Understanding working limb dynamics

[cunruhshoot]

I recently purchased the very large book...Traditional Bowyer, More Unnecessary Fun...by Jack Harrison.

Very good book and a resource that I will draw on continuously in my bow building journey. One thing that I have yet to find in the book and would like to have a better understanding of is the dynamics of the Working Area of the limbs.

I have watched Dean Torges DVD and he talks about this a little. Dean states that having more working limb is a bit of a slower bow but throws a heavier arrow and therefor makes a better hunting bow. Where as less working limb creates a whippier bow with more speed but cannot handle a heavy arrow and makes for a better target bow.

I will frame my question this way.

I have been using the Bingham form design for my 62" R/D Hybrid longbows. Would you say that this design form has more or less working limb as compared to Kenny M's longbow design? And where does a Howard Hill style bow fit in regards to working limb?

[MoeM]

Don`t know Kenny`s LB but I guess it`s around 66", mild R/D, with short riser (~16")?! So the shorter Bingham will have less working limb for sure- 1. shorter limb AND 2. stiffer ends to void stacking.
The Hill style has, exept short riser and such ends, longest working limbs for modern bows (English warbows outrage them as example and are NOT modern)

You can experience this yourself- all you need are two bows, a recurve and a longbow (Hill for best result), both same weight and arrows- one light carbon and one heavy wood with such head...
You`ll be surprised bout the effects visible!

[Roy from Pa]

MoeyM, ya expect us to believe all dat stuff?        

[LittleBen]

I hesitate to throw my two cents in but what the heck.

There are alot of variables which will affect how fast a bow shoots an arrow of light and heavy weight.

If we reduce the variables by taking two nearly identical bows, same riser length, same limb length, same draw weight, same energy storage etc. The only difference being that one bow (A) has a shorter WORKING limb and bow (B) has a longer WORKING limb. Lets say that bow (A) has a shorter WORKING limb because the tips are stiff for the last 8".

1) The stiff tips of bow (A) can be made lighter than the working tips of bow (B). Therefore, total limb mass can be lower on bow (A).

2) A lighter limb can accelerate faster, and can therefore propel a light arrow faster than a heavier limb can.

3) If you made a graph of the arrow speed vs. arrow weight of bow (A) and bow (B), you would find that at low arrow weight bow (A) with its light weight tips would shoot faster than bow (B). As arrow weight increases you will see the difference in speed between the two bows decrease. Eventually, at very heavy arrow weights, the two bows will shoot nearly identical speeds.

4) There is no reason that a bow with less working limb would be less capable or less efficient shooting a heavy arrow than a bow having a greater working limb.

I hope this answers some of your question from the most fundamental basis.

There are so many other variables that will affect arrow speed, trying to compare two bows on the basis of working limb alone will not yield an accurate comparison of the differences in speed at various arrow weights.

[jsweka]

Ya'll think too much.  

[cunruhshoot]

I hear ya...John - Here is why I was asking. I was just trying to understand how you know that more of the limb is working.

[LittleBen]

John, it's a gift and a curse. It got me through engineering school twice, but it also causes me to drive most people nuts talkign about this sort of nonsense

[mwosborn]

I would give my 2 cents worth - but I can't afford it!