Gap Stage Tip

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Well-Known Member
Jul 23, 2002
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I was asked by a Beta Tester to post this tip. During design of the "Double Up" , I used a paper punch to create the side vent holes in the booster. Spend the extra 30 cents at staples and get the heavy duty one, you can punch right through the coupler and the side tube!

Here's a pic.
Double Up Booster

Here's a pic by Keith Stewart

Double Up...Nice paint job!!
wow that is a really good idea, I have always used a drill but it always rips the last bit and causes a big chink of paper sticking out inside
The overlooked paper punch should have better rep...I also use it for making neat notchs in centering rings (for the motor hook) and also for making clean holes in mylar parachutes. I also want to experiment with making baffles!!!!

AAAAHHHH!!! So many little time....:(
i've found that if you apply some epoxy to the inside and outside first and then use a drill the paper will cut clean....
I've also used hard dowels on the inside and that also has worked somewhat

I've been doing the same thing for years...just never mentioned it...I guess I assumed everybody used one.

I also use a paper punch on Monocote Trimcote to make round "portholes" for sci-fi rocket designs. Chrome has a really neat effect.

I agree...a much overlooked tool.

Great tip John. I used it on my gap stage Terrier Sandhawk.

the only time I have used a hole puncher on rockets was on my Estes Honest John. The wrap that goes around the BT needs lots of holes.
I presume from the name that a space exists between the booster and sustainer. Do the holes help to ensure ignition of the sustainer prior to ejection of the boost stage? The only other experience I've had with staging was with an Estes Hercules years ago (My first loss to the drift) . As I recall the motors were cellophane taped together. School me please!

Gap staging is where there is a gap between the booster engine and the upper stage motor. Thus the term "gap staging"

The vent holes relieve some of the excess pressure built up when the booster engine "burns through".

This keeps the stages together for a fraction of a second longer allowing the upper stage to have a better chance of ignition.

Would a tiny bit (1/8 gram) of black powder help ignition of the upper stage? I'm thinking a flashpan type effect.

The potential problem in adding BP to a gap staged effort is twofold:

  1. Increased potential for heat damate to the booster (already an issue with gap staging).
  2. Increased gas pressure encouraging separation prior to upper stage ignition

    I've not done any research personally to verify or dispute the merits of adding BP (and ask anyone here, I've got about a 50/50 shot {at best} of being right or wrong when I think these things out) and would be interested in seeing the results if anyone cares to do so.

    On the flipside, here's a great link on building techniques for gap staging attempts (and a fun read to boot): Wickart/tips3.htm
Wow...I never knew that there was so much you could do with Estes engines. I personal am a fan of High Power, but now amd going to work on a gap staged spool rocket (sprocket) :)
Ah ha Sandman!
so i'm not the only one who "assumes" everyone knows stuff:D
Could you please call my wife and tell her everyone is born knowing "ya Never touch the inside of the tent wall when it's raining";) I've been beatin to death over that one for years.
"ya Never touch the inside of the tent wall when it's raining"


I had that same argument with my wife about 30 years ago!! Recently she asked me if that rule applys to our pop-up camper.


I think gap staging, at least as the term is being used here with the exhaust holes is really just a variation of the old Centuri "passport" staging system....

This was invented by Leroy Piester and a Robert Royal...

I have a copy of the patent filed 3/25/70 and issued 3/20/73..

little bit of model rocketry history .....

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