Ed, I looked at the use of a turnaround with a high start and decided that it was not a good idea. Indeed, the turnaround would eliminate the weight of the rubber. However, an energy calculation indicates that the energy used to lift up the rubber with a conventional high start is a small fraction of the energy used to lift up the plane. If you use a high start with a turn around, there is the obvious problem of wear and drag on the rubber as it runs along the ground. I also looked at how to optimize a high start. My thoughts for a conventional high start can be seen at: http://www.charlesriverrc.org/articles/design/dickwilliamson_histartphysics.htm I went through a similar calculation for a high start with a turn around. The optimization assumes a fixed maximum length of the flying field. The optimization involves choosing the best length of tubing. If the tubing is long, more energy can be stored. If the tubing is short, a higher launch height can be reached before the high start pulls the plane down. When the optimization is done (on paper), the maximum launch height is very similar for a conventional high start and a high start with turn around. There is a third configuration which does look quite nice on paper. In this configuration, a traveling pulley is used on the downwind end of the tubing. The line runs from a stake upwind to the pulley, through the pulley and back downwind to the plane. The tubing used is twice the cross section of the tubing that would be used in a conventional high start. This choice provides the same peak force on the plane. With this configuration, the calculation indicates a launch height about 40% higher than that for a conventional high start. I may try this some day. Dick ================ >Has anyone experimented with using a turnaround with a highstart. The idea >would be to eliminate the weight of the rubber by keeping it on the ground >and using the spring action of the tubing but in a different fashion than >most people use their highstart. > >In theory it seems like it should work better than the traditional way of >using a highstart for launching but since I have not seen others use this >sort of setup I thought I must be missing something. > >I would appreciate hearing from anyone that has actually tried this or know >what results were achieved by others when they did the same. I know this >most certainly is not a new idea but since I have not tried it yet I thought >I'd draw on the experiences of others that have. >Ed -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Dr. Richard C. Williamson Phone: 781-981-7857 Room C-317 FAX: 781-981-0122 Lincoln Laboratory Email: [EMAIL PROTECTED] Massachusetts Institute of Technology 244 Wood Street Lexington, MA 02420-9108 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
