Friday, December 24, 2010

Review: Goonball XL5

This 'goony' version of the Fireball XL5 sci-fi spacecraft is based on the Estes SpaceShipOne kit. That rocket is now my favorite kits to bash.

The modifications included replacing the stock fins, replacing the stock recovery system, and modifying the nose cone. The motor mount is stock.

Parts list:

* Estes SpaceShipOne kit
* 3/16" fin stock
* lead shot
* small eyebolt
* steel fishing leader
* extra elastic chock cord

All of the fins were roughed-out on paper until they looked right. The side fins were made from two pieces of 3/16" stock each. The two pieces touch at their leading edge and are separated by a strip of balsa in the rear. The leading edge was then sanded to a smooth point. The side fins were cut from 3/16" stock. The small fins on the cone are the small fin extensions from the SS1 kit. The kit provided two and I cut the others from the unused fin stock. The balsa-plastic joints were attached with thick CA and wood glue was used on the wood-wood joints.

I attached a steel fishing leader to the top centering ring and the stock elastic cord to that. I had planned to use two chutes due to the expected weight of the nose, so a separate shock cord was provided for it. I knew I'd need a lot of nose weight so I attached the cord to an eyebolt that is embedded in a slurry of lead shot and Gorilla Glue. That way, the weight is securely attached to the recovery system. Of course, the nose weight was the last step. The bottom of the cone was removed to allow access for the nose weight installation and to provide a tad more room for the 'chute if needed.

As I noted earlier, the motor mount is the stock 18mm. I was lucky to have the new RockSim 9 program with its PODS feature. This allowed me to simulate the actual design configuration. I set the nose weight based on this simulation model.

With the unloaded weight sitting at about 5oz, the sim indicated a long rod was need for a stable C6 flight. So, early on, I decided to go for a reload. I got an 18mm Hobbyline case and a pack of D13-10s from Great prices and speedy service!

I did the normal filling/sanding/priming drill. The base coat is a silver primer for the X-Metals paint. I then used brush-on paints for the red and yellow trim. The circles are from the SS1 'decal' set, the colored band was printed on my ink jet, and the 'goony' lettering is vinyl from Michael's craft store.

The D13 was easy to assemble. Since I was at MDRA, I was able to drill the delay using the same method specified for the 29mm and larger motors. I filled the bottom of the body with dog barf, added several pieces of wadding, and then some more dog barf. I decided to go with one 18" chute, which was attached to both shock cords.

At the 11th hour, I realized that I'd used the stock lug and decided this rocket was too heavy and unproven to fly with that. I removed at lug and epoxied on a piece of ¼" compatible launch lug material (e.g. a tube from an AeroTech First Fire igniter).

I set each side fin on a stand-off and hooked up the Copperhead. The rocket flew great with some spin, which was undoubtedly the result of some imperceptible misalignment of one or more fins. After all, I built it.

Ejection was just a tad late and the rocket recovered damage-free.

I love the Fireball design and thing the Estes SpaceShipOne kit is a great subject for kitbashing. This model flew nicely and is a proud member of my Fireball XL5 rocket family.