Inside Drydock 12: refitting a corvette in forty days

In the third quarter we took a 140-metre corvette through a full propulsion and defence refit in forty days. Customers ask what a refit window actually involves, so here is the real schedule, including the part where we lost two days.

The scope

• Replace a failing class 1 motivator with an HD-7
• Fit a DSG-4400 and eight emitters
• Replace four thruster clusters with IT-12 arrays
• Full navicomputer replacement and almanac load
• Recertify the hull

Days 1–6: survey

Nothing gets cut, welded or unshipped until the survey is complete. Six days sounds extravagant. It is the reason the rest of the schedule holds.

The survey found what surveys usually find: the previous motivator cradle had been shimmed non-standard during an earlier repair, which nobody had recorded. Caught on day four. Had we caught it on day twenty-two, with the new drive already in the bay, it would have cost a week.

Days 7–19: the drive

Unshipping a motivator is the long pole in any propulsion refit. The old unit came out on day nine. The cradle adaptation — the shim problem from the survey — took days ten through thirteen. The HD-7 went in on day fourteen and was aligned by day sixteen.

Days seventeen through nineteen were cold alignment verification, which cannot be rushed and cannot be done in parallel with work that induces hull vibration. This is why the shield work did not start until day twenty.

Days 20–31: shields and thrusters

Eight emitters, four thruster clusters, running in parallel with two crews. Emitter placement followed the hull survey rather than the previous emitter positions — the ship had gained a sensor pod at some point and the old geometry left a gap in the ventral sector that had been there, undetected, for at least four years.

Days 32–33: the two days we lost

A thruster hardpoint on the port quarter had corrosion under the mounting ring that the survey missed because it was not visible without removing the ring. We removed the ring on day thirty-two, found it, and stopped.

Two days to cut out the corroded section, fit new plate and re-certify. We ate the cost, which is our policy when a survey misses something. It also went into the survey procedure: mounting rings on any hull over fifteen years old now come off during survey, not during installation.

Days 34–40: certification

Almanac load and verification, shield emitter survey and harmonic tuning, full-power drive test, hull recertification, and the sea trial equivalent — a short lane run with our engineers aboard.

The ship left on day forty. The schedule had forty-two in it, which is the other reason the survey takes six days: the margin has to come from somewhere, and it is cheaper to find problems early than to build slack into every later phase.

If you are planning a refit window, talk to us before you book the dock. Half of what makes forty days possible is deciding the right scope in the first place — see Services for how we structure it.