When to use dual deploy?

[Sparrowhawk]

This evening, I threw together a design in OpenRocket which would reach Mach 1.2 and 1100m on a G80 motor. I'm really worried that if I built it it would just float away on its chute, never to be seen again. Should I look into dual deployment? It seems like a rather expensive endeavor, and since I'm only 15 I won't be using it on L1 and above flights any time soon. Is 1100m too high to use a single ejection?

(By the way, the goal of the design was to hit Mach 1)

 

[blackjack2564]

Show us the design so we can comment.

 

[dhbarr]

If it's thin enough to do M+ on a g80, it's going to be virtually impossible to see from 2+km away.

Even bright orange with a chromed fin would be pretty unlikely to spot.

Just my opinion, but that's based on where I launch and the haze from humidity and/or dust.

 

[Sparrowhawk]

Show us the design so we can comment.

I have attached an OpenRocket file of the design below

If it's thin enough to do M+ on a g80, it's going to be virtually impossible to see from 2+km away.

Even bright orange with a chromed fin would be pretty unlikely to spot.

Just my opinion, but that's based on where I launch and the haze from humidity and/or dust.

yeah, I doubt I'd be able to see it up there lol. Also, it's not long & thin, surprisingly it ended up having a higher mach number when I made it shorter

 

[MClark]

A lot depends on the launch site.
A small area surrounded by trees dual deployment would be good. On a desert dry lake it's not needed.
As a general rule A bright color parachute can be seen at 100 yards for each inch of diameter, (a 14" chute can be seen in clear air at 1400 yards, about a mile)

M

 

[Sparrowhawk]

A lot depends on the launch site.
A small area surrounded by trees dual deployment would be good. On a desert dry lake it's not needed.
As a general rule A bright color parachute can be seen at 100 yards for each inch of diameter, (a 14" chute can be seen in clear air at 1400 yards, about a mile)

M

I'm working with a fairly large field area, with trees interspersed throughout. Also, for a height of around 1100m, I'm not sure how feasible a ~12 inch chute would be without dual...

 

[MClark]

The 14" was just an example for distance.
If you are using electronics use the dual deployment.

 

[Sparrowhawk]

that's the thing, I'm trying to figure out whether using electronics is worth it or not cuz they're expensive as hell

 

[MikeyDSlagle]

Good with a soldering iron? Eggtimer Quark is what 20 bucks now, you just have to build it. Rrc2+ is 40 or so. How much is rocket worth to you?

And does the G80 actually have a long enough delay for your flight? You may need electronics anyway.

I use dual deploy in every rocket I can build it into. If not DD then at the least I use electronics for apogee deployment then the JLCR for pseudo dual deployment.

 

[Eric]

Eggtimer Quark.... Inexpensive as hell. Small, easy to use, and definitely worth the use.


Edit... Due to your age, dual deploy might be difficult using black powder charges.

 

[Sabrina]

Eggtimer Quark.... Inexpensive as hell. Small, easy to use, and definitely worth the use.


Edit... Due to your age, dual deploy might be difficult using black powder charges.

BINGO !!! we have a winner!!! - at 15 you can build a dual deploy rocket... but you can't purchase a G motor or use BP dual deploy without an adult mentor - 18 or older.

SPARROWHAWK - Welcome to the forum! -I recommend you BUILD and fly this "open rocket design idea of yours" - about a dozen times using smaller motors first. Gain some valuable experience with launch and recovery using less expensive E and F motors and motor deploy. Without experience, you might lose sight of the rocket at 1100 feet - a third lower than your predicted 1100 meters.

When you are ready... under crystal clear blue skies... at a club launch with dozens of people to help you watch... using a 10 foot long shiny mylar streamer for recovery (not a parachute)... Go for it!

-p.s. I'm really digging your use of the metric system (1100m). All the really cool rocket scientists use the metric system. Even ones located in the USA.

 

[Sparrowhawk]

When you say an adult mentor, does it have to be someone in the NAR or can someone like my dad fill that role? He already buys me G motors for my Estes Nike Smoke.

I’ve never tried soldering, but I’m sure YouTube can help me out. I’ll look into the eggtimer if it’s legal for me to dual deploy XD

And to answer Mikey’s question, yes the G80 has a long enough delay. Openrocket recommends 9 seconds, so a 14A will be fine. And it’s not so much that the rocket is worth a lot to me, I just really want to go for Mach 1 and try to get as close to HPR as I can without it being illegal XD

 

[jlabrasca]

I have attached an OpenRocket file of the design below

You will need more robust materials and construction. Surface mounted balsa fins are unlikely to withstand the aerodynamic forces.

I just really want to go for Mach 1 and try to get as close to HPR as I can without it being illegal XD

Unless you fly some kind of electronics, you probably won't know if you go supersonic.

As for your original question, the Jolly Logic Chute release might be outside your budget, and it would be a tight fit in a BT60 airframe (smile), but it gets you out from under the black powder restrictions.

Is there a NAR club near where you live?

NAR Club Locator | National Association of Rocketry
https://www.nar.org/find-a-local-club/nar-club-locator/

 

[Sparrowhawk]

You will need more robust materials and construction. Surface mounted balsa fins are unlikely to withstand the aerodynamic forces.

Got it, so should I update the design to incorporate through-the-wall fins? And what should I use in place of balsa?

Also, yes the Jolly Logic chute release is waaay out of my price range lol. (Keep in mind I’m just a kid who is trying to convince his parents to get him supplies for this build) There is indeed an NAR club about an hours drive from me and I launch there fairly often

 

[jlabrasca]

I was editing while you were responding.

Got it, so should I update the design to incorporate through-the-wall fins? And what should I use in place of balsa?

Copying the details of this rocket might be a good place to start your design.

https://www.apogeerockets.com/Rocket-Kits/Skill-Level-2-Model-Rocket-Kits/Aspire

 

[Nytrunner]

Got it, so should I update the design to incorporate through-the-wall fins? And what should I use in place of balsa?

1/8" aircraft plywood is good, but the higher quality stuff with more layers may be expensive.

Some inexpensive stiff fins can be made from 1/32" basswood wood-glued to an inner balsa sheet. 1/16 balsa plus the two sheets of basswood will give you a 1/8" fin that's much stronger.

Then of course theres fiberglass and carbon fiber fins, but you wont need those for awhile

 

[boatgeek]

Are you shooting for Mach or a fun, durable rocket to fly? If it’s the former, you’ll need to build light, though you’ll probably still need plywood fins. If it’s the latter, I’d use plywood fins and a heavy wall LOC tube. It’ll be hard to break Mach with that setup, though it may be possible with high power motors if you get certified later.

I second the advice to fly F and maybe E motors first so you get the hang of how your rocket flies. A good rule of thumb is that you need a field that is half as long as your rocket’s apogee. If you fly to 1100m single deploy, you’ll want a field 500m on a side. That’s pretty big.

When you think about cost of electronics, also keep in mind your other costs. A G80 costs $25 or so, not to mention the casing. Your rocket costs a fair amount of money plus your time. If your electronics let you get that back, they are worth it. Since you’re in your parents’ budget though, you might ask for the Chute Release for Christmas or if you can do extra chores to earn it. Parents love that stuff. If you do get a Chute Release, ask around at the club launch to find someone who has experience using it. There are tricks to it that will make you more successful, especially in a small tube.

Your parents can make your black powder ejection charges for you but if they aren’t gun or rocket people, they may be a lot more comfortable with you doing it and using the Chute Release.

 

[Sparrowhawk]

So I guess I’ll also have to find some place to buy new wood for fins (the hobby store near my house shut down smh).

Just out of curiosity, how does the Chute Release work for dual deploy? It would still need a charge to blow off the nose cone unless I am misunderstanding something. And my parents are neither gun nor rocket people so there’s that

 

[jlabrasca]

Got it, so should I update the design to incorporate through-the-wall fins? And what should I use in place of balsa?

Also, yes the Jolly Logic chute release is waaay out of my price range lol. (Keep in mind I’m just a kid who is trying to convince his parents to get him supplies for this build) There is indeed an NAR club about an hours drive from me and I launch there fairly often

About the fins -- there are too many degrees of freedom here to give a complete answer. For the slender swept fins you've designed, 2mm balsa is risky choice. Changing the fin profile might be easier, and cheaper, than changing the material. Not all kinds of balsa wood are the same. The stuff from Revell or Midwest Products is probably good enough, but there are options.

https://www.specializedbalsa.com/balsa_grain_classification.php

https://sigmfg.com/products/sigb470-balsa-1-32-x-2-x-36-c-grain

Likewise the surface mount/through-wall decision is impossible to pin down. TTW fins offer lots of advantages (not least, they are harder to knock off the rocket on the way to the field), but lots of HPR fliers build minimum diameter rockets where TTW is not an option.

So I guess I’ll also have to find some place to buy new wood for fins (the hobby store near my house shut down smh).

Just out of curiosity, how does the Chute Release work for dual deploy? It would still need a charge to blow off the nose cone unless I am misunderstanding something. And my parents are neither gun nor rocket people so there’s that

Are you a member of the club with which you fly? They might be your best resource for information about where to get materials.

You are correct about the JLCR, for your design you would use the motor deployment. The JLCR would hold the chute bundle closed until the rocket has fallen to some altitude.

 

[Sparrowhawk]

About the fins -- there are too many degrees of freedom here to give a complete answer. For the slender swept fins you've designed, 2mm balsa is risky choice. Changing the fin profile might be easier, and cheaper, than changing the material. Not all kinds of balsa wood are the same. The stuff from Revell or Midwest Products is probably good enough, but there are options.

https://www.specializedbalsa.com/balsa_grain_classification.php

https://sigmfg.com/products/sigb470-balsa-1-32-x-2-x-36-c-grain

Likewise the surface mount/through-wall decision is impossible to pin down. TTW fins offer lots of advantages (not least, they are harder to knock off the rocket on the way to the field better), but lots of HPR fliers build minimum diameter rockets where TTW is not an option.

Hmm... just out of curiosity how do you even hold a composite engine in on a minimum diameter

 

[Steve Shannon]

Hmm... just out of curiosity how do you even hold a composite engine in on a minimum diameter

Tape (friction fitting) works well for all sizes. I know a guy that does it for 98mm motors. Once you move away from ejection charges in the motor, there are other ways involving threaded rods screwed into the forward closure.

 

[manixFan]

Good plywood fins or G10 in the right shape can survive Mach if mated to a good phenolic or fiberglass tube. If you use a clipped delta with an upswept trailing edge you can use a smaller chute or just a streamer. (The upswept TE helps protect the fin on landing.) Your fins as designed will require a slower descent to protect them, which of course means more drift. They also have a lot of area unsupported by a root joint which is not good for any super sonic flight. The fin shape of the Madcow Go Devil is a good design example. (Although you only need to mount the fins about a 1/4" from the rear of the rocket, that keeps the CP farther back.) But the CP is a lot farther forward than your design which often requires nose weight or a longer body tube to keep the rocket stable.

Instead of the complexity and weight of dual deploy a simpler solution is to use an RDF beacon to track the rocket. They can be small enough to easily fit into a 29mm body tube. The biggest issue is the expense so you'd want to try and find someone in a club that has a tracker and will work with you on your flight. I've used RDF beacons to track flights very similar to what you want to do. As long as you are working with someone who is experienced with tracking you should be able to recover your rocket regardless of how high it goes.

I think the biggest issue you are going to run into is building it strong enough to survive Mach and still be able to use a G80. There are plenty of 29mm motors that will do it, but most of them are going to use the reloadable cases and will be H class. An H220T-14 is the ideal Mach busting motor but again, you'd have to find an adult who will help you with the motor.

Good luck,


Tony

 

[Sabrina]

Hi again Sparrowhawk !

Here is some more info you might find useful

Your dad can be your adult mentor. A NAR or TRA membership is useful for the insurance it provides - but might not be a requirement depending on the circumstances.

You can fly your rocket anywhere the law allows. You have to check your local laws. California (for example) has a lot of restrictions and most folks have to fly with a club at designated launch sites to be legal.

You have to have the permission of the land owner. Don't make the mistake of going to a park or baseball diamond and flying without permission. You or your dad might get a ticket if rockets are not legal in your area.

At a club launch, ask about the rules. The club might allow you and your dad to fly with them without a NAR (or Tripoli) membership. There might be a "Launch Fee" at some clubs. >>> Hint - you will get tons of help if you go to a club launch. You will find the most helpful and friendly people in the world at organized rocket launches. I think flying with a club is your best option!!

TTW = Through-The Wall fins using Lite-Ply Plywood. This is a very strong way to attach fins. I get all my plywood and most of my body tubes from Balsa Machining Service (I met "Balsa Bill" in 2017 at NARAM 59 - he is so nice!!!) The 1/8" plywood he sells is super-light weight, the lightest I have ever found, and much stronger than balsa.

Check-out the "Apogee Aspire". This rocket kit from Apogee Components can go supersonic or fly over a mile high depending on the motor you use. Look at this kit to get some ideas for your own rocket. Tim Van Milligan (owner of Apogee) is very nice and he has a TON of helpful Rocket Videos on YouTube.

JLCR - Jolly Logic Chute Release. Think of this as an altimeter that releases a rubber-band. [Jolly Logic website here] The rubber-band holds your parachute tightly closed, and your rocket (with the parachute ejected by the motor ejection charge) just free-falls... until it reaches a low altitude. The JLCR releases the parachute at a low altitude (you can set it for the altitudes you choose) and it works like dual-deploy but without black powder. Many folks call the JLCR a "game-changer" and one of the most innovative rocket products. I used a JLCR on my Jr L1 - M1 rocket. John Beans (owner of Jolly Logic) stands behind his products with excellent customer service.

Here's a picture of me with my Tripoli M1 rocket and my mentor - Tripoli TAP Gus P.

 

[Sparrowhawk]

So what I'm seeing here is a few primary things to work with and change:

Fin design, material and mounting method
JLCR vs Eggtimer + black powder (JLCR is expensive!)
Keeping it light but strong

Am I missing anything?

 

[JohnCoker]

The G80 isn't HPR, but it's pretty close and if you fly it in a rocket light enough for it to go Mach 1, you will definitely experience high forces on all the parts. To get a feel for the materials used in HPR rockets, check out this video on building a level 1 kit:
jcrocket.com/certify-level-1.shtml

 

[Bat-mite]

(Keep in mind I’m just a kid who is trying to convince his parents to get him supplies for this build)

Launching something over Mach 1 that gets lost or destroyed isn't the best way to convince your parents that you can be successful in rocketry. Imagine trying to convince them to buy you a car, and then getting a Corvette, driving it 120 MPH, and smashing it into a wall. Last car for you!

Take Sabrina's advice and fly it successfully on smaller motors several times. Show your parents that you know what you're doing and can be safe and successful doing rocketry. Once they are convinced, then tell them what you could do with a JLCR and see if they will get you one. At that point, try the G80.

 

[Sabrina]

...I just really want to go for Mach 1 and try to get as close to HPR as I can without it being illegal XD

OK - I totally understand this - go fast - use as much motor as legally allowed. - VAROOM!!!!

This is exactly why it's super important to know and understand all the rules and regulations regarding "low-power" model rocketry... Knowledge is power -and knowledge ABOUT power is even better!!!

Carefully read #7 in the Safety Code, and then look closely at the LAST LINE in the "Launch Site Dimension table" [low power model rocket Safety Code]

Yes - you read that correctly - keep the ready-to-fly weight under 1500 grams - and you can use TWO (count-em') TWO G80 Motors and it's still considered a class 1 "Model" Rocket - no cert required.

VAROOM!!!! - ZOOOOOOOMM!!! -better bring binoculars