Overbuilding

[The EGE]

There's two main points I see here.

1) Extreme overbuilding is not acceptable. If a recovery failure will put human lives at risk, then do not fly the rocket. Damaged rockets can be repaired or replaced a lot easier than humans, and a major injury would create massive legal battles. Our hobby is legal and we are allowed to fly up to large rockets with a large amount of self-regulation precisely because we follow basic safety rules. If you can't follow those basic rules of sanity, then do not fly.

If you can't stand any damage, then don't fly your rockets. A damaged rocket after a bad recovery means it was designed properly and it got damaged instead of possibly hurting a person. A damaged rocket after a sucessful recovery means either you used too small a chute, or you got unlucky, or you had extremely weak joints. Epoxy alone is only 10% of the strength; 90% is knowing how to make a sucessful glue bond and fillet. I've had some chute failures where a rocket built with wood glue had all the joints survive, and balsa shatters. I have sent a rocket with all wood glue fillets to the speed of sound, and it deployed at high speed and survived.

2) If a rocket's recovery system deploys correctly, it should lower the rocket to the ground safely at around 15-20 feet per second without damage. A properly designed recovery system will deploy every time, have a properly sized chute / streamer / etc to bring it down at a safe velocity, have protection for the system (wadding, baffle, kevlar sheet, etc), and will incorporate any needed ways to land the rocket in the correct orientation, and prevent it from swinging if needed. DO NOT overbuild your rockets because of recovery failures; learn to recover them safely.

Nylon chutes with thick lines also tangle a lot less than than plastic chutes with thin string for lines. You can sew your own, or CATO Chutes and Sunward, and others, have good cheap ones.

 

[ScrapDaddy]

There's two main points I see here.



Nylon chutes with thick lines also tangle a lot less than than plastic chutes with thin string for lines. You can sew your own, or CATO Chutes and Sunward, and others, have good cheap ones.

Erm I remember my first successful estes parachute deployment, it was last week, and I have been flying for 2 years! I was shocked at the drift, I was used to the typical estes streamer/ parachute hybrid

 

[The EGE]

Erm I remember my first successful estes parachute deployment, it was last week, and I have been flying for 2 years! I was shocked at the drift, I was used to the typical estes streamer/ parachute hybrid

Don't we all. My Estes chutes end up:

30% sucessful deploy
30% melted despite plenty of wadding
30% lines tangle
10% refuse to unfold

I've gotten over 90% sucess with nylon chutes, and they're also easier to get out of trees. The nylon line slides; cotton tangles in branches. I never fly with a stock Estes chute any more. Plastic chutes also refuse to unfold in cold weather; as a fellow northeast cold-weather flier I share your pain.

 

[cjl]

I'd say I have much better luck with plastic chutes than that. I'm at maybe 70% successful, 20% slightly melted (but still functional), and 10% tangled.

 

[Kira_Majeric]

I will admit it am new to rockets, but am I under the understanding that these overbuilt rockets are a violation of the model rocketry safely code. At least the is what I have read in every set of instruction in every kit I have assembled.

Granted, I was a little frustrated when my Renegade went for a ride across the playa at Black Rock and ripped off two fins. But, really this is nothing that a sheet of balsa and a x-acto knife can not fit. I made plastic templates of my fin cut outs.

https://www.nar.org/NARmrsc.html

 

[ScrapDaddy]

am just overjoyed that my rockets are unharmed, and after swing the 12pm chute drift, I am starting to miss my streamer, but estes streamers are quite intresting it has a matte finish to it, it is plastic..... The elastic shock cord and plastic parachutes have always been a thorn in estes

 

[mkadams001]

A bullet regardless of size is still a bullet. Overbuilding like this is really harming our hobby. It's absurd not to reconize such a grave problem when it's staring us in the face. Our hobby has always had a great safety record specifically because we build models to do no harm or as little as possible. With is kind of overbuilding mainstreaming that will no longer be the case. It's time for the LPR community to push back hard against the demise of our hobby by the overbuilders and those who are trying to mainstream it as Normal practice. Exactly what such an article in a National MODEL rocket magazine does. It's only going to take a single accident with one of these overbuilt absurd bullets to start us down the road to excessive restricted hobby death. Keep your head in the sand if you wish, but i'm trying hard to get enough people to gather to demand a retraction and explaination for allowing such an article to be published.

Publishing a counter article is fine but it doesn't really call attention to and rebut to all those how have already seen it and like poor ScrapDaddy been pull in by it. Overbuilding must be minimized...no Stopped in it absurd tracks before it really hurts someone and the entire hobby along with it.

Explain to me where exactly is says that overbuilding a rocket is a violation of a model rocket rule. The guy in the article reenforced a kit with fiberglass and epoxy and guess what, that is considered a plastic; well within the model rocket code. The code also shows a max weight of 53 ounces; his modification increased the weight to a whopping 4 ounces.

I am not the one with my head in the sand. I have not seen a rash of kids bringing out their Estes kit built and reenforced with fiberglass, carbon fiber, and epoxy. However, you and others seem hellbent on maintaining some sort of self imposed standards of rocket construction then, claiming any variation creates an unsafe flight environment. What is the size limitation of a rocket that becomes unsafe? Is a 4 ounce lpr more dangerous than a 32 ounce rocket? Your argument of safety just does not make any sense. The safety factor is building a rocket that has a stable flight and uses an appropriate recovery device along with all the other variables that creates a safe flight environment; not a rocket that self destructs upon impact of anything harder than a cotton ball.

Sport Rocketry magazine covers a wide range of topics. I see no problem with publishing an article about construction techniques regarding materials that some think of as no-no's in rocket building. I don't think that Sport Rocketry is endorsing bulletproofing rockets, but are allowing others to see some of the options out there. If someone wants to glass their low power kit then so-be-it, I wish them the best of luck.

 

[troj]

I will admit it am new to rockets, but am I under the understanding that these overbuilt rockets are a violation of the model rocketry safely code. At least the is what I have read in every set of instruction in every kit I have assembled.

It's not a violation.

In my opinion, though, it is horrible, horrible overkill.

-Kevin

 

[Micromeister]

Lets be clear: by the current "simplification" of our safety code Overbuilding and bulletproofing is not a direct violation of the code but is so far outside the spirit of the code it's beyond rediculous. But this IS a SAFETY Issue that can no longer be ignored.

First Fibreglass is NOT plastic it is spun GLASS. while laminating epoxy can be considered a plastic, the combination is NOT. Further fibreglass, carbon fiber and other reinforcing fabrics have been proven to be totally unnecessary over standard paper and cardboard construction materials.

The mass of the bullet has absolutely NO barring on this argument. a bullet is a bullet regardless of size. model rockets...regardless of mass SHOULD be self-destructing on impact to absorb as much of their kinetic energy as possible rather then expel it.

The Cover Headline reads:

"BulletProof your next Rocket"
What the heck do you think that translates to when read by the masses. It means this construction method is perfectly fine for all model building construction. IT IS NOT! This issue, it's cover headline and the article itself must be retracted.

G Harry Stine mentions in "40 years of Safety" report that the reason we've maintained such an outstanding safety record for all that time can be directly atributed to the fact we build our models to "Self-Destruct" on impact.

Bulletproofing is counter to the aims and methods of model Rocketry. As such the practice must be at least controlled if not eliminated.

We have hard evidence and flight tested proof that overbuilding, and the use of these products involved are totally unnecessary in the first place. encouraging such behavior will only contiune to erode the already dangerously shrinking safety margins maintained at our launches.

Since it's clear we can't really settle anything here I think this well be my last post on the matter. I think we've presented the facts and answered those who disagree. I'll close by asking everyone to be sure to send an e-mail to Tom Beach the Editor of Sport Rocketry requesting action to remove and retract this Hobby hurting article and Cover HEADLINE.
Thanks for helping protecting the hobby we've loved for more the 45 years.

 

[Ironnerd88]

It's not a violation.

In my opinion, though, it is horrible, horrible overkill.

-Kevin

It may not be a violation of the letter of the safety code, but it is certainly a violation of the spirit of the code.

The code states:

Materials. I will use only lightweight, non-metal parts for the nose, body, and fins of my rocket.

The weight of the rocket in questions was more than DOUBLED, so I really can't say the materials were "lightweight".

It also states...
Recovery System. I will use a recovery system such as a streamer or parachute in my rocket so that it returns safely and undamaged and can be flown again, and I will use only flame-resistant or fireproof recovery system wadding in my rocket.

Note that the code sates that it is the job of the RECOVERY SYSTEM, not a super-beefy structure, to prevent damage to the rocket.

 

[Kira_Majeric]

This is good to know, that is is not a violation. Not that I would ever build one. I do not see the point.

I personally feel it is unsafe to have a glassed model. As far as I can tell; model rocketry seems to be a completely unregulated sport, and if we want it to stay that way we should think "Safety First".

I have also seen that these rockets are flown in populated areas such as schools and parks. All you need is one injured child and something in going to hit the fan.

 

[cjl]

This is good to know, that is is not a violation. Not that I would ever build one. I do not see the point.

I personally feel it is unsafe to have a glassed model. As far as I can tell; model rocketry seems to be a completely unregulated sport, and if we want it to stay that way we should think "Safety First".

I have also seen that these rockets are flown in populated areas such as schools and parks. All you need is one injured child and something in going to hit the fan.

I wouldn't go so far as to say all glassed models are unsafe. Sometimes, fiberglass is the lightest and most effective way to strengthen a model. I have a Deuces Wild that I fiberglassed with tip to tip 1/2 oz (one layer only), and it barely added any weight. I did it so that I could fly it on Aerotech D motors, and it worked great.

 

[shreadvector]

Want to know what happens when a "sturdy" rocket hits a human when the recovery system fails?

https://www.cpsc.gov/cpscpub/prerel/prhtml07/07319.html

https://www.rocketryplanet.com/content/view/2153/28/

MODEL Rockets should not be thick hard plastic or thin 'stronger than steel' reinforced composite.

And loading the nose cone with metal nose weight has not been acceptable for decades. NAR competition uses sand and most kit manufacturers use plasticine "clay".

Recovery systems are very important, but if they fail the rocket needs to crunch on landing/crashing rather than burrowing through flesh, bone, and brain.

Your attorney will confirm this advice. Ask them. Please.

 

[jdbectec]

Want to know what happens when a "sturdy" rocket hits a human when the recovery system fails?

https://www.cpsc.gov/cpscpub/prerel/prhtml07/07319.html

https://www.rocketryplanet.com/content/view/2153/28/

MODEL Rockets should not be thick hard plastic or thin 'stronger than steel' reinforced composite.

And loading the nose cone with metal nose weight has not been acceptable for decades. NAR competition uses sand and most kit manufacturers use plasticine "clay".

Recovery systems are very important, but if they fail the rocket needs to crunch on landing/crashing rather than burrowing through flesh, bone, and brain.

Your attorney will confirm this advice. Ask them. Please.

Thanks for those links, I somehow missed the Boy Scout story, that is frightening.

In all honesty, since it was a March/April issue, I was expecting to see some kind of disclaimer at the end of the article, I still have to wonder if it was completely serious, or one of the best executed April Fools I have ever seen.

 

[SecretSquirrel]

The Boy Scout injury was not caused by a failure of the recovery system.

 

[jdbectec]

The Boy Scout injury was not caused by a failure of the recovery system.

Can you elaberate on that?

 

[SecretSquirrel]

I was retained as an expert witness in that case and spent hours reading testimony from witnesses and representatives of Estes.

The rocket struck this boy while still under power or just at the beginning of the coast phase, penetrating a section of his upper arm and his chest. The ejection charge then went off, driving the nose cone deeper into the chest cavity.

The rocket apparently took a 90 degree turn immediately after leaving the launch rod. The boy was at the base of the hill from which they were launching. From the witnesses, the rocket lost altitude as it went along but as they were on a hill, it pretty much followed the slope of the terrain.

 

[GrossApproximator]

Stuff like this makes me fear for model rocketry. I hope this thing doesn't hurt the hobby.

 

[troj]

The rocket apparently took a 90 degree turn immediately after leaving the launch rod. The boy was at the base of the hill from which they were launching. From the witnesses, the rocket lost altitude as it went along but as they were on a hill, it pretty much followed the slope of the terrain.

I suspect that any rocket with a pointed enough nosecone (such as a Black Brant) that goes unstable would, unfortunately, have much the same result.

Regardless, it's a tragedy that this young man was injured. The article doesn't seem to indicate to what extent he recovered, and I do hope it was a full recovery.

-Kevin

 

[RoyAtl]

I suspect that any rocket with a pointed enough nosecone (such as a Black Brant) that goes unstable would, unfortunately, have much the same result.

Regardless, it's a tragedy that this young man was injured. The article doesn't seem to indicate to what extent he recovered, and I do hope it was a full recovery.

-Kevin

I still doubt a Black Brant would have had quite the kinetic energy of an all-plastic rocket such as this (and remember, this was originally a Cox rocket from 1970; all the Cox rockets were ridiculously thick plastic).

 

[SecretSquirrel]

The article doesn't seem to indicate to what extent he recovered, and I do hope it was a full recovery.

I believe he has diminished lung capacity due to scarring and/or loss of tissue, but I do not know to what degree.

 

[plano-doug]

The rocket apparently took a 90 degree turn immediately after leaving the launch rod.

Don,

Can you refresh my memory? I know you said it was not a stability issue. But I can't recall what caused it to tip off. Was it the retainer ring? Or something else?

Thanks. And a belated happy 31st birthday to you

Doug

.

 

[SecretSquirrel]

Don,

Can you refresh my memory? I know you said it was not a stability issue. But I can't recall what caused it to tip off. Was it the retainer ring? Or something else?

That was one of the big questions but the case was settled before all the questions could be answered. My focus was to study and comment on the safety practices of the BSA as they compared to NAR safety codes and practices. Others were charged with studying the flight profile and stability of the rocket and more than likely had different documentation than I did.

From what I was given, it would be difficult if not impossible to determine the exact cause of the problem. I do believe the retainer ring was still intact and tight in the model after the accident. As I recall, the witnesses almost all agreed that it was a rather abrupt turn about 6 feet above the end of the launch rod. I would have to go back and look at my notes but I seem to recall winds in the 10 mph range with gusts to around 15. I could be wrong on this but I don't think the rocket turned into the direction of the wind.

And a belated happy 31st birthday to you

:blush:

 

[troj]

I still doubt a Black Brant would have had quite the kinetic energy of an all-plastic rocket such as this (and remember, this was originally a Cox rocket from 1970; all the Cox rockets were ridiculously thick plastic).

Kinetic energy is dependent on mass and speed, not density.

I've seen pointed balsa nosecones demonstrate an amazing ability to penetrate even rather firm ground, with minimal damage to the body tube. Considering that human flesh is not as hard as the ground, I have no doubt that a pointed balsa nosecone has a rather scary ability to penetrate.

Hopefully it never happens.

-Kevin

 

[jdbectec]

That sounds like a very unfortunate, and very unusual incident, thanks for filling in the blanks.

 

[dixontj93060]

Considering that human flesh is not as hard as the ground, I have no doubt that a pointed balsa nosecone has a rather scary ability to penetrate.

6 feet of it underground, BTW.

 

[jdbectec]

6 feet of it underground, BTW.

That looks like it could be Flatville, Illinois.

 

[Ironnerd88]

Kinetic energy is dependent on mass and speed, not density.

If two rockets are otherwise identical, and travelling at the same speed, the denser of the two will have greater mass, and therefore greater energy.

 

[shreadvector]

Two rockets with the same motors will have the same energy from the motors transferred to them and or the air (momentum of the rocket and air drag/energy dissapated by the air drag).

We could list hundreds of different combinations of diameter, fins size, finish, material density, etc. Why bother? Getting hit by a non-crushable thick plastic rocket with metal in the nose is "BAD".

View attachment themodyn.zip

 

[plano-doug]

If two rockets are otherwise identical, and travelling at the same speed, the denser of the two will have greater mass, and therefore greater energy.

If two rockets, differing only in mass but otherwise identical, are accelerated from rest by the same amount of impulse, which one has the greatest KE at the end of the motor burn?

The point of my question is that you can't assume the one with the greater mass will be travelling as fast. That is, you can't assume the heavier one received the additional impulse to get it up to the same speed as the lighter rocket. A more logical assumption is that they both used the same motors. Hence, the heavier one will obviously not gain as much speed when propelled by an identical motor. So, given, two X-15's, one heavy and one light, both flown on C6 motors, it's not readily apparent which one will have the most KE. You need to find the burnout masses and velocities, then calculate the KE.

Without that, all that can be concluded with certainty is that the denser but otherwise identical rocket has a great ballistic coefficient.

Doug

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