Systems and methods for restraining exhaust gas ducts

A stiffener mechanism for an exhaust duct, the exhaust duct including a first row of flutes and a second row of flutes generally opposite to the first row of flutes, each flute being elongated along a respective axis, the stiffener mechanism comprising:

• at least two flute ties coupling together at least two flutes from the first row of flutes to at least two flutes from the second row of flutes;
• and
• at least one retainer coupled to the at least two flute ties and extending generally perpendicularly to the axis of each of the at least two flutes from the first row of flutes and the at least two flutes from the second row of flutes;
• wherein the at least one retainer is configured to generally restrain relative movement between the at least two flutes from the first row of flutes and the at least two flutes from the second row of flutes.

A method of increasing a resonant frequency of an exhaust system having at least one duct, the at least one duct including a plurality of flutes, each flute including a trough and an elongated portion with a respective axis and a lateral portion extending generally perpendicular to the respective axis, wherein a length of the elongated portion is greater than a width of the lateral portion, the method comprising:

• selecting a first flute from the plurality of flutes, the first flute having a first axis;
• selecting a second flute from the plurality of flutes, the second flute having a second axis generally parallel to the first axis;
• orienting a retainer to extend generally perpendicular to the first and second axes;
• and
• coupling a first portion of the retainer to the trough of the first flute and a second portion of the retainer to the trough of the second flute such that the retainer generally restrains movement between the first flute and the second flute.