Horn/Wood/Sinew ratios in Turkish bows

[Andrew Hall]

I have been looking through the horn/wood/sinew thickness listed for a number of bows in Turk Okculugu. There appears to be a cluster around the 41% horn, 41% core and 18% sinew, but with half the bows with much more horn - from 47 to 52% and correspondingly less core.

I assume that more wood would give a more stable bow that could not be reflexed as far, so could the equal horn/wood bows be war bows and higher horn percentages used for target and flight bows?

I would be grateful for information on the differences.

Andrew

[Redhorse]

I did brace one today that is 4 (36.36%)horn 4 (36.36%) wood and 3 ("27.27%)mm sinew.
48" n/n, mass 420 gram, 50lb at 20", one draw to 65lb at less then 25". Just a 2-3" reflex.

[Adam Karpowicz]

Andrew:

The relative thickness of components varies, depending where exacly in the limb it is measured. Generally, the sinew layer is fairly thin (~2mm) at the apex of the core's cross-sectional curvature, but thicker towards the edges of limbs. Greater thickness of horn makes a more resilient bow, less likely to follow the string. This feature would be desired in a war bow which was (presumably) strung for extended periods of time. On the other hand, more sinew was present in flight bows, sometimes forming a convexity along the back of limbs (stacked sinew). Such bows would respond better to the conditioning process to acquire more stiffness for less mass. At the same time, as you noticed, it is true the thicker core makes a more stable bow. One has to balance the properties for an intended effect.

As to the reflex - bows built within normal parameters can all be reflexed to the same degree, but the differences will be seen in use. I would not go below 2mm for the horn though, unless the bending limbs are reasonably straight and only the grip and/or siyahs are reflexed. It is to reduce the tendency to delaminate when bent.

Adam

[Andrew Hall]

Adam, thanks for the information. It is possible that some of the differences in ratios are due to different points of damage in the bows (I would assume the thicknesses were measured on broken bows).

My bows so far have had roughly equal amounts of horn and wood, with slightly less sinew (but proportionally more than the originals). I am looking to make a bow styled after a Turkish looking bow from Tibetan and I am trying to decide whether to go for an equal horn/core or a ratio with more horn. The bow is not heavily reflexed.

Andrew

[Adam Karpowicz]

Andrew:

If your bow is not too reflexed and the siyahs are relatively longish and rigid, it would be safe to use more horn in the bending section, since there should be no trouble to stabilize it.

Good luck with your bow

Adam

[Andrew Hall]

Adam, thanks for the advice, I will try with a 50% horn thickness.

Andrew