A competition riser can be made a fifth lighter with almost no loss of stiffness

The summary today

The only test of a lightened riser dates from 2004, comes from a single German group and, where it matters, is a calculation: a 25-inch riser designed with an evolutionary algorithm weighs, once built, 871 grams against the 1,114 of the Hoyt Radian used by the German national team, 22 per cent less, and in the structural analysis, with 200 newtons of draw weight, it deflects at most 1.94 millimetres against 1.85. That would be almost the same stiffness, with about 5 per cent more deflection, and the margin was there because the stresses in the aluminium reach 160 newtons per square millimetre against a yield point of around 400. The weight of the built riser is measured, though, and the deflection is not: nobody loaded the real riser, and the stiffness comes only from the computer model. Two further limits remain: a lighter riser usually costs stiffness, since in the two computing runs the models weighed on average 864 and 880 grams but deflected on average 2.74 and 2.63 millimetres, and all we know about how that riser shoots is the opinion of three national team archers, two of them after nine arrows, while the authors themselves write that no study has ever shown that a stiffer riser makes anyone shoot better. In 2016 a second calculation, on a Hoyt Matrix riser, finds the same maximum displacement of 1.85 millimetres at 200 newtons, but it concerns a commercial riser rather than a lightened one, and there too the real riser was never put under load.

Also phrased as: "lightweight riser"; "stiffer riser"; "riser weight"; "heavier riser is more stable"; "riser stiffness"

Evidence

• 2004
  For Model Published later

  The optimised riser, once built, weighs 871 grams against the 1,114 of the Hoyt Radian, 243 grams or 22 per cent less; in the structural analysis, with 200 newtons of draw weight and a 71-centimetre draw, the maximum displacement is 1.94 millimetres against 1.85. The weight is measured on the riser, the deflection is calculated on the model. Comparing the two computer models, 869 grams against 1,048, the saving is 17 per cent.

  Lightweight design optimization of a Bow Riser in Olympic Archery applying evolutionary computing · Jürgen Edelmann‐nusser, Mario Heller, Steffen Clement, Sandor Vajna, André Jordan

• 2004
  For Model Published later

  Among the 1,650 models generated, a fair number came out both lighter and less deformable than the Radian, so the risers on sale were not optimised for the ratio of weight to stiffness; accepting displacements of up to 4 millimetres takes the mass below 800 grams, with the lightest at 779 grams and 3.53 millimetres.

  Lightweight design optimization of a Bow Riser in Olympic Archery applying evolutionary computing · Jürgen Edelmann‐nusser, Mario Heller, Steffen Clement, Sandor Vajna, André Jordan

• 2004
  Context Model Published later

  Lightening comes at a price: in the first computing run, 20 generations, the average model weighs 864 grams and deflects 2.74 millimetres; in the second, 35 generations, 880 grams and 2.63 millimetres, against the modelled Radian at 1,048 grams and 1.85 millimetres.

  Lightweight design optimization of a Bow Riser in Olympic Archery applying evolutionary computing · Jürgen Edelmann‐nusser, Mario Heller, Steffen Clement, Sandor Vajna, André Jordan

• 2004
  Context Model Published later

  The margin exists because the stresses stay far from the material's limit: 135 newtons per square millimetre in the Radian and 160 in the new riser, at 200 newtons of draw weight, against a yield point for the alloy of 403.

  Lightweight design optimization of a Bow Riser in Olympic Archery applying evolutionary computing · Jürgen Edelmann‐nusser, Mario Heller, Steffen Clement, Sandor Vajna, André Jordan

• 2004
  Context Model Published later

  The Radian deflects asymmetrically, 1.42 millimetres at the upper limb pocket and 1.85 at the lower, and twists at the top; the optimised riser deflects almost equally above and below, close to 1.94 millimetres. The authors point to the torsion of the upper pocket as the more plausible criterion for shooting, rather than maximum deflection.

  Lightweight design optimization of a Bow Riser in Olympic Archery applying evolutionary computing · Jürgen Edelmann‐nusser, Mario Heller, Steffen Clement, Sandor Vajna, André Jordan

• 2004
  Context Model Published later

  With 200 newtons of draw weight and long limbs on a 25-inch riser, the forces on the limb pockets lie between about 1,460 and 1,730 newtons and rise as the draw length falls: 1,583 and 1,729 newtons at 710 millimetres, 1,462 and 1,604 at 810.

  Lightweight design optimization of a Bow Riser in Olympic Archery applying evolutionary computing · Jürgen Edelmann‐nusser, Mario Heller, Steffen Clement, Sandor Vajna, André Jordan

• 2004
  Context Model Published later

  The 25-inch Hoyt risers of the time weighed between 1,114 grams (Radian) and 1,374 (Axis), and the stiffest were the heaviest; the German national team archers had turned down the Axis, stiffer but heavier, and stayed with the Radian.

  Lightweight design optimization of a Bow Riser in Olympic Archery applying evolutionary computing · Jürgen Edelmann‐nusser, Mario Heller, Steffen Clement, Sandor Vajna, André Jordan

• 2004
  Context Equipment tests Published later

  Three German national team archers tried the built riser, two for nine arrows and one for 300, and judged it stiff, light and good at damping vibration after the shot; the one who shot 300 arrows said it groups well. These are impressions, with no measurement of score or group.

  Lightweight design optimization of a Bow Riser in Olympic Archery applying evolutionary computing · Jürgen Edelmann‐nusser, Mario Heller, Steffen Clement, Sandor Vajna, André Jordan

• 2016
  Context Model Published later

  Finite element analysis of a 25-inch Hoyt Matrix riser, rebuilt on the computer from a 3D scan, with the forces on the limb pockets derived from the equations of the 2004 German work for 200 newtons of draw weight: the maximum displacement is 1.85 millimetres, which the authors judge consistent with that study. It is a second calculation on a commercial riser: it does not lighten it, does not weigh it and does not measure its deflection under load.

  Analysis of an Olympic Scale of a Recurve Bow Riser on the Basis of Malaysian Under 15 and Under 17 Archers · Farah Ayuni Fauzi, Zahari Taha, Zakri Ghazalli, Januar Parlaungan Siregar, Zulkifli Ahmad, Kumaran Kadirgama, Nasrul Hadi Johari, Danial Mohamed

Status history

1. 1990 Not studied In the registry's bibliography nobody had yet measured how much weight can be taken out of a riser without making it more flexible. That a riser should be heavy and stiff was a criterion for building and choosing one, not a finding: the models on sale were made stiffer by adding material.
2. 2004 Transferred The only test arrives, and its decisive half is a calculation. A 25-inch riser designed with an evolutionary algorithm and then built weighs 871 grams against the 1,114 of the Hoyt Radian, 22 per cent less, and in the structural analysis it deflects at most 1.94 millimetres against 1.85 at 200 newtons of draw weight; the margin is there because the stresses stay at 160 newtons per square millimetre against a yield point of around 400. The weight is that of the real riser, the deflection is not: it comes from the computer model, and nobody measured it on the built riser. On the shooting side there are only the impressions of three archers, two of them after nine arrows. With the stiffness resting on a model alone, the claim stands on a calculation rather than a test.
3. 2016 Transferred A Malaysian group repeats the calculation on a 25-inch Hoyt Matrix riser, with the forces on the limb pockets derived from the same equations as the German work and 200 newtons of draw weight: the maximum displacement comes out at 1.85 millimetres, and the authors judge it consistent with the 2004 study. It makes no attempt to lighten the riser and measures nothing on a real one: it is a second computer model, and the stiffness of a lightened riser still has no bench measurement. The status does not move.

Related

Related articles

• What a bow is made of: what the materials of limbs, riser, string and arrows changeWood, horn, carbon, glass fibre: what bench tests on limbs, risers, strings and arrows have measured, and how much of it reaches the archer's hand.
• Stabilisers in archery: what they actually do, beyond the folkloreWhat research has measured about stabilisers: how the bow moves at release, muscle work, vibration, barebow weights and accuracy.

Research lines

• 10 studiesVibration and stabilisers: what research has measured since 1987

Other claims in this domain

• CorroboratedAlong its flight the arrow loses an appreciable part of its launch speed12 studiesStatus since 2011
• CorroboratedAs it leaves the bow, the arrow flexes and snakes around the riser instead of leaving straight19 studies · 47 archers measuredStatus since 2012
• ReportedA camera-based scoring system misreads some arrows: the ones barely sticking out and the ones that shift the target face7 studies · 2 archers measuredStatus since 2017
• ReportedA chest band with fibre optic sensors measures breathing and mean heart rate with small errors, and an archer can wear it while shooting2 studiesStatus since 2019
• ReportedA compound bow stores between 70 and 100 joules and sheds about two thirds of the force at full draw4 studiesStatus since 2015

See all claims on equipment and tuning