Celtic Kane

Fin design was easily the topic with the least scientific information available. Just due to the fact that I couldn’t really find information on how to make a well designed fin, I decided that I’d just make whatever I felt like making and it didn’t really matter. Hopefully you take a better approach than I did, but honestly I didn’t (and still don’t) know how to design a proper fin.

What are fins made of?

Fins are made out of balsa wood, which is basically just a really weak, soft wood. I used a 1/8″ sheet of balsa wood that I bought at a local hobby store.

How do you cut balsa wood?

I used an xacto knife, but I’m pretty sure you could just use scissors if you wanted to — the wood is honestly that soft.

How did you make a fin?

Well — first off I looked at other fin designs and drew some of my favorites. I went through the Estes Catalogue and decided that since there were so many different types of fins, the actual fin design was rather insignificant, so I just decided to be creative.

What else is involved in fin design?

You have to decide if you want three fins or four. After looking at the Estes Catalogue, it seemed like the majority of the bigger rockets used four fins…so I’m guessing the more fins the more stable. With that in mind, I decided to go with a four-fin design.

Is there any science behind this?

Actually, yes. If you look closely at balsa wood, it has a grain in it. That grain needs to be parallel to the leading edge (The edge that is facing the nose cone). If you’ll look at the diagram below it’ll be a lot more obvious what I’m saying.

How’d your fins turn out?

Well…you have to remember that this was my first time. Since I didn’t really have a set fin design, I just basically cut one the way I liked and tried to cut the others as close to the first as possible (by tracing the first). If I messed up and took too much off one fin, I just took a little off all the fins in an attempt to make them all equal in shape and size. Below is the final blueprint for my fin design and the actual fin (attached to the rocket).

How did you properly space the fins?

You can try to just eyeball where you should glue your fins…but that’s just dumb. Here’s the best procedure:

  1. Wrap a piece of paper around your tube and mark the length of the circumference
  2. Measure the circumference using the paper as the length
  3. Divide by four (for four fins) or three (for three fins) and equally space out four or three lines that will be your fins.
  4. Put the paper around the tube again, just like when you measured it, but this time mark off the correct position for each fin. For me, I cut small, extremely thin rectangles into the paper so when I wrapped it around the tube I just took a marker and filled in the rectangle. This way you don’t have to worry about making the fin marking perpendicular to the tube.

Additional Hints and Tips

Make sure the grain is parallel to the leading edge (unfortunately on mine because my fins were so big, the way I had to cut my fins out prevented me from doing this), I’d recommend sanding off the edges of all your fins except for the root edge (which should be the factory edge) because if you round your root edge it won’t attach to the rocket as well if it was a flat edge. Finally, make sure to use a fin alignment guide so your fins help (not hurt) your flight.

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