Passport Staging Coupler Question

[Bob Thomas]

Added Arcon Hi to my build que and while reviewing the instructions, a question about the staging coupler came to mind. Having used the old "butt and masking tape" staging successfully for years, I wonder if much damage occurs inside the over the mount coupler. Any recommendations are appreciated.

[Doug Sams]

Added Arcon Hi to my build que and while reviewing the instructions, a question about the staging coupler came to mind. Having used the old "butt and masking tape" staging successfully for years, I wonder if much damage occurs inside the over the mount coupler. Any recommendations are appreciated.Hi, Bob,

Which instructions are you looking at? Got a link?

Doug

[Bob Thomas]

Sorry if I wasn't clear. Heres the link to the Centuri KC-3

http://www.dars.org/jimz/kc-3.htm or http://www.dars.org/jimz/centuri/kc-3b.tif

You'll note that there is a coupler fitting over the engine mounts, where the stages meet, with a hole punched in it. It is not the same as the main St-10 tubing and stage coupler. I am wondering if this step is necessary as I believe that it might be too prone to catching fire or burning through. The old masking tape routine gets replaced every trip.

Thanks for the interest
Bob

[Eagle3]

Bob, the Long Tom has a similar arrangement and I never had a problem with the coupler getting scorched. However, the passport on that coupler doesn't do much good unless you put holes in the other coupler as well.

[dtomko]

Bob,

My experience with passport staging is with the Black Widow, which has the coupler on the sustainer. That leads to scorching. The Long Tom/Arcon Hi arrangement makes more sense. Still I would suggest coating the inside of the coupler with CA to minimize damage.

Drew Tomko

[Tweener]

I had two original Centuri Stilettos. (Past tense) One pranged when the 2nd stage failed to ignite. The other got lost when the 2nd stage didn't fail to ignite. :o IIRC, both had a little scorching on the passport coupler on the outside just aft of the ports after a few flights. Inside got a little crusty, but I just rubbed it with a paper towel between flights and it was good to go.

[Bob Thomas]

Still Unclear

I appreciate your experiences, but still wondering if I should skip this coupler anyway. Seems like a useless expense. The booster st10 coupler would be enough, right? The masking tape connection rarely fails. Unless the thought is to relieve some pressure that might otherwise separate the joint and thwart hot contact staging. Then I would have to agree with Buzz, needs another hole.

Simple enough to add after, if I decide to build without. I'll leave it to my parts box, if I got one - its in.......

[Doug Sams]

I appreciate your experiences, but still wondering if I should skip this coupler anyway. Seems like a useless expense. The booster st10 coupler would be enough, right? The masking tape connection rarely fails. Unless the thought is to relieve some pressure that might otherwise separate the joint and thwart hot contact staging. Then I would have to agree with Buzz, needs another hole. Bob,
I agree. The HTC-7CDH coupler is superfluous. The only concern I have is about the spacing between the motors. As long as there's a gap of at least 1/10" or so between the two motors, you should be fine for gap staging. Of course, that assumes you drill vents in the booster airframe, in the vicinity of the forward end of the booster motor.

Conversely, if the motors touch, then just use tape-together staging.

The masking tape connection rarely fails. Masking tape? I always use cellophane tape, 1 wrap. I used to always use the satin polyester tape (green label) but was recently turned on to the glossy vinyl tape (red label). It holds a tad longer providing a little extra insurance for lighting the sustainer.

I've never tried masking tape so I can't say it won't work, but all the staging tips I've ever seen say cellophane.

Whether taped or gapped and vented, always scrape the sustainer nozzle to make sure it's clean. A while back, I flew my Edmonds CiCi2 which uses a gap of ~10" (swag). Two successful stagings and one flown away sustainer :(

Doug

[dwmzmm]

If the engine(s) are directly butted together at launch, I agree using the cellophane tape
method is best. I've flown a two stage, four engine clustered model (eight motors total)
using this method with no failure in flight (except the second stage sailed out of sight, never
to be seen again!). But, if there's a gap or space between the booster and sustainer motors,
then using a passport type staging system is needed. The vent hole(s) in the coupler is to
prevent the pressure of the booster gasses from forcing the two stages apart before the
upperstage motor has the chance to ignite. Hard lesson I learned from my Estes Cineroc/
Omega rocket; the last time I flew this combo the second stage popped from the booster
without ignition, ensuring a lawndart and destroying my Cineroc (1982).

http://www.nasarocketclub.com/gallery/may-21/FH000023

http://www.nasarocketclub.com/gallery/may-21/100B0121

[Bob Thomas]

Once bitten, twice shy...

I had used cellophane as directed until an "über-Tape" experience cost me the loss of a 2 stage Centuri Excalibur. "...as the fireball tumbled towards earth, I was comforted by the sure knowledge that Jerome Park Reservoir would soothe her torment."

Ever since (twenty something years [30+]) I have been using a wrap of masking tape. Seems to be plenty of hold and even if it gets stuck, thin paper burns through faster than the cellophane.

If you could steer me to the right cellophane or vinyl, Doug, I might give it another try. It will save me trial and expensive error.

Dave, I had presumed that was the case for passport staging pressure issues (separation before ignition).

Thanks all

[dwmzmm]

Once bitten, twice shy...

I had used cellophane as directed until an "über-Tape" experience cost me the loss of a 2 stage Centuri Excalibur. "...as the fireball tumbled towards earth, I was comforted by the sure knowledge that Jerome Park Reservoir would soothe her torment."

Ever since (twenty something years [30+]) I have been using a wrap of masking tape. Seems to be plenty of hold and even if it gets stuck, thin paper burns through faster than the cellophane.

If you could steer me to the right cellophane or vinyl, Doug, I might give it another try. It will save me trial and expensive error.

Dave, I had presumed that was the case for passport staging pressure issues (separation before ignition).

Thanks all

Bob, I just use the standard Scotch Tape (the kind that has the hazy film look). The other
factor to consider (in the case of the Saturn - IV/Astrocam model in the link included in my
previous post here) is absolute simultaneous ignition of the first stage clustered engines.
My previous attempt of a similar model (at NSL - 2004 in Hearne, TX) I used the Estes Solar
Igniters and, in that case, two of the three strapons in the upperstage failed to ignite. I
attribute this to the lack of absolute simultaneous ignition (a week later, I flew the same model at JSC, and with the Cineroc working that time, you can see in the video that is, in fact, what happened). Once I switched to QuickBurst Hot Shot igniters, the problem was
solved (of course, we now have the ATF issues with QuickBurst).

And yes, I've been told by several long time model rocketeers that had my Omega's first
stage coupler had vent holes, the pressure issue wouldn't have happened. Plus, I wouldn't have lost my first Cineroc :(

[landsharkking]

Hey I am pretty new at this... I had an estes renegade that exploded mid-flight and set my launch field on fire. I just bought a comanche-3 as a re-entry into staging, could someone give me any tips on how to prevent booster and sustainer from sticking together from the excess pressure of hot staging to prevent mid flight fires ( the renegade exists no more... 1 fire extinguisher down... 2 to go..) :)

[CPMcGraw]

Hey I am pretty new at this... I had an estes renegade that exploded mid-flight and set my launch field on fire. I just bought a comanche-3 as a re-entry into staging, could someone give me any tips on how to prevent booster and sustainer from sticking together from the excess pressure of hot staging to prevent mid flight fires ( the renegade exists no more... 1 fire extinguisher down... 2 to go..) :)

Noticed this was your first post to the forum, but you're the second person in as many days to have a CATO with the Renegade. You need to get with MonsterRocket and share trench stories...:D

Since you posted in this thread, you obviously have seen references to this method of staging. Pass-Port staging is a variation of the Stine vent, described in detail in The Handbook Of Model Rocketry. Essentially, it allows the excess pressure generated by the booster motor to be vented out of the gap between the stages before it can "blow off' the booster. The pressure from the sustainer motor is what should cause the separation. The stages should have just enough "stiction" -- that's a NASA word, BTW, no joke -- not to fall apart when held upside down by the booster. The vents are nothing more than a pair of 1/4" diameter holes placed 180 degrees apart in the booster body.

Pass-Port staging is a variation of this technique, involving two couplers and a complex passageway for the pressure to vent through. The couplers provide the stiction needed. If done properly, you only need one coupler, though. Simple is often a better choice...

Go grab a copy of "the book" and read the chapters on construction and multi-staging. You'll not only get the idea Stine tried to present, but his explanation of why it works. It's an interesting read.