Build Thread: "It'll do L2"

[ArchitectOfSeven]

Hey everyone this is my first post here and also my first build thread so please be gentle with me. I'm fairly new to this hobby and am currently trying to climb the L1-3 ladder with this little creation I'm showing off here.

As a little bit of a heads up I'm one of those people that obsess over things like speed and altitude. Yes I know that this is a cert flight but I'll be damned if I don't break mach 2 while I'm at it haha.

So here is the rundown of what I'm doing:

Starting out, I had a free K520-WH, 2.5in mandrel, a full machine shop, 3d printers, and all the cf pre-preg I can handle. With those constrains I decided to make a single electronic ejection, near-minimum-diameter rocket with a custom printed 5:1 1/2 power series cone, a 2.5in cf tube, and fully tapered and airfoiled aluminum fins.

So far I have manufactured the body tube, nose cone, and avionics bay. I'm currently working on mill fixtures for the fins and will update more as I either finish machining them or give up and use cf plate.

If you are wondering, I'm part of a university rocket club that is currently building a completely in-house designed bi-prop liquid fueled rocket and I'm the poor sap that gets to make parts for it in the machine shop. That also means I can use the machines for my own projects too on occasion which explains the fin ambitions.

Another note, I plan to fire this at RRS or FAR from inside a bunker so the metal fins won't be a significant hazard to anyone.



Here is the nosecone I printed. I epoxied it together from three pieces because the printer wasn't big enough.



This is the bulkhead and attachments. Avionics are housed inside.


A view inside to see how things are laid out.


Raven feather flight computer and battery case on a detachable perfboard. Terminals on the down side to help prevent battery disconnection during burn.


Adafruit 433Mhz Radio Feather and LiPo battery for tracking beacon. Flight sims indicate 14-17k altitude and this is a small rocket so there is no way I am flying without it. I'm not sure how to mount the battery yet and am actually tempted to just leave the tape...



Views of the avionics sled and how it fits into the nose cone. Those holes are left over from when I was bolting the bulkheads together but I realized they were unnecessary so I have to deal with them when I figure out where the ejection charge wires are going.


Body and motor tubes. Not much space to work with but better then nothing...


The whole thing. The white stuff is the part that I've started to bondo. The other end is still uncovered so I can epoxy the fins in better.

Anyway, it is still a work in progress and I will update as time permits. Let me know if I'm screwing something up or if you like what you see.

 

[Rex R]

a couple of zip ties would probably work better than tape. welcome to the forum.
Rex

 

[markkoelsch]

Just curious- the nose cone is printed. What plastic are you using, and what temperature can it take before in begins to soften?


Sent from my iPhone using Rocketry Forum

 

[ksaves2]

If the NC is CF and you don't have the antenna trailing out the back from the bulkhead, your range might be limited. How much power is the tracker? 100mW? I read a bit on the Radio Feather and it's for packet radio. How will you receive the signal and
RDF to it? I would think a 70cm Beeline RDF would be receiveable with a standard Ham Radio Handi-Talkie with a true signal strength meter: https://www.bigredbee.com/zc139/index.php?main_page=index&cPath=65&zenid=oiltnpnsi4cl9ha0svklfup2m1

If your NC is radio-lucent, I'd nonetheless ground test it by setting it up a few feet off the ground. A ladder would be good or if you have an open area with a standing tree you could hoist it up a ways to simulate the rocket coming in. Then walk away and
see what range you get. Then lay it on the ground and that would be the ground footprint. If you are comfortable with the distance then you're good to go. If the NC is not radio-lucent you'll need a trailing antenna that would need to be deployed at
apogee so you can get a fix. Are you using a cutter for main deployment? Kurt

 

[ArchitectOfSeven]

The feather is for packets in normal application but I think I can program it to send out some sort of audible signal tone. If not I'm going to have to either work out a detector circuit or do something else. NC is plastic so I don't think I will have any problems there.

As for the thermal load on the cone... Well I'm going to put a significant ballast in the nose which should help absorb heat, it's actually really thick on its own, and the supersonic time period is really short. Also the power curve gives it a blunt nose so the mach waves should be detached at least a little bit. Add in the Bondo layer going over it and I think it should be okay. If not I'll be picking up a few pieces out of the sage. One thing I was wondering is what sort of paint is tough enough to not shear off during flight?

 

[ArchitectOfSeven]

Are you using a cutter for main deployment? Kurt

That wasn't the plan. I'm firing into a big open area, using radio tracking, and like to run 10k races so I figured it would be alright haha. That said, if there is much wind, I'm not firing. OpenRocket estimate for 5-10 mph winds are .5-1mi drift which is acceptable if I can keep a bead on it.

 

[mrwalsh85]

Hey everyone this is my first post here and also my first build thread so please be gentle with me. I'm fairly new to this hobby and am currently trying to climb the L1-3 ladder with this little creation I'm showing off here.

So let me understand...

You intend to cert L1, L2 with this lil' guy?

Wouldn't the metal fins be in violation of the NAR/TRA code, which you need to abide by, in order to obtain Lx certifications?

How will this work?

If not attempting certification, I suppose you can disregard my questions above.

 

[ArchitectOfSeven]

So let me understand...

You intend to cert L1, L2 with this lil' guy?

Wouldn't the metal fins be in violation of the NAR/TRA code, which you need to abide by, in order to obtain Lx certifications?

How will this work?

If not attempting certification, I suppose you can disregard my questions above.

Well, according to the rule, "Materials. I will use only lightweight materials such as paper, wood, rubber, plastic, fiberglass, or when necessary ductile metal, for the construction of my rocket.", I am allowed to use ductile metal when deemed necessary. Well for the speed that I'm projecting I'm worried that wood would come apart and I don't have any experience in making CF of FG plate. Also, the airfoil design im using would be very difficult to do with a composit material as well. As far as range safety goes, my launch site has full bunkers for when launches are taking place so there isn't any increased risk of injury from the material use. That said, I would never fly this bird at a normal NAR or Tripoli meet and I'll probably never fly it twice. And yes, it is intended for a level 2 certification, L1 is already done. I have a little photo gallery of that rocket uploaded if you want to see it.

 

[Steve Shannon]

Well, according to the rule, "Materials. I will use only lightweight materials such as paper, wood, rubber, plastic, fiberglass, or when necessary ductile metal, for the construction of my rocket.", I am allowed to use ductile metal when deemed necessary. Well for the speed that I'm projecting I'm worried that wood would come apart and I don't have any experience in making CF of FG plate. Also, the airfoil design im using would be very difficult to do with a composit material as well. As far as range safety goes, my launch site has full bunkers for when launches are taking place so there isn't any increased risk of injury from the material use. That said, I would never fly this bird at a normal NAR or Tripoli meet and I'll probably never fly it twice. And yes, it is intended for a level 2 certification, L1 is already done. I have a little photo gallery of that rocket uploaded if you want to see it.

1. The Tripoli policy which covers the use of metal in rockets is here: https://www.tripoli.org/Portals/1/Documents/Safety Code/Metal in Rocket Construction v2.0.pdf
2. However, the fact that you don’t have experience in fiberglass or carbon fiber plate does not really make metal necessary. An RSO or even your certification witness could ask you to justify your use of metal, especially for a certification flight, but it’s seldom challenged and I’m not suggesting that yours should be challenged. I just want people to consider these things and learn as much as possible. Do the fin flutter analysis. I haven’t seen anything in your rocket that makes me believe that CF or fiberglass would be insufficient. For the record I have two different rockets with aluminum fins; I’m not against it.
3. As far as your statement that the design you’re using being difficult to do with a composite, I think most people would agree that compound shapes are typically much easier to do in composite materials than in metal. I’m interested to see what you mean.
4. A certification flight must follow all of the Tripoli Safety Code, including the safe distance tables. Having a bunker does not excuse the need to observe those safe distance tables. That may seem like overkill, but It’s an NFPA thing, probably because NFPA didn’t anticipate amateur rocket clubs having bunkers, but it’s the way it is. NFPA 1127 is currently in its proposal period when interested parties can suggest changes.



Steve Shannon

 

[ArchitectOfSeven]

Well I talked to the RSO at FAR this weekend and the distance issue really is the big damper on the L2 objective. That said, I can still launch whatever the hell I want out there and the RSO loved the idea of aluminum fins. So, carrying on this is not a L2 cert flight but instead is just meant to be good fun. I have a little bit of a progress update on the rocket concerning surface finishing as well as a few pictures of things that happened at FAR on Saturday.


I've made a little progress on filling and sanding the front part of the rocket. The back part is waiting for fins and epoxy before I add filler and try to make it look pretty. Even in the front though I need to fill in low spots and the gap between the BT and NC. More updates will come as I work on things and get them ready to photograph.



These are a few pictures of my college group setting up our test fully assembled test fire. Our test wound up getting scrubbed due to electrical issues but we are going back to try again fairly soon.

Small sad thing: CSU Long Beach was there and sent a 15ft long liquid bi-prop rocket directly at the ground only about 100ft from where the bunkers were at. This in one of the few pieces left over...