Mending a Broken Rocket

You may recall a moderately amusing tale of a model rocket found stuck in a tree, and the bizarre effort to recover the rocket with a balloon. At the time, I promised myself that I would restore the damaged rocket so that it would soar again. The article begins with tips on how to replicate or replace model kit parts. The ending offers sage advice on how to avoid a foreseeable tragedy on the rocket’s first flight after repairs.

(John Caswell pointed out that the rocket is an Estes Star Stryker. So, one 'repair' solution is just to buy another one.)

Damaged model rocket rescued from a tree

Damaged model rocket rescued from a tree.

The salvaged rocket has a lot of issues:

Replacement Rocket Fins

Let’s start with the fins. If your rocket has missing or broken fins, bring one of the fins to a local hardware store. Match the thickness of the fin to a sheet of balsa wood. In my case, the rocket’s fin is 3/32″ thick.

To make a new fin, begin by tracing an intact fin with a pen on the balsa wood. While you are at it, trace a spare fin in case you need an extra for future repairs.

Tracing existing fin onto balsa wood Cutting out fin from balsa wood by multiple passes of a hobby knife

Left: Tracing existing fin onto balsa wood. Right: Cutting out fin from balsa wood by multiple passes of a hobby knife.

To remove the fin, drag an X-ACTO knife over the pen lines. It takes multiple passes to cut all the way through. Place cardboard or a self-healing cutting surface underneath the balsa wood to avoid damaging the tabletop.

Next, sand any rough edges smooth with extra fine sandpaper. The leading edge (toward the sky) and trailing edge (toward the ground) should have rounded edges. The edge that attaches to the body tube (called the “root”) should have square (90°) edges to provide maximum gluing surface.

Fin after cutting and after sanding

Fin after cutting (top) and after sanding (bottom).

Depending on how fancy you want to get, you can lightly sand any surface protrusions and then seal the wood. However, given how mangled my rocket is, I let the kids go directly to painting.

Rather than painting a portion, letting it dry, and then painting the rest, I stuck a ball point pin into the root of the fin and held the ball in a handy helper (normally for soldering). This setup allows the entire fin to be painted, with minimal damage to a side that won’t even be visible.

Painting the fin while held by ball point pin

Painting the fin while held by ball point pin.

After drying overnight, attach the fins to the rocket. I prefer the “double-glue” approach. Use a little bit of CA (cyanoacrylate) glue, which will quickly tack mount the fin in place. At the same time, add some wood glue (such as waterproof Titebond III) for long-term adhesion.

Glue fillets secure rocket fins

Glue fillets secure rocket fins.

You'll need to hold the fin in place long enough for the CA glue to set. Then, with the tip of your finger, you can gently spread the excess wood glue onto the sides of the fin. This creates fillets (concave corners) that both increase holding strength and reduce drag.

Okay, I admit that I got a little sloppy and excessive with the glue. Now let’s turn our attention to the nose cone and parachute...