6 replies to this topic

[whoof]

just curious
Has any manufacturer ever made fin stabilised rockets for nov 5 / thanksgiving type market?
Amateurs use routinely bu all I remember from Fawkes night are stick rockets

[barnsley-mark]

I've seen a couple a few years back, they looked commercial as opposed to home made. I'm guessing difficulties launching and potential lift off / trajectory issues if fins get bent or distorted makes them far too dangerous for commercial sale. A stick does its job very well

[Sparky]

The main problem with adding fins to a firework rocket is getting the centre of drag behind the C of G, For a rocket to fly straight the fins need to create enough drag to offset the tendency for the thing to nose over. So if you had a good size header then thing gets tricky and you'd need big fins on a long body.

One way to test it will fly is to swing test it. Simply tie some string to the centre point (C of G found by simply balancing the rocket on it's side) then swing it round your head until you build up some speed. If you are good it will point into the direction of travel, if not it will tumble or be very unsteady.

Years ago in France I saw some firework rockets with fins but they only had a minimal header and the fins were very roughly made. The result was a rocket with a very erratic flight which I know was the intention (they were called Sky Monkeys). It would have passed the swing test C of G but the fins were probably a little misaligned and was part of the effect.

[megabusa]

I used to put fins on 3lb rockets.

Problem was, if the wind caught it at lift off, it could go in any direction !

[Sparky]

I used to put fins on 3lb rockets.

Problem was, if the wind caught it at lift off, it could go in any direction !

Yep you would need to have launch rod to keep it straight until it reached such a speed where the fins stabilise it enough to keep it straight. They will always head into window though. The stronger the wind the more they will heal over but it's not usually enough to worry about.

[whoof]

Exscuse my ignorance, what proportion of a 1 lb rocket would be propellant in a bp motor?

Edited by whoof, 09 October 2012 - 05:32 PM.

[starseeker]

Exscuse my ignorance, what proportion of a 1 lb rocket would be propellant in a bp motor?

Approx 50g.