The erg-to-boat conversion

The least certain number in the whole system, and why we say so.

Read this before you argue with your erg score. The conversion from an erg split to a boat split is currently uncalibrated. The transfer factor sits at 1.0 — meaning the app applies no correction at all beyond weight — and that is a placeholder, not a finding.

What the app actually does

An erg piece is converted to a boat-equivalent split in two steps:

Weight adjustment. An erg does not care how heavy you are; a boat very much does. A heavier rower moving the same flywheel is not moving the same boat. This step is real and sourced (Kleshnev's on-water weight exponent, 0.054 — deliberately not the erg's 0.222).
A water transfer factor, which is presently 1.0. This is the step that has not been calibrated against real data.

Why it has not been calibrated

Calibrating it honestly needs paired data: the same rowers, erg and water, close enough in time that fitness has not moved. Nobody has produced that for this app yet. Until they do, any factor we picked would be a number we invented wearing the costume of a measured one — which is the single thing this project exists to refuse.

So the placeholder stays at 1.0, visible, and labelled. An honest placeholder is better than a confident guess, because you can see it and argue with it.

What this means for your score

The BoatMover Score is 70% water, 30% erg. The uncertain step is weighted at 30%, and only for the erg half.
Both halves are best-of, never an average. A bad erg cannot drag you down.
Two rowers on the same machine are compared fairly — the uncertainty is in the erg-to-water step, not in erg-versus-erg.
Two rowers on different machines are a separate question. A Concept2 and an RP3 do not agree, and the app applies a per-device correction for that.

How this gets fixed. One club, a handful of rowers, erg and water pieces within a few days of each other. That is all it takes, and it would turn the most-hedged number in the system into a measured one. Until then the app tells you it is provisional rather than pretending.