Repairs Complete

A day later and the repairs are finished. The tail section isn't perfect, but it should fly without complaints. Much like 2x4's, it appears balsa thicknesses have changed over time, so I had to putty the seem where I replaced the broken leading fin. You can totally see the seam.

If it's less than straight in flight, replacing the tail fins with laser-cut plastic, and assembling with a custom fin jig will be the next step. We will see--this guy launches in less than a month!

Rocket Repairs

I was hanging on with my Elmer Chuck (WB6YOK) the other day and the conversation turned from radios to radios in balloons. We have been "working on" a balloon project for what, five years now? We started in with Arduino several years ago and, while we haven't launched anything yet, we've got solid plans and a lot of functioning code for various sensors. As we were talking about the balloon project, I mentioned that I am interested in starting a BSA Nova program (BSA's new STEM initiative, to encourage youth to study science, technology, engineering and math). I told him that we are doing space exploration merit badge in Novemeber and mentioned that I would like to launch a rocket at October's Jamboree on the Air campout, to start to generate some interest.

Well, as it always does, the conversation quickly devolved into some wild fantasizing about having a rocket that was large enough to carry the balloon payload, so we could test it. As we were discussing that, Chuck said "Hang on, wait a minute..." and left the room. He returned with an enormous 3-peice rocket (base, payload bay, and nose cone). "This ought to do what you want," he said. Turns out, Chuck is high-powered certified. This is the rocket he certified with--it's powered by a single "H" motor and should go as high as 8,000 feet or more. 

As we talked further, I got more excited about the possibilities. That rocket could carry an Arduino, a Pi with a camera--pretty much anything! Suddenly Chuck left again and returned with this rocket:

An Estes Maxi-Force 3-engine cluster 50" tall rocket. These were a short-lived rocket built by Estes in the early 80's. Chuck said "It's yours if you want to fix the fins." Well, gosh... How difficult could that be? I took it before he could change his mind! 

Two out of three fins needed repair. The first had several cracks lengthwise, and the second had lost its leading edge. Today's project was to swing by Hobby Lobby after my trail run, to grab a few motors and some balsa wood, and then to fix the fins.

These are the cracks on the first fin (above).

And this is the broken leading fin. 

The fins are made of several peices: the main or base fin, a leading fin above it, and some edging which appears to be made of tougher material to withstand the bumps of landing.

My first plan was to just rip all three fins off and replace them with laser cut plastic fins (another buddy has a laser cutter). The more I thought about that, though, the more I realized it was more work than it's worth. As I looked over the fins again, I realized they were totally fixable. I needed to trace one of the leading fins to make a pattern to cut a new one from balsa, and I needed to glue the cracks together on the other. 

So today I dropped by the store and picked up balsa. After a few chores, I started in. First I opened up all the cracks in the fin, as shown below:

Then with a toothpick, I started to slip Gorilla Glue into all of the cracks. It's not as precise as I would like to be, but it worked. Here is the fin, drying, with a little pressure supplied by a couple rubber bands:

Next I traced an intact leading fin, cut some balsa, and dry-fitted a new leading fin. First I had to carve away the remainder of the leading fin--it isn't perfect, the surface of the rocket body was a bit wavy when I finished but the glue will help with that. Balsa is a really forgiving medium, and the dry-fit went quickly.

Knowing that it would be a challenge to have the new leading fin attach at every point and stay aligned, I opted to only glue where it touches the base fin and where it contacts the rocket body nearby. Once it's dried, I will glue up the rest. It's that easy...

I had to laugh--I spent more time thinking up a variety of ways to replace the fins than I actually spent repairing them. In fact, I've spent more time writing up this blog entry! With only an hour's effort, everything is glued except the front of the leading fin.

My next steps are to sand out the excess Gorilla Glue, then using a light putty I will fill in gaps and holes. Once the fins are smooth and straight, I think I'll paint the base again--probably black, just to put my own touch on the rocket.

The Scouts don't know about this rocket, but this is the one we will launch at JOTA, in an effort to pique their interest. I think it'll get their attention!

If I had unlimited time and funds, I would put together a tiny XBee unit, with an XBee 2 transceiver and a GPS. Then I would find a way to slip that into the nose cone so we could stream telemetry while flying the Maxi-Force. But I decided to keep my focus on building a package for the November launch, instead.