RE: PNW fishboat conversion
It is actually an extra layer of relatively heavy planking applied vertically to the hull. The wood is ironwood or some other extremely tough wood. As I understand it, it serves a couple of purposes. One is to provide an extra layer of protection against collisions with debris in the water. As you know, the waters here and up the coast in BC and SE Alaska are littered with logs, some broken loose from booms and others floated off the beach at high tides. Also the three big rivers along the coast--- the Fraser, Skeena, and Stikine--- as well as countless smaller rivers and streams dump tons of tree branches, root balls, and entire trees into the coastal waters. I've flown over the mouth of the Skeena and Stikine and have seen the water for miles off these rivers dotted almost solid with floating debris that's come down when the rivers are running strong in the spring. These boats often run at night to and from the fishing areas and collisions with logs and other floating debris are inevitable.
The layer of bow planking (it's on both sides) also provides protection from the anchor as it's deployed and retrieved. I assume the theory of this shield is that when it starts getting seriously beat up the planking can be replaced relatively easily, as opposed to replacing the actual hull planking.
On the working boats the bow planking is usually painted a contrasting color to the hull or left unfinished. Here are photos I took in our marina of two working salmon trollers and a Bristol Bay buy-boat from the 1920s. Notice that on the "David B" the shield planking also extends aft just under the waterline to protect the forward part of the hull.
Many wood working boats have extra planking fastened to the sides of the hull where fishing gear is deployed or brought aboard. Sometimes it's painted a contrasting color, other times it's not. The troller in the second photo has this planking on the hull by the "working area" of the boat, and in this case it's painted a contrasting color along with some of the hull planking in that area.
-- Edited by Marin at 23:02, 2008-10-08