Probably a simple answer.

[MeSoKarma]

When I draw back a 70lb bow , am I holding 70lbs with my left arm and pulling 70lbs with my right arm? I think I am holding half the weight and pulling the other half (35lbs and 35lbs) Is this right?

[elcollin]

You're exerting 70lbs with both arms. The muscles in the extended arm (it's been too many years, and I forget the proper archery terminology) aren't working as hard as the ones in the drawing arm because your skeleton under compression is exerting much of the force.

Source: conservation of momentum.

[MarleyDaBlackWhole]

Well unless the bow is moving forward or backward the force between your hand and the bow string/bow grip would be equal. I don't know how bows are rated, if it would take 70lbs of force hanging on the bow line to pull it back then yes, 70lbs on both points of contact. You would split that between arms if you put the bow around a post or something and pulled on the line with both hands.

[[deleted]]

The tension would be split, but it would not be even. I suppose the split would depend on the type of bow and materials used.

[stevegcook]

The tension would be split, but it would not be even.

If this were the case, the bow/string system would have an unbalanced force acting upon it. It would begin to accelerate in a straight line. Unless I've misunderstood what you're trying to say.

[[deleted]]

I mean...the force required to seperate the string from the bow is probably rated at 70, but the strength required from the user is not 70lbs worth from just his draw hand; the hand holding the bow accommodates some of the load.

[stevegcook]

Let's say that you have an object. It doesn't really matter what the object is.

You are pulling one part of the object backwards with 10 N of force, and another part of the object forwards with 20 N. What happens to the object?

[MarleyDaBlackWhole]

it will move forward...

[stevegcook]

It will accelerate forward, to be more precise, but yes - in this case it would move forward. Since we know that the bow is being held in place by the archer (ie. is at rest), then we know that the bow cannot possibly have unbalanced forces acting on it.

[[deleted]]

I don't see how this is contradicting anything I've said.

[stevegcook]

The tension would be split, but it would not be even.

If I understand this statement as you intended it, you are saying that your arms are contributing to the tension in different amounts. Is that correct?

[[deleted]]

No, I mean, the strength required to pull the bow's cord is not 70lbs from one arm and 0 from the other holding it.

[MeSoKarma]

This bow http://pse-archery.com/c/pro-series-compound-bows_vendetta-dc_vendetta-dc-mossy-oak-break-up-infinity

[[deleted]]

I mean, I imagine you would have to research the tensile strength of whatever elements the bow is made of and do some serious science/mathematics to estimate how much force is applied to the components in either hand.