Rocket Nozzle ratio

[dantiberian]

Hi i have searched google and this forum and various pyro sites that my internet filter will let me get too and i am still looking for a 'magic' formula that can give me a ratio of ID to rocket nozzle size. I have already had success with PVC and paper case rockets with a ratio of 18 mm ID to 5 mm nozzle all the way up the pipe. I am using PVC sch 40 and bentonite clay in my construction with a sugar rocket mix. Is this sensible or suggested any where?

[joe609]

pvc rockets wont be as safe as paper ones, and a nozzle formula anyone gives you would be under the assumption that their fuel is exactly the same as yours i.e same power, burn rate, fouling etc. although their probably isnt much in it, it depends on how proficient you are at making the propellant. so basically just experiment with a few rockets that are the same apart from nozzle size choose the best one rember the nozzle to case ratio and there you have it.

[itwasntme]

You should use CPVC and not sch 40. I have a sch 40 "1/2" inch PVC pipe and measured it to be 15 centimeters. So, the ratio will not work. What sugar mix are you using? 75/25 65/35 63/27/10? It will vary. I suggest that you start with cardboard in your experiments because of fragmentation.

Try 1/8th inch nozzles, I had some success with that. If you want a good propellent I reccomend BP, but if you want to stick with sugar and kno3 try Rcandy http://jamesyawn.com/rcandy/index.htm

[dantiberian]

63/27/10 thanks. I have used cardboard but got sick of making it because i wasn't very good at it. I have used BP but for whatever reason it CATO'd so I think i'll stick to sugar. itwasntme what is CPVC/what is it used for?

[joe609]

cpvc is like pvc i think but it can withstand higher temperatures and it has better fire resistance.

[itwasntme]

I think it's used for hot/cold water piping. You can try the gummed rolled tubes like on the teleflite fuel thing.