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Alby

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Let me start off by saying that I'm just getting back into Model Rocketry.
When I was a kid back in the 80s, I was a model rocket junkie. My hobby
fell by the wayside as my little kid funding couldn't support my demand for
rockets and engines. As such, my interest shifted into computers, BBSes,
and the up and coming Internet towards the end of the 80s and early 90s.

Now that I'm older and have money in my pocket, I'm interested in getting
back into model rocketry. I'm looking at building my own rockets as I inch my
way back into the hobby. One question I was pondering is on rocket
construction. I see that most people build their rockets from cardboard and/or
balsa wood. I was wondering, is there any NAR or Tripoli rules or regulations
that prevent you from building rockets with a metal frame and a cardboard
outer skin?

For rockets powered by smaller engines, it might not be a good idea since
weight is likely a problem. But as you swap in larger engines, getting that
rocket airborne shouldn't be an issue. I see that obtaining various Level
certifications grants you access to larger engines. So I'm also going to
start down the road of getting a Level 3 Cert.

In any case, what should I know about construction materials that are and
are not allowed.

Thanks,
 
Metal isn't allowed- it might hurt somebody- and anyway there's not reason to use it. Paper and phenolic are much lighter and a stable rocket doesn't need much transverse stiffness anyway- the stresses are longitudinal most of the time. demonstrate it to yourself- it's much harder to squash a tube lengthways than across its diameter. As long as it's stiff enough to withstand a bit of windshear, you can easily make a fair-sized model rocket out of rolled cardstock.
Such as one of these.
Or some of these, mostly cardboard or paper.
https://homepages.rya-online.net/markdunn
(Click through to IRW).
(COAYC is made of toilet paper cores).

P8221768.jpg
 
Metal isn't allowed- it might hurt somebody- and anyway there's not reason to use it. Paper and phenolic are much lighter and a stable rocket doesn't need much transverse stiffness anyway- the stresses are longitudinal most of the time. demonstrate it to yourself- it's much harder to squash a tube lengthways than across its diameter. As long as it's stiff enough to withstand a bit of windshear, you can easily make a fair-sized model rocket out of rolled cardstock.
Such as one of these.
Or some of these, mostly cardboard or paper.
https://homepages.rya-online.net/markdunn
(Click through to IRW).
(COAYC is made of toilet paper cores).



Thanks for the tip on metal not being allowed. Does that also apply to
High Powered Rocketry running H and Higher motors?
 
Thanks for the tip on metal not being allowed. Does that also apply to High Powered Rocketry running H and Higher motors?

The NAR High Power Safety Code, available here...

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

states that you can only use "lightweight materials such as paper, wood, rubber, plastic, fiberglass, or when necessary ductile metal, for the construction" of a rocket. I believe Tripoli has similar requirements.

from Wikipedia... "Ductility is a mechanical property used to describe the extent to which materials can be deformed plastically without fracture. In materials science, ductility specifically refers to a material's ability to deform under tensile stress; this is often characterized by the material's ability to be stretched into a wire. Malleability, a similar concept, refers to a material's ability to deform under compressive stress; this is often characterized by the material's ability to form a thin sheet by hammering or rolling. If metals were not ductile, there would only be very limited ways to shape a piece of metal into a useful object. Machining, forging, rolling, extrusion, drawing, stamping, punching, coining, bending, hammering, and many more require some ductility. Another aspect is that, if metals were not ductile, it would be very easy for metal things to break. Thing about what happens if you drop a glass or a ceramic plate."

So, there is some room for interpretation. The key wording is "when necessary". You do see some metal in high power rockets. U-bolts, quick links, motor casings and closures, all-threads, etc.

This has previously been discussed in other threads, such as this one ... https://www.rocketryforumarchive.com/showthread.php?t=23512

This comment came from there... "So it seems safe to say that the use of metal body tubes in model rocketry is a violation of the model rocket safety code. It also seems clear the both NAR and Tripoli's HP safety code allow minimal use of "ductile metal". That said it seems to me that minimal is the optimal word here and it is best to avoid the use of metal when a suitable alternative is available."
 
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..then there was the Dr. Rocket all aluminum 4" true minimum diameter. They made enclosures threaded at both ends and a fin can arrangement with slots and set screws to hold the fins. I believe they had a graphite nosecone but I might be wrong about that.

The only thing TRA said about it was you couldn't use one to do a cert with. Too much was already done when you bought it.

(I've always wanted one with a N sized fuel chamber:cyclops: )
 
..then there was the Dr. Rocket all aluminum 4" true minimum diameter. They made enclosures threaded at both ends and a fin can arrangement with slots and set screws to hold the fins. I believe they had a graphite nosecone but I might be wrong about that.

The only thing TRA said about it was you couldn't use one to do a cert with. Too much was already done when you bought it.

(I've always wanted one with a N sized fuel chamber:cyclops: )



Sounds like the Rocket Police aren't enforcing their own High Power Rocket Safety Code.
 
Not really if you think about it. Aluminum fins have been around and avalible for a long time (black sky Optimal for example) Aluminum closeures, motorcases, graphite nozzles and nose cones also. The only added aluminum part is a upper aluminum tube, thats it. It is ductile metal so it meets the critera for a high power rocket and as the manufacturer deems it necessary the rocket is completely legal. These can be made easily with a machine shop to make the enclosuers as I don't think any are around anymore to be purchased:(
 
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