Lofting and Modeling an NACA 4321 airfoil Bob

Lofting and Modeling an NACA 4321 airfoil Bob Koll Technology Education Juanita High School Kirkland, WA, 98034 Phone: 425 -941 -3167 Email: bobkoll 1@comcast. net

Lofting • • Use NACA Loft data Use Calculator or Spreadsheet program Use Drafting tools or CAD program Use Printer

NACA 4321 Loft Data

Draw a horizontal line; this is the chord line.

Calculate station points along the line from left to right. • Multiply the chord length by each chord station % • This number is the ordinate # which will be plotted on the chord line

Draw points at these station points on the line.

Calculate the upper camber points. • Multiply the chord length by each upper camber % • This number is the ordinate # which will be plotted above the chord line ordinate #

Draw the upper camber points above the station points

Calculate the lower camber points. • Multiply the chord length by each lower camber % • This number is the ordinate # which will be plotted below the chord line ordinate #

Draw the lower camber points below the station points.

Draw two interpolated curves through the upper and lower points

Draw the 4/15 slope line from the end of the chord line

Draw the leading edge circle w center pt on the slope line

Trim the Circle to the upper and lower curves

Laser cutter: • • • Join all the curves together Vector-cut of 1/8 plywood Modify the model to accept ‘spars’ A‘spar’ system from drinking straws works Modify chord length to create a model wing

Modeling • Use Styrofoam block • Use Hot Wire cutter • Use Two machining guides

Plot two copies of your lofted airfoil printed on heavy paper works fine

These are your machining guides

Attach to ends of a styrofoam block Cut out with a hot foam cutter using the heavy paper guides.

Cut out airfoil using the hot wire knife to get a wing. Join the wing pieces with ¼ dowels. My students have created a 6 ft wingspan glider with this method