Re: Units of measurement?

From: Slobodan Midic <slomi_at_EUnet.yu>
Date: Mon, 10 Apr 2006 23:24:35 +0200

Excuse me Mark, I must say something about this topic...
After this I will stop ...

Hi Bruce,

I'm an electrotechnical (technical phisic) engineer, live in
Serbia and Montenegro, Novi Sad, and I'm Serb.When I
began my study in Belgrade CGS system was actual. After
some time was MKS system in use. Now we have SI system
in all Europe. As I know US also use SI system in all sciencific
works. You know all this names: CGS, MKS, SI. No one
system is ideal, in each you must have some numeric constants.
That is so in the nature of units, and in the nature general.
You know circumference of circle is Pi: transcendental number ...
in each measuring system.

So, when I began with indoor models I must bue balsa from
US, all in Inch-Pound system. For me, that was no problems.
But when I calculate the weight (mass) of my F1D, or 35cm
model I work with density of all materials in [mg/mm^3], and all
lenghts in [mm]. So I get result of weight in [mg], for each article,
and all model. Note: 1[mg/mm^3]=1[g/cm^3].

About SC (stiffness coefitient):

If some define SC as E[N/cm^2]/(Specific weight) [N/cm^3],
result is in lenght unit [cm]. If you define SC as E/(Specific gravity)^2
I dont know what is this, (for me I dont understand this logic- in this
way density is more faworised than modulus of elasicity), only
perhaps to get result for balsa to be about 100!? You can also
define your owne SC but you must say to other people what
you were work.

If you will discus about thet thing with me please out of group,
I belive other people dont love this ... Thay lowe much more models
to build and to fly ... This group is for this things ...

Regards,
S.M.
Received on Mon Apr 10 2006 - 14:24:08 CEST