Starting Double Diagonal Planking

The hull is now ready for planking, all the structural members have been built and finished! Unlike carvel planking where the first strake placed on the hull is the garboard, on double diagonal planking, the first strake placed is the topside transom piece. 

The first piece was dry fitted and held in place by copper nails that were not driven in all the way, facilitating its removal and keeping the holes fresh. This was also done on a very dry and cold day when the wood is as shrunken as possible. As the wood warms and humidity increases, the wood will swell onto the nails and lock them in place!

With the fit verified, bedding compound was placed on the transom edge because this seam will be external and making it water tight is crucial.

The second piece was also test fitted and then bedded and nailed into place using copper nails. Steel, galvanized or stainless should be avoided on a wooden boat. The wood will hold moisture and cause the galvanized steel to rust forming red rust streaks that will bleed from the holes, while stainless will suffer crevice corrosion and will part internally. Copper and bronze are the preferred material for boat fasteners, though they are overkill for a dinghy.

Once the first strake was nailed on and bedded, the rest of the process proceeded very quickly. The strakes that do not contact the transom did not need bedding compound, as they will eventually be completely covered by the second skin.

As the strakes came in contact with the stem, the same method of dry fitting and then bedding the strakes was used. The stem and stern are the only two areas where we are concerned about water intrusion at this point. All the other parts will eventually be covered by other strakes that will shield them from water.

The planks needed to be trimmed to fit under the sheer, but were left overhanging the chine log. This lackadaisical approach made the planking process proceed much faster. Once the entire side was planked, I then went back through and trimmed up the area around the chine.  

The strakes were all cleaned up and the side looks a lot more neatly planked. The strakes that do not start or end on a frame look out of place, as they are not lined up with the rest of the hull, but this is not a problem. When the second layer is fastened, these planks will be drawn up to the outer skin, thus smoothing out the inner skin planks.

The two layers of topside planks will be finished before the bottom planking is done, offering a large faying surface for the bottom and topside planks to meet. The small gaps between the planks are also not a concern, as the bedding compound of the second skin will fill these voids and make the hull skin water tight.

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