Stupid problem to have.. future project brainstorming

[MikeyDSlagle]

I have been working up some sims and daydreaming/window shopping for a large diameter bird capable of attaining my level 3 but a regular flyer on 75mm Ks and Ls. Trying to decide the diameter and material and what not. Couldn't decide. (no that's not the problem)

So my dad shows up a few days ago with something in the back of his truck. That "something" is the problem: 9 feet long and ~6 7/8" (1/4" thick walls) diameter mailing tube that a flag pole came in, I have no where to store it. My big rocket was going to wait until I had the room for it. And that is only one half, he kept the other half for some reason. "Too heavy for a rocket, probably," he says, "but maybe you can ship something in it. Well unless you had a big enough motor I guess".

I'll ship something alright. To about 6000 feet on a bright red flame. I had alluded to a large diameter short stubby in another thread, this will be it...eventually. I am going to stray from the norm, which is normal for me. Short, fat, 6 fins and blunt nose, lots of drag.

I get to looking at it and it has a large dent in it about 5 feet from one end. Whew, I can cut it and store it. After my rush job cutting it, and figuring I will need to cut both ends again to square em up, I will have about 4 feet of usable tubing and maybe 2 feet on the other end after everything is cut from there as well. It has a plug in one end so I have one bulkhead already.

This will be quite a project. I may can use the 2 feet for something, a payload bay perhaps. But would have to make me a coupler. Something I have never tried. I may try to make me a nose cone out of body tubes, foam and wood. I have a lathe I haven't used in a long time, I could drag it out. May be good a good project for that. All else fails, I'll call on Python Rocketry to spin me one up.



Quick thrown together file.

View attachment V 3 Shortened Elipsoid.ork

I may have a few hangups about the fin shape if I get up around transonic speeds, but preliminary sims shows I should stay down below that until I get into 5 grain/6000 Ns, or some of the meatier 4 grains. But all that will change as I add paint and real world weights so I should be good. And funds will keep me away from those motors for quite a while.

We shall see.

Mikey D

 

[Nytrunner]

So.....98 mm hole? For reasons?

Adapting down is easier than wishing you could go up!

 

[Bat-mite]

Are you going to glass the tube? I wouldn't trust that to retain a level 3 motor, unless you use a thrust plate.

 

[MikeyDSlagle]

98mm:
First reason that comes to mind is cost. Realistically though, I think the costs are fairly close to one another.
Another reason is it will add weight on the business end, and then an adapter will add more, which I will have to compensate for with weight in the nose. Bringing up the weight and lowering the number of motors I can fly. It will probably see one M motor just to get my level 3 and then it will fly on Ks and Ls and rarely even then so I would like a large variety to choose from. I like the thought of big bore 98s, don't get me wrong, but I just don't think it is in the cards. By the time weight is added, there will only be a handful sub-M motors that would safely fly it. This is just an early rough assessment, I may be way off. I am usually all for going bigger and adapting down, so I am not totally against it. And the guys that will likely be my TAPs will surely be for going 98mm. I haven't even approached them with the idea of my getting level 3. I am only level 1 ATM, my Tyrannosaur hopefully gets decals on today then I will work on the innards. We will see how I feel when that time comes. Maybe I will have won the lottery by then.

Fiberglassing:
I am thinking about it. I haven't laid fiberglass in years, and never on a body tube. And if it comes down to that, I will likely do the fins as well. When the time comes I will discuss it with my TAPs.

But why do you think this tube won't hold up to a level 3? I mean absolutely no disrespect nor am I questioning your knowledge or insulting your intelligence. I would like to hear the reason behind that statement. It has 1/4" walls and I intend to use countersunk screws through the airframe into at least the forward ring. Would the motor tear the inside, as in take some of the paper with it? If that is the case, then I would think fiberglassing the outside wouldn't help much. But I really don't know.

Oh and there will likely be a thrust plate, and it will be seated against the fin tabs. I started brainstorming on a thrust plate some time back. Will probably implement that into this build.

I will not have this project in full swing for quite some time. When I get up to that level, I will know a lot more about the larger motors.

All input is appreciated. Thanks guys.

Mikey D

 

[bclark989]

My input would be don't get an L3 if you aren't going to fly M's. Someone talked about that at NARCON 2015 (I wasn't even an L1 yet and was already planning my L3 in my head). Basically, they said your knowledge, ability, and tastes will change so much before you are really ready, you should try to keep from planning it that early. I got my L1 and L2 at the end of that year, and even bought a kit for my L3. Seeing how fun and cheap it is to just fly 38's and small 54's, I sold that kit and haven't flown anything bigger than a J yet.

Not that you can't dream, but I wouldn't keep a 9' long mailer tube not built for rocketry just on the chance that it maybe could be an L3 air frame some day.

Good luck on your L2 =)

 

[Bat-mite]

Fiberglassing:
I am thinking about it. I haven't laid fiberglass in years, and never on a body tube. And if it comes down to that, I will likely do the fins as well. When the time comes I will discuss it with my TAPs.

But why do you think this tube won't hold up to a level 3? I mean absolutely no disrespect nor am I questioning your knowledge or insulting your intelligence. I would like to hear the reason behind that statement. It has 1/4" walls and I intend to use countersunk screws through the airframe into at least the forward ring. Would the motor tear the inside, as in take some of the paper with it? If that is the case, then I would think fiberglassing the outside wouldn't help much. But I really don't know.

Oh and there will likely be a thrust plate, and it will be seated against the fin tabs. I started brainstorming on a thrust plate some time back. Will probably implement that into this build.
Mikey D

Good points. With a thrust plate, the motor pushes on the airframe instead of the fins and the CRs. I think that solves your problem.

I'm not a TAP or a scratch-builder, and I have never glassed a cardboard tube, so take me with a grain of salt. But I am guessing that it doesn't weigh as much as FG. Maybe I'm completely wrong there. But an M motor in a lightweight tube is going to get a lot of acceleration, and you'll need to be sure the tube can withstand the stresses of however many G's you're going to pull.

Another consideration is that you must be able to recover the rocket in flyable condition for a cert flight. So if it comes down in a tree and has to hang there for weeks, the cardboard won't hold up to the weather unless it is glassed. Also, if it comes down in a stream/pond, etc.

Just things to consider. Love to see others' comments.

 

[rstaff3]

You need some old school input from folks who flew Ms before fiberglass tubes were the norm. I know of several unglassed M and N powered rockets. However they were larger in diameter so they may not be apples and oranges. Before you get going on the build, you should contact your friendly neighborhood TAP as they are the ones you have to get by. But if you don't get it approved you could fall back to an L.

 

[MikeyDSlagle]

My input would be don't get an L3 if you aren't going to fly M's. Someone talked about that at NARCON 2015 (I wasn't even an L1 yet and was already planning my L3 in my head). Basically, they said your knowledge, ability, and tastes will change so much before you are really ready, you should try to keep from planning it that early. I got my L1 and L2 at the end of that year, and even bought a kit for my L3. Seeing how fun and cheap it is to just fly 38's and small 54's, I sold that kit and haven't flown anything bigger than a J yet.

Not that you can't dream, but I wouldn't keep a 9' long mailer tube not built for rocketry just on the chance that it maybe could be an L3 air frame some day.

Good luck on your L2 =)

Thanks. Just got decals on. Will work on innards when I get a chance.

I see what your saying. My styles have changed. Heck the biggest I was going was a Big Bertha. I got level 1 to fly sparkies. But I like the smoke and roar of larger motors. Yeah the level 3 project was going to be farther down the road. I have been looking at big kits...just looking mind ya, seeing what is out there. They are too pricey for my blood for the time being. And the big fiberglass birds have to fly on big motors. I didn't mean this is going to be a bird built solely for level 3 motors. This will be a K and L bird, but built to handle a M if I want too. No sense in spending all that money on a large kit only to not be able to fly it because I can't afford the motors to get it in the air. It would just sit there, 500 bucks. If I get TAPs on board and document this as a level 3 build, why not fly for level 3? Then when the stars align, weather is perfect, I get plenty of OT and I find a good deal on a M motor...let er rip. I can take the piece I intend to use to our next launch and see what the guys there think.

And it's not 9 feet anymore, only 5. Tucked into a corner in my back room. I will probably take it to my dad's tomorrow and toss it in his attic. It'll be nice and dry there. The young rocketeer has taken to finger painting the end I cut off. I will probably go with about 42 inches. I'll try to keep it around 15 lbs but we'll see. The nose cone is going to dictate a lot.

 

[MikeyDSlagle]

Good points. With a thrust plate, the motor pushes on the airframe instead of the fins and the CRs. I think that solves your problem.

I'm not a TAP or a scratch-builder, and I have never glassed a cardboard tube, so take me with a grain of salt. But I am guessing that it doesn't weigh as much as FG. Maybe I'm completely wrong there. But an M motor in a lightweight tube is going to get a lot of acceleration, and you'll need to be sure the tube can withstand the stresses of however many G's you're going to pull.

Another consideration is that you must be able to recover the rocket in flyable condition for a cert flight. So if it comes down in a tree and has to hang there for weeks, the cardboard won't hold up to the weather unless it is glassed. Also, if it comes down in a stream/pond, etc.

Just things to consider. Love to see others' comments.

If it comes down in a pond, I'm done for anyway. LOL. We have one or two at the field, one is quite a distance away, over a mile. Seems like there is a drainage ditch that may get me though. Trees are present and that will be my luck. I have already had a rocket land on a power line and hang all night. I'm not really concerned about the inability to recover the rocket though.

As for the tube. I think it will be about the same weight as a 6" fiberglass tube. Structurally though, I don't know. Fiberglassing may be the only way to go. Current sims are showing around 10Gs. Seems low.. I think there is something else to add in when figuring Gs for rockets? I would think a G is a G is a G, but I am no physicist or rocket scientist.

You need some old school input from folks who flew Ms before fiberglass tubes were the norm. I know of several unglassed M and N powered rockets. However they were larger in diameter so they may not be apples and oranges. Before you get going on the build, you should contact your friendly neighborhood TAP as they are the ones you have to get by. But if you don't get it approved you could fall back to an L.

Yes. Exactly. I have that resource at our launches, old school input that is. And I will contact the TAPs at next launch. See what they think. Like you say. If they don't see it working for a level 3 attempt. I'll carry on launching on Ks and Ls. Next launch is September so I have time to gather info on the components I intend to use.

 

[OverTheTop]

My input would be don't get an L3 if you aren't going to fly M's.

I disagree. We all are in the same hobby but work within different constraints and mindsets. If it feels right and you want to, get your L3. If you are only doing because of peer pressure then reconsider. You choose how you fly.

I certified on an N (also considered an O3400 ) since I always like to go at least one designation higher than the minimum required, but that is just me. I haven't flown an L3 bird since, due to an assortment of reasons. I have been happy doing L flights in the meantime. I do have an M prepped for next launch and am working on (and have been for a long time) a two-stage O-M stack.

But if you don't get it approved you could fall back to an L.

There are many M motors these days which have long burn times and resultant lower accelerations and peak thrust. You can design for some of the lower thrust M motors and then adapt down. Yes, a G is a G. The only thing with the bigger impulse motors at lower thrust is that the top speeds are higher than the lower impulse motors. As long as the fins don't flutter and the airframe has some safety margin at peak thrust for the motor you should be fine.

FWIW I would put a fiberglass skin on it. Not too thick, but it would make it much stiffer and a little more waterproof. YMMV.

Before you get going on the build, you should contact your friendly neighborhood TAP as they are the ones you have to get by.

Always. Work with them. They are individuals and requirements can vary.

 

[Tim51]

Quick thrown together file.

View attachment 321212

'Thrown together' or not, I think that's a pretty cool and original design. Nice one! Good luck with the project.

 

[MikeyDSlagle]

I disagree. We all are in the same hobby but work within different constraints and mindsets. If it feels right and you want to, get your L3. If you are only doing because of peer pressure then reconsider. You choose how you fly.

I certified on an N (also considered an O3400 ) since I always like to go at least one designation higher than the minimum required, but that is just me. I haven't flown an L3 bird since, due to an assortment of reasons. I have been happy doing L flights in the meantime. I do have an M prepped for next launch and am working on (and have been for a long time) a two-stage O-M stack.


There are many M motors these days which have long burn times and resultant lower accelerations and peak thrust. You can design for some of the lower thrust M motors and then adapt down. Yes, a G is a G. The only thing with the bigger impulse motors at lower thrust is that the top speeds are higher than the lower impulse motors. As long as the fins don't flutter and the airframe has some safety margin at peak thrust for the motor you should be fine.

FWIW I would put a fiberglass skin on it. Not too thick, but it would make it much stiffer and a little more waterproof. YMMV.



Always. Work with them. They are individuals and requirements can vary.

Fiberglass is for sure an option, even for no other then making finishing easier. I imagine this tube will sop resin like a sponge so it may make it super heavy, do t want that. I have the extra section I can experiment with.

'Thrown together' or not, I think that's a pretty cool and original design. Nice one! Good luck with the project.

Thanks.
I'm not happy with the color, white and sky blue isn't the best choice for a rocket. My level 1 bird changed colors and names several times before I settled on its current theme. With this much real estate I may try something really different, maybe some airbrushes or vinyl work.

I build bays into all my nose cones. Mainly so one will be there in case I need it in the future. But this one may have to be full on HED. I have some HED designs rattling around in my head, this will get me going to get one on paper. The JLCR has made dual deploy in short stubbies so much easier. Of course if the TAPs don't approve it, then i can just use a JLCR for K and L flights.

Thanks for the input and replies folks, keep em coming.

 

[Binder Design]

I throw tubes like that away all the time. Thick mushy cardboard. Tubes like this don't have enough glue between the layers and they are not virgin kraft, they are recycled pulp and wound at the wrong angle. You'd have to glass it at the very least. By all means contact your TAP for their advice but just because you have the tube doesn't mean you have to use it.

 

[Nytrunner]

If they succeed in talking you out of his as an airframe: Tube Fins...........BIG Tube Fins

Or use it as Ring Fins over a smaller body!

 

[MikeyDSlagle]

I throw tubes like that away all the time. Thick mushy cardboard. Tubes like this don't have enough glue between the layers and they are not virgin kraft, they are recycled pulp and wound at the wrong angle. You'd have to glass it at the very least. By all means contact your TAP for their advice but just because you have the tube doesn't mean you have to use it.

Oh no good sir. I have the tube, I must use it! LOL A joke of course. It does seem to peel pretty easily. I'll email my Prefect later this weekend and post over on our Yahoo Group where the good folks of TRA-LA can chime in.

Mike I think you know our Prefect, Paul S. And the TAPs I'd approach with this would be Chris Short and Andrew Grippo. They both attend our launches. I've annoyed Chris enough for the time being with recent emails getting his advice on another project. If he happens to stumble upon this thread, good.

If they succeed in talking you out of his as an airframe: Tube Fins...........BIG Tube Fins

Or use it as Ring Fins over a smaller body!

A ring fin... now I have that in my head. Thanks a lot.

So M motors aside. Any reason this wouldn't stand up to the full range of Ks and maybe lower half L motors? Normal motors, not Super Thunders and VMaxes. Pro75 2 and 3 grain loads look well rounded. A little more simming shows it would fly on high thrust Js as well. Particularly the Red and Blue in the AT 54/1280 case, which I have.

 

[Handeman]

My input would be don't get an L3 if you aren't going to fly M's. Someone talked about that at NARCON 2015 (I wasn't even an L1 yet and was already planning my L3 in my head). Basically, they said your knowledge, ability, and tastes will change so much before you are really ready, you should try to keep from planning it that early. I got my L1 and L2 at the end of that year, and even bought a kit for my L3. Seeing how fun and cheap it is to just fly 38's and small 54's, I sold that kit and haven't flown anything bigger than a J yet.

Not that you can't dream, but I wouldn't keep a 9' long mailer tube not built for rocketry just on the chance that it maybe could be an L3 air frame some day.

Good luck on your L2 =)

Oh no good sir. I have the tube, I must use it! LOL A joke of course. It does seem to peel pretty easily. I'll email my Prefect later this weekend and post over on our Yahoo Group where the good folks of TRA-LA can chime in.

So M motors aside. Any reason this wouldn't stand up to the full range of Ks and maybe lower half L motors? Normal motors, not Super Thunders and VMaxes. Pro75 2 and 3 grain loads look well rounded. A little more simming shows it would fly on high thrust Js as well. Particularly the Red and Blue in the AT 54/1280 case, which I have.

I agree with bclark989. Not that you can't build a L3 capable rocket for use with L2 motors, like using and Estes MPR to get your L1, but I would really recommend you fly L2 for a while before you plan your L3.

I tell people that rocketry is like fishing, you can spend $20 on worms and a pole and sit by a creek, or $1,000,000 on a sport fishing boat and hit the gulf stream, and everything in between. It can all make you happy. The thing is, if you're using a bass boat on a small lake today, don't expect to be able to understand what you'll need to hit the gulf stream in that $1,000,000 ocean going boat later.

If you are just flying L1 now, you will learn a lot about motors, impulse, and what those really mean. It's one thing to watch someone else's rocket, or to run sims and say a rocket will fly so high on a large L, but if you haven't flown an L2 motor before, you really don't have any idea of what an L motor is really all about. They call it experience, I call learning to fly the field. Building your own L2 rockets and flying L2 motors (besides baby Js) gives you a completely different perspective on things and will definitely change your thoughts on what and how you will make that L3 cert attempt.

The other thing about L3, don't expect to be able to do it cheap. I was able to drop my costs a lot by making my own main and drogue chutes, d-bag, reusing altimeters, etc. My cert flight still cost me about $1700. Only $315 of that was propellant so I've been using the same $1400 worth of rocket and motor case since. If you're going to spend that much for a rocket to fly an L3, why only fly L2 motors in it after?

I certainly don't want to discourage you from working for L3, I just don't want you to end up disappointed and discouraged because you put a lot of time and effort into a dream that you realize later isn't what you really want. If you wait, it will come.

Good Luck on the L2!

 

[MikeyDSlagle]

I agree with bclark989. Not that you can't build a L3 capable rocket for use with L2 motors, like using and Estes MPR to get your L1, but I would really recommend you fly L2 for a while before you plan your L3.

I tell people that rocketry is like fishing, you can spend $20 on worms and a pole and sit by a creek, or $1,000,000 on a sport fishing boat and hit the gulf stream, and everything in between. It can all make you happy. The thing is, if you're using a bass boat on a small lake today, don't expect to be able to understand what you'll need to hit the gulf stream in that $1,000,000 ocean going boat later.

If you are just flying L1 now, you will learn a lot about motors, impulse, and what those really mean. It's one thing to watch someone else's rocket, or to run sims and say a rocket will fly so high on a large L, but if you haven't flown an L2 motor before, you really don't have any idea of what an L motor is really all about. They call it experience, I call learning to fly the field. Building your own L2 rockets and flying L2 motors (besides baby Js) gives you a completely different perspective on things and will definitely change your thoughts on what and how you will make that L3 cert attempt.

The other thing about L3, don't expect to be able to do it cheap. I was able to drop my costs a lot by making my own main and drogue chutes, d-bag, reusing altimeters, etc. My cert flight still cost me about $1700. Only $315 of that was propellant so I've been using the same $1400 worth of rocket and motor case since. If you're going to spend that much for a rocket to fly an L3, why only fly L2 motors in it after?

I certainly don't want to discourage you from working for L3, I just don't want you to end up disappointed and discouraged because you put a lot of time and effort into a dream that you realize later isn't what you really want. If you wait, it will come.

Good Luck on the L2!

Well said. Excellent point, actually sounds a lot like I said it myself.

I am usually the guy saying to build the rocket like you want to fly it. If it is built for L1 motors, fly it on L1 motors. My L1 bird was designed to fly on H and I motors, and it flies superbly on those motors. My L2 is intended to fly on Js but it will fly on I's as well and I will likely toss in a K once in a while after I get into tracking and I am able to buy the hardware.

Level 2 has a large range of motors and I will likely spend lots of time there. I really am in no hurry to breeze through the certs. There is a huge difference between a baby J and even a mid range L. I intend to get into tracking, clusters, and air starts just to name a few. Lots of fun to be had from H to L. And like you say, lots of learning.

So, yeah, take my own advice and not fly a L3 motor in a L2 bird. I'll be better off saving up the funds for a full fledged L and M rocket later down the road. But I imagine it will still be a stubby.

I'll try my hand at fiberglassing this tube and build the rocket to fly on Ks and small Ls. That will give me two separate rockets to nearly cover the full range of L2 motors. This build is still a ways away because while storing the tube is no problem, the finished product would be too large. There is a shop in my near future and that will allow me to work on the bigger birds.

Thanks. I keep putting off working on the A/V bay for some reason. Need to get to it. But I have til September.

 

[mccordmw]

I'd glass wrap it if you're planning on anything in the 98 mm range. Heck, even the 75 mm range. You would be surprised at how fast the axial and buckling forces build up to over 1,000 lbs under thrust. I have a calculator online that estimates forces and shows what your airframe can take. I wouldn't trust that tube without reinforcement.

https://docs.google.com/spreadsheet...5nFxY3m08tIn-kY2F8sNV7NQd8k/edit?usp=drivesdk

 

[MikeyDSlagle]

That's a good resource. Thanks.

I'll have to double check my sims but according to the reference and some numbers I remember from the sim I should be GTG at least on an L995. Even using light cardboard shipping tube. I will probably glass it though, for the practice and durability.

Thanks for all the input folks