Rocket fins?

Question

Do 4 fins offer more stability or 3 fins? I'm using cardboard or some type of light weight board to construct the fins. Based on y opinion, I believe that 4 fins will offer more stability due to more surface area, but I would like to hear other opinions. I am building a water rocket btw

Answer 1

A rocket is an inverted pendulum, the fins produce drag that keeps the flight path of the inverted pendulum stable.

Theoretically the more fins you add the more stable a rocket becomes however the drag induced reduced the overall utility of the rocket.

So the answer is you only need enough fins to produce sufficient drag to keep the flight path stable.

Since you are working on a water rocket and not exact tolerance I would suggest canting the fins at the same angle to induce a controlled spin to enhance stability. While you are at it add and aerospike to reduce drag on the leading edge of the rocket for better performance.

Answer 2

It is the more total area of the fins than
the number that determines the drag.
(Three larger fins are marginally better in
stability/drag ratio than four though and
also provide a wider more stable launching base.)

You get best stability by imparting a bit of spin
to your rocket rather than using straight fins.
This may not show up in a water rocket though,
(range too short to matter).

Answer 3

4 fins offer more stability and create more drag,
but more importantly are a lot easier to align when building your own rocket, lots of house hold "guages" are 90degs, not too many household things come in 120 degrees in order to line them up. assuming you don't have a fin alignment set up.

Answer 4

4 fins will allow for greater stability, but it will also create more drag.

Answer 5

u have to find the optimum number by comparing the stability offered and the drag u choose the optimum point