The only problem I have seen with the twist and tuck method is disarming. you have to completely open the av-bay to disarm. there is a risk of a charge going off while disarming.
I agree, I was going to post the same myself.
One of the worst-ever examples of this was a guy in the mid 1990's who had his altimeter inside the main body tube. So, to arm and disarm he put his arm inside of the tube. One day, something went wrong at launch, perhaps it was only one motor of a cluster ignited, or something like that. Anyway, it crashed a few hundred feet away. So, he goes to dis-arm it, sticks his arm into the tube, and "Boom", the altimeter fires the ejection because of the pressure changes inside the tube when he stuck his arm into it. He suffered burns to his hand, arm, and face, one of the most serious ground-ejection accidents I've ever heard of. Also one of the most preventable, and frankly most stupid “accident waiting to happen” design ideas, ever.
I also do not trust magnetic switches either.
The SAFEST WAY is to use some sort of switch that is activated MANUALLY from the OUTSIDE of the rocket.
And actually for a lot of rockets, two switches should exist. One to turn on the system, and one to "Arm" the pyros (ejection, upper stage, whatever). So you turn the system on first. Ideally with a piezo beeper or LED, or something, so you can know the system is turned on properly. And finally, the "Arm" switch, which should be the LAST THING that you do at the pad before getting away from the pad seconds later.
Lots and lots of ground accidental firings have occurred due to not doing that.
Always assume the thing is going to go off by accident........
One project I did, involved two R/C Rocket Boosted Gliders, One (2X SkyDart) riding on piggyback of a larger winged booster. When the booster glider burned out then I flipped a switch on my transmitter to ignite the engine in the 2X SkyDart, for staging. A big concern was accidentally having the upper stage fire while on the ground. So, the “arm” switch for the glider was this simple: The igniter had a plug soldered to it, to fit into a socket in the larger winged booster. The ignitor plug was not put in until shortly before launch, the last thing done before leaving the pad, with liftoff normally 1-2 minutes later.
I am attaching a photo of one of my space shuttle models. This photo shows where the "Power" and "Arm" switches are located (Power to turn on the flight computer, and arming as final arm of the ejection charges). Now, you won't SEE the switches, but that is indeed the point. I'll make another posting later to show where they really are and how they are used.
- George Gassaway