way to a reel drum shown generally at 9 the air carried along with the sheet as well as any unbalanced exhaust present above or below the sheet may cause edge curl and other instability the foils help in minimizing this instability near foil 10 is a directional air jet 15 a baffle 20 a hood surface cleaning air nozzle 30 a lower sensor hood 35 and a support 40 turning now to fig2 these components are seen in greater detail the web passes below upper foil 7 c and above foil 10 its direction of travel is shown by the arrows foil 10 directs the boundary layer laden with dust away from the sheet u201c dust u201d is used throughout as including dust and other contaminants in certain embodiments the foil 10 is made of solid metal in especially preferred embodiments the foil is made of porous metal the porous metal foil which is usually stainless steel has pore sizes on any particular embodiment ranging from 1 to 100 microns mounted at the edge of foil 10 is an air jet 11 air jet 11 introduces air flow into the porous metal foil this air flow creates a high pressure region within foil 10 which causes air flow out of the pores of the porous metal foil this air flow through the porous metal foil generates an u201c air lubricant u201d which reduces friction when the sheet passes over the foil the reduction in friction and associated drag permits higher sheet speeds through the machinery because the porous metal foil helps the sheet to travel at higher speeds the machinery can operate.