Best material to use for airframe

[Tamir Friedman]

Hello,

We are currently starting to design out first mach rocket. We are planning on using K805G motor (by Aerotech) for said rocket, and we want to have an electronic bay fixed inside of the airframe using screws. Do you have any suggestions to the best material to use for this kind of project airframewise? We spoke about using carbon fiber tubing, but I think it might be an overkill pricewise. Based on early simulations we ran with rocksim we expect to reach to approximately 1.5 mach with the rocket.

Thank you in advance!

 

[thzero]

Sounds like you have no real experience. Perhaps you should start with some midpower rockets first?

There are plenty of threads on the forum about people going mach, and what airframe materials they used. K is a level 2 motor, so if you are certified or have a certified instructor/coach/whatever, then one should be able to figure out the appropriate materials.

 

[heada]

Basic cardboard/paper based tube will work and is the cheapest but is also the weakest. LOC is a good source for this. Phenolic impregnated paper is the next best but is heavier and more brittle. Public Missiles (now owned by LOC) is a good source. Next is fiberglass. FWFG is quickly becoming the standard for most high power kits and is stronger than cardboard or phenolic but is heavier than both. Composite Warehouse or Wildman are 2 good sources for FWFG. Lastly is CarbonFiber. CF is strongest and lightest but is expensive and in nearly all cases, overkill for the purpose. A huge drawback to CF is that it is EMF opaque meaning that if you have any radio based telemetry, you need a section that is not CF in order to transmit out. All of these can handle up to M2 for a short period of time. If you're going to be in M2+ for extended time, I would recommend FWFG.

And as said above, I would highly recommend that you build and learn on lower power motors and rockets before jumping to a K for your first high power rocket. The cost of a few H motors and a smaller FWFG kit is lower than the cost of total loss on a larger rocket on that K motor.

 

[Tamir Friedman]

Basic cardboard/paper based tube will work and is the cheapest but is also the weakest. LOC is a good source for this. Phenolic impregnated paper is the next best but is heavier and more brittle. Public Missiles (now owned by LOC) is a good source. Next is fiberglass. FWFG is quickly becoming the standard for most high power kits and is stronger than cardboard or phenolic but is heavier than both. Composite Warehouse or Wildman are 2 good sources for FWFG. Lastly is CarbonFiber. CF is strongest and lightest but is expensive and in nearly all cases, overkill for the purpose. A huge drawback to CF is that it is EMF opaque meaning that if you have any radio based telemetry, you need a section that is not CF in order to transmit out. All of these can handle up to M2 for a short period of time. If you're going to be in M2+ for extended time, I would recommend FWFG.

And as said above, I would highly recommend that you build and learn on lower power motors and rockets before jumping to a K for your first high power rocket. The cost of a few H motors and a smaller FWFG kit is lower than the cost of total loss on a larger rocket on that K motor.

Hey. First of all thanks for the response, we will sure check it out.

It is actually not our first high powered rocket. Our previous rocket used the J425R Aerotech rocket motor and it was a big success for us. The problem for us on testing our skills on lower level motors is that it is really hard to import explosives here. In order to get our J425 we had to join in on a big order involving a big company in order to get reduced import fees, and even then then the import of it cost us around 1200$. We have the opportunity now to get a K motor from a local vendor this time around, which mean we will get it for much cheaper then the J425 cost us before. Our mentor who is working for a big company suggested we will use a fiberglass airframe for our current project due to us reaching mach 1, but I wanted to get second opinions over here. On our last rocket we got carbon fiber airframe and it was extremely expensive. Even though the project was a success I was looking to make it more cost effective this time around.

 

[heada]

In that case. filament wound fiberglass (FWFG) gives great strength per weight and should survive a M2 nominal flight without issue. The paint would more than lightly be the only thing damaged. Since it is becoming very popular in the US, the costs are fairly low but I'm not sure about the costs of shipping and import outside of the US. I would search for a local supply first.

If this is rocket is expected to be used for a limited number of flights and you have good build skills, then cardboard/paper will still be strong enough and lighter than FWFG and cheaper still. If the expectation is that this rocket is to be flown dozens of times or you feel your build skills are not up to it, then FWFG is the best way to go while on a budget.

 

[Tamir Friedman]

In that case. filament wound fiberglass (FWFG) gives great strength per weight and should survive a M2 nominal flight without issue. The paint would more than lightly be the only thing damaged. Since it is becoming very popular in the US, the costs are fairly low but I'm not sure about the costs of shipping and import outside of the US. I would search for a local supply first.

If this is rocket is expected to be used for a limited number of flights and you have good build skills, then cardboard/paper will still be strong enough and lighter than FWFG and cheaper still. If the expectation is that this rocket is to be flown dozens of times or you feel your build skills are not up to it, then FWFG is the best way to go while on a budget.

Thank you!

 

[Tim51]

Thank you!

Remember you can also strengthen Loc tubing or PML phenolic with a wrap of fibreglass cloth. 200g fg cloth is a good choice. If I recall correctly PML used to recommend a fibreglass wrap to mach proof their phenolic. Good luck with your build - and please post some pictures of the build / flight

 

[StreuB1]

Fiberglass wrapped cardboard tubing is a great low-cost alternative to fiberglass tubes when you need that extra strength. Its pretty easy to do and you can achieve really good results with it!

 

[Tamir Friedman]

Remember you can also strengthen Loc tubing or PML phenolic with a wrap of fibreglass cloth. 200g fg cloth is a good choice. If I recall correctly PML used to recommend a fibreglass wrap to mach proof their phenolic. Good luck with your build - and please post some pictures of the build / flight

Fiberglass wrapped cardboard tubing is a great low-cost alternative to fiberglass tubes when you need that extra strength. Its pretty easy to do and you can achieve really good results with it!

We actually have some extra fiberglass fabric and epoxy resin left from our first HPR. We used it to strengthen the fins which were made out of balsa wood. I assumed we might be able to use it to strengthen the body tube, but I was scared it would be much harder because of the round shape of it. I guess I could try find some youtube tutorials and see if it is up our valley

 

[UhClem]

Fiberglassing tubes is easy. Most of what I know about the subject I learned from John Coker.

The one thing I do different is that I don't bother to support the tube but instead double the bag length and push the extra all the back down the inside of the tube. That way there is nothing trying to crush the tube.

 

[Tim51]

We actually have some extra fiberglass fabric and epoxy resin left from our first HPR. We used it to strengthen the fins which were made out of balsa wood. I assumed we might be able to use it to strengthen the body tube, but I was scared it would be much harder because of the round shape of it. I guess I could try find some youtube tutorials and see if it is up our valley

The main thing is to give yourself the time, materials and space to do the job. Make sure you have everything you need ready, and study the technique beforehand. Know your weights, your cure times etc. In my opinion 'glassing is not something you can rush, or do 'on the side' whilst focusing on something else.

 

[StreuB1]

The main thing is to give yourself the time, materials and space to do the job. Make sure you have everything you need ready, and study the technique beforehand. Know your weights, your cure times etc. In my opinion 'glassing is not something you can rush, or do 'on the side' whilst focusing on something else.

I could not agree more.

 

[jderimig]

We actually have some extra fiberglass fabric and epoxy resin left from our first HPR. We used it to strengthen the fins which were made out of balsa wood. I assumed we might be able to use it to strengthen the body tube, but I was scared it would be much harder because of the round shape of it. I guess I could try find some youtube tutorials and see if it is up our valley

I would recommend just buying fiberglass airframe tube and be done with it if you are able. Avoid the time sucking activities....

 

[OzHybrid]

The answer to any "what's the best"(glue, paint,wood,tube,bolt, metal,any other generic thing) is simple.

It depends.........
Lets start with-

Where are you?

This will give us an idea of what stores/ materials are available to you. There might be someone in that country near you that you have no idea about. I discovered that SARA(Scottish amateur rocketry association) was 10 miles from me when I was a kid. If only I'd known...

What's your budget?

Seems goodish from the description..

What is your objective?

End game and immediate goals. Where are you now and what are you wanting to achieve.

What are your specific goals for this rocket?

Attach at a minimum an Open Rocket file. This will also give us an idea of whether you have the design skills.

To answer your specific question. At Mach 1.5 the material you choose for the tube must be able to take some friction heating(depends on how long you'll be at that speed) and survive the loads it may be subjected to(including camera lumps you strap to the side. These don't make much difference below mach but can cause an otherwise stable rocket to become unstable as you transition and go over Mach. A rocket that is unstable above Mach is an EX Rocket very quickly)
The answer is anywhere between cardboard to stainless steel.... ( that also depends on the rule set(s) you launch under)

If you are going above Mach, sim it in Open Rocket first and then check the mach performance in RAS Aero http://rasaero.com/ Unfortunately only runs on Windows. ( Linux version Chuck? )
Supply both files for us to look at......

Help us to help you.

Good luck
Norm

 

[Tamir Friedman]

The answer to any "what's the best"(glue, paint,wood,tube,bolt, metal,any other generic thing) is simple.

It depends.........
Lets start with-

Where are you?

This will give us an idea of what stores/ materials are available to you. There might be someone in that country near you that you have no idea about. I discovered that SARA(Scottish amateur rocketry association) was 10 miles from me when I was a kid. If only I'd known...

What's your budget?

Seems goodish from the description..

What is your objective?

End game and immediate goals. Where are you now and what are you wanting to achieve.

What are your specific goals for this rocket?

Attach at a minimum an Open Rocket file. This will also give us an idea of whether you have the design skills.

To answer your specific question. At Mach 1.5 the material you choose for the tube must be able to take some friction heating(depends on how long you'll be at that speed) and survive the loads it may be subjected to(including camera lumps you strap to the side. These don't make much difference below mach but can cause an otherwise stable rocket to become unstable as you transition and go over Mach. A rocket that is unstable above Mach is an EX Rocket very quickly)
The answer is anywhere between cardboard to stainless steel.... ( that also depends on the rule set(s) you launch under)

If you are going above Mach, sim it in Open Rocket first and then check the mach performance in RAS Aero http://rasaero.com/ Unfortunately only runs on Windows. ( Linux version Chuck? )
Supply both files for us to look at......

Help us to help you.

Good luck
Norm

So I will answer you questions:

1. I live in Israel. Hobby rocketry around here is not a thing and people at large have kind of bad taste when they hear the word "rocket" around here. Couple of years back we started the HUJI rocketry club in order to try and make hobby rocketry around here a thing. What does it mean for us? It mean there are no hobby rockets shops around here that we can get supply from, and basically every person that can help us out is military adjacent. I won't go with you over the bullshit we had to go through to launch a J425 motor powered rocket, but it was... a lot xD. (we even made it over the news):

https://www.jpost.com/israel-news/b...dents-launch-rocket-in-southern-israel-684292
It means that basically all of our rocketry supply are being shipped from overseas or being custom made using a lot of money and expensive equipment (for example we had to pay a lot of money to get our rocket's tailcone 3D printed).

2. Since we are a University club we get some budget from the University, but most of it comes from donations from private people who help us out. Under the right pressure we could squeeze the budget to create an overkill rocket, but that is not our goal here. We are trying to make this club a lasting thing which mean we need to show that we "supply the goods" in exchange to the outside support we get. In our first project we went with the carbon fiber tubes we ordered from the US, but those were very expensive and as I said we are trying to reduce the cost of the whole ordeal to save face. Our mentor is a person who worked for many years on actual rockets, and as much as I respect his expertise I know he comes from an industry that burns millions of dollars like nothing, and I am not sure he comprehend the idea we basically depending on donations. Most of our electronics are also donated to us from private companies for us to test them out (for example an IMU)

3. Our current objective and immidiate goals is to launch a rocket that will pass the 1 mach barrier (even if for a short time), send telemetry in real time to a ground station and land itself safely in a state that allow us to launch it again in the future. I am less involved in the telemetry, but they guys are building up the flight computer from 0.

4. I am attaching a rocksim file (I don't have an open rocket one, I hope it is ok).

Thank you for using your time to help novices like us

 

[Tamir Friedman]

So I will answer you questions:

1. I live in Israel. Hobby rocketry around here is not a thing and people at large have kind of bad taste when they hear the word "rocket" around here. Couple of years back we started the HUJI rocketry club in order to try and make hobby rocketry around here a thing. What does it mean for us? It mean there are no hobby rockets shops around here that we can get supply from, and basically every person that can help us out is military adjacent. I won't go with you over the bullshit we had to go through to launch a J425 motor powered rocket, but it was... a lot xD. (we even made it over the news):

https://www.jpost.com/israel-news/b...dents-launch-rocket-in-southern-israel-684292
It means that basically all of our rocketry supply are being shipped from overseas or being custom made using a lot of money and expensive equipment (for example we had to pay a lot of money to get our rocket's tailcone 3D printed).

2. Since we are a University club we get some budget from the University, but most of it comes from donations from private people who help us out. Under the right pressure we could squeeze the budget to create an overkill rocket, but that is not our goal here. We are trying to make this club a lasting thing which mean we need to show that we "supply the goods" in exchange to the outside support we get. In our first project we went with the carbon fiber tubes we ordered from the US, but those were very expensive and as I said we are trying to reduce the cost of the whole ordeal to save face. Our mentor is a person who worked for many years on actual rockets, and as much as I respect his expertise I know he comes from an industry that burns millions of dollars like nothing, and I am not sure he comprehend the idea we basically depending on donations. Most of our electronics are also donated to us from private companies for us to test them out (for example an IMU)

3. Our current objective and immidiate goals is to launch a rocket that will pass the 1 mach barrier (even if for a short time), send telemetry in real time to a ground station and land itself safely in a state that allow us to launch it again in the future. I am less involved in the telemetry, but they guys are building up the flight computer from 0.

4. I am attaching a rocksim file (I don't have an open rocket one, I hope it is ok).

Thank you for using your time to help novices like us

Forgot to mention that we are also looking for ways to reduce the range of the rocket because it is hard on us to find a location that will let us fly it there, and the bigger the area is the more bureaucracy we got to go through with security personal

 

[heada]

To reduce recovery area, look into building your rocket to support dual-deploy. There are several electronics packages that support it as well as give telemetry. I understand you're building your own electronics but for the first several flights I would include commercial electronics and use them for the primary at least on the first flight.

 

[OzHybrid]

Forgot to mention that we are also looking for ways to reduce the range of the rocket because it is hard on us to find a location that will let us fly it there, and the bigger the area is the more bureaucracy we got to go through with security personal

If Nitrous Oxide is available, hybrid technology motors would allow you to build simple motors there. No import issues.

 

[Tamir Friedman]

If Nitrous Oxide is available, hybrid technology motors would allow you to build simple motors there. No import issues.

We are unfortunately not allowed to work with explosives. Even the motors we imported we are not allowed to activate ourselves. We must have a civilian firework company hold our propellant in a secure location underground (yea, really) and they join us on launch day and they are the only people allowed to remain near the rocket when it is activated. We don't even get to arm the rocket :\

As I said. Bureaucracy around this kind of stuff over here is crazy. That's why we want to try and normalize the ordeal

 

[Tamir Friedman]

We are unfortunately not allowed to work with explosives. Even the motors we imported we are not allowed to activate ourselves. We must have a civilian firework company hold our propellant in a secure location underground (yea, really) and they join us on launch day and they are the only people allowed to remain near the rocket when it is activated. We don't even get to arm the rocket :\

As I said. Bureaucracy around this kind of stuff over here is crazy. That's why we want to try and normalize the ordeal

Also I am aware that Nitrus Oxideis not really "explosives", but the authorities around here don't get nuance. We are not allowed to hold something that is tagged "rocket motor", especially not on University grounds.

 

[Tim51]

We are unfortunately not allowed to work with explosives. Even the motors we imported we are not allowed to activate ourselves. We must have a civilian firework company hold our propellant in a secure location underground (yea, really) and they join us on launch day and they are the only people allowed to remain near the rocket when it is activated. We don't even get to arm the rocket :\

As I said. Bureaucracy around this kind of stuff over here is crazy. That's why we want to try and normalize the ordeal

I'm not an expert on Israeli law, but would Nitrous Oxide be classed as an explosive? Its commonly used in the food industry. Similarly, in a hybrid the solid fuel can be simply wax or nylon. Check out www.aspirespace.org.uk

 

[Tamir Friedman]

I'm not an expert on Israeli law, but would Nitrous Oxide be classed as an explosive? Its commonly used in the food industry. Similarly, in a hybrid the solid fuel can be simply wax or nylon. Check out www.aspirespace.org.uk

Well everyone around here are really "jumpy" about people building up rockets in their backyards. We are pretty far away from the day where we will be allowed to create our own rocket motor, let alone actually use it. We are still testing our boundaries because the authorities don't really know how to digest what we are doing. Hilariously enough when we tried to get a security permission to fly our rocket we had to explain 10 times that it doesn't have a warhead xD

 

[OzHybrid]

You need to work on your profile. Make it clear you DO NOT SUPPORT the replies to your article.


Whatever the issues in Israel, you need to make it clear that Amateur Rocketry has nothing to do with them. Write your own press release. Talk to your university before you do this and discuss with them.

 

[boatgeek]

So I will answer you questions:

1. I live in Israel. Hobby rocketry around here is not a thing and people at large have kind of bad taste when they hear the word "rocket" around here. Couple of years back we started the HUJI rocketry club in order to try and make hobby rocketry around here a thing. What does it mean for us? It mean there are no hobby rockets shops around here that we can get supply from, and basically every person that can help us out is military adjacent. I won't go with you over the bullshit we had to go through to launch a J425 motor powered rocket, but it was... a lot xD. (we even made it over the news):

https://www.jpost.com/israel-news/b...dents-launch-rocket-in-southern-israel-684292
It means that basically all of our rocketry supply are being shipped from overseas or being custom made using a lot of money and expensive equipment (for example we had to pay a lot of money to get our rocket's tailcone 3D printed).

2. Since we are a University club we get some budget from the University, but most of it comes from donations from private people who help us out. Under the right pressure we could squeeze the budget to create an overkill rocket, but that is not our goal here. We are trying to make this club a lasting thing which mean we need to show that we "supply the goods" in exchange to the outside support we get. In our first project we went with the carbon fiber tubes we ordered from the US, but those were very expensive and as I said we are trying to reduce the cost of the whole ordeal to save face. Our mentor is a person who worked for many years on actual rockets, and as much as I respect his expertise I know he comes from an industry that burns millions of dollars like nothing, and I am not sure he comprehend the idea we basically depending on donations. Most of our electronics are also donated to us from private companies for us to test them out (for example an IMU)

3. Our current objective and immidiate goals is to launch a rocket that will pass the 1 mach barrier (even if for a short time), send telemetry in real time to a ground station and land itself safely in a state that allow us to launch it again in the future. I am less involved in the telemetry, but they guys are building up the flight computer from 0.

4. I am attaching a rocksim file (I don't have an open rocket one, I hope it is ok).

Thank you for using your time to help novices like us

Understandable that Israelis are jumpy about the mention of rockets. And you definitely do not want to trigger the Iron Dome!

Understanding that you have a K805 in hand (well, in your pyrotechnics expert's bunker...) and you want to break Mach on the (relative) cheap, I would approach it as follows:
1. Use an equivalent to LOC thick wall cardboard tubing. This is fine for low Mach and light enough that it'll be easier to get up to speed. You can add a thin layer of glass if you like or not.
2. I would try 3" diameter to see if it looks like it would pass Mach by a reasonable margin (say 1.2). If not, try 2.6". Things tend to be a little easier if you have a little space between the motor mount and the body tube.
3. In addition to your team's telemetry and flight computer, I'd suggest an Eggtimer GPS tracking system plus a Quantum and maybe a Quark. That will get you full tracking and dual deploy in a reasonably small package and reasonably cheaply. You'll have to assemble the components, but that's within your skills if you're assembling your own telemetry from an IMU. The reason to use commercial units is that they are tested and will work if your system fails for any reason. The Quantum will get you full dual deploy capability to reduce drift and will record data to show that you passed Mach. The Quark is cheap insurance/redundancy. Your big issue is that you can't fly very much. Building and testing a flight computer takes a fair amount of testing...

Good luck!

 

[OzHybrid]

Your sim seems to have 3 fins and no tailcone. Your photo shows 4 very draggy fins and a tailcone.

 

[Tamir Friedman]

You need to work on your profile. Make it clear you DO NOT SUPPORT the replies to your article.

View attachment 495964
Whatever the issues in Israel, you need to make it clear that Amateur Rocketry has nothing to do with them. Write your own press release. Talk to your university before you do this and discuss with them.

I can't control people's comments, especially not on news sites which are not Israeli (even if they do cover Israeli news). We are just trying to ignore the negativity and we made it clear that our rocket had nothing to do with the military or wars or what so ever. As I said previously, we are trying to change the image rockets have in our region

 

[Tamir Friedman]

Understandable that Israelis are jumpy about the mention of rockets. And you definitely do not want to trigger the Iron Dome!

Understanding that you have a K805 in hand (well, in your pyrotechnics expert's bunker...) and you want to break Mach on the (relative) cheap, I would approach it as follows:
1. Use an equivalent to LOC thick wall cardboard tubing. This is fine for low Mach and light enough that it'll be easier to get up to speed. You can add a thin layer of glass if you like or not.
2. I would try 3" diameter to see if it looks like it would pass Mach by a reasonable margin (say 1.2). If not, try 2.6". Things tend to be a little easier if you have a little space between the motor mount and the body tube.
3. In addition to your team's telemetry and flight computer, I'd suggest an Eggtimer GPS tracking system plus a Quantum and maybe a Quark. That will get you full tracking and dual deploy in a reasonably small package and reasonably cheaply. You'll have to assemble the components, but that's within your skills if you're assembling your own telemetry from an IMU. The reason to use commercial units is that they are tested and will work if your system fails for any reason. The Quantum will get you full dual deploy capability to reduce drift and will record data to show that you passed Mach. The Quark is cheap insurance/redundancy. Your big issue is that you can't fly very much. Building and testing a flight computer takes a fair amount of testing...

Good luck!

Thank you for the advices!

 

[Tamir Friedman]

Your sim seems to have 3 fins. Your photo shows 4 very draggy fins.

The rocket in the photo is our previous built rocket. I don't have photos of the project we are working on right now because it is still in the early design stages. We wanted to lower the fins number in order to reduce drag.

 

[jderimig]

Ok, you only want to exceed mach 1 for a short time and you have limited recovery range. Actually those are good combinations.

The weakness of cardboard tubes going mach is greatly exaggerated. A single or double wrap of 6oz fiberglass cloth on a 3 to 4 inch cardboard will generally work. The next area to be careful are your fin connection and strength and any couplers in your airframe. Since the topic of this thread is airframe and you have limited access to materials I recommend the cardboard/fg wrap for your application.

 

[OzHybrid]

You could use 90mm PVC downpipe and get Mach 1.23. Is that available to you. Is 3D printing available at the university/ What's the capacity?