Arrow pass and set-up in a primitive bow.

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Arrow pass and set-up in a primitive bow.

Rod
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Rod
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Joined: 17 Jun 2005, 23:07

12 Sep 2011, 08:36 #1

A defining characteristic.

One of the defining characteristics of a primitive bow is that it will not be anything close to centre-shot in it's set up. 
As  far as I know, there are no examples of  primitive bows where the pass width is less than the width of the handle. 
Other than by fading from a wide limb to a narrower handle, a primitive bow will make little concession to "nearer to" centre-shot alignment, even to the extent of not narrowing above the handle,  something which is common enough in a "traditional" bow.


There are two kinds of primitive bow.

Looking at it arbitrarily there are two kinds of primitive bow.
One can be set-up so that the arrow can go precisely where it has been pointed at full draw, the other will always shoot off-set to the stiff side regardless of any reasonable adjustment.
These are recognised by permutations of wider pass-width and lower brace-height that create an angle of offset sufficiently large that the shaft will not recover from paradox to go where it has been pointed. 

Does it really matter?

Not as much as we might think, if we accept the notion that "good enough" is always sufficient until someone comes along and forces further development in a culture where the solution currently in use is found wanting.
Which is probably why in true "war bow" cultures, the solution is generally of the first type, permitting a solution where the arrow can be "pointed" in lateral terms, or at worst, will shoot a slightly stiff solution, which is to say, somewhat to the offhand or visually open side.
This is often the case with a thicker English bow where the shaft is also quite substantial.

There are of course enough types of primitive bow where the nature of the pass geometry and set-up will prevent the arrow from going precisely where it has been pointed, but when we chose to use a bow with these characteristics we hopefully do so having understood and accepted the practical consequences of our decision.
It is part and parcel of the challenge integral to the use of such types.

Like all matters to do with accurate shooting, there are always factors which when accepted and negotiated will require an understanding of how to manage the idiosyncrasies of any such set-up.
These will involve elements such as variations in shooting styles, the functions of canting, the use of different anchor locations or draw-lengths, or by manipulating effective spine by an increase in shaft length and or point weight, all of which can relate to an awareness of point on distances and its useful employment.

For example, consider the utility of a long shaft "point-on distance" in relation to the particular requirements of either the issue of parallax in bow fishing, or in a close distance, high elevation shot with a short draw or floating anchor.

The limiting factors.

Bearing all of this this in mind, how wide should we make a primitive bow at the arrow pass if we want the arrow to go precisely where it has been pointed at full draw and what are the factors involved and what are their limits?

Clearly, as the angle of offset (of the arrow at rest on the bow at brace height) increases, so the degree of disruption is increased and the less likely it is that we can obtain such a match.
This is why modern bows employ a near centre-shot cut away solution.

We will be correct in thinking that there may be quite distinct limits to the extent of disruption that an arrow will tolerate and still be able to go exactly where it has been pointed.

1. We must be able to distinguish between shooting variables introduced by the archer, and what the equipment will do without disruption by the archer.

2. We should be aware that our ideal solution is only one of a range of manageable options.

3. We should have an understanding of the necessary compromises involved in achieving such a solution.

What are the factors involved?

Quite simply, it is a matter of selection in the folowing:

1. Pass width.
2. Pass shape, profile and cross section.
This requires appropriate decision making at the bow making stage.

3. Brace height.
This requires set-up adjustment and a shooting test, always being aware of any disruption in the line caused by any idosyncracies in the performance of the archer.

4. Shaft selection.
This is essentially a matter of spine selection but bearing in mind that the diameter of the shaft will modify the real angle of shaft offset, dynamic spine perfomance being modified by shaft length and point weight.

Some conclusions.

As a pragmatic method based largely upon tradition and experience, my rule of thumb is to limit the pass and handle width to not much more than 1" (a usual range of between 15/16" to 1 1/4" ).

Whilst the ideal shape  satisfying both paradox and stability in the hand is undoubtedly a precisely circular cross-section, this has some pratical or stylistic limitations.

A suitable compromise in a stiff handle and pass in a bow with fades will be a shape in cross-section which allows the point of contact of the shaft with the side of the bow to advance slightly from the notional rear corner of the pass, thereby slightly increasing effective dynamic shaft length and so slightly reducing the angle of offset.

The handle and pass depth to width ratio is also a compromise between the  edit from here lateral stability in the hand whilst shooting, though also with the depth slightly modifying the actual brace height.

My preference would be not more than 1 1/4" depth, since a ratio of depth to width where the depth is greater and the width less can predispose to less lateral stability in the hand, prone to what our American friends like to call "torquing" and will tend to "balance" in the hand as compared to a shape "sits" with a more comfortable and stable fit.

A simple example.



Still under revision.
Also a ratio of width to depth in the handle that is too narrow and too deep can make the handle very
It should be emphasised that any complete solution will be a compromise between finding a solution that satisfies the demands upon the shaft in paradox and that of how well the handle will fit in the hand.
Handle geometry in this regard can adversely affect perhaps lateral stability (left/right shooting errors) most of all, but that is another topic.

Many primitive cultures use wide bows and low brace heights which are solutions that necessarily involve aiming off, or extreme canting so as to convert "cast off" into elevation, but this is another matter and such choices are of course acceptable as an informed choice in bow style and shooting style, but for those who seek to
facilitate more accurate shooting it can be a problem when the process is not understood and the choices are uninformed.

Let it be sufficient to say that where the static angle at brace height is less than 5 degrees or so, it should be possible to find an acceptable spine solution.
My most recent Mollegabet set-up which can shoot a decently matched exactly where it has been pointed at full draw has this angle of offset:

Static offset in pass at brace height of 7" :  about 3.5 degrees.
Offset in the centre-line of an 11/32" shaft at brace height:  about 4.9 degrees



Some supplementary topics

Read this for background on spine-matching and bow set-up.
"Understanding arrow spine & paradox".
http://paleoplanet69529.yuku.com/topic/37468


Read this before making the bow with a big lump of an arrow pass.
"Some tables showing examples of angles of offset".
http://paleoplanet69529.yuku.com/topic/51523
Last edited by Rod on 25 Aug 2015, 11:54, edited 64 times in total.
It's meant to be simple, not easy.
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