Brett Buck, LUNAR #763

This is the model Tom chased after (refer to last 'Clips) for 35 some-odd minutes as the "Morning After 42” contest. His description of the model was a bit optimistic. This is one crude bit of work! "One Night" is no joke. I got home from work about 7 on Friday, designed and built it by about midnight, and then got up at 6 the morning of the contest to make the parachute. I haven't built a model this poorly since I was 10. But it works.

I think that this proves that it's pretty easy to build an acceptable contest model. No unusual skill is required. I would encourage everyone to give it a try the next time around.

The design, from the top of the shroud to the tail, is actually a reasonably modern model. Most quality egglofters follow this design. The bond paper shroud is heavier than it probably needs to be, but given time constraints, it was the best I could do. The very best egg lofters are usually vellum, balsa, or fiberglass. Balsa with Japanese tissue/dope is probably as good as it gets as far as strength/weight ratio goes, but it's not something you slap together overnight. But the bottom half of the model is a competitive design. Ideally, the fin span should be a little larger. This is not for static stability purposes (with 120 grams of eggs in the nose, you could probably leave the fins off and have it still be stable in a static sense), but to improve the dynamic response. My fins are sized to fit in a pre-existing launch tower that captures the fins tips as well as the body tube.

The egg section, on the other hand, is straight out of 1971. The discrete cone/tube/transition payload went out with the development of the Kuhn/CMR egg capsule in about 1972. These were, and similar versions still are, vacu-formed from .010 or .020 plastic in the form of the egg, just slightly larger. These can spread the shock loads of boost and landing far better than you can ever do with padding. It's almost cheating because you really have to screw up to break the egg. It's also very light, and very aerodynamic. The arrangement I used was pretty light, and not too bad aerodynamically, but depended on padding (weather stripping and bubble wrap) for egg protection. A factor I simply overlooked was a fixed bulkhead between the eggs. My eggs were just stacked on top of each other with bubble wrap between. I think this would have worked had it stayed in place, but with all the misfires, It wound up beside the bottom egg instead of on top.

As crude as it is, it still only weighs 26 grams without the parachute. The parachute weighs 27 grams. With two standard eggs of 60 grams a piece, and a 24 gram motor+ 10 for miscellaneous, the launch weight was a respectable 207 grams/7.3 oz. It might be possible to knock about an ounce or so off, but that's not bad. A proper egg capsule would definitely improve the aerodynamics, and of course cuts down on the DQ's.

The parachute was made from a "rescue/emergency blanket" that you can get at any camping store for $2. It is .5 mil aluminized mylar. The largest parachute you can make from it is about 54" across the flats. I made mine octagonal. I used 72" shroud lines made from button thread with a "glace" finish I got at a sewing store. They have a lot of great stuff in there, but I definitely felt like I stood out! The only way it will fit in the shroud is if you dispense with most of the wadding. I used only enough to wrap around the parachute like a sleeve. 54" (4 1/2') is actually on the small side for dual eggloft.

I used an AeroTech D21-4 for the motor. The Apogee D10 would probably provide better performance in ideal conditions, but in the wind we had, the D21 really got it off pretty straight. I had 3 misfires with Copperheads, and had to fiddle with the model a lot on the pad, which is how the bubble wrap got slid over. The D21 is a real sledgehammer. I ran over after the third misfire, threw $1.50 at the nice lady at the IgniterMan table, shoved it in there, and off it went. Every single Copperhead I have ever used on a sport flight worked, but I am now 3 for 7 on contest flights. The IgniterMan igniter is a pretty powerful propulsion device in and of itself. It kicked the model about halfway up the tower before the engine came up to pressure.

I launched from a fixed-size tower. I suspect a piston launcher would really help the performance, but piston-launching composite motors is a tricky business even if you know what you're doing, which pretty well lets me out since the last piston lanuch I did was 25 years ago.

The flight itself was obviously pretty good. The simulation suggested about 700 feet for a boost altitude, and about 3 minutes duration without help. I think this was pretty close. There did appear to be a momentary fin stall about 10 feet up from the poor dynamic response that aimed it about 15 degrees away from the desired point. I had initially tried to pick air, but after the misfires I was just happy it went somewhere. The parachute opened right away (even after sitting packed for about an hour and a half) because the delay was a little short and it was still moving pretty good. It seemed to deploy into neutral to slightly down air, and was headed for about 2:45, but at about 2:00 the angular motion stopped, which since it was going away at a prety good clip indicated that it was hooked up and climbing. At about 3:00, the elevation angle started moving up very quickly and I would guesstimate that at around 6 minutes it has gotten well over the boost altitude to maybe 1500 feet. It appeared to be hanging or slightly descending when the timers and I lost sight of it at around 8:00. What happened between 8 and 35 minutes Tom described. I doubt that it descended, and then caught a second bubble later. It's not like a glider that can move from one part of the air mass to another. Parachutes are stuck in a single air mass and move along with it. The only way they get into thermals is to either launch into one, or have one happen to bubble up in the air you are stuck in. Having that once was absurd luck, and having it twice in the same flight is beyond conception.

Getting it back was a complete surprise to me. My eternal thanks, and all the credit, goes to Tom.

Of course, It landed pretty softly. But the lower egg was broken, because all the padding has slipped out. It almost certainly broke during either the misfires, or on the boost. So it was just another big fat 0/DQ.

Should you decide to build one despite its limitations, the plans should be adequate. Glue in 1/4" foam-core board divider halfway down the egg tube to positively separate the eggs and avoid the DQ problem. A moderate amount of thought went into it, but it's certainly a compromise, and there are not particularly critical dimensions. Just make sure a standard egg will fit in the tube.