Dual Deploy or Play it Safe?

frognbuff2.0

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Hey y'all! I'm new to HPR and I'm going to attempt to get an L-1 cert soon. The rocket I intend to use is a LOC Deployer which I've already assembled and is designed for F-H impulse motors, but as the title suggests I'm unsure what means of deployment/recovery to use.

It is designed for dual-deployment and I recently purchased the Apogee E-bay mounting kit and a Entacore AIM altimeter if I go the route the rocket is intended, albeit more risky as it depends on electronics and I've never done this before, and do dual-deploy. On the other hand, I could just buy an H motor with an ejection charge and reconfigure my rocket by putting the main parachute where the streamer for dual-deploy currently is - which I view as the somewhat safer option even though I've never dealt with assembling ejection charges for HPR motors either. I set up everything for dual-deploy and did a static fire with the altimeter which went fine but I still worry about losing my rocket on my L-1 attempt.

What are your guys' thoughts?
 

Scott_650

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I did my L1 recently with motor ejection and a Jolly Logic Chute Release in a fairly heavy “low and slow” rocket over an Aerotech DMS H100. It worked almost exactly the way it simmed so I was a happy guy watching my rocket go to 1200 feet and land within a short walk of the launch pad. But that was the way that I was comfortable with - not the best way or the only way, just my way (sounds like a song 😆). I know folks who built several LPR/MPR rockets setup as full dual deployment rockets and flew them multiple times before building something bigger for their L1 attempt using full dual deployment. To me, doing my L1 was more about learning how to build bigger stronger rockets than about using different flying techniques - I was stressed enough using that big APC motor - adding anything more complex than a Chute Release would’ve totally taken the fun factor out of the experience.

Here’s my advice (you did ask so I’m offering) - figure out the why first before you decide on a how - why do you want your L1 certification? Once you get the why figured out the how will probably be a bit clearer.
 

dhbarr

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I did motor deployment w/ JLCR for both 1 & 2 -- not the cheapest route, but one of the more straightforward approaches.
 

OverTheTop

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It is your flight. If you are comfortable with dual deploy then go for it. I would suggest keeping it simple and just using motor ejection. You could use a JLCR if you are inclined but personally, for L1, I would just put the chute out at apogee. Less stress that way. YMMV.

If you reliably get the chute out properly with LPR and MPR you will be fine. If you have unreliable chute deployment ask some of the more experienced rocketeers for advice.

Good luck with the cert.
 

K'Tesh

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The thing to remember is the KIS principle... Keep It Simple. The goal of a Cert flight is to get Certified... Anything you do that adds complexity increases the odds that the flight will be a failure. I would recommend using the smallest motor that sims indicate will fly safely. I'm not against using a JLCR, but nothing more than that for a L1 flight.

For my L1, the complexity of adding a nose weight was enough for me to fail my first try at it. The rocket came down hard and the 3D printed PLA plastic nosecone broke. It was able to be "fixed" with Union Jack decorated duct tape, and flown again safely, but had it not been for the generosity of the really cool British bloke that is Rob Appleton, there would have been the added cost of the extra flight to contend with.

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Buckeye

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Practice your setup and dual deploy on F-G motors, first. Then go for it on your H motor cert! A cert flight that "does something" is way more cool and impressive.:dancingelephant:
 

ksaves2

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A baby H in a larger rocket can be a simple, viable option. I did a DD for my L1 with an I 200 successfully but I tested extensively. Did a bunch of ground tests with the 4F to blow the chutes and it was successful. I actually made "starters" for the 4F out of nichrome so's not to waste ematches. That way I could test with a 12V launch panel safely.

For the L2, designed a 4 inch thin walled LOC tubed rocket for motor only deploy. I did it in record time but the flight failed. I didn't put enough 4F in the motor deploy well! At least the rocket was naked and I didn't waste time painting it as it was completely trashed. Then I built a replacement, was more careful. I used the empty motor casing and ran the ematch wires down it. I measured the powder and did ground tests with the same 12V system. I determined the optimal 4F charge and simmed the daylights out of the planned J350 flight. About 3k in altitude simmed and that's what I got on the actual flight +- 5%. I drilled the delay charge because it needed to be shorter timed. Got L2 out of the way. On a later flight same rocket, I botched the delay and got a zipper. Did a tube repair, made an ebay and upper parachute bay and turned the rocket into a DD. Flew the heck out of it.

Reason I wanted the L2 "fast" was the local club was moving towards a "Research only" one and according to the TRA rules at the time, I couldn't participate as an L1 only. Shoot, I attended a private motor mixing class as a newly minted L1 and got hooked. Hence the rushed L2. Even after the L2, I flew the heck out of H and I motors and rarely did a J or higher unless it was a "research" aka as "Ex" (back then). Those were fun days and it's nice the rules have since changed for the better.

Kurt Savegnago
 

Zeus-cat

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I say fly the cert flight the same way you will do the rest of your high power flights. If you plan on doing dual deploy after the cert flight, you may as well do it on the cert flight. If dual deploy will be a once in a while thing then just do motor deploy for your cert flight.

Some people twist themselves into knots over their first dual deploy flight and in my opinion it really isn't that difficult.
 

JoePfeiffer

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The only thing that should be new to you on a cert flight is the size of the motor. If you want to DD it get some practice DDing on a G until you're really comfortable with it.

But really, there isn't any reason to go more complex than motor ejection.
 

Steve Shannon

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The only thing that should be new to you on a cert flight is the size of the motor. If you want to DD it get some practice DDing on a G until you're really comfortable with it.

But really, there isn't any reason to go more complex than motor ejection.
This is it in a nutshell. Figure out which you want to do and concentrate on that. Certification is an opportunity to show what you already know, not test new techniques.
 

Bat-mite

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Recovery decisions for ANY rocket are contingent on field size, wind speed, projected altitude, etc. I think it is oversimplifying things to say "should I do this or this" without any of that information.
 

Scott_650

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The only thing that should be new to you on a cert flight is the size of the motor. If you want to DD it get some practice DDing on a G until you're really comfortable with it.

But really, there isn't any reason to go more complex than motor ejection.

This is it in a nutshell. Figure out which you want to do and concentrate on that. Certification is an opportunity to show what you already know, not test new techniques.

Recovery decisions for ANY rocket are contingent on field size, wind speed, projected altitude, etc. I think it is oversimplifying things to say "should I do this or this" without any of that information.

Valid points all around - even though I’m a short, dumpy guy I really enjoy long distance running, mostly on trails - and one of the ironclad adages of LD running is - never try anything different from your training on race day. Race day is not the day to break in a new pair of shoes from a different brand, don’t try a different calorie source than what you’ve trained with, leave the new shorts and shirt and socks for a training run… And from the other side of my life, from my (now retired) professional world - no plan withstands contact with enemy - hobby rocketry is all about being a flexible problem solver.
 

Joekeyo

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I did my L1 recently with motor ejection and a Jolly Logic Chute Release in a fairly heavy “low and slow” rocket over an Aerotech DMS H100.

I won a Madcow Little John at NARAM 62. Thanks again Madcow and the sponsoring organizations.
It was not my intent to get into HPR, but here I am. My vision is a below level 1 test flight, then the cert. flight. After much pondering, I came to the same cert. Launch strategy as you, even the same motor. I am happy with $10 (or less) flights. I don't expect to be burning lots of expensive big motors.
 
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I did motor deployment w/ JLCR for both 1 & 2 -- not the cheapest route, but one of the more straightforward approaches.
I did motor deploy with main chute at apogee for my L1. I'm doing motor deploy with a chute release for my L2. I'm during DD thereafter. If you are doing a cert flight you want to keep it as simple as possible. Once you get the cert you can buy the motors you need to try harder stuff. It's only L3 where you have no choice, since redundant DD is a requirement.
 
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I say fly the cert flight the same way you will do the rest of your high power flights. If you plan on doing dual deploy after the cert flight, you may as well do it on the cert flight. If dual deploy will be a once in a while thing then just do motor deploy for your cert flight.

Some people twist themselves into knots over their first dual deploy flight and in my opinion it really isn't that difficult.
Respectfully disagree. If someone is new to HPR, how familiar are they with working with black powder? With wiring electronics? With what switches to use? With wiring connectors that won't fail during flight? With what batteries to use? If LiPos, how to store and charge them without burning your house down? Choosing the right battery for your altimeter so you don't exceed it's specs? Choosing the right battery so you have enough current for your e-matches? Do you know the difference between and e-match and an igniter? With using shear pins and removable rivets? How to calculate how much BP to use to make sure your shear pins actually shear? How to reinforce the airframe so the shear pins don't tear it?

There are a lot of new components and process steps for flight prep with DD. A cert flight is not the place to try them out. Nor is your cert rocket the one to try these out on a G motor. If you screw up you lost your cert rocket and have to start over. K.I.S.S., get the cert, then move up the food chain of complexity. Build your cert rocket so you can do motor ejection and add DD later if you want, but make DD step #2+.
 

frognbuff2.0

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Thank you all for the input!

I think I'll go the motor-deploy route over the DD route for my L1 and hopefully the rocket survives so I can fly it on some midpower Gs to "break in" my electronics. I do intend to do an L2 cert sometime down the road and I imagine I'll want/need some electronics for that. Not sure when I hope to do that but I don't wanna get too far ahead of myself and just focus on the L1 for now.
 

Sooner Boomer

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I think one thing to keep in mind: Fly The Field/Conditions.

If you have a calm day, motor eject and a JLCR will work well. If it's windy, or you need to bring the rocket down in a limited area, dual deploy might be a better solution.

There are other considerations, too. Not all motors/reloads offer motor eject - will you ever fly with one of these? If you DO go with motor eject, how hard will it be to switch to DD?

For what it's worth, I flew my L1 cert with motor eject and a JLCR. We've got more than a section of flat land to recover in. (now with less Buffalo!)
 

Budro0

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I got a lot of the same advice going into my L1 cert. While good, I decided to go my own route.

I'm a fan of redundancy when possible. I flew my cert with dual RRC2Ls with motor eject as a back up. The RRC2Ls allow you to fly as essentially a single event altimeter. I set them to pop at apogee, +1 sec, and the motor delay to +2 sec. I did have a mentor who was good about helping me to fly my flight the way I wanted to.

Flying it like that allowed me test both altimeters as this was my first time with electronics and gave me a lot of confidence in the system. All three fired beautifully and since I was only at about 800ft, we got to see 3 puffs of smoke at 1sec intervals from the ground.

Fly it how you want, use a checklist, and always have a backup plan. Just my 2¢
 

Handeman

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I'm late to the party, but I say, do the DD. Just ground test a lot. That's what I did on my L1. By the time the flight rolled around, the altimeter and deployment was the least of the things I worried about.
 

Dugway

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If you have a calm day, motor eject and a JLCR will work well. If it's windy, or you need to bring the rocket down in a limited area, dual deploy might be a better solution.

I'm having a hard time coming up with a scenario where a JLCR won't bring you down as close to the pad as dual deploy. I guess if you aren't using any kind of a drogue, you might come down a bit quicker without the chute bundle exposed to the airstream.
 

Sooner Boomer

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I'm having a hard time coming up with a scenario where a JLCR won't bring you down as close to the pad as dual deploy. I guess if you aren't using any kind of a drogue, you might come down a bit quicker without the chute bundle exposed to the airstream.

Yeah, you're probably right...
 

Troy3003

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I'm somewhat gun shy of relying only on motor eject now. I know its not very common but sometimes it does fail.
On a cert flight there will be additional stress that day but honestly the cert flight is no different than any other flight and you won't be penalized if it doesn't work out. A failure is a failure whether it's a cert flight or not.
The downside would be getting another cert motor, especially if you don't have vendors on site.
 
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