rocket rules

I tend to think that we are so clever, creating our own model rockets ourselves, rather than using pre-made model rocket kits.

But I've been listening to some the book "Rocket Boys" that October Sky was based on. They had to make stuff up from scratch. There were not any books or manuals on rockets of any kind. The US could barely make rockets that could fly. The boys had to figure out how to create the propellant from scratch, much less the rocket construction.

We have model rocket study guides, pre-built engines, and endless online resources. We probably wouldn't win any science fairs.

But we don't generally avail ourselves of all those resources. We learned a certain way of building a model rocket, and we stick with it. And most of the time it works.

I've been looking at some of those online manuals and resourses and there are a lot of general guidelines that we don't consider.

Like aspect ratio, the ratio of rocket length to diameter, which is recommended to be 10-20:1.

Or the ideal CG, the center of gravity, which should be head of the center of pressure by 1-2 calipers. (I have no idea what any of that means, so here's more)than anyone cares about.)

Or that a rocket must maintain its rigidity in flight.

Or that the leading edge (top) of the fin should be rounded, the trailing edge (bottom) shaped like a V. The chord edge (side away from rocket) should remain square. (I had to look up which edge was which)

Or that fins need be only 2 times the diameter in root length and span, and 1 times the diameter in chord length to be effective.

There's a whole pile of stuff about recovery:
Streamer length should be 10 times the width
Parachutes should be 3.5 feet per pound.
Tensile strength should be 50 times the weight
Shock cord should be 2-3 times the length of the rocket
Wadding should be 2 times the diameter of the rocket
The nose cone should fit tightly enough to pick up the rocket by just the nose cone (which tightness has not worked for us)
Use nylon shear pins to keep stuff in place until you want it to move

Or that on propulsion you need a 5:1 thrust to weight ratio

Or that the launch lug (straw) should be mounted over the center of gravity. (I think the center of gravity is the point where the rocket balances on your finger)

Or that everything should be sleek and smooth, with no bumps or rough edges in paint or otherwise.

Soooo...........

I'm thinking this post is too long, and I'm trying to decide if we should consider any of this.

We aren't in a competition to gain more altitude.
If our rockets go any higher, we'd lose even more of them.

So I doubt that we need to start making the fin leading edge rounded and the trailing edge V shaped, or worry about the smoothness of the paint.

The rockets could probably be longer, and the fins smaller than we often make them.

We should probably at finding the ideal center of gravity to help our rockets be more stable, but needing to calculate the center of propulsion first, well, that's not likely to happen.

Making rockets overstable is probably a good idea, and doesn't require fancy complications. Make the rockets a bit top heavy by adding modeling clay or some such to the nose cones.

Yep, way too long. Thanks for sticking with me. And best of luck to your rockets.