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When to use dual deployment?

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gary7

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First of all, I am not certified and currently have no plans to be. My question is regarding the decision to make use of a dual deployment system. So when and how does one make that decision? Should I consider size of recovery area? Size of the rocket? My expected or desired altitude (I am happy seeing the rocket go just out of sight then return, I don't need a 1/2 mile high flight)? What about the cost or amount of time for the rocket build? What are your determining factors for using dual deployment? Again I will not be flying anything over a "G" for some time so that limits the size of my rocket but not necessarily the cost or my time in construction etc. Any comments are appreciated. Thank you.
 

GregGleason

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I am in the same "boat".

I decided to start to seriously think about DD when I watched someone else's rocket float off, never to be seen again. It was launched on a "G" motor. Boy, I felt their pain. You lose the rocket and perhaps the case (I don't know if it was a SU motor or not). That was what pushed me in that direction, as a form of active insurance so that I could (hopefully) avoid that pain. That is why I haven't flown anything above an F yet. So I am currently working on a DD project. I am taking it slow (really slow since I moved over New Years Day) and am learning much in the process.

Greg
 

n5wd

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Gary,

I'd suggest that it's time that you seriously think about dual-deployment when (a) your rockets begin to drift outside of the recovery field or (b) you get tired of walking to the ends of the earth to recover your rocket inside the recovery field.

Yeah, doing dual-deployment adds a bit to the cost of the rocket in extra airframe and coupler tubes, some extra bulkheads, an altimeter/flight computer, ejection charge black powder or substitute, wiring, etc. It also makes you think more about what's going on in your flight, and how you need to do things to control that flight.

In return, you learn more about rockets, and that might help you decide whether you want to transition into high power in a big way, or just enough to get your L1 or L2 and then wind up flying mostly the lower powered flights (either through choice or the fact that there's not many high powered launches within convenient driving distance).

Wayne
 

NjCo

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Certainly there is a point below where DD isn't practical. Just about anything launched on black powder just isn't going to go high enough or be large enough to contain the extra material necessary for DD. So that whole group is out. And if you don't want to go above a G that eliminates a lot as well. I guess from there I'd look at my field size and the altitude the rockets you usually launch will reach since they are obviously related to each other. The only time you'd need DD would be if you had a small field size and it would be difficult or unsafe to recover your rocket outside the field or if you want to launch a high performance rocket that will reach a significant altitude.
 

Viperfixr

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Leading up to my L1 and afterwards, the idea of DD seemed daunting, and I wondered the usefulness given the complexity it added. I saw several DD rockets at my club fail on their first DD attempt. I strongly contemplated a motor ejection L2 so I could participate on research days (now a moot point) without having to take on DD headaches.

Not long afterwards, much smarter rocketeers like Crazy Jim and Tom Binford mentioned that I could easily modify my L1 rocket, a BSD 38 Special, for DD. I wasn't crazy about the idea. Then I launched my 38 Special on a Pro38 I205, using motor ejection and a Rocksim determined ejection delay, accurately adjusted with my Pro38 adjustment tool. The rocket barely landed on the field (read: epic walk to the edge of a swamp) and had a nasty zipper 4" down the BT. After that, I reconsidered the DD advice and bought a MAWD and LOC ebay. Several months later, I flew my first DD flight (successful) and completed my L2 the next month, a nearly out of sight flight that used DD & landed about 75 yards from the launch pad! And, no more zippers since then. Configuring an ebay isn't easy for me yet (doing one right now), but it's getting easier as time goes on and I see more examples from others (like on here).

It's another learning curve, and a lot to consider, but worth it and then some when you see it work for you. Ask lots of questions, talk to your club experts, look at as many examples as you can, and then take the most reliable, simple, and doable configuration you can for your first ebay. I found Newton's 3rd ejection canisters a big time saver and have yet to have one fail, and the MAWD was a perfect first alitmeter for me--YMMV. Good luck!
 

quickburst

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First of all, I am not certified and currently have no plans to be. My question is regarding the decision to make use of a dual deployment system. So when and how does one make that decision? Should I consider size of recovery area? Size of the rocket? My expected or desired altitude (I am happy seeing the rocket go just out of sight then return, I don't need a 1/2 mile high flight)? What about the cost or amount of time for the rocket build? What are your determining factors for using dual deployment? Again I will not be flying anything over a "G" for some time so that limits the size of my rocket but not necessarily the cost or my time in construction etc. Any comments are appreciated. Thank you.
Dual Deployment will not guarantee that your rocket recovers within the field, however; it does increase the chances that it will recover much closer than other recovery methods.

When to pull the trigger?
Setting up and maintaining a DD system is a learning experience. When your ready to learn how to use a new tool, tackle dual deployment.

I normally use DD when my rocket is expected to go over 2500 feet, but then again most everything I've flown has broken 2500' I use DD on both my L-1 and L-2 certs. I think it's the best way to go, but maybe thats just me.

Just curious .... why not do any cert flights? Isn't that the point?
 

sylvie369

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Besides the drifting away factor, there are two other good reasons to move to dual deployment:

1 - To get consistent ejection at apogee. No more worrying about what delay to use, and whether or not that delay will be right for this particular flight. Less stress on your recovery harness. If you do it correctly, dual deployment is more reliable than motor deployment. I'm inclined to say that it's a LOT more reliable than motor deployment, though I suppose I might get an argument about that.

2 - Because it's a fun challenge, which is, of course, why we fly rockets in the first place. Easily my favorite part of flying HPR is the moment the main successfully deploys.

A few years ago I did fly a handful of DD flights on D and E motors, in rockets that weren't going to drift away anyway, just because it was fun.
 
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bobkrech

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...I normally use DD when my rocket is expected to go over 2500 feet...
I think that's a really good criteria.

Dual deployment will normally cut the recovery walk down by a factor of 4.

Bob
 

Handeman

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Lots of very good suggestions here. I also used DD for my L1 & L1 certs. I prefer electronic deployment to motor deployment.

Notice I said electronic deployment and not dual deployment, they're not the same. You can use the same electronics for both in most cases. Using electronics for chute deployment at apogee is something that I think is more dependable then trusting the delays on motor deployment.

One of the things about electronic deployment is you don't have to use a canister or other heavy tube to hold the powder. With smaller rockets when weight is critical, an ematch laid on duct tape, the BP poured over it, and the tape sealed around it works well too.

You can use electronic deployment with smaller rockets, you just need to build the system light.

I would also say that the minimum altitude for use of dual deployment is about 50% higher then the minimum altitude the altimeter will deploy the main at. If that is 400 ft, then you should probably fly at least 600 ft to use dual deployment. I did have one flight that only went 468 ft and deployed the main at 400 ft. It worked, but I would recommend a little more difference between the two altitudes.
 

Zeus-cat

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I am with sylvie369, I do it because it is fun and a challenge.

I don't think you need to justify why you do something in a hobby other than you think it will be fun.
 

Sandy H.

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In a club environment, DD flights also set you apart from other fliers. Not that it is as much an ego thing as it is people get to see different events closer to the ground. Often times it helps you see your own faults or strengths.

I have learned that my parachute packing skills do not currently act like others who gracefully deploy. Next launch I will put more effort into creating an artful deploy than a chaotic one.

I have flown DD on G-I flights and see no reason not to do it with E or F motors in a conventional way. For flights below E, I think it could also be cool, just to do it, but might require a bit more planning.

Also, in my experience, it takes 1.5-2 times longer to prep a DD rocket compared to a standard motor ejection flight. That might show a weakness in my DD design, but it is what I have seen so far.

Sandy.
 

kandsrockets

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I use DD on any flight above 2k except for a few lightweight rockets that have been streamer recovery. I like DD over motor ejection because it gives me more control of when I want my main to be deployed. Prep time is longer but I feel it is well worth it.
 

troj

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Interesting discussion, and quite useful!

In regards to the comment that dual deploy takes longer to prep -- it definitely does. It's added complexity, and added elements, so it's naturally going to take longer.

In regards to folks failing their first attempts, more than likely they didn't learn enough before flying, and just jumped in head first. Some of the user manuals out there are hard to read, and can be confusing. That's why I recommend the more basic (but reliable as heck) models such as the MAWD and RRC2 to folks as their first electronics.

But, it's also a good idea to see what folks around you are flying and are familiar with. Why? Because nothing beats being able to yell over "Hey, George, I'm setting this up for the first time. Do you mind coming over and making sure I've got it right?"

It's also a really good idea to spend time seeing how others set things up, and what the pros and cons of each method are.

Dual deploy helps improve the odds of rockets landing closer, but doesn't guarantee it. We've seen lots of dual deploy rockets land a mile away. But then, here in Nebraska, 7MPH wind is considered "calm".

-Kevin
 

Adrian A

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Lots of good comments here.

I think dual deployment is more fun, at any size. It lets you fly higher on the same field than you otherwise could. The deployment altitude for small rockets can be set pretty low, like 300 feet. I regularly fly my Blue Ninja on a D or E with a 300 foot main deployment altitude.

Also, dual deployment lets you use an arbitrarily large chute, which cuts down on landing damage. I use a 24" nylon chute with my Blue Ninja.

For deployment charges, I recommend using Pyrodex in a section of surgical tubing, closed off with zip ties, and with a Quest Q2G2 ignitor. All unregulated materials, easy to make, and very reliable. You should buy a cheap digital scale that has 0.1 gram resolution if you don't have one already, to measure out the powder. And definitely ground test to make sure you're using the right amount of powder for your application.
 
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jdud

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I can say that DD is one of the most rewarding challenges in this hobby. I was excited when I completed my L1 (on motor ejection); but when the main deployed at 400 ft on my first DD, I had a real sense of self accomplishment. :cheers:

I routinely send up smaller rockets (2-2.6" diameter) on G-H motors with a DD setup. They go to about 2-3K, which is plenty high for my tastes, and recover nicely on the field. Some of the guys in our club have modified the 1.6" diameter BSD Thor for DD. There are also several of the smaller LOC kits that lend themselves to DD setups, which could be sent up to modest heights on a G motor. This is a great way to enjoy the thrill AP motors and advanced techniques such as DD without spending the cash on the higher impulse motors.

Also, never say never in this hobby. I thought that I would never have the urge to get my level 2; however, guess whats out in the shop?
 

RocketMonkey

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My first thought when I read the title of this thread was "When your fat like me and dont want to walk 2 miles through the desert to fetch your rocket"
 

MarkII

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I'd like to try to do DD in my FSI Oso clone sometime. (1.17" dia., 30" long.) And then maybe triple-deployment on a two-stager (ED for the booster, DD for the sustainer). :cyclops:

When I fly locally, it is on a very small field. I'm tired of being limited to 400 feet and B motors.

MarkII
 
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jcsalem

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In the tree-infested Northeast, DD tends to be a must for anything you want back that's going to fly over 2,000'.

If recovery is the primary concern, I strongly recommend you first invest in a radio tracker. I've lost an expensive DD rocket because I didn't have a tracker installed. On the other hand, I've never lost a rocket with a (turned on) tracker installed.

The downside to DD is that the prep time significantly increases. Ejection charge prep (up to 3 for main, drogue, and backup motor eject), shear pins, altimeter/battery testing, etc. all adds to the prep time. I love the electronics aspect to it, but DD requires a significant time commitment for building and prep.

If you're building a rocket < 1 lb., rather than DD, I'd recommend building stronger and using a streamer for recovery if you don't want to walk so far.

Overall, I really enjoy the challenge of building a reliable DD rocket. It's let me fly and recover rockets up to 7500' that surely would've been lost without DD.

Jim
 

JDcluster

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Back when I was first getting my feet wet with the DD procedure ( 1997), my first couple of flights didn't even hit 2,000ft. I wanted to make sure everything was working correctly. Lowest recorded flight was about 680ft.
Now, most of my flights are in the 1,800 to 7,000ft range. I like using it due to its complexity.

Most of the flights that I see now utilize DD on a regular basis(Each club maybe different). If the rocket weighs less than 3lbs. it's hardly worth going DD. The setup alone will add more weight. Some can still keep them quite light & makes it tougher to prep due to lack of space.



JD
 

ragid

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Depends where you are. Out on the Bonneville Salt Flats 10,000+ foot flights are still fairly easy to recover without DD . One day I plan on doing a 20,000 foot flight out there without DD, just to say I've done it. Our other launch location has a lot of weeds and sagebrush to walk thru. Even 3,000 foot flights can are a pain to recover without DD. We don't have many trees near our launch locations here. :)
 

Handeman

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Lowest recorded flight was about 680ft.

JD
My lowest was my first DD flight on a G motor. Prep for my L1 cert. It was 464 ft. The main was at 400ft. It worked.

Depends where you are. Out on the Bonneville Salt Flats 10,000+ foot flights are still fairly easy to recover without DD . One day I plan on doing a 20,000 foot flight out there without DD, just to say I've done it. Our other launch location has a lot of weeds and sagebrush to walk thru. Even 3,000 foot flights can are a pain to recover without DD. We don't have many trees near our launch locations here. :)
No trees? :confused: How can you make the required sacrifices to the rocket gods if you don't have rocket eating trees? :eek:

You need to come fly on the east coast. We're lucky to get a 15,000 wavier and anything over 5,000 ft better be DD or you're not likely to see it again.

BTW, no sagebrush to walk through out east, just mud, streams, cow pasture and electric fences.
 

cbrarick

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DD is a good challenge, and you don't need to flying K motors to have fun with it. Granted, it's a little more work to build and set up, but it's worth it. Loc/precision sells a truck load of rockets that scream DD on a G! You don't need a drogue chute, I just put out shock cord at apogee, using the motor delay. My MWAD puts out the chute at (I hope) 500 feet....short walks, cool flight profile. I fly a modified vulconate that gets about 1300 feet, so the whole thing is in sight...

JMHO
 

TheAviator

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I'm working on getting my first DD (Scale Aerobee 300) together. This is mainly so that if the second stage doesn't fire, I don't lawn dart a 100+ hour model like I've seen happen at NARAMs. It isn't pretty and you gotta feel bad for the modeler it happens to. I actually lawn darted my first scale model, an ASP 18mm WAC Corporal at NARAM-49. Wasn't really large enough for DD though.

Anyways, about the time issue, wouldn't it be practical to put everything together before the launch? I know on weeks leading up to contests, I match parachutes to models, build my internal lead FHPL igniters, check slide-wing mechanisms, etc. Why not make charges and pack parachutes before you even step foot on the field? I know you can't hook up the charges, but does it really take that much longer?

Or, maybe I'm missing out on the fact that we're all a bunch of procrastinators. :p
 

blackjack2564

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I usually prep my rockets [DD] a day or two before the launch. Saves confusion and time at the launch.

No distractions either! More time to enjoy the days goings on.
 

Adrian A

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I usually prep my rockets [DD] a day or two before the launch. Saves confusion and time at the launch.

No distractions either! More time to enjoy the days goings on.
I've started to do that, too. Even if it's the day of launch, I'd rather do it in my basement before I pack everything up, and then it's more fun at the field.
 

NjCo

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BTW, no sagebrush to walk through out east, just mud, streams, cow pasture and electric fences.
In a pinch you could use those electric fences as an alternate power source for your launches! :)
 
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