L1 Flight Getting Closer!

JAAerospace

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I’ve finally finished the primer layers for the Zephyr. Now it just needs paint!
Only other question I have is if zipper prevention (the tennis ball, airframe reinforcement, etc.) is necessary on an AT H219T-14W. In the sim the rocket falls for about 1.5 seconds after apogee before chute deployment.

These are just some pictures of the build
 

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Tractionengines

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The H219T-14 is Disposable Motor System (DMS) with adjustable delay. It requires the Universal Delay Drilling Tool to trim delay (Part UDDT). [If you don't have a UDDT ask around for someone to show you how. Just DON'T use the RMS Delay Drilling tool. THEY ARE DIFFERENT. ]

That is how you adjust delay to match sim. If your saying the sim shows it falling for 1.5sec. Use the UDDT tool to take off 2 seconds before loading the black powder into motor ejection charge well. (Don't forget the metal "washer" before adding powder and the red cap.)

This way the charge goes off part of a second before apogee and the nose is still pointing up and rocket is decelerating. If your after apogee the nose is (can be) pointed down, and rocket is accelerating.

Good luck, remember to relax and enjoy the flight.
 
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JAAerospace

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Shows how much I know. The election charge needs to be added manually? And is there Any specific way to do it?
That is how you adjust delay to match sim. If your saying the sim shows it falling for 1.5sec. Use the UDDT tool to take off 2 seconds before loading the black powder into motor ejection charge well. (Don't forget the metal "washer" before adding powder and the red cap.)
 

techrat

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Howdy! I'm about where you are in building a Zephyr, but it's my "backup rocket", as I'd really rather L1 on another rocket I built, a 3" BMS "School Rocket" that I've heavily modified. It's 29mm, but I figure there's a Baby H that'll fit in that motor mount. If I can't do that, then the Zephyr takes over. I also modified the Zephyr as I didn't like the attachment point for the shock cord, so I made a "half baffle" in the coupler (piece of wood with holes in it), with the Eyebolt mounted into that and that should also help prevent zippering as the eyebolt is centered, rather than off to one side. But we'll see. Hopefully, I get to fly the Zephyr a couple of times on a Big G before I fly on an H. I have the 38 to 29mm adapter, so I'd like to test it out before an "important" flight.
 

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Antares JS

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Shows how much I know. The election charge needs to be added manually? And is there Any specific way to do it?
Your DMS motor will include a little packet with the igniter, a metal washer, a vial of BP for your ejection charge, and a red cap. When you unwrap the motor, you will see that the forward end is still open with the forward end of the delay exposed through the ejection charge well's touch hole.

Stick your drilling tool (the aforementioned UDDT) through that touch hole to drill out your delay as desired. As others have said, it sounds like you should drill out two seconds. If you don't understand how to use the tool, get someone to help you rather than guessing.

After drilling the delay, drop the washer in and make sure it's sitting flat at the bottom of the charge well. Then pour the black powder from the vial into the charge well, making sure some of it goes down through the touch hole to contact the delay. For a 4" diameter Zephyr, I think you will want to use the entire vial of powder, but check in the instructions included with the motor to confirm. Once your powder is poured in, put the red cap on and push it down with whatever thin rodlike tool you have available until it is fully seated against the ejection charge.

With that, your DMS motor is ready to fly.
 

Tractionengines

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Shows how much I know. The election charge needs to be added manually? And is there Any specific way to do it?
I would recommend you make a test flight on the DMS Version of G80. (G80NBT-14). It's 29mm, but someone should have a 29mm to 38mm adapter you can borrow. That flight will not need certification. The main thing is the "stuff" packed with the motor, the process of delay adjustment, and ejection charge loading is exactly the same. (But you'll trim off a few more seconds.)

SIM that motor and see if it's an acceptable flight profile .... I don't have a Zephyr so I can't say for sure, but my "mind SIM" says it should be good.

THIS VERSION: (DMS Type, adjustable delay.)

NOT This: ( Fixed delay type with pre-loaded ejection charge.)
 

JAAerospace

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Got it. I couldn’t find it. But anyways the idea is to have it “pop” right at apogee, correct?
 

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Tractionengines

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Yep... that's your igniter, and ejection charge items. The metal washer goes into ejection well after drilling the time, before the black powder. Then the red cap to hold powder down.
There should be 1.4ml (1.4grams) of black powder in that vial.
 

JAAerospace

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Yep... that's your igniter, and ejection charge items. The metal washer goes into ejection well after drilling the time, before the black powder. Then the red cap to hold powder down.
There should be 1.4ml (1.4grams) of black powder in that vial.
Awesome. Thanks! So zipper prevention methods aren’t necessary if you drill the delay properly?
 

dmaaero

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My zephyr weighs 1651 grams, the cg is 40.122 and sims much differant.
Simed on rock sim with the H219-t
9 second delay shows 18 mph deploy
7 second delay shows 46 mph deploy

With the G80-t
7 second delay shows 41 mph deploy
5 second delay shows 20 mph deploy
 

viciouspeanut

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Awesome. Thanks! So zipper prevention methods aren’t necessary if you drill the delay properly?
They shouldn't be, but on cardboard it's never a bad idea to harden the end with a bit of thin CA or use the tennis ball method (I used it back 14 years ago and again 6 years ago). I haven't seen it used much recently, but it works if you have the body tube size!
 

Lt72884

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Fort my level 1 a few months ago, i was worried about this very thing. One of my team mates rounded up to the nearest second for his delay, while i rounded down the nearest second for the time. His zippered, mine did not.

With this said, i would still add the tape ball, harden the edges of the tube, and maybe invite 2 priests, a witch and a cleric because you never know.

in all honesty, the tape ball and some super glue around the edges of the airframe help ease the mind :)

In the image below, here is what it looks like. This is from a 293,000 foot launch from a member on my local team. He was the one that graded my level 1 rocket flight and build.

I do not know if he used the tape ball on this launch for the same purpose you and I are, but none the less, this is what it looks like

Lastly, nice looking build and congrats on the build. Hope the flight goes well

1680189623692.png
 

viciouspeanut

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Ah yes, the tape shock cord loops is another good technique I used. I was quite concerned about zipper too I guess! Haha

Good luck and I’m sure it will be fine and if not the worst case is build another rocket and fly again!
 

JAAerospace

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This is my sim data
If y’all are saying drill the delay, then that’s what I’ll do. But this is just my current setup as it sits.
 

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viciouspeanut

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75 mph is 110 ft/sec, which is extremely high and will result in a bad zipper. You need that to be as close as possible to 0. Try it with a 6, 8 and 10 second delay and see what you get.

How have you picked the delay times for smaller rockets flown?
 

Patternflyer

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From what I see there, your sim recommended close to 9 sec. delay. At 14 seconds your rocket will be traveling at 75 mph. That is extremely fast for an ejection and can cause significant damage to the airframe and components.

Respectfully, because this is your L1 attempt, I wouldn’t experiment with results that could hinder your success. Wishing you the best and good luck!
 

Lt72884

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Personally, i would not drill the delay until launch day, when you have the RSO or even an L2 there to help. Mainly because once you drill it, thats it and youll be nervous too.

Your sim data says it will deploy at 15 seconds at 75MPH, thats going to most likely rip the airframe in half from so much force.

When i did my L1, my delay was 11 seconds for optimal according to Openrocket. This was around 19MPH for deployment.

My sim data showed that apogee was at 11.5 seconds and deployment should be 11.0 seconds.
Hope this helps. Nothing wrong with exploring and wanting to jump ahead, but for your first L1 flight, KEEP IT SIMPLE and relaxed. Youll have time to do some great stuff, but like all great things, you have to learn the small stuff first
 

dmaaero

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Try an run your sim again, this time with a 9 sec delay an see what you get.
I"d bet someone at your launch would be more than happy to help you drill your first motor, an even has the correct drilling tool you can use.
Asking for help doesen"t show you don"t know what your doing, it shows your being responsible with a high power motor.
Print a copy of your sim an take it with you. (when you get the deploy speed down to around 20 mph)
 

JAAerospace

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Sweet. I ran some simulations with the 9 sec delay and it was around 11mph at deployment, which, from what I'm hearing, is good. Thanks again everybody for your advice. It's been helping out tremendously. The weather's been getting nicer, so hopefully the flight will be in another couple months or so. I'll be sure to tell y'all how it goes!
 

waltr

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What I see about L1 cert is this is really NO different than an LPR flight just with a heavier rocket and more thrust from the motor.
You need to pick the correct ejection delay the same as if you are flying a 1/2A motor else deployment system failure is a big possibility.

A good method to help reduce a recovery failure (even with LPR) is the either Braid or do taped bundles on the shock cord. This absorbs energy with greatly reduces any 'shock' from the cord pulling tight.

As others said, do over think it.
 

JAAerospace

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Paint Added.
I’m going for the color scheme similar to the CW Air Strike 354
 

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