18 replies to this topic

[pyromaniac303]

Yes. Also the fuse has an effect . I remember that happend to me too, specially when you have a fast burning BP or a small nozzle with a large fuse diameter.

I have a way of getting round this, but it is not usually neccesary with larger rockets. For the main part of the delay fuse use standard visco or blackmatch, then as the fuse enters the rocket you link some visquick (sometimes known as 'shogun fuse' or a number of other names). It burns away completely in the same way as normal visco, but burns at 2 seconds per foot which is fast enough for it to have almost vanished before the rocket produces enough pressure to launch (or CATO, which was the idea). Tested this a couple of times but since then just slightly slowed my fuel down and it is no longer needed.

I do not know many suppliers that stock fast visco, at least that will post to the UK. It seems every time it becomes available it has gone within a couple of days. Quickmatch is unsuitable due to the tube being left behind which would actually make the problem worse.

[karlfoxman]

The fromula I have used worked great for 1/2" and 3/4" rocket motors, try my formula/ball mill time and see what happens. If you go with a mixture that is proven you know where the problem is. Only change one thing at a time or you will never know what made it work.

LINK TO MY ROCKETS DETAILS

[shadowpyro]

Does anyone know of a simple delay composition for a bottle rocket?

Edited by shadowpyro, 26 November 2006 - 01:16 AM.

[moonshot]

Pendulum you are experiencing something that every rocket builder has gone through. Your BP is obviously fast enough since your rockets are CATOing. I found out that fast isn't always best. Rocket propellent needs to be slowed down by changing the ratio of fuel and oxidizer in the basic 75 15 10 mix when making core burning nozzled rocket motors. I use 71 24 5 but from what I've seen posted on this and other forums 60 30 10 works ok too. You said you started adding more charcoal to your mix and your rokcets don't CATO. Your on the right track. I mill my meal BP dry and grain it by lightly moistening it with 75% H20 25% alchohol and screening it through a 10 to 15 mesh noodle strainer. I ram my motors like you and graining the powder keeps the dust down. The size motors I make are close to the ones your doing and I have found a 3mm nozzle diameter is optimum. Play around with your fuel oxidizer ratio and you will come up with a good mix that won't CATO your rockets but will still lift 35 to 40 gram headers. Like other rocket builders I had to do a lot of trial and error to get a good propellent but once you do it's a whole lot of fun! Have fun and be safe!