Junior L1 certification behemoth- scratch built

[brentius]

I'm planning to get my Junior L1 certification next month with this behemoth of a rocket- standing at 5'7'' (it's taller than me), it's the biggest L1 cert I've seen on here. I'm relatively new to this hobby, so please do give a few comments if I've made any mistakes. Thanks!

 

[David Schwantz]

H3ll, 5'9" is taller than most of us
Good luck with the cert. I don't do ork files. I am sure some else will be able to open it with you.

 

[Steve Shannon]

If you truly would like comments, post details rather than limiting the conversation to those who open it up in OpenRocket. What’s the predicted altitude? What’s the thrust to weight ratio?

 

[brentius]

If you truly would like comments, post details rather than limiting the conversation to those who open it up in OpenRocket. What’s the predicted altitude? What’s the thrust to weight ratio?

The predicted altitude is 455 meters on an H255. The rocket is 176 cm tall (abt 5'7'') and its TWR is about 13:1. It is 4'' diameter and uses Cesaroni 29mm reloads. (My school has a few of those lying around)

 

[brentius]

Also, here's the stats sheet:

 

[loopy]

Looks pretty good! I might recommend doing 38mm motor mount. You can always adapt down, but once you glue that thing in there, you can't go bigger if you want to.

What are you planning for motor retention? Also, guessing the shock cord runs from the bulkhead in the coupler down to the upper centering ring?

 

[NTP2]

I love it!! So low and slow! You clearly understand the importance of KISS

 

[brentius]

Looks pretty good! I might recommend doing 38mm motor mount. You can always adapt down, but once you glue that thing in there, you can't go bigger if you want to.

What are you planning for motor retention? Also, guessing the shock cord runs from the bulkhead in the coupler down to the upper centering ring?

Well, my school just happens to have a 2-grain and a 4-grain motor casing, so i figured that I would just as well use those. The original design also used a 38mm, but I switched that to 29mm after finding that the starter pack for Cesaroni 38mm motors was $160...

For motor retention, there's a motor retainer at the back (not shown).

As for the shock cord, it gets attatched to the nosecone, then it runs through the bulkhead (there's a hole in the middle), then down to the upper centering ring.

 

[loopy]

Well, my school just happens to have a 2-grain and a 4-grain motor casing, so i figured that I would just as well use those. The original design also used a 38mm, but I switched that to 29mm after finding that the starter pack for Cesaroni 38mm motors was $160...

For motor retention, there's a motor retainer at the back (not shown).

As for the shock cord, it gets attatched to the nosecone, then it runs through the bulkhead (there's a hole in the middle), then down to the upper centering ring.

I understand the reason for going 29, but my point is that you can get an adapter to fly 29mm in a 38mm mount for the time being. If you plan on being in this hobby for any length of time, you'll move up to 38mm at some point, and could still be flying this rocket at that time. Just a thought.

What kind of retainer are you using?

What is the reason for running the shock cord through the bulkhead to the nose cone? If you're planning on just doing this as recovery through the nose, it would be easier to remove the bulkhead and not worry about it.

The other option would be to attach the shock cord to the bulkhead so you can use the upper tube for things like altimeters or whatever in the future.

 

[brentius]

I understand the reason for going 29, but my point is that you can get an adapter to fly 29mm in a 38mm mount for the time being. If you plan on being in this hobby for any length of time, you'll move up to 38mm at some point, and could still be flying this rocket at that time. Just a thought.

What kind of retainer are you using?

What is the reason for running the shock cord through the bulkhead to the nose cone? If you're planning on just doing this as recovery through the nose, it would be easier to remove the bulkhead and not worry about it.

The other option would be to attach the shock cord to the bulkhead so you can use the upper tube for things like altimeters or whatever in the future.

I'm using LOC Pro's retainer, but a 29-38mm adapter... that's quite a good idea, considering that I might also use this for my Junior L2 later in the year. (I'm in the UK, and the UKRA allows under-18s to certify up to L2.) How will I stop the motor from flying into the nose cone with a 38mm motor retainer, and do I still need the motor casing?

 

[SDramstad]

Just make sure the motor that you are using has enough black powder to deploy the chute in a rocket this big. Good luck!

 

[loopy]

I'm using LOC Pro's retainer, but a 29-38mm adapter... that's quite a good idea, considering that I might also use this for my Junior L2 later in the year. (I'm in the UK, and the UKRA allows under-18s to certify up to L2.) How will I stop the motor from flying into the nose cone with a 38mm motor retainer, and do I still need the motor casing?

Aeropack and the like sell adapters that basically slide into the 38mm motor tube and allow you to then load your 29mm motor into the adapter and use the same retainer. I think the Aeropack 38/29mm adapters will work with the LOC retainers, but a question on here could probably answer that for sure.

I just don't want you to paint yourself into a corner with the build.

That being said - if there is a possibility this could be used for your L2, I wouldn't permanently attach the coupler between the two body tube sections in case you want to make it dual deploy for the future. Just a though.

 

[Capt. Eric]

You might want to spread the rail buttons out a little more. I would put the lower one down close to, if not into, the lowest centering ring. The upper button would be better closer to the center of gravity, if not above.

 

[brentius]

Just make sure the motor that you are using has enough black powder to deploy the chute in a rocket this big. Good luck!

Speaking of which, that's a problem I'm facing. I'm using Pro29 motors, which have 1.2g of BP. Is that enough, and how can I calculate the amount of BP needed?

 

[Art Upton]

Speaking of which, that's a problem I'm facing. I'm using Pro29 motors, which have 1.2g of BP. Is that enough, and how can I calculate the amount of BP needed?

It "Might" be sketchy. I would boost it just a little more, maybe .3g more?

Read up on how to BOOST the CTI charges by putting masking tape around the top closure adding more BP and folding the tape over and put some on top to keep it closed.

Perhaps looking on YouTube so you can see it being done.

 

[tsmith1315]

I'm using LOC Pro's retainer, but a 29-38mm adapter... that's quite a good idea, considering that I might also use this for my Junior L2 later in the year. (I'm in the UK, and the UKRA allows under-18s to certify up to L2.) How will I stop the motor from flying into the nose cone with a 38mm motor retainer, and do I still need the motor casing?

The thrust ring does that. The top is a LOC motor mount adapter. It is made of a motor tube, two centering rings, and a tube sized to fit your rocket's motor mount:



This one uses a thrust ring made of cardboard, but you can also just wrap masking tape around the back side to form a thick ring. I have at least one that is 30 years old with the tape thrust ring still in place. This works for motors that don't have a built-in thrust ring as well.


https://locprecision.com/collections/loc-precision-motor-mount-adaptors/products/motor-mount-adapter

 

[Capt. Eric]

Speaking of which, that's a problem I'm facing. I'm using Pro29 motors, which have 1.2g of BP. Is that enough, and how can I calculate the amount of BP needed?

There are a few calculators online that can help you figure out the required amount. Here are a couple:

https://rocketrycalculator.com/rocketry-calculator/bp-estimator/https://www.insanerocketry.com/blackpowder.html

 

[NTP2]

(I'm in the UK, and the UKRA allows under-18s to certify up to L2.)

Lucky!!!

 

[thzero]

I'm planning to get my Junior L1 certification next month with this behemoth of a rocket- standing at 5'7'' (it's taller than me), it's the biggest L1 cert I've seen on here. I'm relatively new to this hobby, so please do give a few comments if I've made any mistakes. Thanks!

Maybe scale back ambitions?

There are some good Icarus kits, like from LOC.

As far as ejection... Calculator and testing, which is harder without an altimeter or other device.

You can compare your design with other know designs from vendors. If your volume that is being pressurized by the ejection charge is no bigger than a proven design, then you might be ok.

 

[brentius]

Maybe scale back ambitions?

There are some good Icarus kits, like from LOC.

As far as ejection... Calculator and testing, which is harder without an altimeter or other device.

You can compare your design with other know designs from vendors. If your volume that is being pressurized by the ejection charge is no bigger than a proven design, then you might be ok.

I mean, ProjectAir's carbon fiber rocket looks even heavier than this one and has a longer payload section and flew on Pro29 motors, so 1.2g probably will do... i guess.

 

[brentius]

Lucky!!!

Yeah, but we have tons and tons of laws around rocketry. We can't buy black powder, and we can't make our own motors due to apcp being classed as a bomb. Our school's rocketry society once built a 38mm hybrid motor with nitrous oxide and acrylic once, but nitrous oxide's been classed as a drug recently due to the sheer amount of people getting high from it. As for amateur liquid rockets, I've thought about making something similar to Half Cat Rocketry's Half Cat, but that also requires nitrous

 

[NTP2]

Yeah, but we have tons and tons of laws around rocketry. We can't buy black powder, and we can't make our own motors due to apcp being classed as a bomb. Our school's rocketry society once built a 38mm hybrid motor with nitrous oxide and acrylic once, but nitrous oxide's been classed as a drug recently due to the sheer amount of people getting high from it. As for amateur liquid rockets, I've thought about making something similar to Half Cat Rocketry's Half Cat, but that also requires nitrous

But at least you get to say you build a rocket fueled by drugs! And you still can’t do experimental here but at least you might be able to get into the research forum with that L2 I’m not sure.

 

[brentius]

But at least you get to say you build a rocket fueled by drugs! And you still can’t do experimental here but at least you might be able to get into the research forum with that L2 I’m not sure.

Well, to get into the research forum, I have to be a US national, which I'm not. (stupid ITAR) but the L2 is something I'm actively chasing, and it's too early to tell (I'm in Year 9 over here, which is Grade 8 in the States), but I'm eying a university in the US, so maybe I might actually get to build a motor in the future.

Over here, secondary school starts at Year 9.

 

[NTP2]

Well, to get into the research forum, I have to be a US national, which I'm not. (stupid ITAR) but the L2 is something I'm actively chasing, and it's too early to tell (I'm in Year 9 over here, which is Grade 8 in the States), but I'm eying a university in the US, so maybe I might actually get to build a motor in the future.

Over here, secondary school starts at Year 9.

Ok I need to go sit down and figure out how the UK school’s work. Because it seems like you’re saying that college starts after middle school??!

 

[brentius]

Ok I need to go sit down and figure out how the UK school’s work. Because it seems like you’re saying that college starts after middle school??!

Yes, it does. Theres no middle school here, its just primary and secondary schools.

 

[NTP2]

Ok I need to go sit down and figure out how the UK school’s work. Because it seems like you’re saying that college starts after middle school??!

Ok Wikipedia did not help so could you explain it to me as if I was 3? Please!

 

[Art Upton]

Secondary School Is High School.