The Big Bertha: Is a very old model built in the 1970s by my brother. Very popular model, you probably have this or one of its many derivatives yourself. This rocket is the classic '70s kit. It is big, fat, slow flier with a retro look. This one isn't retro-"looking" though; it's the real retro thing. It is painted in the original mid-70’s catalog scheme, but with a lighter - more 50's style - cream yellow. I would prefer the newer all-black look Estes is showing now, or maybe some red/white/blue patriotic scheme.
It sure eats a lot of wadding with that big BT60 tube! I installed a Nomex cloth so it will never need wadding again, and a nylon cloth parachute. I have modified this rocket with my "Iris" altimeter bay, which adds another 2.88 inches in length and 14.6 grams of weight. (Iris is named after the Greek god of the rainbow. She is a messenger of the gods, linking the gods with humanity.) This model always seemed to weathercock a lot for me, I hoped that the extra nose-weight of the newly added payload would have helped a bit, but it just slowed it down some more, the Nomex and heavier Nylon cloth didn't help either, I just made Big Bertha into Big & Heavy Bertha. With a C6 motor his rocket has flown higher than the the Saturn V Apollo spacecraft, and the famous Spire of Dublin. But with the extra weight and drag I added, this slow flier seems to always be sensitive to the wind.
A late ejection on a B6-4 (I should have used a -2), damaged the engine mount in a high-speed impact with the mud, so this was re-built with a larger motor mount so she can fly again with D12 power. (The original stuffer-tube was removed.) The added impulse should get her up in a hurry and the longer burn time should produce some really high flights, I would expect more than 600 feet at least, possibly 7 or 8 big ones. We will see...
...we did see. It has now flown higher than the Two Liberty Place Building in Philly, the US Steel Tower in Pittsburg, and the Chase Tower in Indianapolis IN.
| Flight Date: | 2012-06-10 |
| Rocket Name: | Big Bertha |
| Kit Name: | Estes - Big Bertha {Kit} (1948, 23, 7007) |
| Flyer's Name: | Rich DeAngelis |
| Motors: | C6-5 |
| Launch Site: | Halifax, PA |
| Actual Altitude: | 277.00 Feet |
This was the eleventh and last flight of the day. I vacillated over which model to fly before choosing the venerable Big Bertha. The choice of motor was more difficult. The D12 is a great choice, although it would produce altitudes a bit too high for my comfort today, and I was saving them for another rocket to carry a camera. The C11 was the next best choice, but I didn’t have any. I would have to use the 18-24mm adaptor and a C6-something. The -3 was a bit short on delay time, but a 5 second delay could be a repeat disaster if this wind-cock-prone model caught a gust on liftoff and veered horizontally. It was generally calm but late in the afternoon occasional gusts would appear at random. I decided on the 5 second delay but chose to wait out any gusts and launch only in absolute calm. This decision paid off as the model accelerated off the pad with a 5.6 G peak and an average for the 1.9 second burn of 1.8 Gs. Travelling straight up, Bertha beat the wind. It then coasted to apogee in 3.2 seconds while dissipating its energy of 73 mph. It then turned over and lost 29 feet as it descended for the next 1.3 seconds before the ejection fired early (at only 4.5 seconds). The apogee was at 277 feet (much lower than average), and the ejection was at 248 feet. The nylon parachute opened well and the model descended at 12 mph to the land in the grass about 200 feet away for a flight time of 20.1 seconds. Thus ended a great day of flying with no significant damage, loss or injury!
| Stage | Motor(s) |
|---|---|
| 1 | Estes C6-5 |
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