Steel harpoon in my rocket, legal?

Sorry, this is kind of a 'tongue-in-cheek' post after reading others involving metal and rockets.

How the heck is it that a flimsy aluminum can as a part of a body tube is 'illegal' but people use 1/4" steel threaded rod all the time?

Which would you rather be hit with?

Heck, I'd take getting whacked with the aluminum can over even a 9v battery...

Flimsy aluminum can is fine. Whoever told you otherwise is...... well they be off.

It seems to be an extremely 'grey' area on metal. I won't quote it directly, but NAR seems pretty specific on implying no metal, but yet it seems to happen quite often, at least 'internally'. (i.e., inside the rocket)

A cardboard tube rocket coming in ballistic is one thing, but with electronics, batteries and threaded rod in it's gut, it's a whole other animal, but who would know until it...hit?


Edit- I just read the NAR rule from the 'other' post. Non metal for the tube, fins and nosecone.

I've seen metal tipped nosecones, and full on metal fin cans, how do those slide by?

The non-metal statement is in the NAR Model Rocket Safety Code.
When you exceed the limits of total model weight at liftoff, propellant weight or total impulse for a model rocket, then the High Power Rocket Safety Code comes into play. This is where ductile metal is allowed when necessary. By the time you're putting electronics into e-bays with all-thread rods to secure them, you've likely slipped into the HPR code even if you're using a mid-power motor.

Just my :2:

I'm not too worried about threaded rods in the av bay but if a 30 lb fiberglass rocket with a pointy metal tipped nosecone comes down ballistic, even sitting in your car is not going to protect you. That's why I try to pay attention to every flight when I'm at a launch, especially high power.

Take it from Nathan. He's seen some crashes in his day. :wink:

Nathan said:

I'm not too worried about threaded rods in the av bay but if a 30 lb fiberglass rocket with a pointy metal tipped nosecone comes down ballistic, even sitting in your car is not going to protect you. That's why I try to pay attention to every flight when I'm at a launch, especially high power.

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+1,000,000

I love watching every flight when I'm at a launch, so this is second nature for me. However, when any family or friends come to a launch with me I feel responsible for them and am extremely vigilant reminding them to pay attention to every flight.

And stand up when the LCO says "Stand up!" At the MDRA November launch, they called for a stand-up due a large rocket's first flight. I had to walk up half the spectator row urging people to stand up and pay attention.

And stand up when the LCO says "Stand up!" At the MDRA November launch, they called for a stand-up due a large rocket's first flight. I had to walk up half the spectator row urging people to stand up and pay attention.

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Dear God, yes. The only significant injury I've seen was when somebody in the bleachers wasn't watching a flight that came in ballistic. It wasn't even a stand-up flight, just a medium size mid-power that failed to eject the nose cone. They still went into surgery that night.

At our TARC teams' most recent launch, I rolled out the no cell phones rule, with exceptions for timers and people taking video. My daughter bumped it up to "I'll ask you to sit in the car if I see you texting," which I think is totally valid. Studies on drivers show texting is as bad as drinking, and it's pretty common to have no alcohol while flights are going rules at launches.

Oh don't even get me started on the parents that let their kids just wander around. I've seen the LCO almost shut down the range for kids wandering into the flight line, more than once.

More to the OP's point, I think anything big enough to have a threaded rod in it is going to ruin your day if it comes down ballistic on your head whether it has metal parts or not. While the "no metal structural parts" is a nice bright line to draw in the rules, I'm not sure it makes that much difference for larger LPR and medium MPR rockets. For the 30-lb fiberglass rocket mentioned above, I don't think the metal tip makes a bit of difference in how dead you'd be or how big the hole in your car would be. Maybe in how big the hole in the ground under the car is, though.

These scenarios are not unlike the people at baseball games with seats down along 1st and 3rd. Several times a year someone is not watching as the ball is pitched and a screaming foul ball (or bat) dents their face.... or worse. The first time I saw a decent sized rocket come in ballistic and land within a few hundred feet (so I could hear the impact), I had several thoughts go through my mind.

1) Pay attention to every launch
2) Follow the rocketry safety codes - NO EXCEPTIONS
2) Be vigilant in how I build, prep and fly my own rockets. This is the one that sometimes keeps me up at night. Given the recent rocketry related death and a some injuries I have read/heard about, I can't imagine how awful I would feel if my rocket was responsible. I know there is no 100% safe guarantee, but I am commited to trying to be perfect in that regard.

Back to the OP - I never really thought about the specifics of the threaded rods and the damage they could possibly cause on ballistic entry or a dangerous trajectory off the rail/rod. I know the question was brought up somewhat sarcastically in response to the discussion about the 'aluminum can wrap on booster'. However, it still makes me think about different ways to do things. There have been threads about coupler AV-bay construction without threaded rods. Seemed like the motivation was primarily mass reduction, but another benefit would be an upgrade in safety in that a section of coupler without threaded rods would be more likely to crush and dissipate energy in a 'collision'.... similar to the bumper of our new to us used car. Ask me how I know (think 16 y.o. son backing into a post... ugh!)

boatgeek said:

More to the OP's point, I think anything big enough to have a threaded rod in it is going to ruin your day if it comes down ballistic on your head whether it has metal parts or not. While the "no metal structural parts" is a nice bright line to draw in the rules, I'm not sure it makes that much difference for larger LPR and medium MPR rockets. For the 30-lb fiberglass rocket mentioned above, I don't think the metal tip makes a bit of difference in how dead you'd be or how big the hole in your car would be. Maybe in how big the hole in the ground under the car is, though.

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+1
Yes, that sharp pointy thing on top with mass behind it coming in ballistic is going to be a problem with or without threaded rods... That is the one thing I think about most in building and prep of the recovery system, GET THE AIRFRAME SEPARATED!

Most important to remember, if the rocket is not built to code, is allowed to launch, and results in death/injury/damage....NAR insurance will not cover any tort. The person launching the rocket and club sponsoring the launch would be totally liable.

Funny you should mention someone getting hit by a foul ball. I think I was about 14 at the time... May explain some, m-m-mm-maybe, but I digress.

I have another thread I mentioned I build rockets to FLY, not to land. I see no point in excessive overbuilding, unnecessary even detrimental added mass. If my rocket lands flat on a slab of concrete from 25fps, I would -expect- it to pop a fin.

When I build, I HOPE it lands in the grass, I don't PLAN for it to land on the road, if that makes sense?

No matter what material, size, or under X amount of power, as it's been mentioned -

Whether it's yours, or more importantly -someone else's-...


KEEP AN EYE ON THE ROCKET!

The worst thing I see is when a rocket launches, people look, see the rocket, lose it in the air (even though it's kinda coming towards them), and they just keep on doing what they are doing.

IF YOU DON'T SEE THE ROCKET... LOOK FOR IT. At least 1 person will have the rocket in their sights (hopefully). And if you see the rocket, point at it.

Another thing which struck me - not literally, fortunately - was many years ago when I was watching some HPR flights. One rocket had a metal body, failed to deploy, and if someone had been standing at ground zero then they'd have been injured. Another had a phenolic body, failed to deploy, and if someone had been standing near ground zero then they'd have been injured by the shrapnel. Maybe not as badly as if they'd been directly hit by either rocket, but being about 2' away from where the phenolic rocket struck would be worse than being about 2' away from where the metal rocket struck.