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After several Chat discussions with other Kite Life members I was encouraged to share the following information: Carbon Tube Deflection and Weight Comparisons I have created my own standard method for measuring stiffness-to-weight ratios for carbon tubing commonly used for sport kite construction for my own personal use as a kite builder and hopefully this information will be helpful to others who would like to build or mod their own frames. In this report you will see how my testing of a group of commercially available tubes compare against this standard. Any frame material can potentially be compared using this test. Test Definition: A deflection test has been defined to measure the standard deflection of a 62“ length of carbon tubing suspended with a fulcrum at it’s center-point, 31”. This length was chosen for convenience since it represents the length of two standard revolution 1.5/B-Pro spars. A 1 pound weight is suspended against a 62” length of tubing. A fulcrum is placed at the center of the length to suspend the tube vertically; a loose or permanent ferrule is used to connect multiple sections of tubing and is placed in the center for the measurement to create the 62” length. The 1 pound weight is suspended with 37” of line on each end of the 62” length forming a triangle with 37” sides. A second line is then attached to each end of the 62” length of the tube being measured to create a parallel line beneath the bow that is created by the weight. The distance from the center of the tube to this line is then measured. The weight of the tubing is calculated without ferrules. This defines the nominal weight of the tube in g/in. SU1: Stiffness units (version 1 is where the 1 comes from in SU1) are defined by the amount of deflection at the centerline of the 62” bow and are in units of inches. W: is the weight of the tubing sample used in g/in. This is a measurement of the tube without a ferrule. These results are the average of several tubes. SU1/W: represents a stiffness-to-weight ratio and can be used to compare other tube materials. This becomes the standard for comparison in my chart and the chart is sorted from the highest value to the lowest value. A high value means that the tube will weigh less but be less stiff (more deflection). A low value means that a tube will perhaps weigh more but be more stiff (not deflect as easily). For frame weight comparisons, nominal weights were calculated for a Rev 1.5/B-pro frame and a Rev B-2 frame. Nominal weight values do not include the weight of ferrules or adhesives. Note: m2 stands for measurement of a second group of tubes. in case the picture can't be enlarged, here is the chart again in text format: Rod SU1 W g/in SU1/W Rev 1.5 Nom. Frame wt g Rev B2 Nom. Frame wt g Sky Shark P90 4.5000 0.3226 13.9492 50.0030 39.5185 Sky Shark P1X m2 3.7500 0.4021 9.3260 62.3255 49.2573 Sky Shark P1X 3.7500 0.4154 9.0274 64.3870 50.8865 Race Rods 31" silver 3.7500 0.4194 8.9413 65.0070 51.3765 Rev Race Rod silver B-2 3.7500 0.4286 8.7494 66.4330 52.5035 Sky Shark P1X m3 3.6250 0.4021 9.0152 62.3255 49.2573 Rev 2 Wrap silver 3.4375 0.4597 7.4777 71.2535 56.3133 Sky Shark P2X 3.1250 0.4516 6.9198 69.9980 55.3210 Sky Shark P2X m2 3.1250 0.4740 6.5928 73.4700 58.0650 Sky Shark P200 3.0000 0.4677 6.4144 72.4935 57.2933 Sky Shark P3X 2.8750 0.5323 5.4011 82.5065 65.2068 Sky Shark P3X m2 2.7500 0.5265 5.2232 81.6075 64.4963 Rev 3 Wrap silver 2.5000 0.5000 5.0000 77.5000 61.2500 Sky Shark P400 2.5000 0.7282 3.4331 112.8710 89.2045 Rev 3 Wrap w/ Green Stripes 2.3125 0.4194 5.5138 65.0070 51.3765 MODERATOR UPDATE: