Engine choice scratch build L1

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Jacktango22

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I am back into the hobby about one year after retirement. Scratch build a lot of low and mid power and want to build a high power for a certification flight this year.

Thus far I have a 34 inch 3 inch tube and nose cone. At a club flight yesterday I asked a vendor about motors I could use those to test before certification and to use for a certification flight. It is a 29 mm.
It was recommended and I purchased the following two motors: G125T-14A, and H 135w-14A.

My is with the 14 second time delay. I ran them through open rocket and they both seem to be about 5 to 7 seconds longer than what the simulation says they should be. I actually don’t have a problem with the motors because I can build something to suit them, but I would need some advice on what type of rocket would need so long a time delay so I can do it right. Any help would be appreciated.
 
Thank you all so far. I still have a lot to learn. I open the instructions and you guys are right. I need to read them and study the ways to adjust the delay charge. Luckily, I have good support in the club here in Connecticut and can perhaps get someone to give me an assist before I launch these babies again, thanks and I have a lot to learn.
 
With the H135, 10 seconds is about right for a 3" cardboard and plywood rocket. Doesn't matter much.
 
I am back into the hobby about one year after retirement. Scratch build a lot of low and mid power and want to build a high power for a certification flight this year.

Thus far I have a 34 inch 3 inch tube and nose cone. At a club flight yesterday I asked a vendor about motors I could use those to test before certification and to use for a certification flight. It is a 29 mm.
It was recommended and I purchased the following two motors: G125T-14A, and H 135w-14A.

That G125 is actually considered a high power motor, as it exceeds 80 N-s average thrust. Don't be surprised if your club doesn't allow you to fly it before your L1 cert flight is successful, they shouldn't. IIRC, the Aerotech G80 is the most potent single-use motor you can fly without certification.

You can see the info under the heading "Where Is The Line Between Model and High Power Rocketry" here:
https://www.nar.org/high-power-rocketry-info/


I like to see scratch-built cert rockets, show us some pics as you start to build!
 
Flew the H135 and the 14 sec delay is WAY too long. It made my ejection about 1/2 way down which ripped the shroud lines apart and ruined my Cert attempt. Second time I used a delay drilling tool and went down to 9 seconds which was perfect.
 
Thanks

Getting started on the build. Here’s photos of tube and nose cone and the centering rings in process. Using 1/8 inch plywood for the rings.
 

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Just saying!

NAR says:

  1. The Level 1 High Power Certification Candidate must demonstrate their ability to build and fly a rocket containing at least one H or I impulse class motor. Cluster or staged models used for certification may not contain over 640.00 Newton seconds total impulse. In the case of a cluster or staged model, at least one of the individual motors must be an H or I impulse motor. Combinations of smaller impulse motors that add up to meet the impulse requirements do not qualify as the model does not contain at least one H or I impulse motor. Single use, reloadable, or hybrid technology motors are permitted. The Level 1 High Power Certification Candidate must assemble the reloadable motor, if used, in the presence of a Certification Team member.
H130's 8-9 s/d. RocSim it.

mebbee.... 38"T w/ Aeropack 9r tainers for more fun. Nix on the haZMAT!

Custom help: Wildman or LOC. Easy Peasy. Those dudes care.

Hey- stuff takes a LONG time to build. Ask me how I know. Make mistakes and corrections at home. Keep it KISS, stress test, get yer L1 pin, hi-5 yer buds.... then, few/many flights later, stomp on it- hard, in increments, see what ya got. Then make another one if it ghosts. You got this....

P/S...take lots of pics, cuz I dinit. (ugh.)
 
Thanks. Dumb question: mine would be a simple build. Can I plan to simply use recovery wadding or dogbarf as such? Or Nomax chute protector? Or should I plan on a baffle?
 
Thanks. Dumb question (NO dumb questions):


mine would be a simple build. (No issues there, build what you're comfortable with)


Can I plan to simply use recovery wadding or dogbarf as such? (Yes, that's how most folks would go about it)Or Nomax chute protector? (Nomex is often the 'go to' these days, often augmented by dog barf

Or should I plan on a baffle? (I find them to be unreliable and overcomplicate a 'simple build')
 
Build it however you want to. My L1 was flown with dog barf below a nomex blanket. Many of my builds since then have included a simple 'half moon baffle', especially if I build the MMT long, but I still use a nomex blanket as well.

Mine was a kit. No G test flights, just jumped in with both feet. Used an AT 238T in a 4" cardboard and plywood rocket to about 1400ft. Nice slow visible flight. (But that is me, you do you)
 
I am back into the hobby about one year after retirement. Scratch build a lot of low and mid power and want to build a high power for a certification flight this year.

Thus far I have a 34 inch 3 inch tube and nose cone. At a club flight yesterday I asked a vendor about motors I could use those to test before certification and to use for a certification flight. It is a 29 mm.
It was recommended and I purchased the following two motors: G125T-14A, and H 135w-14A.

My is with the 14 second time delay. I ran them through open rocket and they both seem to be about 5 to 7 seconds longer than what the simulation says they should be. I actually don’t have a problem with the motors because I can build something to suit them, but I would need some advice on what type of rocket would need so long a time delay so I can do it right. Any help would be appreciated.

Congrat's on your retirement!

Have you considered a motor like a G74-4 for a shake down flight? It's not a HP classified motor... or maybe a G80?
 
Theres two of the delay drilling tools. One is a universal the other is a RMS. For RMS or LMS motors use the RMS tool. For DMS motors use the universal tool.
RMS= reloadable motor system
DMS= disposial motor system
Lms= loadable motor system
 
To answer one of your other questions, the 14-second delay would be for a light, minimum diameter rocket that's headed for high altitude. None of that is good for a certification flight (unless you want to and know the risks of loss). The manufacturers make the delay for more or less the longest delay they expect someone to need, and users adjust the delay as needed for their rocket.
 
i think you should go with a 38 mm motor mount. this will give you more flexibility later on. use a 29 mm to 38 mm adapter for test flights and windy days. i fly a Zephyr on 29mm H 220 and H 250 AT reloads. my cert flight was 38 mm H100 single use.
 
I wish the cert folks did not allow this. you missed a whole lot of learning.
The whole point of L1 is to get to L2. L2 is where you’re able to learn a lot about Dual Deployment, Telemetry, Downlink, Recovery. Also using the same rocket and motor diameter you can say money to spend on electronics and more sophisticated rockets.
 
The whole point of L1 is to get to L2. L2 is where you’re able to learn a lot about Dual Deployment, Telemetry, Downlink, Recovery. Also using the same rocket and motor diameter you can say money to spend on electronics and more sophisticated rockets.
As someone yet to achieve their L1, but an enthusiast, I would respectfully disagree. None of the 'objectives' you've mentioned need be the exclusive 'domain' of L2 rocketry. I've built and flown a MPR equivalent of a 2.6" Darkstar, constructed using Estes PS II 2.5" airframe components that is my 'dual deployment test-bed', allowing me to explore that aspect of the hobby. It would be no issue at all to fabricate a bay in the nose cone of same to install a tracker of one sort or another...
 
As someone yet to achieve their L1, but an enthusiast, I would respectfully disagree. None of the 'objectives' you've mentioned need be the exclusive 'domain' of L2 rocketry. I've built and flown a MPR equivalent of a 2.6" Darkstar, constructed using Estes PS II 2.5" airframe components that is my 'dual deployment test-bed', allowing me to explore that aspect of the hobby. It would be no issue at all to fabricate a bay in the nose cone of same to install a tracker of one sort or another...
Not to mention that it's a totally valid choice to stop at L1 and not go on to L2. One of the best rocketeers I know did exactly that.
 
The whole point of L1 is to get to L2. L2 is where you’re able to learn a lot about Dual Deployment, Telemetry, Downlink, Recovery.

I would bet you'd be hard-pressed to find more than a handful of people here who agree with that. You can do all those things at or before L1. What makes you think you'd need L2 to do any of that?
 
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