When does fiberglass become necessary?

[MichaelRapp]

Hi all,

While HPR is very, very far in my future....this is one thing I am not clear on: As one goes to ever-increasing rocket diameters, at what point do paper tubes become impractical and one needs to use fiberglass? Also, is it primarily a weight issue or a strength-of-materials-issue?

(What actually brought this question to my mind a few moments ago is that I was doing some work on one of my telescopes. For those familiar with it, it is an old 1970's Meade equatorial reflector and tube is 51" long, about 9" in diameter, constructed of spiral heavy paper coated with fiberglass and I started wondering about HPR tubes....)

 

[cbrarick]

Ahh, one last fiberglass vs paper threads for the year.

Loc commercially produces a line of7.51 inch diameter cardboard rockets.
Rocketman makes a 11.4 inch diameter phenolic rocket (Big Kahuna)
that's just 2 examples

People will debate the speed of paper...not that I'm an expert, but my stretched LOC vulconite (morning after bad Thai food) has been to mach 1.6 on the J600, dead stock without any reinforcement anywhere (once again I'm not the expert here, just giving one example of mach+ paper)

I do love my fiberglass rockets, though and don't have many paper ones, most of those were done early in my rocketry experience. Why? because fiberglass is much more durable, bounces around in my truck nicely without any damage. fly them, chuck them in the bed and drive them home. Dirty? not a problem for my garden hose. Drop them in the METRA river, once again, hose them out and fly again.....(although the electronics deoesn't like that)

I guess if you were doing big, punishing motors fiberglass is very important, or for those little screaming MD birds well into the mach 2+ world, but for most of us fiberglass conveys a convenience factor, paid for in weight.
The hardest part of your question is that for every rule someone proposes there's definitely someone out there who can show you an exception....

Just my 2 cents.

 

[Steve Shannon]

Ahh, one last fiberglass vs paper threads for the year.

Loc commercially produces a line of7.51 inch diameter cardboard rockets.
Rocketman makes a 11.4 inch diameter phenolic rocket (Big Kahuna)
that's just 2 examples

People will debate the speed of paper...not that I'm an expert, but my stretched LOC vulconite (morning after bad Thai food) has been to mach 1.6 on the J600, dead stock without any reinforcement anywhere (once again I'm not the expert here, just giving one example of mach+ paper)

I do love my fiberglass rockets, though and don't have many paper ones, most of those were done early in my rocketry experience. Why? because fiberglass is much more durable, bounces around in my truck nicely without any damage. fly them, chuck them in the bed and drive them home. Dirty? not a problem for my garden hose. Drop them in the METRA river, once again, hose them out and fly again.....(although the electronics deoesn't like that)

I guess if you were doing big, punishing motors fiberglass is very important, or for those little screaming MD birds well into the mach 2+ world, but for most of us fiberglass conveys a convenience factor, paid for in weight.
The hardest part of your question is that for every rule someone proposes there's definitely someone out there who can show you an exception....

Just my 2 cents.

My 2¢ also.


Steve Shannon

 

[djkingsley]

I have switched to fiberglass mostly due to the humidity found here on the eastern shore of MD, I found that several of my HPR cardboard tubes were getting soft. I do not fly for extreme altitudes so the extra weight is not an issue for me either and I like the durability.

 

[MichaelRapp]

Cleaning a rocket with a garden hose...that does have a certain allure. And wow, I thought fiberglass was lighter than paper..... wow did I have that backwards! (Much to learn, I have...)

 

[rstaff3]

I think you have been given good advice. This is a subject that will generate a variety of opinions. You must remember that the up and down parts of a rocket flight have varying strength requirements. The down in my experience (although I don't stress many rockets like the big dogs of TRF) is often harder on them than the up. You will find someone who will fly an unglassed cardboard rocket 50 times with no damage. I personally don't always get the laundry out perfectly all the time and cardboard tubes sometimes suffer. Also, I build a lot of stuff from non-rocetry tubing and that stuff, while it works, is not as robust as, say, an LOC tube. But, I view any minor damage as an opportunity to work on a rocket. YMMV

 

[KenRico]

Paper or fg wrapped paper birds fly on smaller motors , but you have to pay attention to the punchier motors .. Also ANY catastrophic event can damage it ..

Filament Wound fg rockets you almost never have to ask the question 'is this too much motor ' ..you do - but not if the rocket can take it..its more of is it too much for the field or event.

For me most of my fw fg rockets are NOT painted ..and my paper ones are. Although they are built well - any damage like a fin or a fillet that is repaired needs to be repainted too.. I always worked to lay nice paint and make my scale match ...but am really sick as on 3rd repaint on them and now need a 4th and not into it.

Kenny



Sent from my LG-LS997 using Rocketry Forum mobile app

 

[Nytrunner]

For examples of very strong capable cardboard rockets, look for any of ECayemberg's build threads. His LOC-N-Load is a 5.5" cardboard rocket for flights on N's that's under construction currently.

 

[DavidMcCann]

FG becomes necessary somewhere in the bed of my truck...

 

[Onebadhawk]

Cleaning a rocket with a garden hose...that does have a certain allure. And wow, I thought fiberglass was lighter than paper..... wow did I have that backwards! (Much to learn, I have...)

You're correct Mike,,
Fiberglass is generally a lot heavier than paper tube..
Here in the north east we have irrigation ditches more frequently then on farms out west..
I don't understand why this is, but it is..
The first big reason as already stated is just washing off the rocket with soap and water..
But someone mentioned the cardboard tubes get soft after a bit...
You'll get far higher and faster on a given motor with cardboard, no doubt..
But that is paid for with longevity..

Teddy

 

[Bat-mite]

A good midway material is canvas phenolic, as sold by https://macperformancerocketry.com It is a lot tougher than paper but not as heavy as FG.

 

[MichaelRapp]

Thanks for the information all!

I really did think it was a natural progression; that is, above a certain size or thrust one needed to use fiberglass.

Interesting to learn about some of the other considerations.


Sent from my iPhone using Rocketry Forum

 

[RodRocket]

Isnt sonotube paper? I have watched some monster rockets launch at Argonia made out of sonotube. I believe KBMax was one! Have also watched fiberglass rockets get rekitted!

Building with fiberglass isnt difficult, just different methods. Find a smaller fiberglass kit and give it a try. Madcow has a few kits in both paper and fiberglass versions.

Paper will take more than you think. I toughened up an estes mege mosquito kit and fly 24mm ap motors. Really jumps off pad with an f white lightning, only modification was ply centering rings, aeropac retainer and a nice shock cord. I just got the Madcow version and it has a 29mm mount, Hello G's!

One thing I can think of is when a fiberglass rocket becomes difficult to find, it will survive the elements better than paper.

 

[ksaves2]

To answer the question, how long do you want the rocket to last?? If you have a tendency to lose the rockets, make them biodegradable. If you are lucky at finding them months later, fiberglass stands up to the elements better, as many have already said.Kurt

 

[Andrew_ASC]

I really did think it was a natural progression; that is, above a certain size or thrust one needed to use fiberglass.

It's hard to answer your specific question as the rocket is a tailored application of math or lots of experimenting with lots more experience for a certain performance goal. Sometimes it takes both to get it right. To get real vague I'd lump it in cardboard's material strength is not optimal beyond certain expected flight performances, and people may not have a great grasp of where it will fail in what rocket application yet, because no one has tested it to that point. People like being a tad conservative as no material is flawless itself compared to the ideal properties on tables of it plus when you have the math there may be real world unknowns that you want accounted for by an increased material strength for application.

The material is chosen to match applications based on its material properties, forces expected, and listed stresses. You have multiple considerations to consider regarding, thermal loads, thrust force, burn time, drag force, tubing length with possible bending in flight, tubing wall thickness for area reasons, and other forces expected.

Drag force is squared by velocity, so speed will be concern for that force. For thrust forces when these flyers claim punchier motor assume a Warp9 Aerotech or CTI VMAX, those have ultra low burn times in tenths of seconds as that very high for class of motor thrust force is nearly an instant force loading on airframe tube in a compressive force. You can take carbon fiber airframe tubes, sand down the OD to reduce wall thickness and even the "superior" material will fail from it's customized new maximum stress level based on material properties and areas not matching what is required of it in application because the cross sectional tubing area taking the severe force load is compromised. Once you pass Mach 1 there's theoretically oblique shockwaves on nosecone, rapid pressure changes so now you've got a variable force literally from the pressure change on the nosecone itself very briefly as it's passing sound barrier, and beyond Mach 1.6 you're well into entry aero heating with harder to notice concerns until well in Mach 2 range.

What you find is flying large diameter thicker wall cardboard tubes to Mach 1.6 on J motors or greater with certain sized tube walls, thick bulkheads, works, but in a minimum diameter rocket with less thrust even H-I class, more rapid acceleration pushed to extreme ends of performance range into higher mach numbers the result would not end well. See that simplified rant isn't even considering the airframe tube flexing or bending in flight by length and turbulent flow/unbalanced forces by motor burns in reality.

You may on paper encounter MPR flights requiring fiberglass in certain very aggressive performance goals versus less aggressive performance goals. I don't think the progression is natural due to how a rocket is either minimum diameter or it isn't at a lot of different motor options, tube sizes, and flight expectations in design will rule out an easier rule of blah class motor use blah material. A lot of people like the overkill aspect of some materials. Now I can post about some of my CF and FG experiences if you want... It's almost a structure design in a very hard to predict environment but you can shove all that math crap aside and take in what others have learned from experience too. Because math doesn't always predict reality well either.

I'm still an engineering student. There's hobbyist non engineers that have flown rockets well beyond what I've done, an other engineers on here with more experience.

 

[Nathan]

Yeah fiberglass rockets are a lot heavier than cardboard. That just gives me an excuse to fly bigger louder motors.

 

[Bat-mite]

Yeah fiberglass rockets are a lot heavier than cardboard. That just gives me an excuse to fly bigger louder motors.

That's about the size of it. (pun intended)

 

[ECayemberg]

This is a good thread!

To answer the Original Poster's Question: NEVER! There is never a point at which fiberglass becomes necessary....as CW said right up front, some of the biggest rockets are not constructed of fiberglass....

That said, I LOVE fiberglass in the right application! Some may be surprised that I have and fly a lot of glass rockets, carbon rockets, cardboard, and glassed rockets. Let me pose a few comparisons.

The Gizmo XL vs. 7.7" Bruiser. Had both....flew the Bruiser at a 3:1 ratio compared to the same sized Giz XL....one weighed a lot more than the other. And YES, my paper Bruiser flies on N motors! Got rid of the Giz XL...too clunky for my tastes. To be fair, I glassed the Bruiser (I said I love glass!).

Airfest 2017: I had a great time at Airfest this year...but only got around to flying two rockets. One with 8187 Ns of power and the other with 4614 Ns of power. The 8187 went in a 3" little carbon ship to 30k'; the 4614 in a 12' tall 7.67" diameter paper ship to 5k'. I'd bet a nickel that if we took a poll to see which flight people remembered...the nod would go to the big lumbering brute on the lower total impulse. Point is...sometime more is less...and there's no way I could've or would've flown a glass project that size on that minimal amount of motor. BUT...I do have a 7.67" glass bird for 6" motors (I told you I love glass).

Two more, then I'll shut up!

5"/5.5" stubbies: We have drag raced 5.5" Minie Maggs at Bong launches since the mid-to-late 90's...great fun (though diminished now due to "new" drag race rules...but I digress). For a short time, the race were opened up to 5" glass Gizmos....but it didn't really work because the Maggs flew to 1600' or so on 38-3G I motors whereas the Gizmos need a 54-3G J to achieve the same. Cost was more expensive, and so on. Returned to flying Maggs. BUT, I did enjoy flying my 5" Gizmo on K motors for a while! We have local Class 1 launches monthly....I can fly a lightly built 5.5" Minie Magg on an H123W and the crowd goes wild....just under 3.3lbs and 125 grams of propellant. Can't do that with the comparably sized glass Gizmo. Moral: they each have their place; though I enjoy the versatility of one over the other.

One last comparison: 3" rockets. I'll compare a Loc Caliber ISP to a minimum diameter ship (such as Wildman Falcon). The Caliber ISP is paper and built lightly is a featherweight. I've flown mine on an Aerotech I65 and even a 29-3G G motor....couldn't do that with a glass or carbon ship. I've also flown the Caliber on I and J motors...quite a versatile bird. Now, a minimum diameter bird like the Falcon is amazing on the right motor! Capable of 30-40k' as single stagers on M motors, there are things that should only be tried with glass and carbon...like minimum diameter, Mach 2+, and 30k'+. I can fly one close to home on a variety of motors whereas the other flies only once every few years at launch sites 12+ hours from home....same size rockets, totally different applications and intentions.

To close, I'd just like to note that we're fortunate to have so many options in rocketry nowadays! Glass prices are incredible, which make them attractive. I'll admit that glass rockets at my Class 1 launches make me nervous...a glass rocket is so solid that when it comes down hard in the aluminum bleachers, rubber track, or sod football field, it leaves an imprint on the facilites that we're guests at. Cardboard and thin ply generally give up before they damage surfaces. To that tune, overbuilding of rockets is a concern and an aggravation point for a lot of old timers in the hobby. There's a place for glass rockets and a place for cardboard rockets. Some flight profiles are more appropriate with different base materials. I can do things with my cardboard rockets that *can't* be done with glass rockets. But I can also do things with glass and carbon rockets that *can't* be done with cardboard rockets. Don't discount either...decide what and how you want to fly and go from there. Lastly: strategically and intelligently glassed rockets are likely the best of both worlds....lighter than all glass, stronger than plain paper and ply...reinforce where and when necessary and you have an engineered rocket, rather than just a pig of a rocket that needs more power simply because of heavy base materials. But that does take a bit more effort...

'Nuff of my ramblings for now. Have fun out there, folks!:smile:

 

[JohnCoker]

I wish we had a good answer to that question. As hobbyists, we don't have detailed specs on the materials and adhesives we use (even assuming they are consistent).

The easiest way to be confident is to over-build. The main downside of overbuilding is that making rockets heavier increases the forces on them and in turn increases risk. I've watched kids fly their Estes rockets again and again with indifferent (to be kind) packing of the parachute and they just keep surviving, even when the chute is a wad.

The normal progress is that hobbyists work up from model to HPR rockets one step at a time and get comfortable with what works for them.

As we move more into additive manufacturing, parts will become more repeatable and we may be able to narrow the overbuilding.

 

[Steve Shannon]

I wish we had a good answer to that question. As hobbyists, we don't have detailed specs on the materials and adhesives we use (even assuming they are consistent).

The easiest way to be confident is to over-build. The main downside of overbuilding is that making rockets heavier increases the forces on them and in turn increases risk. I've watched kids fly their Estes rockets again and again with indifferent (to be kind) packing of the parachute and they just keep surviving, even when the chute is a wad.

The normal progress is that hobbyists work up from model to HPR rockets one step at a time and get comfortable with what works for them.

As we move more into additive manufacturing, parts will become more repeatable and we may be able to narrow the overbuilding.

I underlined a sentence in John Coker’s post that really stood out. I feel like this is something that this “normal progress” is happening less recently. I feel like more people are trying to leapfrog past those experience building steps in an effort to achieve higher altitudes and greater velocities. I’d like to know if others are seeing the same thing that I am.


Steve Shannon

 

[rstaff3]

I underlined a sentence in John Coker’s post that really stood out. I feel like this is something that this “normal progress” is happening less recently. I feel like more people are trying to leapfrog past those experience building steps in an effort to achieve higher altitudes and greater velocities. I’d like to know if others are seeing the same thing that I am.


Steve Shannon

My general sense from hanging out here (since 2002-ish) is that there have always been newbies who fit that mold.

 

[rstaff3]

I wish we had a good answer to that question. As hobbyists, we don't have detailed specs on the materials and adhesives we use (even assuming they are consistent).

The easiest way to be confident is to over-build. The main downside of overbuilding is that making rockets heavier increases the forces on them and in turn increases risk. I've watched kids fly their Estes rockets again and again with indifferent (to be kind) packing of the parachute and they just keep surviving, even when the chute is a wad.

The normal progress is that hobbyists work up from model to HPR rockets one step at a time and get comfortable with what works for them.

As we move more into additive manufacturing, parts will become more repeatable and we may be able to narrow the overbuilding.

Great observations. Another issue is that even if you know your materials, the processes used are also important and these vary by the rocketeer.

 

[Steve Shannon]

My general sense from hanging out here (since 2002-ish) is that there have always been newbies who fit that mold.

Yeah, I guess you’re right.


Steve Shannon

 

[pondman]

I underlined a sentence in John Coker’s post that really stood out. I feel like this is something that this “normal progress” is happening less recently. I feel like more people are trying to leapfrog past those experience building steps in an effort to achieve higher altitudes and greater velocities. I’d like to know if others are seeing the same thing that I am.


Steve Shannon

Steve, I have seen this since I got into the hobby 20+ years ago. I have also seen the "now what?" syndrome from a lot of folks who have done this.

 

[Steve Shannon]

Steve, I have seen this since I got into the hobby 20+ years ago. I have also seen the "now what?" syndrome from a lot of folks who have done this.

Exactly. My worry is whether we see more of it now. When you and I started it took a greater investment in time and effort. We didn’t have the vast assortment of G12 airfare or G10 fins that we have now. People glassed cardboard or phenolic tubes and plywood fins.
Don’t get me wrong; I’m not looking for a return to the “good old days” that we remember more rosy than they really were. I don’t want to have to jump into a pool with a glassed body tube to soften the cardboard enough to remove. I like the composite materials that are available; I just worry that it has become too formulaic to achieve the three levels of certification, then fly as high as possible at BALLS, declare triumph, and move on to the next hobby. And maybe that doesn’t truly hurt anything.


Steve Shannon

 

[Nytrunner]

Easier ways to access information can lead to more people getting interested in Hi-power rockets with little-to-no interest in smaller stuff.
Or adults who shot small rockets as a kid, and want to make/fly bigger rockets now without revisiting model rockets.

There's enough info out there that people can figure stuff out, they just won't have certain knowledge gained by making/flying/troubleshooting L/MPR.
It's certainly doable, they may just have a rougher time in a few areas, or end up spending more money/time than they would otherwise.

Also, some adults may not have the time/budget for as many practice flights or xp rockets as others. That's where access to information, clubs, or forums can answer their questions and help guide them along.
Unless someone comes along and tells them "If you don't have the time/money for XYZ, rocketry isn't for you.....". Certainly doesn't help grow the community.

With more avenues into the hobby, what was "normal" may become one option out of several for entry. (who was it that said "The world's first variable was 'Normal'."?)

I love low, mid, and high power rockets. There's great lessons to be learned at each level that can aid people at the others.
That being said, I'm glad there isn't a requirement to fly 2-3 Low/mid rockets before being able to certify. (at least for NAR anyway. Pretty sure someone from Tripoli could gag at the suggestion lol).


None of the above applies to EX motor flying in my opinion though. Please learn how to make a certifiably safe rocket before you compound things by sticking a potential bomb in it!


**Then there's the whole topic of college competitions. In short, they're great opportunities, I love them, they nudged me into high-power. They also run the risk of pushing people into rushed certification.
Of course these students may never want to make rocketry a hobby/sport, they're looking for a career and an opportunity to distinguish themselves from the crowd.

 

[rstaff3]

Exactly. My worry is whether we see more of it now. When you and I started it took a greater investment in time and effort. We didn’t have the vast assortment of G12 airfare or G10 fins that we have now. People glassed cardboard or phenolic tubes and plywood fins.
Don’t get me wrong; I’m not looking for a return to the “good old days” that we remember more rosy than they really were. I don’t want to have to jump into a pool with a glassed body tube to soften the cardboard enough to remove. I like the composite materials that are available; I just worry that it has become too formulaic to achieve the three levels of certification, then fly as high as possible at BALLS, declare triumph, and move on to the next hobby. And maybe that doesn’t truly hurt anything.


Steve Shannon

I know it is nothing new but there may be more of it. A lot of the people who skip to HP seem to hit a plateau and lose interest. I also know what the majority of fliers don't use TRF, or are mostly lurkers. So, it could be the actual number of such fliers has increased and I haven't noticed. It's those people that make me happy there is a cert program that at least gives some minimal oversight.

 

[Bat-mite]

Some people will race their way through any hobby. It is a matter of personality. Some people want to experience a large variety of things; others want to get really good at one thing and stay with it.

For me, rocketry is as much about spending a day outside, talking to interesting people, serving and helping where I can, being with my kids, etc., as it is about building and launching rockets. Others will get tired of it in a few years. That's life.

 

[afadeev]

I underlined a sentence in John Coker’s post that really stood out. I feel like this is something that this “normal progress” is happening less recently. I feel like more people are trying to leapfrog past those experience building steps in an effort to achieve higher altitudes and greater velocities. I’d like to know if others are seeing the same thing that I am.

My general sense from hanging out here (since 2002-ish) is that there have always been newbies who fit that mold.

Neah, you are just might be getting cranky with age....
:lol:

The first and only question my kids asked when I gave them complete freedom to order their own rockets was: "which one goes the highest?"

And you know what - I remember sorting my rocket preferences by exactly the same criteria 30+odd years ago.
I bet so did YOU, and most everyone else here, if you think back to your younger days!

Geee, lets go "low and slow" - that was NOT how any of us got excited about this hobby.
We all wanted to go high, and fast!

The only major difference now is that it's WAY easier and cheaper to go crazy high and stupid fast today, then it was decades ago.

Frankly, I'm super happy that my eight year old has soldered together her very own GPS transmitter/receiver, and built her first mid-power FG model. I exited the hobby as a teenager long before either GPS or FG components became affordable and readily available.

Kids are having so much more fun these days then we did.
Good for them!

My worry is whether we see more of it now. When you and I started it took a greater investment in time and effort. We didn’t have the vast assortment of G12 airfare or G10 fins that we have now. People glassed cardboard or phenolic tubes and plywood fins.
Don’t get me wrong; I’m not looking for a return to the “good old days” that we remember more rosy than they really were. I don’t want to have to jump into a pool with a glassed body tube to soften the cardboard enough to remove. I like the composite materials that are available; I just worry that it has become too formulaic to achieve the three levels of certification, then fly as high as possible at BALLS, declare triumph, and move on to the next hobby. And maybe that doesn’t truly hurt anything.

Hurts nothing, other than the wallets.
:surprised:

Which is all music to the ears of the vendors, of which there are easily 10x of what I remember from the last time around (largely due to the online storefronts).

a

P.S.: You want non-formulaic certs? Consider adding the following:
Level 4 cert: hit Karman line.
Level 5 cert: enter Earth's orbit, and return with full recovery.
Level 6 cert: enter Mars's orbit, and return with full recovery. Present model to cert team for inspection after flight.

 

[rharshberger]

Honestly if anything there needs to be a certain amount of time between certs, and yes I did mine rather quickly, but in hindsight more time between certs would have improved my learning experience and been a bit less stressful.