Wednesday, February 16, 2011


 When I was in high school, stickers where those pesky little picker things that stuck to your sleeves and socks when you were out hunting. A real pain. For bridge work stickers are the small pieces of wood placed between the layer of wood so that the air can circulate all around each board as it is dried in the heated Kiln (KD). It would be less expensive to just let it Air Dry (AD) naturally outside but that would take a long time and it would be difficult to lower the moisture to the 17% relative moisture that we require.

Up to this point we have spent most of our time looking a the raw material that will be used to built our 32 foot long Town Lattice Truss covered bridge. Five years ago I had no idea there even was such a thing. The only contact I had with covered bridges was from the movie Bridges Of Madison County with Clint Eastwood!  Now there seems to be no end to it. Ithiel Town, an architect by training patented his design in 1820. His design was pretty simple. Made with many similar size parts and requiring no complicated joinery and almost no metal fasteners it caught on. Another plus was the design was capable of clear spans of 100 feet. Also the length of the bridge could be extended by just continuing the lattice. In the pictures you can get a feel for the design and how to works.

The South Wayne bridge bridge will have three main parts. The deck, the trusses and the roof system. We will get into the details over the next few blog posts. For now, the deck will be 6' - 8" wide and 32' long. The trusses will be 8' deep when measured from the center of the bottom chord to the center of the top chord. The roof will have an 8:12 pitch with 2 foot over hangs at the eaves and 4 foot rake extensions on each end to protect the deck and bottom truss chords from the weather. We will use 4,750 Bd ft of pine and the green dead weight of the bridge will be a little over 11,000 pounds. Target date for completion is July 30, 2011. 

Puzzler - How many different bridge designs can you name?

Tech Vocab - Doyle,  International,  Scribner

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