Hello everyone. New to Rocketry Forum and re-found my love for model rockets after having built a number 20 years ago as a kid. Built a couple of Estes systems and I'm starting to move up to Mid Power rockets. I had a rather unsuccessful launch of a Boosted Bertha this weekend that I wanted to get peoples thoughts on to make sure I don't replicate in the mid powered world.
Standard Estes Boosted Bertha, super fun build. No modifications, although took my time with the finishing which meant sealing fins, filler primer and a couple of coats of paint. Flew the "Bertha" rocket without the booster stage first on C5-6. Great flight no issues. Next, I loaded up the booster stage with a C6-0 and a C6-7 in the sustainer. When I put it on the pad my spidey sense started tingling since the rocket seemed pretty unstable with alot of rod flex. The Boosted Bertha uses a 1/8" launch lug, but since the first flight didn't have any issues I want against my better judgement. As soon as I pressed the fire button my brain said "uh-oh". I could instantly tell it was way to slow off the launch pad. The rocket kicked over ( although very little wind on launch day) and shot out sideways at a 45 degree angle. The sustainer ignited and it continued basically parallel to the ground. I was luckily in a pretty remote place and the rocket landed in a famers field a long ways away. The nose cone deployed, but the laundry stayed in the body, I'm assuming due to the high speed it was traveling at ejection. I was able to recovery the rocket and minus some dents and scorch marks it looks in take and able to be flow again with some minor repairs.
My first thought when I got home was to weigh it (mistake #1). I checked CG and it was in front of the rear fins. Given the massive fin section at the back of the rocket I assumed this would be in front of CP (couldn't find a rocksim or open rocket file for this rocket and was lazy). It came in a160g 140g compared to the estes published 113g. This really surprised me since I didn't modify the kit and thought I was pretty reasonable with glue during assembly, just used titebond II. I probably got a bit heavy with the paint and will do fewer coats in the future. I don't think sealing the fins added too much weight, but their are 8 of them on this rocket? I'm assuming in the future its best practice to weigh the kit prior to assembly and also after build to assess weight compared to the design?
Is there general guidance on max weight for various launch rod diameters? I'm nervous to fly this again as is and was thinking about cutting off the current lug and replacing with a 1/4" lug to use on my larger PVC launch pad with a 6' rod.
Any thing else I should be considering in my post mortem? I remember loving multistage rockets as a kid and was really excited about this one, but now I'm a bit nervous as it could have been a dangerous launch in a less remote area.
Standard Estes Boosted Bertha, super fun build. No modifications, although took my time with the finishing which meant sealing fins, filler primer and a couple of coats of paint. Flew the "Bertha" rocket without the booster stage first on C5-6. Great flight no issues. Next, I loaded up the booster stage with a C6-0 and a C6-7 in the sustainer. When I put it on the pad my spidey sense started tingling since the rocket seemed pretty unstable with alot of rod flex. The Boosted Bertha uses a 1/8" launch lug, but since the first flight didn't have any issues I want against my better judgement. As soon as I pressed the fire button my brain said "uh-oh". I could instantly tell it was way to slow off the launch pad. The rocket kicked over ( although very little wind on launch day) and shot out sideways at a 45 degree angle. The sustainer ignited and it continued basically parallel to the ground. I was luckily in a pretty remote place and the rocket landed in a famers field a long ways away. The nose cone deployed, but the laundry stayed in the body, I'm assuming due to the high speed it was traveling at ejection. I was able to recovery the rocket and minus some dents and scorch marks it looks in take and able to be flow again with some minor repairs.
My first thought when I got home was to weigh it (mistake #1). I checked CG and it was in front of the rear fins. Given the massive fin section at the back of the rocket I assumed this would be in front of CP (couldn't find a rocksim or open rocket file for this rocket and was lazy). It came in a
Is there general guidance on max weight for various launch rod diameters? I'm nervous to fly this again as is and was thinking about cutting off the current lug and replacing with a 1/4" lug to use on my larger PVC launch pad with a 6' rod.
Any thing else I should be considering in my post mortem? I remember loving multistage rockets as a kid and was really excited about this one, but now I'm a bit nervous as it could have been a dangerous launch in a less remote area.
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