AboutDave Combs Expertise Can: Nearly all low-power and some high-power rocketry questions.
Can't: Anything that approaches violations of NAR/TRA safety codes; advanced high-power rocketry questions beyond L1 (I'm still learning those myself).
Experience NAR Level 1 high-power certification; BSA Space Exploration Merit Badge counselor; many years of experience in building and flying rockets from mini-motors (A3-4T) up to H impulse.
Organizations National Association of Rocketry; NAR Section 703 TORC in Dayton, OH.
Question I'm a middle school teacher who is starting a rocket club at my school. I have been building a rocket to get practice and am having the most difficult time getting the balsa fins to stay on. I am using Elmer's wood glue. If I reinforce the sides of the fin with the glue after placing glue on the root side, will it affect the launch? I remember using a hot glue gun as a kid to attach fins, but I don't want my students to get burnt.
Answer First and foremost, CONGRATULATIONS and well done to you for starting a rocketry club at school! Your efforts will inspire your students to do well in your classes and get at least a few to consider careers in the aerospace industry and engineering.
To answer your question: First, Elmer's wood glue or Carpenter's glue is exactly the right glue to use for pretty much any low-power (up to F or G motor-powered) rocket. Don't use white glue if you can avoid it, and also stay away from hot melt glue for safety and also because it really isn't the right glue for the job.
What you're looking for is a better technique for joining the fins to the airframe, and there is one called the "double-glue joint". I tried to find a good link to an example but came up empty, so here's the process:
1. If necessary, sand the body tube just enough to remove the glassine coating (which makes the body tube shiny) where the fins will attach with very fine sandpaper (220 or 320 grit).
2. Apply a very thin film of glue onto the root edge of the fin, and set the fin aside long enough to allow the glue to dry.
3. Put another thin layer of glue on the fin, and put it into place on the body tube. Hold the fin firmly for at least 15 seconds and you'll find that it stays in place very well.
So, in essence, you're gluing together layers of glue, which result in a really strong bond. And to answer another of your questions, you certainly do want to put some additional glue on the seam where the fin meets the body tube. This is called a glue fillet, and it's beneficial in two ways: First, the extra glue will strengthen the fin's attachment to the airframe. But it will also REDUCE the aerodynamic drag because the fin's attachment point is much smoother, and so you will get additional altitude. A good thing in both respects!
The double glue joint method is described in the instructions of most Quest Aerospace kits, as they are the biggest proponents (if not the inventors) of this method. Here is a link to the instructions (in PDF) from one of their models that I have built, the Super Bird; look at step 7c (the first application of glue) and then step 8 (more glue and attachment in 8a, and then the fillets in 8b).
I hope you find this useful. If you need to ask any more questions, feel free to contact me either through AllExperts, or directly at davecombs@earthlink.net . I've enjoyed rocketry as a hobby since (believe it or not) middle school science class, and now I'm NAR High Power Level 1 Certified and I am a Space Exploration Merit Badge counselor for our Boy Scout district. I still manage to put something in the air at least once a month.
