We contracted with Bayview Edison Industries in Mount Vernon, Washington to build the plugs.

Inside duct plug

Outside duct plug

The next step is to sand the plugs to a fine finish, and then  spray the plugs with a surfacing primer that will allow us to fabricate the molds while leaving the plugs intact. 

Next, we make the molds and connect the two halves to make the duct.

In the picture on the left, Bryan and Bill are preparing the mold to make parts.  In the background, Adam, is finishing the second molds.

The picture above is the completed duct on our mock-up of the deck.