Performance Database

Every day you sail with Njord, you're building something more valuable than just that day's analysis. The Performance Database stores pre-aggregated summaries from each event so you can compare polars, track how a rig change played out across different wind ranges, and watch your boat's performance evolve over a whole season — or multiple seasons.

Unlike ad-hoc multi-event loading, the database works at scale. Data is averaged into fixed-duration phases at the time each collection is created, so season-long comparisons are fast regardless of how many events you include.

How it differs from ad-hoc multi-event analysis

Ad-hoc analysis (via Aggregate Analysis) loads raw data for a handful of selected races on demand — useful for quick comparisons but slower when many races are involved.

The Performance Database scales to much larger datasets. Data is averaged into fixed-duration phases at the time the collection is created, so subsequent analysis is fast regardless of how many events are included.

Creating a phases collection

Events are not added to the Performance Database automatically — you add them yourself, which lets you exclude practice races or poor-data days.

  1. In the Data section, select your boat and choose Performance Database from the sidebar.
  2. Click Phases Database or Manage Phases… to open the collection list.
  3. Click New Phases Collection.
  4. Select an event, enter a name (including the event name and conditions makes it easier to find later), and select the races and/or trainings to include.
  5. Choose a phase duration (see below) and click Create Phases Collection.

Choosing phase duration

Each race is divided into consecutive phases of the chosen duration (maneuvers are excluded). All data within a phase is averaged into a single row.

  • 10 seconds — captures more variation within a race; creates larger collections; better for detailed boat-speed or trim analysis.
  • 30 seconds — smoother averages; smaller collections; better for season-level trend analysis and polar comparisons.

Use the same phase duration across all collections you intend to compare — mixing durations in the same analysis can produce misleading differences.

Selecting collections for analysis

In the Performance Database view, select one or more phase collections. Most visualization types treat each collection as a separate dataset, making it easy to compare performance between events side by side. See Useful visualization types below for the most relevant views.

Use the Filter button to narrow the data by:

  • Point of sail (upwind / downwind / reaching)
  • Tack (port / starboard)
  • Hoisted sails (if sail changes were recorded)

Useful visualization types

  • Targets — compare boat speed and VMG against polar targets across events; the primary view for tracking performance trends over a season.
  • Polar Diagram — overlays measured boat speed polar from each phase collection; immediately shows whether speed has improved or regressed at any TWA/TWS combination.
  • Scatter Chart — plot any two metrics against each other across events; useful for detailed analysis of speed vs TWA or heel vs boatspeed relationships.
  • Bin Table — shows average metrics in TWA × TWS bins per collection; useful for spotting consistent gains or losses in specific wind conditions.
  • Statistics / Gain Loss — compare average metrics (VMG%, BSP%, heel) per event collection at a glance.

Managing collections

Collections are not updated automatically when you change a race's course or wind data. After making corrections, delete the affected collection and recreate it.

To delete a collection, open Manage Phases… and remove it from the list.

Tips

  • Add events to the database shortly after they happen while the context (conditions, boat setup) is still fresh.
  • Exclude races with missing or poor wind data — they will skew polar comparisons.
  • Use consistent phase duration across all collections you plan to compare.