SmartStroke's Testing Process
The canoe parts were tested according to different ASTM standards as well as with another custom test designed to test torsion. Because each part is subjected to different forces and loads, SmartStroke set pre-determined minimum values to achieve during testing to resemble similar forces the paddle will be exposed to in the field. The CME 480 Design Project required that a minimum of three different tests be performed on the final paddle. SmartStroke determined the three most important tests for a canoe paddle to be the following: Moisture Absorption (ASTM D5229), Blade Torsion (Custom Test), and a Flexural Test (ASTM D790).
A moisture absorption test was chosen since a canoe paddle is continually exposed to water. According to ASTM D5229, the maximum allowable water absorption is 1%. After the blade and handle were submerged in room temperature water for 48 hours, the two parts were both under the allowable absorption. The handle absorbed 0.9% water and the blade absorbed 0.8% water. The results would be even better if the actual finals parts were tested, as there were noticeable holes and resin-poor areas in the tested parts.
A torsion test was selected to simulate the torque a blade will experience from the water. A custom test was designed to put torque on the paddle blade until failure. The portion of the blade that meets the shaft was clamped in place by a vice and pin system allowing only the tip of the blade to rotate. A deflection of 63.47 degrees was produced during the test. Using a radius of 4 inches produced by a perpendicular support, an ultimate torque of 520.48 lb-in was produced. This substantially exceeded the minimum value of 44 lbf.
The paddle shaft is constantly being bent under forces resembling three point loading. A span of 23 inches was chosen to resemble the width of the paddler's hands. Taken from the Human Factors Design Guide, an average person is capable of pulling 44 lbf. Wanting to achieve a safety factor of 1.5, we were successful in putting a load of 66.40 lbf on the paddle shaft. The other properties determined in the test were the following: Strain of 0.11%, Stress of 8.44 ksi, and Modulus of 73.8 ksi.