Where the numbers come from, what they assume, and where they stop being trustworthy.
Why this page exists. On 7 August 2026 the derivation and the reference ranges were taken out of the app's rigging screen, on the understanding that they would live in a guide. Until today that guide did not exist — so this information was nowhere. If you have wondered where a suggested inboard came from, the answer was unavailable. That is what this page fixes.
Your rigging card is a starting point derived from your height, not a measurement of your boat and not a prescription. It answers one question: if nothing else were known about you, what rig would the published research put you closest to?
It is sculling only. Every number below was derived for single scullers. It must not be reused for sweep, and the app does not offer it there.
The source is Valery Kleshnev, Rowing Equipment and Rigging, chapter 6. Two different things happen, and the difference matters:
This is the one relationship the book states as a clean equation, and it is used live:
arc = 0.297 × height + 109 (centimetres)
Checked against the book's own tabulated arc column, it agrees to within 0.6 cm across the whole range — which is why it is trusted as a formula rather than looked up.
These are not re-derived. They are read from Kleshnev's Table 6.4 and interpolated to your exact height:
| Height cm | Arc cm | Oar cm | Inboard cm | Span cm |
|---|---|---|---|---|
| 160 | 157 | 272 | 83.0 | 149 |
| 170 | 160 | 277 | 84.5 | 152 |
| 180 | 163 | 281 | 86.0 | 155 |
| 190 | 166 | 286 | 87.5 | 158 |
| 200 | 169 | 291 | 89.0 | 161 |
Why look them up instead of calculating them? Because calculating them honestly is not possible from what the book states. The prose gives an inboard equation using a total blade angle of 114°, and separately quotes a gearing ratio of 2.11. But Table 6.4's own numbers imply a handle arc of about 108.5° and an outboard-to-inboard ratio near 2.27 — different quantities, measured differently.
We could have hard-coded 108.5 and 2.27, reverse-engineered from the table, and presented them as formulae. That would look more rigorous and be less honest. Instead the published table is treated as the answer and interpolated. Arc is a formula because it checks out; the rest are Kleshnev's measurements because they are.
These are reference ranges for a sculling boat, from the same chapter. They are not derived from your height — they are what a correctly set-up boat generally sits within, shown so you can compare what your boat actually measures against what is usual.
| Setting | Usual range |
|---|---|
| Span (sculling) | 158–160 cm |
| Overlap (sculling) | 19–21 cm |
| Gate height above seat | 14–18 cm |
| Gate height difference (sculling) | 1–2 cm |
| Stretcher position | 55–65 cm |
| Blade pitch | 4–8° |
Overlap, for sculling, is inboard × 2 − span + 4. If your measured overlap falls
outside 19–21 cm, that is worth a conversation with your coach — it is not automatically wrong.
The short version for a rower. A shorter rower cannot reach the same arc as a taller crewmate on the same oar and the same span — the geometry will not allow it. The fix is a shorter inboard and oar, which restores the arc. That is the whole idea this card is built on.