Building to scale

[Lancer]

I'm going to be building a catamaran in the Philippines but the plan I have may be a tad small. I'm thinking if I double all dimentions it should work out just fine, right?

The boat would just be twice the size, yes? I know this is likely an epicly stupid question but whatever.

[snoopy369]

I don't think you exactly double everything, because of things like surface area and displacement not being precisely linear. But I'm not sure, due to me not knowing much about boats

[Lancer]

That's what I was wondering about snoopy. If I double the frame does the skin double or need revision?

[Aeson]

"You're gonna need a bigger boat" - Jaws

I'm just guessing, but there might be some issues with using the same materials at a larger dimension.

[Lancer]

That's a good point.

[Zkribbler]

If you double all linear measurements, you'll be fine. For example, let's say your original measure is 3 [somethings]. If you double a line, it'd be 6 -- no problem.

The only conceivable problem -- & I don't think you'll come up against it -- is if there's a meaurement of area or volume. Say, if you're working with an area, doubling a both sides of an area which is originally 3 sq. somethings, would result in 12 sq. somethings. And if you dealing with volume, if you double the length, width and breadth measures which originally gave 3 cu. somethings of volume, you get 28 cu. somethings.

[Lancer]

I think you're right, I won't run into area measurements. It should just be linear. The displacement bit that Snoopy mentioned might be a tad off tho. The volume increases exponentially which increases flotation more than double methinks.

[Zkribbler]

You thinks right.

[Lancer]

Was bound to happen sooner or later.

[Zkribbler]

Hey, even a broken clock tells the correct time twice a day.

[Lancer]

6:02

[Sirotnikov]

Material strength is a very important point.

Volume and mass would increase in a non-linear manner and it would have serious consequences.

One of Israel's largest mass-tragedies was when the builders of a bridge, decided to increase it in a linear fashion without re-performing calculations.

It crashed under its own weight and loads of people drowned.

[Lancer]

Good point, I'll have someone else take it out first time.

[Lancer]

Ditched the 55 gallon drums, hang on I'll post a link in a sec

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=6589467484&ssPageName=MERCOSI_VI_ROSI_PR4_PCN_BIX_Stores&refitem=290156552078&itemcount=4&refwidgetloc=closed_view_item&refwidgettype=osi_widget

If you hunt around the site you can find a pic of the cat.

[VetLegion]

Re: Building to scale

Originally posted by Lancer
I'm going to be building a catamaran in the Philippines but the plan I have may be a tad small. I'm thinking if I double all dimentions it should work out just fine, right?

The boat would just be twice the size, yes? I know this is likely an epicly stupid question but whatever.

The answer is NO. It will NOT be OK if you simply double the dimensions. Don't gamble your health on something like this.

Mechanical strength of something is dependent on the external dimensions, but also on the shape of the cross section and the distribution of the material in the cross section. It is not at all linear!

If you purchased the plans for the ship, sell them and purchase new ones for a bigger ship. If you drew them yourself, recalculate everything.