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: | 2012-02-05 |
| Rocket Name: | Big Bertha |
| Kit Name: | Estes - Big Bertha {Kit} (1948, 23, 7007) |
| Flyer's Name: | Rich DeAngelis |
| Motors: | C6-3 |
| Launch Site: | Penn Manor School Lancaster PA |
| Actual Altitude: | 428 Feet |
With a newly rebuilt and larger 24mm motor mount, the Bertha needed a test flight. I wanted to use a D12-5 on this, expecting 600 feet or more, but it was just too windy for that kind of altitude, so I opted for a C6-3. As usual for this model, it ended up weathercocking quickly after launch and ended up flying horizontal into the wind after more than 2 seconds of burn. I just can't expect vertical flights with this model in any wind because of it's slow lift-off speed. The maximum acceleration was 4.8G and averaged only 1.3G through the 2.3 second burn time. It reached a speed of 65 mph and an apogee of 428 feet (a new record for this model). The coast to apogee was 3.6 seconds (a bit longer than spec'd), and then it deployed a full nylon parachute at 187 feet and descended at 12 mph. Duration of the flight was 15.8 seconds.
| Stage | Motor(s) |
|---|---|
| 1 | Estes C6-3 |
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