Materials question

[Maxhiker14]

So me and a friend are doing a school project and chose HPR. We are planning to go 14k with a 2 stage I rocket. We ordered the tubes from Madcow Rocketry. The only thing is they are really thin and flimsy. I'm afraid that they might shred, as the rockets top speed is Mach 1.6
Has anyone used these for something similar, or have recommendations if they are safe to use? We are on a tight budget so fiberglass is not really an option. Would the apogee high power or blue tube be better? Here is a pic
So another question, the laser cutter at my high school can only cut 1/8" MDF board or at least the teacher only wants us to. Is there any reason not to use this type of wood? It seems strong enough, but I'm not sure how well it bonds with epoxy and stuff like that. The cut turned out nice though.
Thanks in advance!

 

[blackbrandt]

Welcome aboard!

One thing you may consider (I may just be reading your post wrong, if so please ignore this), but have you considered fiberglassing the tube? It's much cheaper than buying full fiberglass tubes, and adds a considerable amount of strength. It's also not too difficult.

Just curious, how much rocketry experience do you have? Also, do you have a mentor or someone who is HPR certified?


This sounds like a neat project. Could you share some more details? Maybe an OpenRocket (Open source rocket modeling and simulation program, https://openrocket.sourceforge.net/) file or at least a drawing of the rocket? Just a warning,,, two stage high power isn't an incredibly easy endeavor (I have still yet to make one successfully launch), but with a mentor/knowledgeable person helping you, it can be done.

There is a massive amount of knowledge on 2 stage rockets on the forum. Search around and you'll find plenty of threads where people have built similar sized rockets.

Once again, welcome to the madness we call TRF!

Matt

 

[Cl(VII)]

I don't think those fins are going to make mach 1.6 and stay on the rocket. Maybe 1/8" aircraft ply (the good stuff, ~11 layers). If you give them a coat or two of fiberglass or carbon fiber you would be in buisness, but I getting that is outside what you are looking to do. You can have any material cut for you...several vendors (rocketry warehouse, upscale cnc, PML, I'm sure others too) will make you fins out of varying materials.

I would also be wary of those tubes to taht speed. I know ypu can push cardboard past mach 1, but I don't know how far past. I know I launched a perfectly smooth (spirals filled) madcow 2.1" rocket to about Mach 0.6 on a high, but not crazy, acceleration flight. When I recovered it the spirals were evident from the fore CR forward...I assume there was some compression just from my pedestrian (by your flight profile standards) flight. Blue tube you can do almost unspeakable things to. I have spanked a blue tube rocket hard off the pad (>60 G) with no issues at all. This is at the cost of weight and money though.

In summary, I think you materials are HP capable, but not necessarily for the flight you envision. In general a two stage flight to mach 1.6 and 14 k on a scratch built rocket is no simple matter. I know I'm not there (yet). I'm typically not one to suggest folks back off their goals as I think most things in rocketry are a matter of study as much as experience, but this project is really ambitious/complex and for me would require some incremental build up.

You are definately going to need some HP certified assistance for this project...getting motors, launch, etc. Perhaps reaching out to someone who will help you get this thing in the air locally would be a good start.

Also, try not to take the not good natured sounding "advice" I fear you may get here the wrong way. The vast majority of us want to see people, especially school age folk, learn and pull off cool projects. We however, do want it to be done safely, and I fear a rocket as you have proposed build from those materials (especially if the 2nd stage ignition is not extreme fail safe) would be decidedly unsafe.

In any event, good luck, and keep asking questions.

 

[Maxhiker14]

Welcome aboard!

One thing you may consider (I may just be reading your post wrong, if so please ignore this), but have you considered fiberglassing the tube? It's much cheaper than buying full fiberglass tubes, and adds a considerable amount of strength. It's also not too difficult.

Just curious, how much rocketry experience do you have? Also, do you have a mentor or someone who is HPR certified?


This sounds like a neat project. Could you share some more details? Maybe an OpenRocket (Open source rocket modeling and simulation program, https://openrocket.sourceforge.net/) file or at least a drawing of the rocket? Just a warning,,, two stage high power isn't an incredibly easy endeavor (I have still yet to make one successfully launch), but with a mentor/knowledgeable person helping you, it can be done.

There is a massive amount of knowledge on 2 stage rockets on the forum. Search around and you'll find plenty of threads where people have built similar sized rockets.

Once again, welcome to the madness we call TRF!

Matt

Thank you for the advice. I have looked into glassing the tubes and it looks pretty cool, but I have never done it and it seems hard and messy. I will definitely do some more research on it. As for my experience, I am a NAR junior level 1 and have launched several high power rockets( mostly my 4 inch patriot and super DX3). We do have a mentor who is an Aerospace engineer at CU who is helping us with staging. I do have an open rocket simulation of it, so I will put that on as soon as I have the time. Stability is 3 calipers with booster and 1.75 without. Motors are I-566 booster and I-216 sustainer. Me and the same friend did a similar project last year which was basically a minimum diameter version of the sustainer and hit 8k, but we used blue tube for that.
Thank You!

 

[Cl(VII)]

Consider Soller composites fiberglass sleeves and heat shrink tubing. It is a straightforward way to glass a tube with little learning curve.

 

[Maxhiker14]

I don't think those fins are going to make mach 1.6 and stay on the rocket. Maybe 1/8" aircraft ply (the good stuff, ~11 layers). If you give them a coat or two of fiberglass or carbon fiber you would be in buisness, but I getting that is outside what you are looking to do. You can have any material cut for you...several vendors (rocketry warehouse, upscale cnc, PML, I'm sure others too) will make you fins out of varying materials.

I would also be wary of those tubes to taht speed. I know ypu can push cardboard past mach 1, but I don't know how far past. I know I launched a perfectly smooth (spirals filled) madcow 2.1" rocket to about Mach 0.6 on a high, but not crazy, acceleration flight. When I recovered it the spirals were evident from the fore CR forward...I assume there was some compression just from my pedestrian (by your flight profile standards) flight. Blue tube you can do almost unspeakable things to. I have spanked a blue tube rocket hard off the pad (>60 G) with no issues at all. This is at the cost of weight and money though.

In summary, I think you materials are HP capable, but not necessarily for the flight you envision. In general a two stage flight to mach 1.6 and 14 k on a scratch built rocket is no simple matter. I know I'm not there (yet). I'm typically not one to suggest folks back off their goals as I think most things in rocketry are a matter of study as much as experience, but this project is really ambitious/complex and for me would require some incremental build up.

You are definately going to need some HP certified assistance for this project...getting motors, launch, etc. Perhaps reaching out to someone who will help you get this thing in the air locally would be a good start.

Also, try not to take the not good natured sounding "advice" I fear you may get here the wrong way. The vast majority of us want to see people, especially school age folk, learn and pull off cool projects. We however, do want it to be done safely, and I fear a rocket as you have proposed build from those materials (especially if the 2nd stage ignition is not extreme fail safe) would be decidedly unsafe.

In any event, good luck, and keep asking questions.

Thank you for the advice. We will definitely get better materials. We will make the fins from the plywood you were saying and find a new lace to cut them. As for tube, I'm thinking blue tube. I figured the tubes we had were too weak. We do have some experience, I'm junior level 1 and have done several HPR flights. Last year me and the friend successfully launched and recovered a minimum diameter I to 8k without help. It was blue tube. For this project we do have a mentor who's an aerospace engineer to make sure we at safe and help us with the staging thing.
Thank You!

 

[Maxhiker14]

Consider Soller composites fiberglass sleeves and heat shrink tubing. It is a straightforward way to glass a tube with little learning curve.

Cool, thanks I'll look into that

 

[Cl(VII)]

Thank you for the advice. We will definitely get better materials. We will make the fins from the plywood you were saying and find a new lace to cut them. As for tube, I'm thinking blue tube. I figured the tubes we had were too weak. We do have some experience, I'm junior level 1 and have done several HPR flights. Last year me and the friend successfully launched and recovered a minimum diameter I to 8k without help. It was blue tube. For this project we do have a mentor who's an aerospace engineer to make sure we at safe and help us with the staging thing.
Thank You!

Sounds like you have a good balance of background and advising for this project. The ply I recomended I would consider the lower limit of materials for that application. Fin shape as a lot to do with what will survive flight stresses, and I don't possess the properly calibrated eyeball for exactly what material would be best for your rocket. I tend to slap a layer of fiberglass or carbon fiber on all high power fins to strengthen them (mainly to prevent landing damage), so that may lend me to over estimate material strength because I am greatly boosting the strength of all my fins. Your engineer friend should definately be able to advise you on best materials for the fins. I would be shocked if blue tube isn't up to the task as your airframe material.

Again, good luck.

 

[RocketFeller]

You may want to check if there are any composites manufacturing facilities nearby - you may be able to score some fin/cr material for free if you explain the project. As a public school teacher on a budget, I've learned that polite begging can be very fruitful....

 

[Maxhiker14]

Here is a video of last years project. It is essentially the same design of the sustainer for this project
[video=youtube_share;7-Zeh6YXjJ0]https://youtu.be/7-Zeh6YXjJ0[/video]