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of the bottom plate is critical. Too close to the edge and the bottom of the body tube will not be able to fully rest on the plate. Too far from the edge and there will not be clearance for the bottom fin to clear the plate. See Figure 7 to see how the bot- tom fin just clears the jig base plate when the final fin is attached. Note that this jig would not work for four finned rockets. Fortunately, those are typically not used SPORT ROCKETRY JANUARY/FEBRUARY 2020 13 ARA Press 785 Jefferson Ave. Livermore, CA 94550 (925) 583-5126 www.arapress.com ARA Press The Spaceship Enthusiasts' One-Stop Data Shop! Visit our website to order on-line. All Credit Cards and PayPal accepted. Call or write "info@arapress.com" for shipping options. Sales Tax added for CA orders Follow us on Facebook! 244 pages, Softcover Color cover w/ B&W illustrations Over 400 photos and diagrams A project-oriented guide to the rock- et hobby, primari- ly for people in- terested in rock- ets in the A to G motor range. There are tips for hobbyists of every skill level so that it will continue to prove useful as the reader gains expe- rience in the hobby Only $19.95! (plus shipping) Seize The Sky A Builder's Guide to Model Rocketry by Mario Perdue Available Again! This book may seem horribly out of date since it spends most of the time describing how to adapt compact film cameras for flight. This in- cludes building large payload bays and methods of mechanically and/or electrical- ly triggering the cameras. Only $14.95 ea! (plus shipping) Figure 7. Bottom view of fin jig showing how the bottom fin just clears the jig while attaching the final fin. Figure 6. Attachment of third fin. Note fin jig is raised so the "bottom" fin has room to extend below jig. for rocketry competition. Once all the fins are attached, fillets must be applied, typi- cally CA or epoxy fillets. I prefer epoxy as I struggle to get nice clean fillets with CA. Your mileage may vary. That's the simple Wolf fin jig concept that has been used for building NAR com- petition rockets for over 20 years. I hope you can use this idea or that it will inspire you to come up with your own method for fin attachment. If you do, please share it with others.