On Fri, 4 Nov 2005 05:17:24 -0500, "Mike Marlow"
wrote:


"Robert Allison" wrote in message
news:idCaf.30009$bb3.11443@trnddc02...


We set up a piece of plywood in front of a table saw once and
drew a target on it. We would leave the fence slightly loose,
run a piece of 1x4 through the saw (to make a 3/4 x 3/4
piece), then push the fence into the piece and send it flying
back (intentional kickback). You can put a 6 foot piece of
3/4 x 3/4 pine about 3 feet through a 3/4 inch thick piece of
plywood from 15 feet away that way. Really makes you respect
the power. Love those Powermatics!

Hmmmmm... My compound bow will launch an arrow at somewhere above 240fps.
That translates to around 160mph if I do the math correctly. It won't come
near to putting an arrow through a 3/4in piece of plywood from any distance.
I have to confess, I've never tried to put it through a piece of wood at 5
yards, but I have hit a target frame or two over the years at 20 yards and
penetration is only an inch or two. A six foot piece of 1x1 will surely
have little enough spine to distort upon impact and just makes me have to
question its ability to penetrate a piece of plywood any amount at 5 yards,
let alone penetrate it three feet.


the physics involved look something like this:
your compound bow is human powered. you can never put into it more
than about 1/3HP. it stores a bit and releases it progressively, but I
doubt that it's applying more than that 1/3HP. this is why your arrows
are so light- otherwise they wouldn't be able to go so fast.

a longbow shoots a heavier arrow, but it takes one very strong guy to
draw it. a longbow was supposed to be able to penetrate chain mail-
it'd probbly penetrate 3/4" plywood.

crossbows usually are too high a draw to be pulled by human arms.
they are mechanically cranked, and shoot an even heavier bolt. they
would penetrate plate armor. prolly not even slow down much through
plywood.

my tablesaw is 3HP. it can launch a chunk of wood approximately 9
times as heavy as your bow can shoot an arrow, as fast. that is a lot
more energy being delivered to that piece of plywood.

I don't know if it would penetrate 3/4" plywood in a kickback. I hope
I never find out.