The sails log

1 Where it lives, and who can do what

Open Boats. Each boat’s row ends with five links — Polar, Targets, Calibration, Sails, Race plans. Take Sails. That row is the only way in; there is no separate nav entry.

The page carries three things with two different authorities, and it is worth knowing which you are touching:

Everyone reads all of it. Controls you cannot use are not shown greyed out — they are simply absent, and the page’s opening line tells you which part is yours.

None of the three is billing-locked. Your wardrobe, your log and your journals are your own record and stay open whatever the boat’s coverage says. Two panels further down do need coverage, for a reason section 9 explains.

2 Register the wardrobe

Nothing else works until the sails exist: the tablet offers this list when the crew hoists, and every minute in the log is attached to one of these rows.

1. In Add a sail, put the crew’s own word for the sail in Label — M1, J2, A1.5. Up to 20 characters.
2. Pick a Category: Mainsail, Headsail, Staysail, Code, Spinnaker, Asymmetric or Other. It defaults to Headsail.
3. Tick Carded if the sail spent one of the boat’s season cards, and check the year it fills in. Leave it alone otherwise — Carded sails below has the detail.
4. Optionally set Delivered — the day the sail arrived. It starts empty rather than at today, because a sail is registered when somebody gets round to it and that is rarely the day it turned up.
5. Optionally tick Wind ranges and step the four numbers to the wind this sail is for. Together the wardrobe’s ranges are the boat’s crossover chart — the table that says which sail now, on the tablet and on a routed course alike. Wind ranges, and the crossover chart below has the detail.
6. Optionally add Notes — cloth, sailmaker, whatever you will want to read beside the sail. One line about what the sail is; what has happened to it goes in its journal, which section 3 covers.
7. Press Add sail.
8. Repeat for the whole wardrobe, retired sails included.

A label has to be unique among the sails still in the wardrobe. That is deliberate rather than restrictive: retiring a sail frees its word, so the new J2 gets to be called J2 while the old one keeps its hours under the same name.

The categories are deliberately coarse — they exist to answer which sails compete with this one, not to model a sailmaker’s catalogue. Finer distinctions belong in the label, which is your own word and free. Asymmetric is the newest of them and sits beside Spinnaker in the list for that reason: an asymmetric is the sail you fly instead of a symmetric kite. Nothing was re-categorised when it arrived, so a kite you registered earlier is still filed under Spinnaker until you move it with Edit — and moving it changes nothing historical.

Carded sails

Some classes ration new sails with a yearly card list: each boat gets a fixed number of cards per season, and a new sail declared against one spends it. The 52 SUPER SERIES is the best-known circuit that works this way. If yours does, your wardrobe is really two lists at once — what is in the container, and what was declared this season.

• Ticking Carded reveals a year and fills in the current season, because that is nearly always the answer. It stays editable.
• Entering last season’s list afterwards is the ordinary case, not a workaround. Edit on any row — retired sails included — sets, corrects or clears the year, and unticking the box clears it.
• A carded sail carries a Carded 2026 chip in its row, and keeps it after it is retired: the card was spent that season whatever became of the sail.
• When any sail carries the current season’s card, a one-line tally appears above the table — Carded 2026: 3.

Delivery date

Delivered is one calendar day: when the sail arrived. A dated sail carries a Delivered 12 Feb 2026 chip in its row, and keeps it after it is retired — the sail turned up on that day whatever became of it since.

• A date in the future is fine. A sail on order has a delivery date before it has cloth, and registering it early is how the crew stops arguing about when it is due.
• Empty is fine too. Most wardrobes are typed in years after the sails arrived. Edit sets, corrects or clears the date later on any row, retired ones included.
• The field accepts days between 1 Jan 1980 and 31 Dec 2100. Those bounds are there to catch a mistyped year, not to insist the sail has already arrived.

Nothing on the page is counted from it. It is there so the question how old is this sail has an answer that is not somebody’s memory — and so a trend that starts flattening can be read against the season the sail came out of the container.

Wind ranges, and the crossover chart

Wind ranges on a sail say what that sail is for: the wind speeds it covers, the wind angles it covers, and a priority that decides which sail wins water two of them both claim. Together the wardrobe’s ranges are the boat’s crossover chart — the table that answers which sail now.

• Nothing measures them. They are what the crew declares, which is a different thing from the minutes the sail actually flew in. Those are further down this page, in the wind statistics, and reading the two side by side is the point of having both.
• Angles are off the bow and cover both tacks. 25° to 90° is 25° to 90° on port and on starboard: a jib does not care which tack it is on.
• The lower priority wins. Where two sails both cover a patch of water, the one with the smaller number gets it. Leave every sail on 0 and the narrower range wins instead, which is usually what a crew means anyway.
• Ticking the box offers a starting shape for that category — the ordinary range for a jib, a kite, a code — so there are four plausible numbers to step from rather than four blanks. Step them to what this boat sails.
• The tablet reads the same ranges. Set them here or in Race Control aboard; both surfaces show one chart, and an edit made offshore reaches this page when the tablet next has a link.

Chart axes, under the wardrobe, is how finely the chart is drawn: how wide a wind-speed band is, where the top band starts — everything above it is one open band — and how wide a wind-angle sector is. A boat that sets none is drawn on 2-knot bands, one open band from 30 knots up, and 15° sectors, which is what every screen already uses. Typing those three back is how a boat goes back to them.

Routing ashore reads this chart: every board on a routed path carries the sail it calls for, and every leg the changes along it. A boat that has declared no ranges is routed on a chart seeded from each sail’s category, and that page says so.

Retiring, and the one case for deleting

Retire on a row says something about the future. The sail leaves the tablet’s hoist picker and its label comes free; every minute it flew stays exactly where it is, and the row stays in the list, dimmed, for ever. Un-retire puts it back.

The small × at the end of the row is a real delete, and it only comes alive for a sail that has never flown and is not flying now — a sail entered twice, or on the wrong boat. Hover it on any other row and it tells you why it is inert.

Edit turns the row into fields in place, so a rename is one click and the log follows it — the minutes are attached to the sail, not to the spelling.

3 The sail’s journal

The wardrobe says what a sail is. The journal says what has happened to it — delivery, recuts, repairs, measurements, and what the crew made of it on the day. Every row in Inventory carries a toggle beside its label: Notes · 3 when there are entries, Add a note when there are none. Opening it drops a panel under the row.

Anyone can read a journal. Adding, correcting and deleting entries takes a member or above — a logbook is the crew’s, exactly like the usage log — so a viewer sees the list and no form under it.

1. Set Day it happened. It offers today and you change it.
2. Write the entry in What happened. Up to 2000 characters; a counter appears once you are near that, and line breaks are kept, so a measurement table pasted from the loft stays a table.
3. Press Add entry.

What to do with something longer than 2000 characters. An entry over the limit is refused, and the counter keeps counting past it so you can see how much is too much. The journal takes text only and has no attachments, so a full sail report or a survey does not go in it: keep the document where it already lives — with the loft that wrote it — and put one entry here saying what it is, when it was done and where the file is. That way the journal still shows a reader that the report exists.

Edit opens an entry in place; an edited one carries a quiet edited chip afterwards and keeps its author and the moment it was first written. The × deletes, confirming first.

That delete is a plain delete, and it is worth knowing why it differs from the one in the usage log below. A usage row the app recorded comes back after a delete, so the platform refuses it and offers Void instead. Nothing derives a journal entry. It is one person’s sentence about a sail, it is recomputed from nothing, and removing it removes it — the sail, its minutes and its totals are untouched.

A retired sail keeps its journal, and still accepts new entries. The sail whose history matters most is usually the one already replaced: its record is what justified the replacement and what the replacement gets judged against. Deleting the sail itself is the only thing that takes its journal with it, and that verb already refuses any sail that has ever flown.

4 Let the log fill itself

With the wardrobe registered and Race Control running, the crew taps sails up, down and away on the tablet, and the rows appear here on their own. Nothing to do afterwards.

Each tap sends the complete set that is flying at that instant rather than a single change, which is why a press somebody missed in a hoist costs one boundary rather than the rest of the day. How minutes per sail compute themselves has the working.

5 Type in what the tablet was not there for

The delivery leg, the practice day, the seasons before you had a tablet. At the bottom of Usage log, under Log a use by hand:

1. Pick the Sail. Retired sails are offered too — you are recording the past.
2. Set Up (UTC). It is pre-filled with the current minute.
3. Give Down (UTC) or or minutes. They are two spellings of one fact and fill each other in — type 47 minutes and the down time appears; pick a down time and the duration appears. Clearing either clears the other.
4. Press Log it.

Leave both the down time and the duration empty for a sail that is still up. The row is created open, and it counts toward nothing until it is closed.

A hand-logged row hides any app-recorded interval for the same sail that overlaps it, which is what makes it a correction rather than a second opinion. Two of your own manual rows overlapping is refused, and the message names the row already covering that time. Different sails overlapping is not a conflict at all: a main, a jib and a kite up together is a boat sailing downwind.

6 Choosing what you are looking at

Above the log sit From (UTC), To (UTC, inclusive), a Sail filter and Show. The window opens on the last 90 days.

• The two dates take effect when you press Show. The sail filter applies the moment you change it — a half-typed year is not a window, but a chosen sail is a decision.
• Both days are included. Pick the 14th as the end and you get all of the 14th.
• A window spans at most 366 days — a season, plus the day a leap year adds.

Rows are shown whole and never cut to the window, so an interval that started before it keeps its real up time.

7 Reading a row

Each row carries the sail, Up (UTC), Down (UTC), a duration, and a Source chip saying where it came from. Three chips exist, and the third is the one worth learning:

A row still open shows flying and how long it has been open, in days if it has come to that. A voided row stays listed, dimmed, and out of every total.

Totals count closed, non-voided intervals only. A sail up right now adds nothing until it comes down.

8 Fixing what is wrong

Correcting an interval

Edit opens the same fields in place. On a row the app recorded, a warning sits above them before you change anything: editing its times or its sail makes the row yours, your version will stand, and the recorded one is kept underneath it. The next tap on the boat will neither overwrite what you typed nor add a second copy beside it.

Changing the sail or either time is what flips a row to yours. Voiding never does.

Void, or delete

There is one control at the end of a row and which verb it offers is not a preference:

• Void — for anything the app’s recording anchors, including a row you have already corrected. It strikes the interval out of every total and leaves it in the log, dimmed. It is the durable way to say this did not happen: the events behind it are still on the boat, so a delete would simply be recomputed. Un-void puts it back.
• × — a real delete, offered only on a row that was typed in and nothing else. It confirms first, and the confirm says the thing you need to know: a manual row hides the app-recorded intervals it overlaps, so deleting it lets them back. An interval reappearing afterwards is the boat’s own record resurfacing, not the delete failing.

Closing an interval somebody left open

Nothing closes an interval for you. The platform cannot tell a sail still up from a tablet that died, and inventing a time would put minutes in the season’s totals that nobody measured.

So the log nudges instead. Any open, non-voided row gets a callout above the table listing it with a Close now button, which stamps this instant. If that is not the real time, use Edit and pick it.

9 What a sail has actually done

Click a sail’s label in Inventory — the whole cell is a button — and a panel opens under its row, scoped to the same window as the log. One sail at a time.

Wind this sail worked in

Median true wind speed, minutes flown in the window, number of uses, and the hours split into 2-knot bands with an open top. A band with no minutes is left out rather than drawn as a zero, so the list is the shape of the sail’s real use.

Two honesty lines to expect here. If the instruments were not recording for part of the flying, a line says how much of it had wind data and that the median and the bands rest on the sampled part only. And because wind is read through the boat’s calibration, a correction entered after a regatta moves these bands. That is the point of it.

Speed over this sail’s life

A chart whose horizontal axis is the sail’s own cumulative flying hours rather than the calendar, so a sail used twice a season and one used every weekend are read the same way. Each point is one interval from the log above.

• The dashed baseline is this sail’s own median over its first five flying hours — it is measured against itself, not against a fleet.
• The band around it is the median scatter within a single use. A point inside the band is not distinguishable from the baseline, which is what lets you tell a real decline from noise.
• Hollow points on the axis are uses with under two minutes of steady sailing. They have no median and are shown rather than dropped, because a gap with no explanation is worse.
• Vertical marks are where the yardstick moved — a new polar became active, or a calibration took effect. Neither changes the sail and both can change the number, so a step at a mark is the platform’s doing.

Hover any point for its date, how far into the sail’s life it sits, the per cent of target with its spread, and the wind it was measured in.

The chart needs an active polar on the boat to have a yardstick at all. With none, it says so and points at the Polar page. The tuning-targets table is deliberately not used instead — its wind-angle convention differs, so the percentages would quietly mean something else.

Why these two panels need coverage

These are the only parts of the page that can be locked, and when they are, the panel says why rather than showing a bare padlock: the inventory, the log and the journals stay open whatever a boat’s coverage, but these two read the boat’s telemetry to answer, and telemetry is the part a subscription, day pass or trial pays for. See billing takes you to fix it.

10 The performance page

Open the full analysis in the panel above opens a page for that one sail. It has its own address, so it can be bookmarked or sent to a sailmaker, and everything needed to weigh the numbers on it is on the same screen.

It answers a harder question than the panel does: not is anything happening but how much, in which wind, and how sure are you.

The two cards at the top

One for upwind and one for downwind. Each card shows the difference between the sail’s earliest sailing and its most recent sailing, the interval around that difference, one word, and a sentence with every number in it.

The word is read from the interval and from nothing else:

• down — the whole interval is below zero. Shown in red.
• up — the whole interval is above zero. Shown in green.
• no detectable change — the interval contains zero. This is not the same as “the sail is fine”; it means this much sailing cannot separate the sail from no change at all.
• not enough evidence — there is no interval yet. A difference may still be shown, and it is not read as a change.

There is no threshold behind those words. A large difference with a wide interval reads no detectable change, and a small difference with a narrow interval reads down. The line underneath each card is what the answer stands on: hours of steady sailing, segments, sailing days and wind bands.

The metric and axis controls

VMG % of polar is the default and the one to read. It compares the speed the boat made toward or away from the wind with the best the polar says the boat could make at that wind speed, so it falls whether the boat is slower or sailing lower. Boat speed % of target is the number the panel in section 9 plots. Pointing deficit is how many degrees off the polar’s best angle the boat was sailing.

The axis switches between the sail’s cumulative flying hours and the calendar. Flying hours is the sail’s own life and is what every number is computed against; the calendar is a reading aid.

The trend, and the diamonds under it

One point per sailing day rather than per hoist, filterable to a single wind band. Vertical dashed marks are where the yardstick moved — a new polar, or a calibration taking effect.

The small diamonds along the bottom are this sail’s journal entries and its delivery date, placed where they fall in the sail’s life. Hover one to read it. They are drawn on the chart and feed no number on the page: a recut you wrote down is a note, not a measurement.

By wind band

One row per 2-knot band. The hollow dot is where the sail was in its earliest sailing, the filled dot is where it is now, and the grey bar behind them is the interval around the move. A bar that covers the hollow dot is a band that has not been shown to move.

Each row carries a chip — measured, thin or counts only — and a sentence saying which gate it did not pass. A row with too little sailing behind it is dimmed and keeps its counts rather than disappearing.

Rows also carry the boat’s own drift: the same comparison over every sail that flew in that band. If this sail’s difference sits inside that, the row says indistinguishable from the boat’s own drift — which is the expected answer for a mainsail that is up all day, and which is what the next panel exists for.

Against its siblings

Pick a second sail and a point of sail. The platform finds the days both sails flew that band and compares them day by day. Anything that made the whole boat fast or slow that day — the sea state, the crew, the rig, the calibration — is the same for both sails and cancels out.

Beside the difference is a count: on how many of the paired days the first sail was ahead. Every paired day is listed, and every chart on the page has a Show as table control beside it if you would rather read the numbers.

What is behind these numbers

The bottom of the page is a ledger: which sails were up alongside this one and for how long, how many segments were excluded because they crossed a sail change, how many intervals are still open or voided, what polar and which calibration entries the numbers were measured against, and what is not modelled.

The method itself — how a second of sailing becomes a segment, how the interval is computed, the amounts that fill the two windows, and the sixteen limits it carries — is written out in Measuring sail degradation.

A page still filling in says so at the top: sailing days are read a batch at a time on first open, everything shown is measured on the days that are ready, and the page fetches the rest itself.