Well, first off, welcome to the hobby and the forum. You're definitely doing the right thing by asking questions and being safe. What I've already said about this question is true of lots of questions you are likely to ask: be as specific as you can, since this will help us to help you.
Next, some general advice:
- I'd recommend building a few kits of lower power rockets and then working your way up. The rocket kits designed around 18 mm A, B, and C engines may seem like little toys, but the fact is that you can learn a lot by building a few of those while the risks and costs are a lot lower than jumping up to G and H motors and a rocket build for them.
- Is there any amount of enthusiasm for the hobby in your area? We encourage people to join a local club if there is one, since that would hook you up with a place to launch and with people to learn from in person.
- Here in the US, and in Canada, and in many countries there are rules about high power rocketry. Here that basically means anything using H motors and bigger (though there are some other situations that make a thing count as high power also). I don't know what EU or Spanish rules exist, but you'd best find out.
Now, back to your original topic. Some rockets are made with no motor tube inside the body tube at all, known as "minimum diameter" rockets. While they present some interesting design challenges in high power, you can see that there is no real minimum gap.
Attaching one's parachute harness to the forward centering ring is just one of many ways to attach it. You're right that it's a nice way, and you're right that with only 3.5 mm it's not suited to this design. So you'll use another method.
Any more such concerns you may have along similar lines will bring a similar answer: there's always another way to do it. There's nothing wrong with your tube sizes.
Thanks for the welcoming and kind message. I'll try my best to always be as specific as possible.
I know that the best way to get into rocketry would be to start with some kits, building up my knowledge and crafting skills with time and experience, I really do, and I feel "wrong" for doing it this way and not the way it's common (it's the way it is for a reason, that's for sure). Why do I want to do it this way and stick with it, atleast for this project? Because (this is something I explained on my introduction post to the forum, in case someone wanna read it more in detail) in November I'll be presenting a research project called "design and construction of an experimental rocket". I really want to be who has investigated, designed and constructed the hole rocket and motor (as far as possible), to know why things are the way they are. Also, this project would serve myself as my introduction to rocketry, bearing in mind that if everything goes according to plan, in september 2023 I should be starting the aerospace engineering career.
I know that there are dangers 1) by building an experimental rocket --> handmade motor, and 2) starting from this point, but after a long time trying to decide to do this or that or this way or another, I decided to do this but with the most research possible and doing it safely. I started doing my research around november last year till now, and since may/june I spend almost every day working on this.
I'm aware that at least one amateur rocketry group exists here in Spain (a Tripoli prefecture) but they don't seem to be really active (not saying they are, just seems like to me) and tend to do launches really far away from where I live, given that I'm currently studying again, it's impossible for me to go to those launches. This said, I'll try to gather more info about it and join it if I can, but given that I like the experimental side of rocketry, maybe that will be an inconvenience.
I have searched for the rules and legality of rocketry here in Spain but I've found that for the moment it's an unregulated subject. They do regulate drones, aeromodelling, etc but not rocketry. So what I'll do is follow the official safety rules followed in the US to do it the best I can.
I'm aware of minimum diameter rockets and I have been questioning if mine should be designed as one but I think I'll stick with a "normal". One of the main doubts I have at the moment is about the motor retaining system I should use, but that's another topic I'll probably post about later (I feel like I'm posting too much and feel kinda bad). Thought there maybe was a jump from a min dia rocket to an stablished difference in diameters.
Then my question is: in case I don't change the tubes, what method could I use to link the lower BT to the av bay (I'll mostly sure add one)? I've seen that some people glue the shock cord to the BT itself but it could maybe unglue with the ejection force or brake the wall if thin enough, right?
Thanks again for your comment!
I appreciate it.
~Alex
lol
