20,000 feet or BUST!!

[Neutronium95]

At my launch site, there is a challenge to hit 20,000 feet, but not break the wiaver of 25,000 feet. All of the other atempts have been single stage M motors. I plan to do it with a two stage 29mm rocket with two CTI I224 s. The body tubes will be carbon wrapped Apogee tubes that are saturated in epoxy. Fins will be .0625" G10, and nose will be a composite Von Karmen design. (In the simulations it is a cone to get a more accurate sim).Electronics will be a Raven and a beeline.
Now for the hard parts https://www.nar.org/hpcert/jrhppreq.html
scroll down to section 5.
I'm not allowed to use electronic deployment, or possabley staging.
To deal with these issues, I just might have to put my dad's name on the flight card.
Also, I want some tips on making the nose cone, I was thinking about making it on a foam male mold, then using acetone to dissolve the foam.
Any input is welcome

View attachment 20k.rkt

 

[ScrapDaddy]

Just some quick notes, if you are allowed to stage, you will need electronic deployment, or the streamer will deploy at 135 MPH with a 15 second delay and if you use the 15 second delay in the booster to kick out the chute, it will deploy at over 87 MPH, and also, if you allow this to deploy, you will only reach a total of 8087 feet.



Noe:i am veiwing using open rocket.

 

[cjl]

First, I would not attempt a two stage without electronic deployment in the top stage. If you don't have electronics in the top stage, and the top stage doesn't light, you just guaranteed that it will lawn dart.

Looks like an interesting project though - 20k is quite high. I haven't made it there yet.

 

[Neutronium95]

I have decided to technically have my dad fly it, but mention myself in the comments section of the flight card.

 

[The EGE]

Wow. Just wow. I thought I was ambitious. This sounds very cool, keep us updated.

 

[ben_ullman]

I have decided to technically have my dad fly it, but mention myself in the comments section of the flight card.

Your thinking to hard about that man. Just build the rocket. Dont worry about flying it, that will get itself taken care of if you trully know what you are doing.

Ben

 

[DTH Rocket]

!!!!!!!!!!!!!!!!!!!!!!!!!!

Very cool and awesome. I'm glad you had the ingenuity to think outside the box, even though you're only Jr. L1! Hope you hit 20k.

~DTH Rocket

 

[Neutronium95]

Just a few notes: Due to length concerns, I am swithcing to BMS tubes that will be soaked in epoxy and given a thin layer of carbon. The tradeoffs are: I don't need to join two tubes without a coupler, but the BMS tubes are thicker, so will have more drag and will weigh more. Any source for a longer thinner 29mm tube would be appreciated. Also for running wires for the stage seperation charge and second stage ignition I was thinking of using this stuff https://www.geckocable.com/index.html Also, I used the optimum mass function of Roc Sim, and got a very weird graph last night, I'll post it when I get to my desktop.

 

[bobkrech]

At my launch site, there is a challenge to hit 20,000 feet, but not break the waiver of 25,000 feet. All of the other attempts have been single stage M motors. I plan to do it with a two stage 29mm rocket with two CTI I224 s. The body tubes will be carbon wrapped Apogee tubes that are saturated in epoxy. Fins will be .0625" G10, and nose will be a composite Von Karmen design. (In the simulations it is a cone to get a more accurate sim).Electronics will be a Raven and a beeline.
Now for the hard parts https://www.nar.org/hpcert/jrhppreq.html
scroll down to section 5.
I'm not allowed to use electronic deployment, or possibly staging.
To deal with these issues, I just might have to put my dad's name on the flight card.
Also, I want some tips on making the nose cone, I was thinking about making it on a foam male mold, then using acetone to dissolve the foam.
Any input is welcome

Sorry to repeat the rules but a Jr. Level 1 Participant is not allowed to launch 2 I motors as the total impulse is >640 NS. 2 H motors are ok, but you would need electronics to stage an APCP motor, and you will need active recovery on the booster.

Additionally 1/16" fins may be marginal considering fin flutter.

Bob

 

[troj]

Just a few notes: Due to length concerns, I am swithcing to BMS tubes that will be soaked in epoxy and given a thin layer of carbon.

No need to soak them in epoxy, especially if adding the carbon -- it'd just be adding weight, with no real benefit.

Also for running wires for the stage seperation charge and second stage ignition I was thinking of using this stuff https://www.geckocable.com/index.html

Why not just epoxy a thin tube (brass or CF) inside the airframe, and pass wires through that? Less expensive, and easier to replace the wire, should the need arise.

-Kevin

 

[Neutronium95]

bobkrech- I will be designing and building it, and my dad will fly it. And troj, coud you show a picture, because I can't see that working without interfering with the motor.

 

[troj]

And troj, coud you show a picture, because I can't see that working without interfering with the motor.

Wait.... You planned to run the wires inside the motor mount, alongside the motor casing? If so, I'd plan on them being single use, if it even makes it possible to still slip the motor in.

-Kevin

 

[JimJarvis50]

I use gecko cable for my two-stager (the 422 I believe). After you stick it down, it is possible to peel off the top protective layer and then cover that with scotch tape. This makes it really thin.

This works for my 75mm and larger motors, but I think it would be hard to do at 29mm. It would take a pretty loose fit around the motor and the curvature of the motor would make it difficult to manage the wires below the motor.

In addition, if you're doing this minimum diameter with the motor as the coupler, then the gecko wires would actually be part of the coupler. I have made this work by sanding a channel into the receptor (i.e., the part that the motor slides in to), but this would not be possible for 29mm.

Jim

 

[Neutronium95]

Thank you for your advice, and I guess that I will have to redesign how I will run the wires. Thanks!

 

[bobkrech]

In many commercial rockets, wires are run externally on the outside of the stages in wire conduits. Easy to service and easy to connect.

DB pins and sockets are a good way to go, however it is probably simpler to have an electronics bay between the booster and the second stage. A timer would light the second stage motor, and the a secondary channel would deploy the booster chute a few seconds later.

The second stage recovery really should have another single or dual channel recovery altimeter. You could also use the altimeter to ignite the second stage if you used ejection charge recovery deployment for the booster, but the wiring is a little more complicated.

Bob

 

[redsox15]

going along with jim jarvis' idea going outside the body tube to wire the igniter. I have attached a rough drawing of something that might work. It is a head on view of the bottom of the rocket with an tube that you can run the igniter through to the engine. It is functionalable as well as cosmetic. Just my :2:

Matt

 

[Neutronium95]

Right now, I am kicking around a few ideas to run wires with little or no drag increase. If I remember correctly, the launch lug on a model rocket can account for up to 15% of the drag. (yes I know that there are ways to minimize the drag, but due to the motor length the tunnel would be more then a foot long, so it would still add a lot of drag.) While I haven't had the opportunity to model a tunnel on the outside of the second stage, I am fairly sure that it would make it very hard to make the 20,000 foot goal. Thank you for your input as always.

 

[redsox15]

In all honesty, at mach 2 (says the sim) is a small tube for an igniter or launch lug going to make that much of a difference? Just my opinion, not trying to shoot down your ideas. Best of luck with the build and launch keep us updated!

Matt

 

[Neutronium95]

I am trying to squeeze as much performance out of this rocket, including tower launching and a von karmen nose cone, I extremely dislike the idea of the tunnel, because it will hamper performance. (sorry if that sounded rude, I just am very strongly opinionated about this. I will run the sims for due diligence and I just want to thank you for your input.) I have been looking at Mc Master Carr, and I think that I have pieced together an idea that will build tubes for wires into the thicker BMS cardboard tubes, but this forum got me started on it, thank you.

 

[troj]

I am trying to squeeze as much performance out of this rocket, including tower launching and a von karmen nose cone, I extremely dislike the idea of the tunnel, because it will hamper performance. (sorry if that sounded rude, I just am very strongly opinionated about this. I will run the sims for due diligence and I just want to thank you for your input.) I have been looking at Mc Master Carr, and I think that I have pieced together an idea that will build tubes for wires into the thicker BMS cardboard tubes, but this forum got me started on it, thank you.

Why not stick with your original wiring idea, but run them on the outside of the airframe, then protect them with a single wrap of lightweight fiberglass over the top?

The only disadvantage is that you have no way to replace the wires, should something happen to them.

-Kevin

 

[Adrian A]

If you get enamel-coated magnet wire from Radio Shack, you can probably fit the wires between the motor and the airframe. People often overestimate the size of wire required. If you use a dipped Q2G2 ignitor, you only need 200 mAmps, and a small li-poly cell will easily provide that, even with a few of Ohms of resistance from using a few feet of hair-thin wire.

 

[Neutronium95]

Adrian, the magnet wire idea sounds intriguing, but is there a possibility of the wires shorting across the motor case? Thanks for the great tip.

 

[Adrian A]

Adrian, the magnet wire idea sounds intriguing, but is there a possibility of the wires shorting across the motor case? Thanks for the great tip.

The insulation, though thin, is pretty robust. I experimented with taking the motor in and out, and testing the continuity. I never got any shorts. I did, however, have a wire break at separation in my flight. Assuming you're using the motor as a coupler, be sure to protect the wire with some tape at least, and don't over-do the separation charge. It's not a safe ground test in a flight-like configuration, however (with the motor loaded), so that one is kind of tricky.

 

[daveyfire]

In all honesty, at mach 2 (says the sim) is a small tube for an igniter or launch lug going to make that much of a difference?

Yea, it'll be *worse* at Mach 2. Your avatar is a good explanation of why!

 

[Neutronium95]

Is there a specific gauge magnet wire that you would recomend Adrian? Also for the booster, I will be using a perfectflite altimeter to deploy the parachute. Once again thank you for all of your advice, parts will be ordered and construction will start next week. I will post an improved rocsim file soon

 

[Adrian A]

Is there a specific gauge magnet wire that you would recommend Adrian? Also for the booster, I will be using a perfectflite altimeter to deploy the parachute. Once again thank you for all of your advice, parts will be ordered and construction will start next week. I will post an improved rocsim file soon

Use the largest wire that will fit, mostly for strength. The Radio shack magnet wire pack has several different gauges, so you can try several to see what works best. The red wire is what I used for my 38mm 3-stage attempt.

 

[rockets2000]

Just thinking out of the box here, but could you cut or dremel a long slot(s) in the inside of the airframe to run the wires? Obviously, cut only as much material out as you have to...Then you could coat the inside of the cut slots with epoxy for strength or even launch lug stock cut lenghtwise to fit. If you're covering it in fiber then I doubt you'll have much of a stress path.

 

[Neutronium95]

The G10 fin stock arrived yesterday. I decided to go with 3/32" G10 for the fins instead of 1/16". I am planning on using the raven for the electronics in the upper stage. I am using it to: seperate the stages, light the second stage and deploy the parachute. Now there are four outputs, and I am using three functions. Should I use the fourth output as a backup for the main charge, or deploy a reefed chute and de-reef it at a low altitude. What is the prefered method for cutting G10? My dad is of the opinion that we should score an snap it, but I just want a second opinion.

 

[cjl]

Scoring and snapping probably won't work well, as the fibers will not necessarily break cleanly. I use a jigsaw with a tungsten carbide abrasive blade.

 

[Adrian A]

The G10 fin stock arrived yesterday. I decided to go with 3/32" G10 for the fins instead of 1/16". I am planning on using the raven for the electronics in the upper stage. I am using it to: seperate the stages, light the second stage and deploy the parachute. Now there are four outputs, and I am using three functions. Should I use the fourth output as a backup for the main charge, or deploy a reefed chute and de-reef it at a low altitude. What is the prefered method for cutting G10? My dad is of the opinion that we should score an snap it, but I just want a second opinion.

I think a reefing adds a lot of risk, so unless you have a proven reefing system, and/or you can't do a regular dual deploy setup and/or you can't stand the potential drift from apogee, I'd recommend against it. I'm always having fun experimenting with novel recovery setups, but I lose a lot of rockets that way, too.

The best way to cut G10 that I know of is a diamond blade tile saw. I have a cheap consumer model that works great for that, wet or dry. A rotozip or even a dremel work o.k. too. I have destroyed a hand tool miter saw on FWFG tubing.