"River kayak" is not very specific. Any SOF would work well on the Hudson River but not the New River.
Clark Craft offers a generic 11' by 28" SOF but I don't think it will hold up if you ricochet off boulders and scrape bottom a lot.
http://www.clarkcraft.com/cgi-local/shop_new.pl?type=item&categ=014&item=934897693&cart_id=9fc6f3b4a9e44ed17566b3e076e62ed6

: i would like to purchase a set of sof kayak plans to build a river
: kayak 10-13 ft long---a few yers ago i bought plans from
: laughing loon and built a cedar strip canoe---any
: suggestions---thanks--phil