Sorry Carl, I tried to give the information without the post going on and on.
First off
Spine/Spine weight refers to the arrow shaft in other words how flexible it is.
Draw length refers to the distance from bow to the string at full draw.
So if you buy arrow shafts, they usually measure 32" and are spined accordingly. If you shorten them you also stiffen them, thereby increasing the spine weight.
Imagine holding a bow with the arrow nocked on the string and resting on the back of your hand (index finger knuckle). The arrow will point slightly to the left due to the thickness of the bow. Correctly spined arrows are essential and this is known as the 'archers paradox'. That is the arrow must bend around the bow before continuing on its course.
Another point that I did not mention was the tillering of bow limbs. The lower limb is stiffer because the arrow is not fired from a central (top to bottom) position on the bow.
Hope this helps
......Orda
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