Rocketry Planet

In December 2008, I documented the construction of a three-inch carbon fiber rocket in my "TooCarbYen Tutorial". The documentation was converted into an article called The Jarvis Illustrated Guide to Carbon Fiber Construction and posted to Rocketry Planet in October 2009. In the time since the article was written, I have learned more about the strength of the rockets I've built.

Unfortunately, I've found (and exceeded) the limit of that strength on several occasions. The data suggest that for 3- and 4-inch rockets, the process summarized in the article will keep a rocket together up to about Mach 2.5. For more prolonged high-speed flight, such as the sustainer of a two-stage rocket, the limit might be a little lower. Since I want to fly faster than that, or at least to have more of a safety factor, I have experimented with several techniques that I hope will improve the strength and durability of my designs.

The project documented in The Jarvis Illustrated Guide to Carbon Fiber Construction, Part 2 is a 4-inch minimum-diameter two-stager that the author hopes to fly at BALLS 20.

I'm very happy with the outcome, so I've decided to do a companion article (let's call it Part 2), to document these procedures.

As before, Part 2 isn't about how you should build rockets, it's just about how I do it (now), with enough detail to fully document the process. If you're planning to challenge the "speed of carbon", feel free to incorporate these ideas into your own designs. Some of the techniques discussed in Part 2 are "advanced" in the sense that they require more building skill, equipment or time. In other cases, though, I've just come up with a better approach than what I included in Part 1.

The project documented in Part 2 is a 4-inch minimum-diameter two-stager that I hope to fly it at BALLS 20. The design is similar to my project at BALLS 19, except that in that flight, the sustainer came apart shortly after motor burnout. The rocket was at 30,000 feet and slowing through Mach 2.3 after over 20 seconds of flight. Nuts!

As usual at BALLS, Tony Alcocer brought back the pieces (from about 5 miles out this time). What I got back was a fin can with no fins and an upper airframe that was torn apart in at least three places. So, did the fins fail first or did the airframe? Or did the fins delaminate due to heating and then pull off the airframe? Unfortunately, I don't know. Consequently, I have taken the approach of trying to make incremental improvements in a number of areas. I haven't documented the entire build though. Instead, Part 2 includes just the things that I did differently or that I think are improvements over the techniques included in Part 1.

Here are the topics addressed in this article:

• Rolling stronger carbon fiber airframes;
• Laminating and attaching fins;
• Making an improved fin fillet;
• Vacuum bagging the tip-to-tip carbon; and
• Applying heat-resistant leading edges to fins.