DARS Model Rocket Launch - Frisco, Texas

DARS Model Rocket Launch
Broken Fin City
Frisco, Texas - November 22, 2008

I made it to the DARS model rocket launch in Frisco, Texas today. Between the southeastern wind and the cold weather making the ground hard, the result was lots of broken fins.

My first flight of the day was my Super Big Bertha. It sports a cluster of 9 motor tubes - 1x24mm, 4x18mm and 4x13mm. Today it was loaded with three C6-5 motors, one C6-7 and one C11-7 in the center. The 13mm motor tubes were plugged. A 30" chute was loaded for recovery.

In the pic below, you can clearly see all five motors burning.

Right: Here's a great shot of it in the air.

It put in a great flight, and got the chute out near the top. I went running across the field chasing after it hoping to maybe catch it, but it was moving too fast for me to get to. I watched it hit the ground and saw something fly up. As I approached it, I hoped that was soil I had seen, but alas, it was a fin that broke off upon contacting the ground. I'll have to repair it, but it's already been damaged before, so instead of merely gluing it back together, I may repaint the fin this time :)

Here's a good shot of Jason Ware's X-Wing leaving the pad.

My next flight was my three motor cluster upscale Midget, the Thridget-70. It had three B6-0 boosters staged to three A8-5 sustainers. I'm beginning to think this thing is jinxed.

I can think of three times I've flown it, and now two of those have resulted in wrecks :(

As can be seen in the picture at right, the motor in the red booster fin didn't light.

In the picture at left, two booster fins have fallen away while the red one is still attached.

At this point, it arced over and never got very high. Finally, just before it hit the ground, it ejected. Unfortunately, it parted the shock cord with the result that the airframe impacted the ground breaking two fins. Plus, since the red fin went along for the ride, it got blistered pretty good by the two sustainers that lit.

The hard jerk at ejection also put a small zipper in the airframe.

Forturnately, it could have been worse. As it is, I can repair the zipper and glue the fins back on. I'll probably repaint it, but I'll wait and see how the scars look first :)

The section of shock cord which broke was nylon ribbon, so when I repair it, I'll add some nomex over it. My thinking is that the ejection charges of previous flights tended to make the nylon brittle and weak, and that the nomex will make the replacement ribbon more durable.

At this point, the day is looking bad - two flights, three broken fins and a pretty good wreck.

Deciding that a change of pace was in order, I put my three stage Super3 up next. It staged a B6-0 to an A10-0T to an A8-5 and had a great flight with all three sections recovered in fine shape.

Returning to the main theme of the day - clusters - I set out next to fly my Better Bertha on a cluster of two B6-6 motors with two A10-PT's for extra kick off the pad. As I was getting ready to load, the heads up call came over the PA, so I looked skyward and tracked this rocket right on to the pad in front of me.

At left, two motor exhausts are clearly visible. In fact, all four motors lit. The flight was fine, and the chute came out near apogee. Again, I chased after it, but couldn't get comfortably under it at landing. I did't want to lunge for it and risk possibly crushing it, so I let it go only to have it hit hard enough to break yet another fin. #$%^&!

As it turned out, this fin has been broken before, and already features some scars, so I'll just glue it back together and have a couple more.

Continuing the theme, next up was my 5-motor cluster called the Douger. Apparently, this was the maiden flight since it was reconstructed following an airframe rupture in its earlier incarnation. I find it surprising I haven't flown it yet, but there are no signs that any motor has ever been burned in this thing.

Below, you can see the network of wires used to cluster the motors. Instead of my usual use of lead extensions on each motor, I instead soldered wires to the ignitors after they were installed, and was able to connect some of the ignitor leads together thereby reducing the amount of extra wire.

The pink paint turned out great. I mixed it myself. The two center of pressure indicators are for the Barrowman and Rocksim CP's.

Right: Here's a shot of the launch. All the flames are not clear, but I got all five motors lit. There were two B motors and three A motors, for a GPA of 3.6 :)

As before, I chased it hard, but couldn't quite get to it. It hit on one fin, and sure enough, another one snapped :(

I'll glue it back together, but I'll have a hard time not putting a proper finish over the mend - the paint job on this one is just too nice to leave a jagged scar.

I had one more flight for the day, another 3-stager, and this one had a good flight. All three motors lit, and things were going fine up to ejection at which point only the nosecone came off; the streamer stayed stuck inside :( I probably was in a hurry during my pre-flight re-packing of the streamer, and likely failed to get it wrapped up tight enough. Thus, it expanded a bit wedging it in a little too snug. That said, the 1/2A3-4T motors have recently had such potent ejection charges, it's usually not a problem. This time, it appears I got a wimpy charge instead.

The good news is that the rocket landed in a soft spot with no landing damage - all the fins are intact. The surprising thing was a slight ding on the airframe opening. These are usually caused by the recovery system jerking the rocket, but since only the nosecone came off, there shouldn't have been much of a jerk.

Anyway, all parts of the rocket were recovered, and the ding amounts to little more than normal wear and tear.

It was great to get out and fly. Thanks to Don Magness and the DARS gang for a great launch.

Doug

November 22, 2008