Wood flights used on collectors in settling tanks have a performance record superior to that of flights made from any other material.  The specific gravity of wood lends the desired buoyancy required to carry metal chain and flights.

In turn, the wood flight is not so heavy that it drags the bottom causing needless wear and abrasion.  Nor are additional weights required to hold the flight down.

  There has been one problem - that of the wood flight decaying while in service.  Because of this problem, the industry has searched for an acceptable substitute.  Thus far nothing has been found that will equal the performance of wood for heavier loading and grit.

Of the wood flights used in the past, Redwood has been the species most commonly used.  This is primarily because of its natural decay resistance.  Unfortunately, Redwood is not one of the most desirable species for this application.  Redwood is one of two species found to contain the greatest amount of "Tannin" Crannic Acid).  Tannic Acid in the wood accelerates corrosion in the metal connectors and promotes electrolysis.  This in turn causes the wood to undergo "Hydrolysis," weakening the wood.  

Timber Forest Products has developed a method to greatly reduce the decay hazard through the use of specially designed Flight Grade Laminated Douglas Fir and insulated fittings. Timber Forest Products has developed a sealant pad used as an expansion joint material between the attachment link and the Flight to protect against the passage of electrical current generated as a result of electrolysis.  Further, bolts and washers should be stainless steel or should be coated with an Epoxy-Bonded Fluoropolymer to protect them from electrolytic corrosion.