Subsonic G-I rocket

[Ryaer]

Hello, this is my first time posting, please inform me if this is the wrong place. I'm working on building my first scratch built rocket, and I have a few questions. Firstly, I'm building motors for it. I'm very aware of the dangers of this and treat those motors like nitro. Anyways, I'm putting a store bought high thrust G motor in it to test the aerodynamics and dual deployment, I'm worried when the full size motor is introduced (Probably a mid I motor with a long burn time) that I'll destroy my fins. They're 1/8 inch pine (Very beefy, I think) but they have a subtle airfoil on them. Software and calculations say ill be fine, but from the experiences of others, do subsonic fins have a tendency to rip off at transonic to supersonic speeds? Additionally, are dual deployment systems hard to use? It's a perfectflite stratologger, and I did order the data kit for it.

 

[Zeus-cat]

I would not use pine. You want plywood.

Dual deployment is not hard, but it can be intimidating. I suggest having someone mentor you if possible. Much easier to learn from someone with experience. Are you near a club?

 

[Andrew_ASC]

Transonic should be fine as long as duration is short. Avoid high supersonic unless confident in simulations.

 

[Ryaer]

I would not use pine. You want plywood.

Dual deployment is not hard, but it can be intimidating. I suggest having someone mentor you if possible. Much easier to learn from someone with experience. Are you near a club?

Alas, I am not in a club. I do have a teacher who did some MPR in the day, but he never did anything supersonic or with dual deployment. Any way to find a club in my area (websites, etc)?

 

[Zeus-cat]

Go to the National Association of Rocketry (NAR) website. You can also try Tripoli.

 

[Ryaer]

Sure thing. I appreciate the help

 

[Zeus-cat]

Keep in mind that you will not be allowed to launch any homemade motors at an organized launch.

 

[pondman]

Keep in mind that you will not be allowed to launch any homemade motors at an organized launch.

Unless it is a TRA launch operating under Research Rules. However, there are rules.......

 

[Zeus-cat]

Unless it is a TRA launch operating under Research Rules. However, there are rules.......

Agreed, but he's got to be at least level 2 high power certified in Tripoli. And since I bet he's never even heard of Tripoli I didn't see the need to go there and get his hopes up. And I bet he's using PVC pipe for his motor case.

 

[pondman]

Agreed, but he's got to be at least level 2 high power certified in Tripoli. And since I bet he's never even heard of Tripoli I didn't see the need to go there and get his hopes up. And I bet he's using PVC pipe for his motor case.

Carter, good points.

 

[Ryaer]

Hey now, I can read this. Homebuilt motors don't fly at clubs, it's unnecessary dangerous, I'm aware of it. I've heard of NAR and Tripoli before, and I've looked for a club. There is currently none within 70 miles of me. I'm a poor High School student with a gas guzzling car and a drive like that isn't worth it to me. I'm aware of certifications and I can receive NONE as I'm under 18. That's the reason for HPR homebuilt motors, as I'm impatient to a fault about what I like to do. The motors are PVC, as a lathe capable of turning steel or even graphite to decent +/- 10 thou margians is expensive. You and I both know this. (Trust me, I tried to make metal motors. Turns out lathe work on a shitty lathe is dangerous and makes for bad work). Additionally, I've experimented with homebrew APCP that lights like a can of WP, hybrids and a few "other" things. I simply asked a question about fin design as I don't have a lot of knowledge in transonic and supersonic airfoils, I also have a tendency to overbuild. Next time I'll just look up typical high stall-angle supersonic airfoils and copy that.

One last thing to think about, I'm one of those crazy people who love to design things and then build them. Building motors made me fall in love with rocketry and astronautics as a whole. I know more than you about motor design, because that's my passion. I asked a question about Dual Deployment and airfoils because I know that's someone's passion, and they're probably better than me at it.

 

[Zeus-cat]

To launch a high power motor you need two things from the FAA. First, you need the FAA to certify the field you will launch from as an appropriate launch location. So you need to find a farm field or other large area and get the landowner's permission to launch from there. You need to send the appropriate data to the FAA and have them review and hopefully approve the area. They will determine the maximum altitude for the site. Then on the day of the launch you will need an FAA waiver authorizing you to use the airspace for a high power launch. You may not exceed the specified altitude. If you don't do both of these you will be in violation of FAA regulations and could be subject to fines and arrest. This is why launching with a club is so much easier.

PVC is a terrible choice for motor cases. Search this site for the threads on why it is bad.

 

[Ryaer]

PVC, when done right, is fine. It's all about knowing the limits of the material you're working with. PVC isn't ideal, I'll give you that, but metals are out of the question unfortunately. Long
burn motors are a molten plastic pipe bomb waiting to happen, but unless you want to help me shop for a decent lathe, I'm SOL.

I'm aware of the FAA regulations and required forms, I got a friend at the local municipal airport helping me out, I'm currently filling out all the forms and gathering data on altitude, launch site size, and range direction and estimations. Secondly, the field is not a problem. I have around 200 acres to launch on, and a 1/2 a mile in some directions. I'm looking at, with a less than generous trust output from a I, about 5K-10K. Quite the range, I'm aware.

The whole problem is that I'm under 18, and clubs don't let you fly anything remotely serious without certs, which I can't get, it's a long workaround, but worth it.

And honestly, I don't even want a fight. Who gives a flying f*** about two guys having a spat over the technicalities of a homebuilt rocket, on a small hobby forum, at midnight? I simply want some answers to some questions I had. Thank you.

 

[Zeus-cat]

Both NAR and Tripoli have mentor programs that allow people under 18 to get certified.

 

[mdnehez]

Here is a good overview of dual deployment:
https://www.apogeerockets.com/Intro-to-Dual-Deployment

I use a stratologger myself, and they are great.

You'll want to static fire any experimental motor design several times before you should consider flying it in a rocket,
and you don't need paperwork or certs for that, just an open field somewhere and a bucket of water.

Hope this helps,
-Mike

 

[Ryaer]

Here is a good overview of dual deployment:
https://www.apogeerockets.com/Intro-to-Dual-Deployment

I use a stratologger myself, and they are great.

You'll want to static fire any experimental motor design several times before you should consider flying it in a rocket,
and you don't need paperwork or certs for that, just an open field somewhere and a bucket of water.

Hope this helps,
-Mike

Thanks. I’ll look into the article. Are ground testing them with a vacuum necessary? As I have heard of that.

 

[Nytrunner]

Thanks. I’ll look into the article. Are ground testing them with a vacuum necessary? As I have heard of that.

It may be an ease of mind thing to vacuum test your altimeter and make sure the events fire (resistor and LED work for that purpose)

I do my ground tests for charge sizing by hooking an ematch to my normal Estes launch controller. (Heck, john Coker did it with a 9v battery on his workbench)

 

[Andrew_ASC]

Hook a vaccuum cleaner up to the altimeter to trick the barometer into thinking pressure drop altitude rises. Turn it off. Charges go bang on ground. That way you don’t f*** up Recovery from a programming error while on its first flight.