volume.
A 1:8 scale model will contain 1/64 the of the Volume of a full scale item.
1x1x1 -->8x8x8=64
Ummmmm..... 8x8x8=64?
Leif

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Re: How's my math/reasoning (canoes)?

Post by John Gray »

Leif wrote:Ummmmm..... 8x8x8=64?
8x8x8=64 for particular values of 8...
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ChrisGreaves
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Re: How's my math/reasoning (canoes)?

Post by ChrisGreaves »

DaveA wrote: In most cases you are talking about area 1:8, but your conclusion is wanting Volume.
Hi Dave; I didn't think I was wrong.
Whatever model I build, if I double all dimensions (length, breadth, height) then the volume (of the shell, not necessarily the displaced water) is multiplied by eight. regardless of the length of the model. That's true for a cube, a sphere, any solid AFAIK.

I haven't settled on a final size. I figured to build a working model, then determine by what factor I must scale it up to carry the required load (me + sandwiches + PDF)
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ChrisGreaves
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Re: How's my math/reasoning (canoes)?

Post by ChrisGreaves »

Rudi wrote:Coming back on topic, here are some:...
Thanks Rudi (Wanders off to study them ...) :headinbook:
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