Some design and build considerations for beginning scratch builders.

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I went to my first club launch.
I launched one of my scratch builds, a couple times, and brought it home unscathed.
Some other rockets, at this event, weren't so lucky.
It would appear that failure of recovery systems is fairly common.
The most common result is a crumpling of the first several inches of body tube.
If you have a really long rocket, cutting off a few inches, and then adding some weight to the nose, will fix the problem.
I would suggest considering a replaceable front section on the rocket as an insurance policy.
I saw one rocket become unstable and lawn dart severely, yet it received no damage, because it was fiberglass.
I looked into fiberglass parts and they are really expensive, but the cost might be justified, in the long run.
I've bought baffles for a couple of my builds. I'll probably glue half into the bottom section of body tube and leave the other half unglued. Hopefully, the upper tube won't come off when the ejection charge goes off.
 
build it to fly, not to crash.
(understand why they crashed, and you can learn from them. while recovery failure is common, it shouldn't be on every 2nd or 3rd rocket. something is wrong there. our club will see one or two. The few big events 've been to, only a few there as well...)

Build light, flies right.
Build straight, flies great!
 
It is commonly said that the up part is the easy part. Down is harder, and the source of most failures.
build it to fly, not to crash.
+1000
I've bought baffles for a couple of my builds. I'll probably glue half into the bottom section of body tube and leave the other half unglued. Hopefully, the upper tube won't come off when the ejection charge goes off.
Not recommended! Some sort of secure retention should hold the airframe together, either glue or screws, or something.
 
What size were these rockets that failed? While it's not uncommon to have recovery failures, it shouldn't happen that often. With LPR the problems are usually parachute related--chute wadded, chute stuck in body tube, chute line breaks. Talcum powder and folding and rolling better help here.
 
Solid fiberglass parts are resilient but $$$ and HEAVY. Hard to justify for smaller rockets. Doing a fiberglass wrap or tip to tip on the fins can give added strength without as much weight and cost.

Using a baffle as a coupler can work but it isn't standard and you'll want to make sure that it has enough air-flow that the back pressure wont blow it out the rest of the way. Another option is a piston. Some people don't like pistons but I've found that as long as it is similar materials (cardboard piston in a cardboard airframe) that they work well.
 
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