Composite bows absorbing shock?

Sinsigel · Post by **Sinsigel** » Tue Sep 05, 2006 3:32 am

For several times, I've read from some archery related books that

Composite bows of horn, wood, sinew are able to absorb the shock

after the release of the arrow.(Or, does it happen in other type of

bows other than composite ones?)

If so, what causes this "absorb of shock", and how does this absorption

work?

Sorry for bringing another minor question.(-_- ;)

Stephen Selby · Post by **Stephen Selby** » Wed Sep 06, 2006 2:16 am

I don't believe that composite bows are different from self bows in this respect. Actually, many composite bows that are small and light casue a large amount of shock.

Adam Karpowicz · Post by **Adam Karpowicz** » Wed Sep 06, 2006 9:53 am

All bows absorb shock one way or another. The lighter the draw weight, the lower the mechanical efficiency, so more energy is wasted on shock to be felt by the archer.

Adam

Sinsigel · Post by **Sinsigel** » Thu Sep 07, 2006 3:34 am

Lighter draw weight leads to lower (mechanical) efficiency?

That's interesting.

Thank you for answering, Mr. Selby and Mr. Karpowicz.

Stephen Selby · Post by **Stephen Selby** » Thu Sep 07, 2006 3:55 am

The lighter the draw weight, the lower the mechanical efficiency, so more energy is wasted on shock to be felt by the archer.

Adam: does your comment apply only where the mass of the limbs remains the same? Does it still apply if the mass of the limbs is reduced in proportion to the the draw-weight?

Adam Karpowicz · Post by **Adam Karpowicz** » Thu Sep 07, 2006 10:19 am

The problem is the mass of limbs can not be reduced in proportion to draw weight. If this was done, then the stability would suffer, because the static ends would have to be reduced also, together with the bending sections of limbs. Such thin ends would be too weak and liable to twist. I believe in existing designs it is impossible to make a well performing bow of less than 60lb weight.

Adam

Nick · Post by **Nick** » Fri Sep 08, 2006 12:24 pm

Hi,

This is a very interesting discussion - and it relates a bit to my thread a few weeks ago (re. feel of draw etc.). I will add that I am no expert in making bows but have made a few ELBs and flatbows from self and laminated wood and have owned and shot a number of various weapons also (my knowledge here will not be in that same league as Adam!). One thing I noticed was the difference in hand-shock and also ease or 'smoothness' of draw. This can be down to design factors, but also the type of wood. Yew generally gives very sweet-shooting bows - both smooth to draw and giving little hand-shock (providing the design and making of the bow is good). However ash, though servicable gave a harder draw and more kick. I can only put this down to the micro-structure of the wood and how the cellular structure within shears and flexes maybe? In composites I am sure the situation will be more complex with such factors as proportion of wood to horn and sinew, siyah length etc.

I suppose the main advantage of the modern recurve over the traditional composite designs is better performance at low draw weights? The fully working recurve was only possible with modern materials i.e. fibreglass - the high tensile/compressive strength and stiffness allowing siyahs to be reduced or dispensed with. At low draw weights, the bow would not have to move the weight of the siyah. Am I right in supposing that the modern type recurve didn't really have any true antecedents in traditional composite bows? I thought that in the west we had effectively 're-invented the wheel' there by developing from laminated flatbows in the 1940's and 50's.

Adam Karpowicz · Post by **Adam Karpowicz** » Fri Sep 08, 2006 3:09 pm

You may be right in saying the modern materials make it esier to design a recurve with full working limbs and still take advantage of the superiour stiffness and resiliency of glass. The modern designs all sem to be based on the "double C" bow by Hickman for better energy storage. However, fiberglass and the full-working limb design do not eliminate all problems, for example light weight recurves have limbs so thin that stabilty may suffer too, just as in the case of static-tipped old bow replicas with excessively narrow siyahs. The cutting edge modern bowyers are still searching for ways to reduce the limbs mass to maximize performance - by the use of lighter woods, carbon or inventing new tip construction. Note also the modern bows have very heavy risers to absorb the hand shock. In short, modern materials have advantages, but old problems remain.

Adam