Sunday, 31 March 2019

HULL REPAIRS

Replacing planks in shell-built hulls is tricky. Of course it can be done and was a common necessity.

Nidhug is a Gokstad-type Viking Period ship now more than 20 years old. It is not a narrow warship but a general purpose hull which is a bit deeper and rounder than one would like for fast rowing.

On the stocks - note shallow draught. (unladen)
Several planks need replacing having begun to weaken.

An upper plank needs replacing. The hole was easily knocked through after the plank was taken off.




 Planks removed reveal the lightness of construction. It is the edge-fastened planks which give th ehull most of its strength, not the internal fittings.


From the inside..th eupper strake nice and light coloured is the one shown rotten above. The clamps allow th eplank to be set fast in place before nailing. The floors and knees defining each sess or rowing place (interscalmium on an ancient galley). The cross-timber is a tofte, equivalent of a zuga.


The planks are fastened with a nail/spike that is driven in from the outside and rivetted over a rove or washer on the inside, so joining two planks together through their overlapping edges. This is clinker construction.

Copper spike and rove. These woul db eiron in the Viking Period. We use copper for security and because hand-smithed boatspikes cost a lot of money and are not always available.
Over-lapped joint with nail heads visible. They ar ein the old holes in the existing plank.
From the inside you can see the overlap joint of th enew and old planks. The spike end is rivetted over the rove.

Another type of joint is the scarf which overlaps two thinned-out plank ends to maintain the single thickness. This is  nailed close along its length.
Scarf gaping before closing.
Line of roves showing scarf fastened along its breadth,

The other end of the lap jointed plank. Looks great. Note lovely texture from years of tar application on old planks.
The replaced planking looking nice and new and neatly fitted into the hull.
Replacing planking in a draw-tongue edge fastened shell like the ancient war galleys was also tricky. Even more tricky than this. I will do a note on that to follow.

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