NAR rule clarification

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rocketsonly

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

So that means the NOSE, BODY, and FIN cannot be made of metal, but other parts CAN be? Including metal screws that go through the body tube and into a coupler? Or is a nylon screw better?

Thanks.
 

powderburner

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I think you are OK to use a few metal screws.

The original thinking behind this rule was to reduce the hazard that a crashing rocket would present to bystanders on the ground. You are supposed to build using 'crush-able' materials and such, and you are supposed to minimize the use of metal.

Back in the olden days when these rules were first made, we routinely used metal eye screws in the base of nose cones (they were balsa back then) to attach to the rest of the rocket. We even used strips of lead foil (horrors! shudder! cringe!) as ballast.

Currently, we frequently use strips of metal in the form of motor retainer clips, and that is right next to the motor (where a burst case could turn the metal into dangerous shrapnel). Your use of a few screws to secure a payload section is fine.
 

jetra2

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You have to realize one thing about that rule. It is the NAR's Model Rocketry Code. It differs from the HPR code somewhat. But yes, your understanding is correct - as long as it is a NON-structural part, i.e. if it's not there the rocket will still fly, it may be onboard.

For model rocket work, a nylon screw would probably be better, just because it's lighter than a similarly sized metal screw.

Jason
 

DynaSoar

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Originally posted by rocketsonly
"#1 Materials. I will use only lightweight, non-metal parts for the nose, body, and fins of my rocket. "

So that means the NOSE, BODY, and FIN cannot be made of metal, but other parts CAN be? Including metal screws that go through the body tube and into a coupler? Or is a nylon screw better?

Thanks.
The NAR HPR code mentions "only sufficient ductile metal" for strength necessary to the rocket. TRA says pretty much the same thing. The intent is that there be no major structural metal components. This comes from the FAA regs, which state "containing no substantial metal parts " as part of the definition of a model rocket.

Screws is not a problem. Metal screw eyes have been used for over 40 years. Nylon's lighter, certainly.
 

Micromeister

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Tiny metal screwheads, Pin heads, metal foil "plate antenna's, brass or copper wire probes, tiny metal (usually brass) internal ejection ducting tubes, booster support/seperator telescoping alum. tubes. all manor of latches, wire springs and clasps, foil bandings and many other SMALL NON structural metal parts have been used in natinal and international Model rocket competition for a very long time. I regularly use 000-120 to as large as 2-56 threaded brass, stainless and alum. fasteners in many scale models, some are functional, most simply decorative.
As many have mentioned earlier, these rules are intended to restrictly the use of metal airfames, nosecones and fins. We want our models to crush easily lessening the damage done if they were to hit an object or person...though the currently available injection modeled plastic nose cones are very penetrating if hitting flesh. We had to have a PNC-20R surgically removed from a club members leg last weekend:(
Hope this helps.
 

Elapid

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Originally posted by Micromeister
We had to have a PNC-20R surgically removed from a club members leg last weekend:(
Hope this helps.
got pics?
:eek:
 

powderburner

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Now there just has to be a story to go with that injury report. I mean, how in the heck do you get shot in the leg with a rocket? Did the pad blow over or something?
 

Micromeister

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Originally posted by Elapid
got pics?
:eek:
Oh Elapid NO I don't have a pic...That's really tacky!

Powder:
It wasn't a pretty thing, I'm not sure I really want to talk about it but there is a GOOD LEASON in this accident so I'll post most of incident.
During our Launch Saturday, someone flew one of those larger 8 or 9" long foam shuttle gliders...NOTE is said ONE foam glider! piggy backed on what looked to me like a BT-20 bodied rocket. the model was only about twice as long as the shuttle from inspection after the fact. I understand from the RSO the model owner explained he had added an enlarged fin OPPOSITE the shuttle.. Red flag!!! Which did absolutely nothing to balance the Drag caused by the shuttles girth. TWO Shuttles no problem ONE shuttle..Short Booster red flag 2...HO man!!!
Flying on a B motor, at ignition the model did exactly what the physics said it should do...Reached the end of the rod and took a HARD right to the shuttle mount side. Followed a slightly arching path under power into the thigh of another member sitting under his canopy preping one of his models....He's Ok, had to spend the rest of the weekend in the hospital but no permenant muscle or ligiment damage and seems in good spirits after the surgury to remove the PNC-20 completely imbedded in the leg. OUCH!

A couple of REALLY GOOD LESSONS for the readers here.

1) Any small foam glider attached to the side of a vary long model, positioned well back from the center of gravity will fly just fine... HOWEVER! never add a single glider to the side of a short stubby rocket or a large hulkin mass of any kind to one side of a free flying vehicle. Remember everything in free flight revolves around the center of gravity. The added weight and Girth will cause the free flying model to turn in the direction of the add-on mass and Drag. Lift from a glider wing airfoil also add a little to this problem.

2) Flat or fat slabs of anything mounted on one side of a vehicle act like an air break (major Drag feature) to that side of the vehicle. "Balance the load" with a second glider or something with at least as much cross section and mass as whatever has been added to the other side.

3) Be observant all the time but especially while on the flying field. I feel somewhat responsible for this accident, Had I been paying attention to what was being flown instead of perping my own models or yacking with the wife this might not have happened. No I wasn't the RSO or LCO but if we're on the field we are ALL supposed to be keeping an eye on what's flying. Had I seen this contrapsion on the pad I would NEVER have let it fly...If you see something you think isn't right immediately SAY something... I usually scream HOLD! than talk to the RSO or someone in charge.. Don't be afraid...Speak up... if anyone had really looked at this model.... this accident might have been avoided.
Sorry I don't mean to preach, I'll get off my badly broken soapbox now. Hoping everyone has leaned something.
 

powderburner

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Originally posted by Micromeister
[B}3) Be observant all the time but especially while on the flying field. I feel somewhat responsible for this accident, Had I been paying attention to what was being flown instead of perping my own models or yacking with the wife this might not have happened. No I wasn't the RSO or LCO but if we're on the field we are ALL supposed to be keeping an eye on what's flying. Had I seen this contrapsion on the pad I would NEVER have let it fly...If you see something you think isn't right immediately SAY something... I usually scream HOLD! than talk to the RSO or someone in charge.. Don't be afraid...Speak up... if anyone had really looked at this model.... this accident might have been avoided.
[/B]
Micro makes a VERY important point: safety is not just the responsibility of the RSO! We all have to use our heads!
 

Mad Rocketeer

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I'm with Micro. I don't want pics. I hope that was just a joke.

This puts me in mind of all I read from people who build "cast iron" rockets. You know the posts. "My rocket came down ballistic from 3000 feet onto solid concrete and didn't take a scratch. Man, is that puppy built, or what? I love to build 'em tough! :) "

:eek:

My thought each time is that that's fine for the rocket, but what about everything under the rocket? Granted, anything directly under a rocket making a streamlined return to Earth is going to be at some degree of risk, but something built like (and as heavy as) a kevlar reinforced brick is going to do corresponding damage if its owner rolls snake eyes and it lands on someone's house, car, . . . or head.

We need to be looking to advance the science and art of strong-but-light rockets that handle the stresses of launch, ejection, and landing but crush safely if they hit something solid. Tough fins that handle a K motor's thrust but pop off in a prang would fit. The nose and tube could absorb the damage, leaving the motor mount, fins, chute, shock cord and mount, centering rings, motor retention, and perhaps payload intact.

I like the exploration being made into alternative adhesives and into correct amendments to epoxy. Fillet design is advancing too. It's not all heavy monolithic epoxy any more. People are reinforcing with balsa or basswood strips at the fin roots and a lot more, rather than just pouring the epoxy can over the rocket and calling it good.

Lighter rockets can fly on smaller motors too, and if they are still strong, they can handle the larger motors too. These are good things.

Finesse and good engineering can take us to a new plateau. Meet ya' at the top! :cool:
 

Micromeister

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Right on! Right on for the overdrawn..or Overbuilt as the case may be:D
Could not agree with you more, I cringe at the bullet proof model threads also...
 
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