Maybe you could use booster motors and then something like
https://www.picoalt.com/ for deployment?
I'm not sure that this suggestion is a step in the right direction for Cornyl. (And I'm not picking on Will either; there are many people who make these sorts of alternate suggestions.)
Yeah, I know lots of you guys use these electronics all the time in bigger rockets and it's no big deal, but you have to remember that there are also many of us who specifically do NOT want to use electronics:
-- A low-power rocket often simply does not have extra internal volume to install a timer, a battery, switches, and wires, or a good place for a usable-sized access door without completely ruining the rest of the rocket
-- A low-power rocket often cannot stand the added weight of an electronics bay without seriously impacting the flight performance (in a bad way)
-- It is definitely more expensive, often many times the cost of the rocket kit, if you have to go buy the electronics just for this one job
-- It is definitely more complex, not that it is "impossible" to manage, just that it makes
simple low-power rocketry into something different
-- Electronic timing goes with external (non-motor-based) ejection systems, which generally require electrical igniters and black powder, both of which usually require LEUPs and all sorts of other government nonsense, which completely changes low-power rocketry into a whole different animal
-- Sometimes you just like to try to master the design/engineering/craftsmanship aspects of a more complex configuration, and to try new techniques to complete a new rocket concept
-- It doesn't "feel" like model rocketry
-- Keep it simple (and something else?)
I have also asked questions about the acceptability of unconventional materials and design approaches. These questions do not seem to receive much serious evaluation, instead generally triggering only knee-jerk reactions like "you CAN'T do that!!!" or "use electronics." I would instead encourage everyone to look over the NAR rules, to consider common sense, and to give the question more than two seconds of thought. If you have a safety concern, by all means DO voice it, but we should avoid blanket condemnations when we don't even know the details of the rocket design at hand.
Cornyl;
There are many examples of "accepted" design practices using these sorts of materials in the immediate neighborhood of motors. The one that stands out to me is the use of a (low-power) steel motor retaining clip, positioned literally right on top of the motor. Or, steel retaining hardware immediately next to the nozzle end, from which a clip or bolt or nut could be thrown. Then you have the widespread use of styrene plastic (relatively brittle) fin cans that surround the motor mount, and could easily generate sharp shrapnel in the event of a major CATO. And steel eye-bolts in motor mounts, and steel all-thread in motor mounts, and.......
I am reading into your question that you have a proper awareness of the relative safety aspects of using MOTC (materials other than cardboard). I suspect that you have already puzzled through some alternate design approaches and have settled (painted yourself into this corner?) on using aluminum tubing as the "best" way to go. The fact that you are even asking this question shows that you are sensitive to the problem, and probably not trying to create some terrorist disaster. Unless your design is clearly and obviously beyond the NAR safety rules, or goes against common sense and wisdom, at some point you just have to go try it.
Before you give up completely on ducting ejection gas with cardboard BT, remember that there are things you can do to reinforce it. You can coat the inside with CA or glue, or glue a metal tape liner inside (wait a minute....). You can wrap the outside with another layer of cardboard BT, or with fiberglass. You can add braces in structurally strategic places, and they can be visually unobtrusive if you use thin bamboo sticks (skewers) or carbon fiber rods, or if you paint them black. You can use clear plastic sheet products to fashion a reinforcing web that is still structurally useful (but be sure to use polycarbonates, not acrylics, or you will trigger the wrath of Micromeister).
Make a few ground "flights" to test the durability of your materials in the severe thermal environment of ejection, and see whether your design requires repairs between each launch. (Ground testing has challenges too, to figure out how to safely immobilize your rocket and still allow all the moving parts to be free.) Make some test flights by yourself, without risking bystanders. Find another experienced hobbyist and talk it over with them. Contact the NAR safety guys (
there's some
experience!) and talk it over with them.
And when you get it working, and master the new materials and techniques, and get published in a magazine or post your build-thread online, resist the temptation to tell us "I
TOLD you so!"
