Appears to be sealed on the inside with a single layer of glass and epoxy, and epoxy and or varnish on the outside. Feels to weigh around 100 lbs. or just slightly more (guess). Includes original plans used to build it plus the the original book the builder used.

Here is a quote about the boat from the book (published in 1985):

"The Cosine Wherry is a strong, lightweight, beautiful, high performance 14-foot rowing boat, the newest design by John Hartsock of Emonds, Washington. Combining years of rowing experience with his knowledge of computerized hull designs, Mr. Hartsock has created a single rowboat to satisfy the various recreational requirements of a family, the practical demands of the sportsman, and the competitive desires of the serious rower. The Cosine Wherry offers the best of both worlds: it's light, fast, and a joy to row, yet stable, and capable of hauling plenty of passengers and gear."

MULTI-ESTATE & MACY'S INVENTORY AUCTION AT RUM CREEK