AboutDave Landgraf Expertise I will be happy to take on questions about low-power rocketry in general, including rocket design, operating characteristics of blackpowder motors, low-power motor selection, rocket construction, aerodynamics, parachute and streamer duration competition, boost glide (and a little rocket glide), egg loft, altitude competition, and scale competition. I can help you with Barrowman stability calculations, but I am not a rocksim user. I know the basics of mid-power rocketry and small composite motors but I don't fly them much (I'd rather stretch my money by sticking with low-power). I believe I can explain many concepts in a way that just about anyone can follow (and maybe even over-explain?). I absolutely do not mind "newbie" questions one bit; the only bad question is the one you don't ask!
Experience I have flown model rockets for some 40 years, including a few early years of NAR competition. I have been active at the local club level as well as in the NAR. I enjoy designing and developing unconventional designs (the kind of thing you look at and say "it won't fly!").
Organizations National Association of Rocketry
Publications Model Rocketry (magazine)
Education/Credentials I am an aerospace engineer who has worked professionally in the field for over 30 years. I have worked often with local school, church, and scout groups to lead introductory build-n-fly sessions.
Question I am building a 3-finned rocket and I was wondering how to precisely install the fins so that they are not angled or tilted etc. (I do not want to do it by eye because it could be off). Is there a simple method/tool I can use to do this? Thank you.
Answer Hi Peter,
Before you give up on using the old "eyeball" method, you really should give it a try sometime. If you sight down the length of the body tube, from the nose, you might be surprised how easy it is to get good fin alignment.
You can also lay the rocket on a table and use a short stack of magazines to support the fin...at least, the first fin. Put a layer of waxed paper under your work area to keep any extra glue drops from messing up a nice tabletop. Put a small piece of waxed paper under the fin to keep glue from getting on the magazines. Use a stack of magazines or paper that is tall enough to be equal to half the body tube diameter minus half the fin thickness. When you get your rocket, fin, and magazine stack all set up and glued, let it set for a good hour for the glue to dry. Finish with a reinforcing glue fillet on the outside of the root (while you are gluing the next fin?).
For the second (and third, and fourth) fin, you will have to raise things high enough so the last fins don't hit the table when they rotate downward. If you have a few big books, or a flat work surface that you can lay on top of something, you can move your work surface up on top and keep adding the last fins. You will also have to move the stack of magazines (for proper fin location) to the new, elevated work surface.
Now, you can use the ideas above with any kind of glue or epoxy, but the following method is for water-based glues like Elmer's or Titebond. If you can learn to trust eyeball alignment, a technique that may be helpful is to use the "double-glue" approach. You apply a thin layer of glue to the fin root, press it carefully in position on the body tube, and then remove the fin. After the glue is partly dry (about ten minutes later) you add another thin layer of glue to the fin root and press it back into place on the body tube. The second bit of glue helps re-activate the first and the glue will quickly grab and hold the fin. After you let it dry completely (overnight?) you can add small fillets of glue on the fin roots for reinforcement.
I hope some of that will give you a way to attach your fins.
