rib and panel math

[Ron Nossaman]

John,
A couple more things. Here's the other half of the compression crown
equations. These return panel PSI from given rib dimensions and measured
crown. I put these together this evening. This time you get the Pascal code,
but it's pretty easily followed. I incorporated the moment of inertia into
the equations, but I left it separated too so you could see where it fits in. 

function panel_comp_in(span,height,width,thick,crown:real):real;
{input rib and panel dimensions in inches, output panel psi} 
var panel_leverage,moment_of_inertia, def_full:real;
begin
   moment_of_inertia:=(width*height*height*height)/12;
   panel_leverage:=((348*E*((width*height*height*height)/12)
                   *crown)/(span*span*span))/5;
   panel_comp_in:=(panel_leverage/2)/(((height/2)+(thick/2))/(span/2));
end;

function panel_comp_mm(span,height,width,thick,crown:real):real;
{input rib and panel dimensions in millimeters, output panel psi}
var panel_leverage,moment_of_inertia, def_full:real;
begin
   moment_of_inertia:=(width*height*height*height);
   panel_leverage:=((E*width*height*height*height*0.04495*crown)
                     /(span*span*span))/5;
   panel_comp_mm:=(panel_leverage/2)/(((height/2)+(thick/2))/(span/2));
end;


Some rib deflection tests I did a couple of years ago indicated that (my)
feathering was the equivalent of taking about 12% off the height of the rib.
I don't know any other practical way of factoring this in other than a few
empirical trials and an appropriate windage adjustment on the computations.
I haven't a clue how to compute the feathering allowance directly. 

Thoughts?

 Ron N