Dual deployment

I certified Level 1 the other month and now I would like to build a rocket with electronics. I have a 4 inch airframe and I would like to learn about different methods before I start construction. For example, what is the minimum size for the main and drogue compartments? I can not find this info anywhere. I have looked at "Missile Works" site and an article in High Power Rocketry by Ed Miller. I am looking to do it right and not necessarily the easiest way. Any sugestions would be helpful, web sites and personal experiences. I just found this site and hopefully someone can point me in the right direction.

Mike,

I am no expert and have yet to build a rocket with dual deployment or electronics, but have come to understand exactly how the dual deployment is set up.

Here is one good place to check out in case you haven't found it already.

https://www.info-central.org/index.cgi?recovery

This is Rocketry Online's INFOCentral.

I'll let the experts describe this one. If no one else hops in, I'd be glad to give you my interpretation. Granted, there's no experience to back it up, thus the reason I'll wait 'til the pro's chime in.

Mike,

Welcome to the forum! Unfortunately, I have no experience whatsoever with electronics, so I can't help ya there. My guess would be that as long as you can fit what needs to be there in the compartment, it's big enough. I'm sure it won't take long to get a real answer though from someone who's done it a whole buncha times.

Jon

I've never seen dual-deployment done in anything smaller than a 2.14" ID [inner diameter] tube. Theoretically, most of the dual-deploying altimeters will fit into a 1.52" ID tube, but then you've got to figure out how to mount it so it stays put.

Now, if you're talking about size of the parachutes to use, well, there are a few recovery descent rate tables out there on the web [Public Missles has one, I think]. This will help you decide appropriate chute sizes.

As for how to build the electronics bay, there's a couple of ways to do it, but most involve deploying the drogue chute from the lower section of the rocket [below the payload bulkhead], and the main chute from the payload section itself. Both ends of the payload coupler would be "capped" [bulkhead plate at both ends].

By all means, don't be afraid to ask questions. That is how you gain knowledge, and there's plenty of knowledge to be gained from folks on TRF. Welcome aboard!

Mike,

A BIG welcome to you to The Rocketry Forum...I think you're going to find this place is a great resource with an audience containing a wide variety of skill sets in the rocketry field. You should post lots of pics of your projects and just have fun!

As far as dual deploy goes, there are indeed many ways to utilize Dual-Deploy in a rocket. "Tried and True" methods are used from the smallest models through the Large "Level 3" projects and have proven their worth. As mentioned, one of the more popular methods is to have the lower section of your model split with a drogue, then deploy the main from the upper bodytube at a specified altitude. I have personally used this on Level 1 - Level 3 projects with great success.

My first dual deploy was with a PML Amraam 4 model, using the PML "CPR3000" dual deployment unit. They have a great system for newcomers and veterans alike that is both reliable and easy to use; a real confidence builder. Go to their site at https://publicmissiles.com/ and check out the CPR3000 unit, available for kits from 2" - 7.5" diameter. Their system sets up easily and seals very well, which is key to getting deployment to work correctly. Other methods are also available; some are cheaper in cost than the PML and provide good reliability, but none are easier to use.

Whatever you use, make sure your altimeter bay is completely sealed from the parachute bays so the ejection blast doesn't damage the Altimeter. As far as amount of room needed, my Amraam 4 lower fin can has a 15' shock cord and small 18" nylon drogue chute for this lower section and it fits in a four inch long chamber between the fin can bulkhead below and piston ejection above. The upper body tube is about 28" in length and contains the upper piston, another 15' length of shockcord and the 60" Main Parachute. Considering this is a 4" diameter model, it all fits pretty well. Take a look at PML's Website and ROL for additional ideas and good luck. Keep us posted with you efforts.

Once again, welcome to the Forum,

Carl

What's up Carl! Thought I'd chime in here.

I've flown DD 24mm tubes up to 4" now. So far, so good, the key for me is keeping it modular. I've tried 3 types (one was specifically for the 24mm) and the other two were definitely modular in nature. The first one is a common set up used by my NWestern buddies and is a fine setup where the rocket is basically screwed together via the altimeter bay. You have an all-thread through the middle and it connects to permanantly attached coupler ends via a coupler nut. the entire bay moves from rocket to rocket. Again a fine setup that I used for my L2. However, it had some issues that I really didn't like. I hooked up with a friend of mine who used a very similar setup except for the fixed coupler attachment tubes and hashed out what has become my favorite design.

Same basic setup with the all thread except the fixed couplers are no more and the bay itself is secure with one side being permantly attached and now ONLY the guts are moved from rocket to rocket along with the fore and aft bulkhead. When I get home, I'll try to remember to attach some pics. Good luck.

Shane Heilman

What's up Carl! Thought I'd chime in here.

I've flown DD 24mm tubes up to 4" now. So far, so good, the key for me is keeping it modular. I've tried 3 types (one was specifically for the 24mm) and the other two were definitely modular in nature. The first one is a common set up used by my NWestern buddies and is a fine setup where the rocket is basically screwed together via the altimeter bay. You have an all-thread through the middle and it connects to permanantly attached coupler ends via a coupler nut. the entire bay moves from rocket to rocket. Again a fine setup that I used for my L2. However, it had some issues that I really didn't like. I hooked up with a friend of mine who used a very similar setup except for the fixed coupler attachment tubes and hashed out what has become my favorite design.

Same basic setup with the all thread except the fixed couplers are no more and the bay itself is secure with one side being permantly attached and now ONLY the guts are moved from rocket to rocket along with the fore and aft bulkhead. When I get home, I'll try to remember to attach some pics. Good luck.

Shane Heilman

Shane,

Great to see you joining on in!!! BTW people, Shane is one of our local Cincinnati Fliers and the one that pretty much pioneered dual deploy on non hpr rockets in our area. Thanks for some great input bro and post a pic or two...

...we love pics!!!

Great to see ya here man...

Carl

Gotta love dual deployment

Sorry for the inconvenience as I don't have a website to post these to. I'll just throw up two - the first method I used and what I've come to love. If you want more, I'll post them.

Shane

and one more...

Shane

I don't know about anyone else but, I'd like to see some more pics. What diameter are the pics from the above posts? I'd also like to hear how you made some of these bays.

CLICK HERE for instructions for my Missile Works RRC2.

I used it in this rocket:HERE

and this one: HERE

I have some pics of a G-Wiz Alt in an extremely tight fitting bay:HERE

Binder Design and Giant Leap sell a 3.9" bay: HERE and HERE

Then there is Bob Fortune's unique way: HERE

Sorry for all the click outs, but this is all the info I could find on my site.

- Nick

My initial design was similar to Binder's design (this may cut down on the pics I have to post). Except that inquired it via Texas. The one I use now is much enhanced and I must give credit where credit is due - Gary Dickinson had a nice assist in the improvement of my design. Again, everything but the coupler & lining moves very easily from rocket to rocket.

Shane

Here's a couple more pics. Sorry, I thought I was in the game, but I guess I'll have to get me a website now.

The first pick is from the perspective of looking down toward the fore bulkhead post assembly. The silver thing is an I-nut, and the brass knurled nuts are my connection points.

The second pic is showing a closer view of the fore bulkhead with my "switches" on either side for dual altimeters.

I don't have a picture of it right now, but the coupler (AB) as I said last night is fixed at one end to the BT. There is a sleeve, if you will, that is then positioned inside of that coupler to form insets at both ends for the bulkheads. One end is (for my 6") 1/2" shy of the aft end. The other end is about 3/4" shy of the fore end (I put a lip on my fore bulkhead). This allows the bulkhead to seat down into the outer coupler and form a very tight seal against the sleeve. I usually make a very thin "tooled" silicone bead where the bulkhead seats against the inner sleeve to form an airtight seal.

I hope these instructions are clear enough. If not, I'll take pictures.

Shane

#2

well, if this isnt like an online QUARK reunion!

im getting into dual deployment, im building a Blackhawk RD
SA-2, and bashing it to 2 stage. so far i have 3 perfectflite timer kits built (hafta get a new transistor for one tho) and im going to need an altimeter for the sustainer. ive been looking at the perfect flite MAWD timer... is this a good choice?

it should be done not too long after christmas, all i have to do is finish constructing the alt bay (gettin the TC i need from Ross this weekend) the do the actual building (you know, fins, glue the mmt, glass, that kinda stuff)

Scott McNeely
NAR 79800

Scott,

See my post to Chan Stevens on the Quark board for my lengthy response concerning Perfectflight equipment.

In a nut-shell, Peter at PF has VASTLY improved his product line. 3 very successful flights with his new alts.

Shane

Scott,

I think if you were going to invest in a timer for the sustainer, you may as well go all the way and get an altimeter instead. Timers have to be set up for delay times, while an altimeter uses sensors to fire off charges excactly at the right moment, no calculating of delay required. It is just more versatile in my oppinion and easily adapts to any sized motor you may want to use.

Also, since you are probably talking about the two stage, delay/additional timer calcs would not be needed for the booster if you used an altimeter...it once again would sense apogee and deploy.

Good Luck,

Carl
PS: Yea, does seem like a reunion, huh

Carl has an excellent point here. Considering how money can be an issue with this crazy addiction, it's worth a period of delay to get the right thing the first time. Try to learn from those who've flown before you and always be forward thinking. I TRY not to buy for project specific things by looking to what I can use the equipment for later. How can I duplicate designs, etc? You see the pattern.

Those little timers you purchased are pretty handy and for $17 or so they can't be all that bad....I have one. But consider this - the next timer up from that is capable of handling a heavier load of current AND has a field set timer that can be set to the tenth of a second. The older generation has to be soldered to change the delay (this is a royal pain in the field and not a real good option). It also has to be initiated with a breakwire. This limits your use in the field and cramps the convenience factor in moving it between multiple rockets. Save an extra month an you have yourself a REAL nice little timer!

Please don't be discouraged by my comments as these are derrived from making mistakes along that way as we all do.

Sucks! That hind-sight stuff....


Shane

im short on space, and even shorter on $$$ else i would have gotten the more expensive timers. i paid 9.50 for each kit, so for what i spent on the three, i would have only gotten one timer. i have the one in the booster set to i sec, so one sec after the booster comes off, it will deploy the chute. thats all it needs to do, i dont need it to record alt or anything else, so a 10X increase in price isnt what i needed. (the cehapest alt ive seen is the MAWD which ive been lookin at which is 99 bux)

i wast able to find a 2 event timer that would fit and not make me go broke, so i got the smaller ones. one will be set to seperate the booster and the sustainer, the other will then be activated at that time, using 1/8 th" headphone plugs. one will deploy the booster chute a 1 sec after sep, the other will light the motor at i sec after sep. i need the altimeter for the sustainers dual deployment.

does what im doing make sense?

Scott McNeely
NAR 79800

Scott,

There is a ton of calculation that goes into this, but from what I understand to be the case I would allow more than one second between your separation and booster chute deployment. Reason: What if the separation isn't clean? You'll have a toasted chute assuming it's at the top of the fin can. It won't hurt to let it free-fall for a bit. In fact, I would want it to. Here you could let your LONG delay do the work for you and not have to worry about using the timer for anything other than a back up or something.

One other thing! and again this is if I understand your setup - if you set that little beast to 1 second that means that after you break the wire you have one second until it fires and it's only going to fire one time. So I have to ask - what is going to separate your parts?

Secondly, firing the sustainer motor one second after separation SEEMS a bit long to me. It gives the sustainer time to tilt. Here there is a "window" of opportunity and I would have see what you have to give any better suggestion than to carefully calculate here. Your goal (Carl chime in here) should be to almost separate and light simultaneously. And thus the challenge of two stagers! There are other things that may change this, but this is kind of the idea behind the old Estes CHAD method (cheap and dirty).

OH YEAH - a lesson learned - figure out a way to arm your timers post setup. The WILL go off in your hand and that is all I'm going to say about that

Originally posted by mshaner
OH YEAH - a lesson learned - figure out a way to arm your timers post setup. The WILL go off in your hand and that is all I'm going to say about that

Click to expand...

That sounds like a painful lesson!

Welcome to the Forum!

I was looking at the MAWD myself. Anyone had experience with that? For features vs. price, there just isn't anything out there that's even in the neighborhood. But, like anything, it seems almost too good to be true, so I'm soliciting anyone's experience who has any. Thanks in advance!

My group of rocket buds have been using the perfectflite MAWD, and the thing is great! Gets it's apogee event at apogee, and it's data collection is very good. Other features that I like are: at startup, it reports its switch settings, and if you want to use redundant altimeters, you can set one up on for an apogee delay of 2 seconds. It can also rebound from an inflight power failure of up to two seconds.........

Highly recommended! Great stuff!

Todd

Fortunately, the experience wasn't painful. But it did remind me of the old roman candles we used to hold in our hand as kids.

As for the Perfectflight 25K altimeters I have nothing but great things to say about it. Like I told Scott in yesterday's post - this guy has done his homework, beefed up his product and I personally don't think you can beat the price. I was and still am a die-hard Gwiz fan for the simple fact that you can multi-task them, but for a straight up alt....

Scott, do you have a rocsim file for your two stager?

Shane

i'll put up some pics of what i have, hopefully they will help

for arming, i was thinking of using the 1/8th inch mini phone jacks for arming, if theres an open circuit on the male part of the jack, then the other side also has an open, remove the plug, and tha part that stays with the rocket ends up with a closed circuit.

My page of pictures

Scott McNeely
NAR 79800

Scott,

Here's what I continue to think I understand - I'll go through the sequence and you see if you can see potential issues.

OK. The rocket takes off and for dicussion purposes let's say you have a burn time of 1 second. That's not very far off the rod, but let's keep going for now.

Now you've burned the one second and your timer fires blowing your chute out AND separating the rocket. Sounds like to me your sending your chute right into harms way with this setup. Yeah the pressure should separate it, but the chute' is right into the flame - not good. As for the booster being under 'chute for a lengthy period of time, I personally don't think you'll have much to worry about. Watch a dual deploy next time or Jim G's two stager or mine for that matter. It's a pretty sloppy free-fall at best. With no nose cone it will loose much of it's aerodyanmic abilities to come in severely ballistic. Trust me, we'll all be watching anyway.

But again, let's say things go well and the separation works pulling out a pin/plug in the sustainer starting another period of one second. I'd file that little pin down just a bit as they have a tendency to grab as they slide. Not too much though. At this point your tug has to cause no deviation from the straight and narrow plus you'd better have a very short distance from the the plug to the sustainer else you have the scenario I mentioned in the earlier post - a horizontal flight path and if the motor lights...well, an unguided missle. Jim German can attest to this delightful chase and "oh crap" mishap. Again, one second is a long time at that point of the game. You need it to fire almost simultaneously.

BUT again, let's say it goes as planned now you have timer that has hopefully ignited the sustainer and it's sailing along. Did you say that you'd be starting two timers in the sustainer? And if so, how long is that one set for? As you will need to carefully calculate apogee here or WAMO a nice zipper in your hard earned rocket.

Scott, you're on the right path. Just keep thinking it through. It sounds like to me you need to take up some slack in the system. I have experience with the timer you're using and I can attest to it's good and bad points.

Keep the questions coming you can't learn any younger!

Shane

Originally posted by scm86


for arming, i was thinking of using the 1/8th inch mini phone jacks for arming,



Scott McNeely
NAR 79800

Click to expand...

Thats what I use to turn on the video camera/transmitter in my Video Rocket. Works fine so far.

Now you've burned the one second and your timer fires blowing your chute out AND separating the rocket. Sounds like to me your sending your chute right into harms way with this setup. Yeah the pressure should separate it, but the chute' is right into the flame - not good. As for the booster being under 'chute for a lengthy period of time, I personally don't think you'll have much to worry about. Watch a dual deploy next time or Jim G's two stager or mine for that matter. It's a pretty sloppy free-fall at best. With no nose cone it will loose much of it's aerodyanmic abilities to come in severely ballistic. Trust me, we'll all be watching anyway.

Click to expand...

yeah, my dad built a tone genartor that uses the minplug to turn on, it has to be filed down, theres a big spot on the end of it that catches.

also, it seems that im not sommunicating the function of the timers right, or im not understanding what your saying about the zipper.

one timer will deploy the boosters chute. one will separate the stages. one will light the motor in the sustainer (and after what youve said, im thinkin of rigging up a relay to set off a bigger battery to the ignitor at the same time the stages separate.) an altimeter will deploy the sustainer chute.

the reason i said i want the booster under chute is that i read somewhere a few peoples stories having a booster go into a low ballistic trajectory, destroying the booster

how do you guys have things set up for booster deploy and separation?

Scott McNeely
NAR 79800