I think that the difference in both strength and stiffness can be attributed to the difference in distance between the top and bottom boron fibers. For a spar 0.050" high, the boron (assume 0.004" boron) centers are 0.054" apart. If the boron is put into 0.004" deep grooves, the boron fiber centers are now 0.046" apart. Both the bending stiffness and bending strength (coming from the boron) are proportional to the square of the distance between the boron centers. This lessening of the center to center distance results in but (46/54)^2 = .73 or 73% of the non-grooved stiffness and strength. This consistent Vladimir's testing.
An interesting story comes to mind. Back when I was first getting started with indoor duration flying, I had a many conversations with Jim Richmond, a fellow Hoosier. We spoke about the use of boron among many other things. When I asked about using grooves to help the boron adhere to the spars, Jim was quite positive that grooving was a bad idea for the above reason. Jim's language and opinions about those who used grooves were expressed in a way that was more "salty" than can be relayed in a family setting.
LeoP
Received on Fri Jan 22 2016 - 15:27:52 CET
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:48 CET