Clear body section rocket flying on a G motor

[qwopguy]

Hello all,

I am a student just starting out in hobby rocketry so please forgive me if I say anything silly or make weird design decisions . I am looking to build a rocket with a clear section in the middle that a camera mounted on a dc motor can look out of, to be able to turn the camera during flight. This is for a competition that has a scoring component on payload novelty, hence the complicated idea. The clear section will be a clear polycarbonate or acrylic tube, something like this: https://www.apogeerockets.com/Build...me-Tubes/Clear-Airframe-Tube-41-6mm-18in-1-pk. The desired effect:


So having such a feature would obviously complicate many things, which is what I would like to seek your advice and opinions on. The competition is also scored based on maximum altitude, so the rocket is going quite high and decently fast (0.5 Mach). To maximize altitude we want to keep the mass down, so we would like to make the rest of the airframe out of a more conventional material like phenolic or fibreglass. Fibreglass because it is stronger than cardboard, so I can potentially make it with a thinner wall thickness for lighter. I couldn't find anything on how thin you can make a fibreglass tube, i.e. how many layers at minimum, say if I were to use 4oz fabric.

Any input will be greatly appreciated, thank you!

 

[teepot]

Of you the three materials you mentioned the Apogee tube is the lightest by far. I used a clear acrylic tube for a whole rocket. It is heavy. I have several night flying rockets that I built with the Apogee tubes. They are thin walled and very light. But with couplers or a nose cone they are strong enough to not flex at launch. I don't think they are optically clear but might be clear enough. Get one and see for yourself.

 

[K'Tesh]

Why not look into a rocket that is designed for that... The SBR Fusion comes to mind. [EDIT] I hadn't read the entire post before responding... I was reading it on my phone quickly, and couldn't look at the .ork file.

For what it's worth, Binder Design (and likely SBR's) cardboard tubes can take up to a K motor, according to Mike Fisher. And to be honest, I don't know what the mass difference is between FG and cardboard, I've only bought one FG kit, and it seemed to me to be heavier than a similar cardboard tube. For clear tubes I use Lithonia Clear Tube Guards (for T12 Fluorescent Bulbs)(Available at Lowes for less than $7 USD for 8'). It's slightly bigger than BT-60, but BT-60 parts can be shimmed to fit with the tube.

 

[smstachwick]

Regarding the camera panning, you may be able to get this with just the rocket’s natural tendency to spin. Give it a camera-rolling test flight without the DC motor if you can, or with a payload that will measure your spin rate, and see what kind of RPMs you get. If it’s suitable, you can eliminate the DC motor to save precious weight.

I think the best application for the DC motor would be if you had it hooked up to something that would keep the camera’s direction or spin rate fixed regardless of the rocket’s spin. Apologies if this was already the idea. You hadn’t specified and I wanted to cover those bases.

 

[qwopguy]

Thank you for your replies!

Of you the three materials you mentioned the Apogee tube is the lightest by far. I used a clear acrylic tube for a whole rocket. It is heavy. I have several night flying rockets that I built with the Apogee tubes. They are thin walled and very light. But with couplers or a nose cone they are strong enough to not flex at launch. I don't think they are optically clear but might be clear enough. Get one and see for yourself.

Yes the apogee tubes do seem lighter, my main concern is structural, they seem quite thin and our initial acceleration is massive (up to 27G, on a CTI G116 White Thunder). Getting one isn't really an option for me as I don't live in the US, but I found some local suppliers that do polycarbonate tubes with 1mm thick walls and might try using those. If I were to use regular kraft paper tube, would it hold up? This actually brings me to another point I was hoping to seek clarification on, is how do you properly size body tubes? I'm assuming the loads it needs to carry are shock loads during deployment and compression load when it lands.

Why not look into a rocket that is designed for that... The SBR Fusion comes to mind. [EDIT] I hadn't read the entire post before responding... I was reading it on my phone quickly, and couldn't look at the .ork file.

For what it's worth, Binder Design (and likely SBR's) cardboard tubes can take up to a K motor, according to Mike Fisher. And to be honest, I don't know what the mass difference is between FG and cardboard, I've only bought one FG kit, and it seemed to me to be heavier than a similar cardboard tube. For clear tubes I use Lithonia Clear Tube Guards (for T12 Fluorescent Bulbs)(Available at Lowes for less than $7 USD for 8'). It's slightly bigger than BT-60, but BT-60 parts can be shimmed to fit with the tube.

Thanks for the suggestions! Unfortunately we need to scratch build the rocket for the competition, I'll look at the kit and maybe see what I can adapt from it.

Regarding the camera panning, you may be able to get this with just the rocket’s natural tendency to spin. Give it a camera-rolling test flight without the DC motor if you can, or with a payload that will measure your spin rate, and see what kind of RPMs you get. If it’s suitable, you can eliminate the DC motor to save precious weight.

I think the best application for the DC motor would be if you had it hooked up to something that would keep the camera’s direction or spin rate fixed regardless of the rocket’s spin. Apologies if this was already the idea. You hadn’t specified and I wanted to cover those bases.

Yes that was the plan actually! Sorry I didn't state it explicitly. It has an onboard IMU which we will use the gyro measurements to get the state of the rocket.

 

[Tramper Al]

Crossed posts. Technology now well above my pay grade.

 

[mikec]

Why does the clear section have to be in the middle? Putting it in a payload section just below the nose cone would minimize the loads on it. This would be doable even if the rocket was dual-deploy.

I have no experience with the Apogee tubing.

 

[Grant_Edwards]

Why does the clear section have to be in the middle? Putting it in a payload section just below the nose cone would minimize the loads on it.

Keeping the heavy stuff farther forward would also increase the stability of the rocket allowing you to have smaller fins and/or less nosecone weight.

 

[green dragon]

+1 on the flourescent light tubes..... have built entire rockets from those , and flown on old h125 ( 29mm, full 320 ns ). strong enough for the G, no worries

 

[K'Tesh]

https://l.facebook.com/l.php?u=http...yGzdD2qoNVW5mc1zb9YK8_JQ1zDSHomCku9D33qEfnfuV

 

[teepot]

Thank you for your replies!



Yes the apogee tubes do seem lighter, my main concern is structural, they seem quite thin and our initial acceleration is massive (up to 27G, on a CTI G116 White Thunder). Getting one isn't really an option for me as I don't live in the US, but I found some local suppliers that do polycarbonate tubes with 1mm thick walls and might try using those. If I were to use regular kraft paper tube, would it hold up? This actually brings me to another point I was hoping to seek clarification on, is how do you properly size body tubes? I'm assuming the loads it needs to carry are shock loads during deployment and compression load when it lands.



Thanks for the suggestions! Unfortunately we need to scratch build the rocket for the competition, I'll look at the kit and maybe see what I can adapt from it.



Yes that was the plan actually! Sorry I didn't state it explicitly. It has an onboard IMU which we will use the gyro measurements to get the state of the rocket.

I've launched HPR rockets that had the Apogee clear tubes. I haven't pushed them to 27 G's though. Only half of that.