From limb tension to stored energy
A bow is a spring. As you draw the string back, the limbs bend and store elastic potential energy equal to the area under the draw-force curve. For a simple recurve the force rises almost linearly with draw, so a first approximation treats the curve as a triangle:
E_stored = ∫ F(x) dx ≈ ½ · F_peak · s_powerTake a 40 lbf bow — roughly 178 N at full draw — and a power stroke of 0.50 m, the distance between brace height and full draw. The triangle estimate gives about 44.5 J of stored energy. Real limbs store somewhat more because their force curve bulges above a straight line early in the draw, but the estimate is close enough to reason with on the range.
Kinetic energy transfer and efficiency
Not all of that energy reaches the arrow. Some moves the limbs themselves, some vibrates the string and riser, and some is lost to hysteresis in the limb materials. Efficiency η for a well-tuned target bow typically falls between 0.75 and 0.85. Launch velocity then follows directly from energy conservation:
KE = ½ · m · v₀² = η · E_stored → v₀ = √(2 · η · E_stored / m)With η = 0.85, E = 44.5 J and a 20 g arrow, v₀ ≈ 61.5 m/s — almost exactly the 62 m/s ceiling of the Teamstoviewticker engine. The simulator's arrow weighs 19.5 g and leaves at 37.5 J of kinetic energy when fully drawn. Heavier arrows fly slower but hold energy better in wind; lighter arrows are faster with a flatter trajectory but drift more once they slow down.
How the engine maps draw to velocity
For a linear force curve, stored energy scales with the square of how far you draw, so launch velocity scales linearly with draw fraction d. The engine models exactly that: v₀ = 62 × d m/s, reaching full draw after 1.35 seconds of hold. Your sight mark is solved for d = 1, so any short draw launches a slower arrow on the correct angle, and gravity has longer to work.
elevation error ≈ Δy_drop · (1 / d² − 1) (Δy_drop ≈ 6.31 m at 70 m)| Draw | v₀ | KE | Impact vs gold | Result on 122 cm face |
|---|---|---|---|---|
| 100% | 62.0 m/s | 37.5 J | 0 cm | Gold |
| 99% | 61.4 m/s | 36.7 J | ≈ 13 cm low | Red, ring 8 |
| 98% | 60.8 m/s | 36.0 J | ≈ 26 cm low | Blue, ring 6 |
| 95% | 58.9 m/s | 33.8 J | ≈ 68 cm low | Off the face |
| 90% | 55.8 m/s | 30.4 J | ≈ 148 cm low | Ground strike |
The lesson is brutal and accurate: at 70 m, every 1% of draw you fail to complete costs about 13 cm of elevation — more than two ring widths. Consistency of draw length is not a refinement; it is the foundation of long-distance scoring.
Recurve stacking and compound let-off
Different bow designs shape the force curve differently. Recurve limbs can "stack" near the end of the draw, where force climbs steeply over the final few centimetres; this makes short draws feel easier and therefore more tempting. Compound bows use cams to create a let-off, dropping holding weight by a large fraction at full draw and giving a hard mechanical stop. That stop is why compound archers achieve such repeatable arrow speeds — the draw length is enforced by the machine rather than the body.
Release consistency training
For the recurve archer, consistency comes from a repeatable anchor, steady back tension and a clean, relaxed release. A clicker — a thin blade that drops off the arrow at a set draw length — gives an audible cue that full draw has been reached. The simulator's draw meter plays the same role: the ring around the reticle turns neon green when you hit 100%.
- Blank-bale work: shoot at close range with eyes closed to feel expansion through the shot without the distraction of aiming.
- Timed holds: draw, anchor and hold for a fixed count, then let down. Build to repeated holds at full draw before any arrow is released.
- Shot rhythm: aim to release within a consistent window after reaching full draw. In the engine, fatigue sway begins 2.4 s after full draw — a realistic cue to either shoot or let down.
- Let-down discipline: if the shot does not feel right, come down and restart. In the simulator, releasing below 15% draw lets the arrow down safely without counting it.
Range drill: shoot ten arrows at 70 m in calm wind and track only the Draw Strength readout. Target ten readings of 100%. Once that is automatic, every remaining error on the face belongs to aim and wind — and those are far easier to fix.