weight to scale

[3pepper]

just curious
if you build a scale model of a boat at 1" = 1' , can you use something like 1 pound = one ounce , and load the model boat to see how it sits in the water with different loads and load positions ?

is there a formula to accuratly load the model boat?

thanks
stephen

[P.I. Stazzer-Newt]

Divide real world weights by 1728. (12 cubed)

[3pepper]

wow ! that simple , thanks

stephen

[Thorne]

Just remember that you can't shrink the water molecules or laws of physics, so many elements like surface tension and wave/swell action will be different, causing interactions that aren't accurate when compared to the 'real world' no matter how good the model...

[Ken Hutchins]

1728, but also need to consider salt/fresh water density if model is going to be used in fresh and full size boat to be used in salt water.

[paladin]

and...depending on how big your water tank is....you can add a couple of tablespoons of alcohol to reduce the surface tension...

[3pepper]

thanks again
i also planned to weigh the model hull to see if the scale weight compared to the calculated weight of the full size hull and alter as nessisary . i only wanted to try this to see what the ballance and draft of the hull would be under different cercumstances . i posted about the ozark john boat and decided i should know the weight of the hull as is and the weight of the hull if i increased the beam , to decide a "width at the cost of weight" compromise . i also would like to know the effect of two marien batteries and there placemant fore and aft in the hull , and their relation to one or two fisherman . this is only to help me understand draft , hull weight , cargo capacity and trim . this is great fun , at worst it will perform better than the aluminium jon i had growing up with .
thanks
stephen

[Lucky Luke]

This is an excellent way to do, pepper. It will help you understanding what we otherwise do with the click of a mouse using the Naval Archtecture programs. Go ahead and have fun, but do not expect much accuracy with a 1 to 12 model of a already small boat.

[Bruce Hooke]

You are going to have to work VERY carefully to get any sort of accurate weight. Consider that paint alone adds a few pounds to a boat, and you will realize that there are some things that are hard to scale down to a model of this size. None-the-less, it is a very worthwhile exercise for someone in your position.

[Ron Carter]

Had a great article years ago on just what you are doing. It used pennies as the basic unit of weight and had a long list of how many pennies converted to what object. People, batteries, various engines etc. Spent several days looking for it last winter and it apparently is gone entirely. I thought is was Payson but that turned out to be a dead end too.

[Keith Wilson]

A reference book: if you can find Weston Farmer's From My Old Boat Shop, it has a couple of good chapters on model testing. The book's kind of old-timey, certainly pre-electronics, but air and water and the laws of physics haven't changed. I think that's the article Ron is referring to; he uses pennies for weights. It may have been reprinted in Messing About In Boats at one point.

[Ron Carter]

Keith,
I'll bet that's the one. Will have to see il I can find it now I know where to look. Thanks.
edit to add,
Just looked on Amazon.com $60-100 used. Guess I'll try the interlibrary loan first.

[carlg]

That was reprinted recently, and for less than $60 - $100. I don't remember where I saw it.

[3pepper]

thanks
great artical , i will float test my models tonight .
thanks again