(formerly "Reel Capacity Planner")
A standalone Android app (Flutter) for planning line capacity on saltwater reels — spinning and conventional — across mono, solid-core braid, and hollow-core braid, including topshot mixes (a fixed topshot over backing that fills the rest of the spool).
Separate project from OpenTides — its own repo, package, and Play listing.
| Calculator | Straight result | Topshot + backing |
|---|---|---|
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| Split by length / % | Reel picker | Favorites |
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Line occupies spool volume proportional to length × diameter². Each reel is anchored to one
published capacity, giving a spool constant:
K = anchorYards × anchorDiameter² × anchorPackingFactor (inches)
Any other line of diameter d then fills yards = K / (d² × packingFactor). A topshot mix pins one
segment to a fixed length, subtracts its volume, and fills the remainder with the other line.
Why packingFactor: published braid diameters understate how much spool volume the line really
occupies once it's wound (hollow core worst), so a naive mono-anchored diameter² conversion badly
over-estimates braid. Each line construction carries a calibrated factor — mono/fluoro 1.0,
solid braid 1.2, hollow braid 1.85 — and a reel applies the same factor to its anchor capacity
so braid-anchored and mono-anchored reels stay consistent. The factors are calibrated against real
spool data (Penn Fathom 40N solid-braid capacities; an Avet 80W holding ~1,900 yd of 100 lb hollow).
A per-line packing_factor in the catalog JSON overrides the type default.
The engine lives in lib/services/capacity_calculator.dart (pure Dart, no Flutter deps) and is
covered by test/capacity_calculator_test.dart.
⚠️ Results are estimates. Real fill depends on how evenly line is laid and how tight it is packed. Catalog entries whosesourcecontainsVERIFYare approximate placeholders and must be confirmed against current manufacturer spec sheets before the numbers are trusted. Line diameter is the accuracy-critical field.
- Read-only seed catalog ships as JSON assets:
assets/data/reels.json,assets/data/lines.json. - User data — saved loadouts plus any custom reels/lines — is stored locally in SQLite
(
lib/data/db.dart). Custom catalog entries merge with the seed at load.
lib/
main.dart, app_state.dart
models/ reel, line, line_segment, loadout (+ enums)
services/ capacity_calculator (engine), unit_converter, settings
data/ catalog (asset+db loader), db (sqflite), loadout_repository
ui/screens/ home (calculator), reel_picker, line_picker, loadouts, settings
ui/widgets/ capacity_result_card
theme/ app_theme
assets/data/ reels.json, lines.json
test/ capacity_calculator_test.dart
Flutter SDK lives in the ubuntu-chrome container (/root/flutter/bin/flutter); the project is
synced to /root/reel_planner there to build against the Pixel9 emulator.
flutter pub get
flutter test
flutter build apk --release
# install on emulator (adb at /opt/android-sdk/platform-tools/adb in the container)
adb install -r build/app/outputs/flutter-apk/app-release.apkApp id: com.mattbettinger.openspool.
docs/INTERNALS.md— behavior-level reference: UI flows, favorites (save/dedupe/delete+undo/reorder), persistence shape, and the regression guards. Kept in sync with the code.docs/PREBUILD.md— the pre-build checklist. Updating the docs above when a change alters a flow/screen/behavior is step 1 of every build, not an afterthought.- QA: the
reel-qaskill drives a full-app walkthrough on the emulator and enforces the doc-sync step.
Mix is backing + topshot (2 segments). Not yet: 3+ segments, remote catalog sync, iOS build, empirical per-brand packing calibration, loadout import/export.
The highest-value contribution is accurate data — correct line diameters and reel capacity
anchors with a manufacturer source. See CONTRIBUTING.md. Wrong number?
Open an issue or use the email link in the app's Settings.
OpenSpool collects no data and makes no network requests — everything runs offline on your
device. See PRIVACY.md (hosted:
https://silasmarner.github.io/open-spool/privacy.html).
MIT © 2026 Matt Bettinger.