Fluttering Airfoil Development
Fluttering Airfoil Development from Thomas LaMothe
Fluttering Airfoil Development

This airfoil is one of many components that will be used to study the correlation of free-play in control surfaces on aircraft and flutter. Aeroelastic flutter is a phenomenon in which an airfoil will tend to oscillate with a combination of torsion and bending . Flutter is undesirable because is generally a divergent property meaning that once it has started, it can lead to a catastrophic failure if it is not properly dampened. As aircraft exist today, there is no method of dampening these oscillations. Aeroelastic flutter caused the famous Tacoma Narrows bridge to collapse into the water below in 1940 [1].

This airfoil is separated into 8 segments and is held together by a central spar. The airfoil is segmented to reduce the torsional and bending stiffness of the structure. This is important because it reduces the wind tunnel velocity required to induce fluttering.

[1] http://www.ketchum.org/billah/Billah-Scanlan.pdf

This is a fully assembled airfoil section. The one major component that hasn't been discussed yet is the wooden band attached to the exterior of the right most rib. This 'sacrificial edge' is used as a fail-safe. The gap between the different sections was determined by applying a conservative load on the spar. The maximum deflection angle was determined with an FEA package. This angle was used to calculate the gap to prevent the sections from contacting one another during testing. However, this analysis was done with static conditions while the actual displacements experienced by the airfoil will be dynamic. Intuitively, this is not a safe assumption especially knowing the complex motion flutter can exhibit. To prevent the need to make another airfoil do to collisions during testing, wood can be removed from this 'sacrificial edge' to increase the gap. Intuition on the problem will prevent us from creating huge problems to fix later.
These were the first prototype leading edges cut on the CNC. The balsa required too much sanding after the cutting operations to meet our time restrictions so mahogany was used in the final versions.
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Fluttering Airfoil Development

This airfoil is one of many components that will be used to study the correlation of free-play in control surfaces on aircraft and flutter. Aeroelastic flutter is a phenomenon in which an airfoil will tend to oscillate with a combination of torsion and bending . Flutter is undesirable because is generally a divergent property meaning that once it has started, it can lead to a catastrophic failure if it is not properly dampened. As aircraft exist today, there is no method of dampening these oscillations. Aeroelastic flutter caused the famous Tacoma Narrows bridge to collapse into the water below in 1940 [1].

This airfoil is separated into 8 segments and is held together by a central spar. The airfoil is segmented to reduce the torsional and bending stiffness of the structure. This is important because it reduces the wind tunnel velocity required to induce fluttering.

[1] http://www.ketchum.org/billah/Billah-Scanlan.pdf

Thomas LaMothe
Student Ames, IA