Beginner questions for first nozzleless BP rocket

[DonCopal]

I already wrote above that I use some Veline Magenta delay in every rocket that carries a head, that gives a good delay.

[Col]

I think the topic went from clay bulkheads to delays 4 increments will serve as a bulkhead, saving him messing around with hot glue. I use hot fuel for delay, the apogee isnt affected, it just takes more increments.

The delay comp is also responsible for the rockets tail effect, its all part of the artistic scheme of things.

Edited December 22, 2015 by Col

[DonCopal]

I've already poured in the hot glue, just to make sure

I'll launch the rocket today or tomorrow, hopefully it flies well. I've also attached 140g of lead to see how much weight it can lift.

Edited December 22, 2015 by DonCopal

[DonCopal]

I launched it today and it flew about 5 meters and then popped. It was most likely because the hot glue was not strong enough to hold the pressure. But I'm pretty confident it will work next time with a clay bulkhead.

[lloyd]

Do away with the payload until you see how they fly. Those bits of heavy (or explosive) stuff can create hazards for you.

 

Lloyd

[nater]

How do you determine how much delay? Do certain comps burn at certain speeds?

Yes, different comps burn at different speeds. One can determine the delay grain length by trial and error, or by using a thrust stand with software to predict the time to apogee for a given header weight. Then one would test the burn speed of the delay and add the right amount to achieve the desired effect. Even with these tests, it still takes trial and error to get everything just right. These experiments are lots of fun too. Just be careful about your heading choices while you dial them in.

 

For delay on BP or hybrid motors, I typically use C6 plus 20% metal or more coal for different effects. It burns slower than the core comp, but not so slow that you need a wafer thin delay grain.

Edited December 27, 2015 by nater

[mabuse00]

 

I use some Veline Magenta delay in every rocket that carries a head

But then you must use the press!

Never ram perchlorate based stuff!

 

I prefer rather fast burning delays, because the timing is more precise. On the other hand, the tube needs to be long enough.

[schroedinger]

Since you are using 15 tooling a standard tube has 150 mm lenght and a core lenght of 11, 2 cm and 1cm shoulder height. So you are left with about 2cm usable space to use for delay and bulkhead, but you will need about 2.3 seconds delay. To get the maximum power out of the rocket you need to press about 0.5 cm of fast bp above the spindle, 0.5 cm is needed for a bulkhead leaves you with 1 cm of delay fuel. This isn't very much. Only real options here are color comps and TT / Willow or leave out the bulkhead and use a glitter comp. J39 works ok, as well as green mix with some 100 mesh charcoal or medium titan.

 

I would recommend you to leave out the bulkhead and just use a straight delay colum pressed with just a fuel just a little bit damp (best wet it and let sit for a couple hours, 2-4% water is all we are talking about). If you have zinc powder try the spreader formula, it is suited very good, since it burns slow but when pressed wet creates a rock solid bulk head. Test these you may find that you have to drill it back a couple mm.

 

In 1 lb rockets have a lot more space for the delay and can use faster fuel as delay. E.g. whistle with 10 % Ti makes a beautifull delay charge.

[Col]

I would consider making a set of rammers to allow the use of longer tubes. It also saves having to mess around with tube extensions to accomodate the final increments of fuel (or clay) before pressing.

Edited January 3, 2016 by Col