A dried-out timber hull will take water when it goes back in, and that is the system working as designed. Planking shrinks on the hard; the seams open; on relaunch the timber swells and closes them again. What separates a routine take-up from an emergency is knowing which is which — and having pumps, power and a person aboard while you find out.
Why it happens
Carvel planking relies on seams that are caulked and then held closed by the swelling of the timber itself. Out of the water and under tropical sun, planks lose moisture and shrink across their width. Multiply a small shrinkage by every plank in the hull and the cumulative seam opening is significant. Put the boat back in and the process reverses — but not instantly, because water has to be absorbed into the timber before it expands.
The consequence is a hull that leaks meaningfully for a period after relaunch and then, if everything was done properly, stops. The longer and hotter the dry period, the more pronounced the effect.
Managing the dry period to reduce take-up
Keep the sun off
Shade over the topsides and deck during a long stay dramatically reduces drying and therefore shrinkage. Low-cost, simple, routinely skipped.
Wet the hull
Where a vessel must sit for weeks, periodic wetting of the planking slows moisture loss. It is not a substitute for shade but it helps.
Do not over-caulk to compensate
Driving extra caulking into seams that are only open because the hull is dry will force them apart when the timber swells — a classic way to create a leak that was not there before.
Plan the stay
The shortest dry period consistent with doing the work properly is the right one. Long stays are sometimes unavoidable; they should at least be deliberate.
Before she goes back in
- Seam checkWalk the whole hull and confirm the caulking is where it should be and the stopping is intact.
- Skin fittings and seacocksEvery through-hull opened, inspected and confirmed closed or serviced. This is the single most common source of “take-up” that is not take-up.
- Shaft seal and stern gearPacking renewed or seal checked, and alignment verified as described in the article on engine removal and shaft alignment.
- AnodesFitted and bonded, because the first weeks afloat are not the time to discover they were forgotten.
- Pumps and powerBilge pumps tested under load, batteries charged, float switches verified, manual pump accessible.
- A person aboardFor the first nights at least. Automatic pumps fail silently; people do not.
Distinguish take-up from a defect
Take-up is diffuse: water enters along seams across a broad area and the rate falls day by day. A defect is local and persistent — a steady flow at one fitting, one fastening, one plank end — and the rate does not improve. If you can trace the water to a point, it is not take-up.
Monitoring properly
“It seems less today” is not monitoring. Record the interval between pump cycles, or the time taken for the bilge to reach a marked level with the pump off and someone watching. Do this at the same points each day. A falling trend across two or three days is the reassurance you want; a flat or rising trend is a signal to haul again or to investigate while the vessel is still afloat and accessible.
When take-up does not complete
If the rate stabilises at a level that requires regular pumping, the usual causes are worn plank edges that could not hold caulking properly, seams that were over-caulked while the hull was dry, fastening wastage allowing movement at the plank ends, or a hull that has distorted while badly supported on the hard. Each of these is a structural conversation rather than a maintenance one, and each is covered under hull repair and caulking.
This is also the moment when the quality of the support arrangement during the stay becomes visible, which is why blocking and shoring is treated as structural work rather than logistics.
The handover record
At the end of a haul the desk issues a written record: what was replaced, what was repaired, what was deliberately left, and what the take-up behaviour was over the monitoring period. That last item matters more than owners expect. It is the baseline against which the next haul-out is judged, and without it, every future assessment starts from memory.
The first week afloat
Treat the week after relaunch as part of the yard programme rather than as the start of normal operation. Bilge levels are logged at consistent intervals, seacocks and shaft seals are checked daily, and the engine is run and the alignment reassessed once the hull has settled into its floating shape. Anything that needs correcting is far easier to reach alongside than after a passage.
It is also the period in which any error made on the hard becomes visible. A hull that was over-caulked while dry, or supported badly for weeks, will announce itself now — and it will announce itself as a leak that does not diminish. Catching that within days, while the yard team is still assembled and the vessel is metres from the beach, costs a fraction of what it costs after the boat has left.