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Terms of Use

By using Tackcall at tackcall.app, you agree to these Terms. If you do not agree, do not use the app.

Tackcall is a browser-based sailing tactics tool for tracking wind shifts, tack headings, and boat speed performance. It runs entirely in your browser — there is no account, login, or server-side storage of your sailing data. All logs, calibration data, and settings stay on your own device.

Tackcall is a tactical training and performance aid — it is not a certified navigation, safety, or collision-avoidance instrument. Do not rely on it as your sole or primary source of navigational information. Headings, wind-shift detection, and performance percentages come from your device's sensors, which are subject to error, drift, magnetic interference, and delay — particularly on boats with significant heel angle.

You are solely responsible for the safe operation of your vessel, compliance with the Racing Rules of Sailing, local navigation rules, and good seamanship, regardless of what the app displays. The developer accepts no responsibility for collisions, groundings, protests, disqualifications, or any other outcome connected to use of the app on the water.

All sailing logs (headings, GPS points, calibration means, polar performance history) are stored locally in your browser on your own device. The developer does not receive, transmit, or have access to this data, and does not back it up — you're responsible for exporting your own data if you want to keep it.

The developer reserves the right to run a basic, aggregate visitor counter on tackcall.app. This is separate from your sailing data, which never leaves your device.

The Tackcall source code is published under the MIT License on GitHub (github.com/vesa-fioni/tackcall). These Terms govern your use of the hosted app; the MIT License governs the source code if you obtain it separately.

The app is provided "as is" and "as available," without warranties of any kind. It is under active development — features, thresholds, and behavior may change without notice.

To the fullest extent permitted by law, the developer is not liable for any damages arising from your use of, or inability to use, the app — including loss of data, loss of race results, or any physical, property, or financial damage on the water.

The developer may update, modify, suspend, or discontinue the app or these Terms at any time without prior notice. Continued use after changes means you accept the update.

These Terms are governed by the laws of Finland. Any disputes are subject to the exclusive jurisdiction of the Finnish courts.

Vesa Lindqvist — vesa.lindqvist@fioni.fi (personal contact address, not affiliated with any company for the purposes of this app).

Privacy Policy

Tackcall is designed to keep your sailing data on your own device. This page explains what little data is involved when you use tackcall.app.

Tackcall stores heading and GPS logs, calculated tack means, calibration data, polar performance history, and your app settings directly in your browser's local storage. This data is never transmitted to, or accessible by, the developer. It stays on your device unless you export or share it yourself. If you clear your browser data, uninstall the app, or switch devices, this data is lost unless you've exported it.

The developer reserves the right to run a lightweight, aggregate visitor counter on tackcall.app — a count of page loads, plus basic technical information inherent to any web request (e.g. approximate country, browser type). This is aggregate, not used to profile or track you across sites, and is never linked to your sailing logs. No advertising or cross-site tracking is used.

Tackcall does not use cookies for tracking or advertising. Any minimal technical storage needed to avoid duplicate visit counts is limited to that purpose only.

Tackcall does not sell, rent, or share any data with third parties for advertising. The app is hosted as a static site — your device talks directly to the hosting provider to load the page, as with any website.

Because any aggregate analytics data is minimal and non-identifying, there is generally no personal data for the developer to hold, access, correct, or delete on your behalf — your sailing data lives only on your device, under your control. If you believe any data connected to your visit qualifies as personal data under GDPR, contact the developer below.

Tackcall is not directed at children and does not knowingly collect personal data from anyone.

This policy may be updated as the app evolves — for example, if analytics tooling changes.

Vesa Lindqvist — vesa.lindqvist@fioni.fi (personal contact address, not affiliated with any company for the purposes of this app).

How to use

1. Sail steadily on one tack and settle into your groove at full upwind speed.
2. Tap SET UPWIND MEAN to store your average heading — and, because you're settled at full speed, your boat's top upwind speed for these conditions. Do this on both starboard and port.
3. The bar then shows how far you've shifted from that mean, and the tones tell you lift, header or time to tack.

The large red number is your current heading. STBD / PORT shows the tack you're on — automatically or manually, set in Settings.

Speed made good along the wind axis, in knots — how fast you're progressing to windward (upwind) or to leeward (downwind). It's derived from your speed and the angle to the estimated wind, so it needs both means set and GPS on. Shown in coral, with SOG in amber, since SOG is the direct reading and VMG is computed.

Shows your current speed compared to your own good speed at the same wind angle. The app learns this as you sail — nothing to enter. 100% means you're going as well as you normally do at your best in this angle; over 100% means better than usual (this is good — the number is allowed to go above 100, it's not an error); under 100% means there's speed to gain, so try your trim or a small course change.

The brightness tells you how much to trust it: "--" means this angle hasn't been measured yet — the meter isn't broken, just keep sailing and the number appears; a dim number means the app is still learning this angle, so treat it as a rough guide; a bright number means there's enough data to trust. Sail different angles and wind strengths and PERF learns faster, turning from dim to bright.

In Settings, turn on Offshore (COG) to replace the compass with GPS course over ground — useful if you want to avoid compass mounting/tilt issues entirely. The heading number turns pink/violet to show it's GPS-based. GPS switches on automatically if it wasn't already. Below 3 kn SOG, GPS course is unreliable, so the display shows "WAITING FOR SPEED" until you're back up to speed. Note that COG includes leeway (it's not exactly the boat's true heading), and it lags a few seconds after each tack while the GPS fix settles.

Audio alerts play distinct tones for lift, header and tack. Turn them on or off in Settings.

Setting a mean while settled close-hauled records not just your heading but your boat's top upwind speed in the current wind. The pre-start assistant uses that speed as its target — no wind instrument needed, because the boat's own speed measures what's achievable right now. Set your means in the breeze you'll start in, and re-set them if the wind strength changes.

Open it from Settings → Pre-start. Mark each end of the line with Set boat end and Set pin end (GPS on), set the countdown timer, and tap SYNC on the start signal. It then shows your distance to the line and counts you down — with a gauge for when to head in so you cross as the gun goes, not before.

Re-set the mean whenever the average wind direction shifts, or use "Reset means" in Settings to start over.

Session summary BETA

Pre-start BETA