Direct-staging methods?

[JRThro]

Everyone,

When you've done 2-stage model rockets, what staging method(s) have you used and had the most success with?

Direct-staging using cellophane tape to hold the motors together until the sustainer ignites?

Direct gap-staging with vent holes to keep the booster from popping off until the sustainer lights?

Something else?

I've got a Quest Zenith II still in the bag, but I really want both stages to work when I finally build it.

Thanks!

 

[rabidsheeep]

i havent done it much, but on a 3 stage aztec and a few times with it on 2 stages, we taped the motors together (i think it was the aztec) with alittle masking tape... in everyone one all stages did light

 

[Stymye]

both ways work very well, I haven't had a failure yet with the direct cellophane tape methoed.

 

[JStarStar]

Tape-staging has always worked for me - I can't ever remember the second (or third) stage not lighting.

Never tried gap staging - that was avante-garde stuff back in my first rocketry career in the 1970s - but I wanna try it and see how it works. A Tiny Tim-WAC Corporal model would be a good way to test it out. Maybe I'll whip one up in the next few weeks.

 

[jerryb]

I built my zeneth II stock.. and used 4 1/16 vent holes on the booster section. I've only flown it once, and the 2nd stage lit perfectly.

one word of warning, you will need to tape the payload cone into the payload, as the fit on mine was not secure enough and mine came down missing the nose cone.

later
jerryb

Originally posted by JRThro
Everyone,

When you've done 2-stage model rockets, what staging method(s) have you used and had the most success with?

Direct-staging using cellophane tape to hold the motors together until the sustainer ignites?

Direct gap-staging with vent holes to keep the booster from popping off until the sustainer lights?

Something else?

I've got a Quest Zenith II still in the bag, but I really want both stages to work when I finally build it.

Thanks!

 

[AlexM]

When done right, gap staaging is just as reliable. You just gotta remember the vent holes.

 

[Rocket Flier VB]

Here is a picture of gap staging

Eric

 

[jerryb]

here are a couple of photos of the vents on my zenith II

they were 1/16 originally, but seem to have opened a bit during that first launch..

 

[hokkyokusei]

I've done gap more gap staging than taped together staging, just because I have more rockets configured to stage that way.

Gap staging is pretty reliable, though I have had some failures. Most were diagnosed to one of the problems below:

Liner blocked vent hole
Upper stage motor had clay obscuring the nozzle
Upperstage motor in serted upside down - DOH!

So, to give a few tips -

Always check the nozzle of the upperstage motor(s) to make sure you can see actual propellant. If you can't, scrape away any clay with a blunt instrument

Use a sacrificial liner paper in the gap between the motors. This will help to protect the inside of the booster tube form being scorched, which will ultimately weaken the tube. However, if you do this, make sure the liner has holes that line up with the corresponding vent holes!

Check that the upperstage motor is the right way up!

 

[astronboy]

I have had failures over the years with direct (taped) staging.

My recent models have all been built using vented gap staging with a stuffer tube. I vent out through the bottom of the booster stage using vent holes the centering rings. My Apogoon that I flew successfully at NARAM is vented this way. I have had zero failures with thhis method over the past three years of flying.

Venting through the bottom of the booster not only makes the rocket look nicer, but it also adds a last but of 'push' to the booster, ensuring that it stays with the sustainer until the sustainer motor is ignited.

As a final note: when you vent through the centering rings, there are no holes in the BT to block with the replacable paper liner.



Phred

 

[nialloswald]

I have used both methods with success, no ignition failures with either. What I have had is a couple of sep failures with gap staging, but I know why. This was on my 2-stage fireflash, with a D12 booster and 18mm sustainer. The booster stage was unfortunately stable, so came in ballistic and made a bit of a mess of the coupler. I then flew it again, and the sustainer lit, but the booster didnt separate, which made for some interesting scorch marks on the booster.

On another flight, the coupler on the booster was very tight on the rather scorched sustainer BT, and again failed to separate. This time the booster disintegrated with a bang and returned to earth in many pieces. The sustainer flew fine, but I only got back 1" of the booster.

I have had no problem with boosters being tight otherwise, I think small (3mm) vent holes are about right, and make sure the nozzle of the sustainer motor is clean.

The most stages I've flown is three, using the 'tape together' method. All three lit, unfortunately the entire flight took place in a horizonal fashion a couple of hundred feet up!

(In short, both are good!)

 

[bcdlr]

When you're using the tape method, I assume one round of 'scotch' tape is enough?
Basically just enough to hold it together right? I could see myself putting it together TOO good.
I've got two scratch builds I'm going to try. One will be a MiniCobra (13 mm engines), and one will be some really simple plans I got an old 'Model Rocetry' magazine off of Ninefinger's site (min. dia. BT-20 BT, 7" lg.).
I also have an Estes Echostar kit on my workbench...
I think I have a place now big enough to shoot some staged and D-G rockets.

 

[Gus]

I've always had good success with tape staging.

But Sandman posted a picture a while back of an interesting gap-staging sustainer motor hook that he used on a recent project.

Picture is here: https://www.rocketryforum.com/attachment.php?s=&postid=92369

And Astronboy, could you provide a pic of how you vent through the motor mount?

Thanks

 

[adrian]

Gap staging rules!

I have used both methods - tape staging with old Estes kits, gap staging with one non-Estes kit (MIRV Gryphon) and all my own multi-stage designs. The tape staging usually worked, but one failure was all it took to wreck the sustainer of each model. Gap staging has never failed for me.

As for venting out the back, I've done that too, but not through centring rings. That's because the booster doesn't have centring rings! Instead, the motor mount is held in place by strips of balsa whose thickness equals the difference in radius between the motor mount outside and the body tube inside.

If the booster is too long, e.g. for a scale model, tape a piece of Quickmatch fuse into the sustainer motor and let it dangle somewhere near the front end of the booster motor.

Take a look at the current RMR Descon, in which the theme is multi-engined designs, so several entries are multi-staged.

 

[nialloswald]

Originally posted by bcdlr
When you're using the tape method, I assume one round of 'scotch' tape is enough?
Basically just enough to hold it together right? I could see myself putting it together TOO good.

I have used a couple of wraps of scotch tape no problem (Estes Mongoose) but I (and others) have also used more substantial taping. I think the last chad-staged flight I did had a couple of wraps of blue electrical tape, followed by a couple of masking tape, so it was pretty solid. I don't think you'll make a good enough seal to stop the tape burning through, and I guess the longer the booster motor is there, the better. The main reason for less tape IMHO is to make it fit in a booster!

But as Adrian has said, gap-staging is good too! I've made a few gap-staged flights now and have never had a problem. On my 2-stage SA-2 descon entry I used the QM technique, but I suspect it would gapstage fine (meaning an E9 could be used in the booster )

 

[SpartaChris]

ok, so this is a really dumb question, but what is gap staging? i understand the basic principle of there being a gap between the booster and sustainer motors, but why vent holes, how does it work, etc etc? i have only used the tape method, so this interests me.

thanks. sorry for the n00b question.

-Chris

 

[rocketdad0934]

I succesfully gap staged a single 18mm booster to a 3-18mm cluster, unfortunatly the c6-0 was not strong enough to lift all that weight the results were not pretty but the thing did light the cluster :kill:

 

[astronboy]

<what is gap staging?> <why vent holes?>

That is a great question SpartaChris, and is explained in G Harry Stine's "Handbook of Model Rocketry". I will paraphrase:

Gap Staging is simply staging where there is a gap between the booster and the sustainer motor. I have heard of gap staged ignition that has been successful at up to a 12" seperation between the booster and the sustainer motors!

Since most staged rockets these days are not minimum diameter, there needs to be a way to get the burning particles from the booster motor funnelled into the nozzle of the sustainer motor in order to ensure ignition of the second (or third) stage. Typically this is accomplished by a stuffer tube inside of the booster airframe that is an extension of the motor mount tube, and ends just before the booster motor. Think of a shotgun of tiny burning propellant particles bouncing up the sustainer tube, with just enough of them getting into the nozzle of the sustainer to ignite it.

<why the vent holes?>

Keeping thinking of the shotgun idea.... in addition to the burning particles of propellant is pressurized gas which bursts forward into the stuffer tube. If the booster stage is not vented to allow these gasses to escape, there is a chance that they will pop the booster and sustainer apart before ignition of the sustainer motor occurs. Venting releases this pressure; typically via vents in the sides of the stuffer tube, and out through vent holes in the sides of the booster airframe.

Another variation (which I now use exclusively) is to vent out through holes punched into the stuffer tube, through holes in the centering rings, and out the back of the booster. Not only does this method provide the needed venting, but also provides a bit of extra boost (if minimal) in order to keep the booster attached to the sustainer until sustainer motor ignition blows the booster away. Additionally, it looks better as there are no holes in the side of the booster.

Sorry for being long-winded, but I feel the need to get some use out of my English degree every once in a while.

Phred

 

[bcdlr]

This has been very educational. Thanks everybody!