Re: [Harp-L] widening out/opening up the backs of harps

[Michelle LeFree <mlefree@xxxxxxxxxxxxxxxxxxxxx>]

Rick Dempster wrote:

> I agree, no difference worth noticing; but what, for example, Joe Spiers
> does makes the plates stronger,
> so my 'pocket' harp does much better with this particular mod.
> RD

I have to disagree here, Rick. stock SP20 cover plates are significantly 
stronger than "opened" plates for two reasons.

First, from a vector mechanics (physics) viewpoint, the vertical 
component of the right angle flange at the back of  the harp contains a 
lot more metal to resist vertical downward force (or upward on the 
bottom plate) than opened plates do. This is the same concept that 
engineers apply in their use of structural I beams.

That vertical part of stock cover plates also contain struts that help 
stabilize the cover plates. When you open the back you flatten those 
struts out.

The comb's plastic struts support the center of the cover plates but the 
other two mechanisms for resisting downward forces are gone when you 
flatten those vertical flanges.

But, it does look cool. 8^)

Michelle