View Full Version : Shrinking Wood

David Powell
12-23-2007, 01:59 PM
I have a Danish vessel that is 60 years old. It is constructed with oak frames and planks, which are huge; 2 ˝ inches thick and around 8 inches wide.. The gaps between the hull planks above the waterline are quite large in some places – up to 3/8 inch on the outside but obviously less on the inside.

Everything is traditionally caulked (oakum stopped over with putty/paint mix) but this year’s summer season (the boat is in Spain) has created a few loose seams. I am trying to determine if planks shrink more and more as they age or is the process cyclical with season and moisture content in the wood?

Any thoughts please?

mike hanyi
12-23-2007, 02:06 PM
yes the wood shrinks over the years... now please tell me the boat is NOT black?!

if you are in the med paint her white to shed off the sun, it will destroy your boat

there are 2 colors for a boat, white and only a fool would paint his boat black-Nathanael Herreshoff

David Powell
12-23-2007, 02:16 PM
The boat is not black - its green (which is almost as bad) with white being added as I work on it.

Bob Smalser
12-23-2007, 04:51 PM
The phenomena is called compression set. Compression set is when the planks swell sufficiently to crush their edges against each other, damaging the wood. Damaged wood loses its resilience, and doesn't swell back as far the next time it dries and swells. It usually gets worse over time with repeated cycles and owner attempts to stop the leaks or speed taking up. It occurs in all planking species, but is usually worse in the denser, less seasonally stable species like oak. Moving a boat between climate extremes doesn't help either.

The repair for old planking is to glue a wedge of planking wood to one side of the seam to bring the gap back to normal, then recaulk traditionally. Don't confuse this repair with a "wedged seams" modification where the caulking is entirely replaced by a softwood wedge glued to both sides of the planking seam. This may sound like a good solution, but has zero chance of working with 10/4 oak. Your planking moves too much and with way too much force to successfully glue it together into a continuous panel.

12-23-2007, 05:10 PM
I have seen this in abandoned houses with 1x6 T&G floors. this boards dry out and the cracks fill with dust then summer comes and they swell against the dust filled cracks if the house doesn't fall down eventually the cracks widen to the point that the tongue no longer meets the groove.

David Powell
12-23-2007, 06:21 PM
Thanks Bob for your comments. I have considered fitting a thin strip to one edge of the planks as a repair. It will reduce the gap and the huge cost of oakum and putty it takes to caulk and stop the seams.

Anyone have a guide for the ideal gap on thick wide planks?

As far as T&G in houses goes - never mind abandoned houses - I have that problem in the house I am living in!