The question every sailing skipper asks before crossing France is the same one I asked: do I really have to take the mast down? The short answer is almost certainly yes. The longer answer, and the reason this article exists, is that getting your air draft wrong is the single most expensive mistake you can make on a canal passage, and it is entirely avoidable with a tape measure and ten minutes of arithmetic.
What air draft actually means
Air draft is the height of the highest fixed point of your boat above the waterline. For a sailing yacht that is the masthead, plus the VHF aerial, the wind instruments and anything else bolted up there. People forget the aerial and lose it on a bridge. Do not be those people.
On a motor boat your air draft is usually the radar arch, the flybridge or a folded antenna, and it is much lower, which is why motor cruisers cross France mast-up and stress-free. This whole problem is a sailing-boat problem.
The numbers that decide it
French canal bridges are built to a standard, and the relevant figures are not negotiable. Here is what governs the decision:
- The Freycinet gauge requires bridges to give 3.7 m of clearance above the water in principle.
- In practice, the usable air draft on the main cruising routes is about 3.5 m, and many guides advise 3.4 m to be safe.
- Some fixed structures, old bridges and tunnel mouths, are lower than the nominal figure.
- Water levels rise after rain, reducing your clearance under a fixed bridge.
- The Freycinet network also limits boats to about 38.5 m length and 1.8 m draught, the same standard that defines the locks.
So the working rule is this: if your air draft mast-up is more than roughly 3.4 to 3.5 m, the mast comes down. For any real cruising yacht the masthead alone is 15 to 20 m up, so there is no contest. The mast comes down. The same Freycinet standard caps you at about 38.5 m length, 5.0 to 5.05 m beam and 1.8 m draught, so air draft is only one of four numbers, but it is the one that ends the mast-up dream. If you want the rest of the box your boat has to fit inside, the Freycinet gauge canal dimensions are set out in full.
The low points that actually catch people
The 3.5 m figure is a planning ceiling, not a guarantee, and a few specific structures are tighter. Old hump-backed road bridges and the mouths of canal tunnels are the usual culprits, because they were built to the nominal clearance with no margin and the arch is lowest at the centre, exactly where you want to be. Tunnels are the worst of it: on the Marne-Rhine route you pass long bores like Mauvages and Arzviller, and the curve of the roof eats into your headroom well before the walls do. The Saint-Louis-Arzviller inclined plane on that same canal is the famous exception, a boat lift that raises you 45 m in a few minutes and skips 17 locks in 4 km, but the lift caisson and the approach bridges still hold you to the canal gauge.
Water level is the other variable nobody controls. A wet week raises the canal and the river reaches and quietly steals 100 to 300 mm of clearance under a fixed bridge. If you are creeping under a marginal structure, do it after a dry spell, and if the gauges are up, wait. The bridge will not move.
The motor-cruiser exception
There is a narrow band of small motor boats, some trailer-sailers, and a handful of low-profile launches that genuinely fit under mast-up because their highest fixed point is below 3.4 m. If that is you, count your blessings, fold every antenna, and still measure twice. The margin under a 3.5 m bridge with a 3.4 m air draft is 100 mm, which a passing barge's wash can erase in a second.
For everyone with a stepped mast, read on.
Taking the mast down properly
You do not lift the mast yourself in the car park. You use a mast-stepping service at one of the entry ports. The standard arrangement at the Channel end, often Le Havre, is that a yard cranes the mast out, and you have two choices for the journey.
Some crews lay the mast horizontally on deck on a set of trestles or gallows, with the boat carrying it the whole way across France. This keeps everything aboard but the overhanging spar makes the boat longer and harder to handle in locks, and you live with it underfoot for weeks.
The cleaner option is to have the mast trucked by road to a yard at the Mediterranean end, around Port-Saint-Louis or Port Napoleon, where it is stepped again when you arrive. You cross France with a clear deck, then collect and re-rig at the far end. It costs more and it relies on the logistics working, but it is far more comfortable. We did this in 2024 and would not go back to carrying the spar on deck.
On money, get firm quotes rather than trusting forum hearsay, because the numbers swing with the size and weight of your rig. As a rough order of magnitude, the crane-out and crane-in at a well-drilled yard such as Port Napoleon is often a few hundred euros at each end, and the road transport of a 12-to-16 m spar the length of France runs into several hundred euros more on top, so the full mast-down-and-trucked exercise is comfortably a four-figure budget once you count both yards and the haulier. Book it in the spring, because the entry-port and exit-port yards have a finite number of slots and they fill in the peak crossing months.
Either way, label and bag every fitting, photograph the rig before it comes down, and protect the spreaders and instruments. The re-rig at the far end is much faster if you have not lost the small parts.
Where this fits the bigger picture
The mast question is inseparable from the route question. If you are weighing up the whole transit, the air draft limit is one of the two numbers, along with your draught, that decides which canals you can use. I have set out the full route picture in crossing France by canal from the Channel to the Med.
And remember the mast does not go back up until you reach the sea end. That means the entire inland passage, including the final big run, is done as a low-profile motorboat. If your route ends down the river, read down the Rhone from Lyon to the Mediterranean so you understand what the last leg demands of a de-rigged boat in fast commercial water.
The mistakes I have watched people make
The classic error is assuming the published clearance is the clearance you get. It is not. Water level, an old bridge, a misjudged tunnel, all eat your margin. Treat 3.5 m as a hard ceiling and build in a buffer.
The second error is forgetting the aerials and instruments when measuring. A boat that is 3.3 m to the cabin top is not 3.3 m air draft if there is a 600 mm VHF whip standing proud.
The third is leaving the mast logistics until the last minute and finding the entry-port yard fully booked in peak season. Ring ahead in spring, book your slot, confirm the road transport if you are using it.
Measure your real air draft, add the aerial, and be honest with yourself. If the number is over 3.4 m, plan the mast down from the start, budget for both ends, and stop worrying about it. The decision is almost always made for you by physics. The only real question is whether you carry the spar or send it by truck.
