I've been seeing the term 'virtual mass' in Norb Mullaney's bow reports for-freakin'-ever and never have been able to figure out what virtual mass actually is. Come on, somebody, and make me smart like you. 'Splain it to me.

Thank God I'm not the only one who doesn't know!!!!!

Seems pretty self-splanitory to me

First thing I learned when I picked up a bow.

though everyone knew it.

If you have to ask - then you don't need to know[]

I don't know either,but I've know some women that could qualify...Bob

Just curious, when he mentions it, what kind of figures does he give? In other words, give us an example of a number (or whatever it is) that he uses to describe it.

http://home.att.net/~sajackson/archery3.html

http://www.bowyersedge.com/arrows.html

Every search I do keeps coming up with these same two links. Haven't read them fully yet, but hopefully they'll provide some clues.

Straightarrow, here's an example, one of Norb's reports-

http://www.martinarchery.com/mag/bwfury.html

IIRC it's a figure (expressed as XXX.Y grains) that is derived from results of the arrow velocity/weight tests of a bow and is used to extrapolate/approximate efficiency and speed at differing draw weights. Bows that have higher virtual mass will not lose as much efficiency at lower draw weights than bows with lower virtual mass.

I think that's it anyways. Something along those lines.

:shrug:

I'm gonna take a stab and say that virtual mass is the amount of energy inefficiency that is not passed to the arrow, similar to if it was mass weight on the arrow itself.

Using Norbs report above, if you had a bow with 100% efficiency and added 143 grains to the arrow, the resultant reduced speed is comparable to what the bow does as at less than 100% efficiency. It's potential energy that is lost in the transaction of flinging an arrow.

Did that make any sense?

Yeah, one of his "big two" terms that say..."I'm an engineer, and you're not!"

Static Hysteresis and Virtual Mass.

I was under the impression that the lower the virtual mass, the greater the speed gain with lighter arrows. I do remember (back from when I used to read his reports every single issue) that the Mathews Z-Max had one of the lowest Average Virtual Mass #'s of any bow test I can remember. That bow definitely showed a bigger gain with lighter arrows than other bows of the mid-late nineties.

I really liked the test procedure he used, and he certainly has done and continues to do a great service to the archery industry in general. I wish I still had some of those old issues around to give Norb's own definition. I may still have one or two in the garage. I'll post again if I find the info.

Good answer!

Undoubtedly true! Been shooting bows for nearly 50 years and don't know, for sure, what it is.

I know virtual mass is a measure of inefficiency but I don't understand exactly what it means...???? Reading Jackson's article just made my brain hurt.[X(]

Reading Torges' article got me lathered up to make another selfbow. [&:] Good reading about Fred Bear's ballistic penduluum tests with various weight arrows if you scan on down towards the end of that article.

Yet another perfectly true and applicable point. LOL