Gap staging with an extra "Upff"

[slackdaddy]

Not sure is this is considered EX or not ?

Working on a semi-scale 2stage rocket (SAM)

D's on the 1st and 2nd stage.
There will be about a 3" gap, I was looking at "priming" this void with BP or Pyrodex, and Priming the nozzle with a "paint on" type primer for sure ignition of the 2nd stage.
This will add a little "puf-bang" at staging.

So is this considered EX in the "sport rocket" circles ?
If it is, where is the "line" that this crosses ?

What is the name of "that" paint on "igniter primer" I have heard about. Or those quick fuses that we used with flash bulbs years ago.

Of course I would do a few static runs, to make sure it is safe to fly.

Slack

 

[slackdaddy]

Just re-read the FAQ's

Delete
"If it is, where is the "line" that this crosses ?"

from My post .

Slack

 

[shockwaveriderz]

well a cursory look at the model rocketry safety code says not to alter motors...is "painting" the nozzle with an pyrogen an alteration of the motor? I do know that people "paint" their AP cores with pyrogen to ensure ignition, is this a motor alteration?

I personally don't think paiting the nozzle is necessary.....do a search here on gap staging and you will find a great deal of information and techniques....

 

[powderburner]

Pyrodex?
I'm not sure this is the right stuff to try. I think the burning properties of Pyrodex might make upper stage ignition a little more risky. Also, I think you run a risk of damaging the interstage area if you use very much of this.
BP?
You will be walking a fine line between any 'improvement' in staging ignition and just plain explosion. With a gap stage of only three inches you should not need any enhancement at all. Make sure to use the proper vents for gap staging.
Paint the nozzle?
I doubt this is a rule violation, as many people have done this in the past. I also doubt that you need to do this as long as you check (clean out) the upper stage nozzle before you load the motors.

 

[astronboy]

I have 100% successfully gap staged 18mm rockets with a 3-4" gap, and no motor alterations. I would use a CA soaked stuffer tube for 24mm Black Powder D to D ignition. Alternatively, you can cut a paper liner to fit inside the stuffer tube. The liner can be replaced each flight, and will prevent the booster's stuffer tube from getting scorched.

Be sure that the booster stage is vented to prevent the pressure from blowing off the booster stage before sustainer stage ignition. I vent my booster stages by punching 3-4 holes into the upper end of the booster's stuffer tube and 4 in the booster centering rings. This vents the pressure out the back of the booster stage. Airframe side vents can also be used, but I these add to drag, and I feel that they detract from the looks of the rocket.

As long as the booster is well built and vented, I think that you will be fine without needing to add any extra features that may move you into motor alteration or ex.

Phred

 

[Micromeister]

I also have never had a problem with a gap staged model up to 6 inches. Lot's of NIke/Plus models The only trick seems to be working out a way to vent the burn thur gas build-up at or in the interstage coupling to prevent premature pressure seperation. which would almost certainly happen using BP or pyrodex.
Get yourself a copy of Stines Handbook of model rockery, there is a section devoted to staging techniques, Gap staging is one of the predominate topics.
Gap Staging works great without adding anything.

 

[astronboy]

Micromeister worte: "Lots of NIke/Plus models"

I have a question about something I have been working on for a while.... How do you recover the Nike stage of a Nike-Asp, etc? Do you rely on Tumble, or somehow have a recovery system?

Ph

 

[adrian]

One way to have a recovery system is if the booster and sustainer are not minimum diameter. It is then possible to wrap a Nomex streamer round the coupler. For example, see the Descon entry for my Rheinbote.

The main problem there was that the long boosters were likely to come down ballistic. The streamers don't slow the boosters down much, but do destabilise them. Nevertheless, I used the same technique to slow the descent of the booster of my Skylark.

 

[astronboy]

Thanks Adrian,

I did use dual parachutes in a sport model for booster recovery, so I am familiar with how little drag the streamers really provide.

My thoughts always seem to circle back to clustering: Using a center 18mm motor as a booster motor, and a pair of 13mm motors with delays to fire out a pair of parachutes. As this is pretty complicated, even given the redundancy of a dual recovery system, I have shied away so far.

Also, as this would be a scale model, it just does not make sense to me to have a triple motor cluster on a scale model of a single motorbooster...

Ph

 

[Micromeister]

Phred:
Adrain has one of the ways which works well on larger diameter models.
I like to use a pull out string on the booster streamers attached to the motor block or clip on the sustainer. sounds more complicated than it is. Sorry, I don't have a photo of this. I'll try to take one in the next day or two. but it will work for either streamers or small chutes if in a blast protector.
Another method is to install a streamer chamber at the interstage point that seperates the upper stage motor from the streamer with a kick out wire held down by the upperstage.as the two seperate the spring lifts the streamer into the airflow which drags it out

hope this helps a little

 

[slackdaddy]

Heh, heh,
I think You guys are "missing" My intent with the extra BP in the "gap"
I WANT the extra smoke and noise, I am not trying to make it more reliable, just more enjoyable !

Kind of a "woosh-bang" at 2nd stage light off.

Slack

 

[Micromeister]

Originally posted by slackdaddy
Heh, heh,
I think You guys are "missing" My intent with the extra BP in the "gap"
I WANT the extra smoke and noise, I am not trying to make it more reliable, just more enjoyable !

Kind of a "woosh-bang" at 2nd stage light off.

Sorry Slackdaddy:
You're not likely to get more than the bang because the upper stage will very likely NOT have time to ignite before being Blown off the booster by the added BP or pyrodex generated gas pressure. There are reasons Model Rocketeers don't do some things and this is a great example of something that shouldn't be done. Sets a very bad example for the younger readers on the forum. I'd strongly suggest staying within the safety code and NOT adding anything that will more then likely cause your second stage to come in unlite and ballastic. Very unsafe and not what I'd call an enjoyable Flight.

 

[powderburner]

As Micromeister says, it's not a matter of whether you can add some special effects to the staging event, it really boils down to whether the staging works successfully at all.

I tried to express the same thing---let me say it again.
Pyrodex?
I think you run a risk of damaging (incinerating) the interstage area if you use very much of this.
BP?
You will be walking a fine line between any 'improvement' in staging ignition and just plain explosion.

Both of these approaches are likely to reduce the chances of getting second stage ignition.

 

[slackdaddy]

Dat is why i was getting advice, before putting my hair brained plan into motion

I'll stick with a "pretty" streamer for special effects.

Slack