Re: Units of measurement?

From: izgo <izgo_at_yahoo.com>
Date: Sun, 09 Apr 2006 21:39:17 -0000

You welcome.

Besides I prefer and use metric units, I still use
pounds/cu. ft. for balsa density. Why? because almost
nobody (in indoor model) use metric units for that.

In a normal conversation with other modelist,
we say: For EZB props you need balsa wood
of '4' or not heavier than '4.5' lb/cu.ft.

Im just speaking on how things are here.
If you are going to do a scientist investigation
probably you need to stick to metric units. But if
you work is for other modelist I belive will be more
practical to use lb/cu.ft. units for density.

Probably, you can give an option in your calculator
to input metric units for lenght, width and
thikness and result come in lb/cu.ft.

I use very often that way to compute density for
spars and small pieces of balsa. I do all measurments
in milimeters and weight in miligrams. Later:

Wight [mg] / (volume [mm^3] *0.016) = density [lb/cu.ft.]

As you can see, 0.016 is the conversion factor.

Same formula can be used to know wich is the maximal
volume (in cu. milimiters) for a piece given a certain
density and the desired (maximal) weight. Then I
play with the dimensions.

Sometimes when you read a plan you have the dimensions
of a piece and the weight, but the density is missing.
I use that formula to know from what wood (in lb/cu.ft.)
I have to cut the piece. Or, if you know the volume
and the density, you can find how much will weight
the piece (in miligrams), all that before cutting :)

Sometimes is hard to find the volume of piece
(tapered booms and spars, props, etc) but
aproximations works ok.

Sorry, im out of topic. Just I wanted to explain
better why I still prefer density in lb/cu.ft.
regardless I use metric units for anything else.

Bye!

Ignacio




--- "Bruce McCrory" wrote:

> Thank you, Ignacio. US Common for density is always
> pounds/cubic foot. Would the commonly used metric
> measurement for balsa density in modeling be
> g/cm^3? Or, kg/m^3?
>
> Bruce in Seattle
Received on Sun Apr 09 2006 - 14:40:17 CEST