Booster plug

[Nateairman]

Hello everyone!

I have read a few threads regarding Estes booster engine plugs. What I have taken away is any permanent modification of a engine makes it experimental and booster plugs should be friction fit.

I designed and built a Jayhawk that has a cluster configuration using an e12 and a c6. It has flown a handful of times now 1/2 of the flights as a single engine rocket and half as a boosted rocket. When flying it as a boosted rocket the booster was plugged with a piece of hardwood glued in. After reading so much about rules and modifications of engines I decided to use a friction fit plug. The booster tube is not vented to the atmosphere. The flight with a friction fit plug did not go as planned. The plug came out and separated the rocket at 500' AGL. The JLCR was set to 300 and the recovery was fine.

So my question is how much of an issue is permanently plugging a zero motor? Is there a better way to friction fit plug a motor? Maybe a threaded plug?

 

[BABAR]

there are multiple different answers.

the one thing I think is absolutely wrong under any circumstances is to friction fit or use ANY motor retention WITHOUT venting on an UNPLUGGED motor, that just about guarantees you will blow out the tube, UNLESS you are lucky and the friction fit fails and the motor spits out. If you want to keep the motor on board, either plug it or vent it.

the next variable is where you fly. Any RSO under NAR, if they stick to the rules, won’t let you fly a motor that is plugged by anyone but the manufacturer. So if it didn’t come from the factory that way, they may well nix the flight. Your particular RSO may vary, but I wouldn’t count on it and would definitely check with them before showing up at the launch planning on trying it.

for me, unless you buy plugged motors, for 18 mm and 13 mm, I think the best option is to EJECT the motors. A VERY loose friction fit (basically just enough to keep it from falling out of the rocket on the pad) and the motor should spit easily, whether it is zero or standard delay. Again, however, you need to check in advance the rules of the FIELD. There is nothing in NAR rules that prohibits engine spitting for SPORT flying, in COMPETITION usually its a no go. But some FIELDS don’t allow it, some RSOs don’t like it, and some may be fine with it except when fire risk is high (usually something like “No Sparky motors and no Motor Ejects Due to elevate fire danger.”

for booster (zero delay) motors, motor eject is definitely a performance enhancer, not only do you dump the casing mass but you even get a little kick of thrust according to Newton when you blow the casing out the back!

when I use this technique (I do it regularly with my Helis and AirBrakers) I briefly try to find the casing to keep the park clean as a courtesy, but I am not a fanatic about it. Every part is biodegradable so it’s no major or even minor crime if I miss one where I fly.

lots of people plug their motors with epoxy, I’ve never done it because I’ve never needed to, maybe someone will post exactly how they do it here.

again the key questions are whether it is a club sponsored launch and what are the local field rules.

hope you get multiple straight trails!

 

[heada]

Talk to the club. Some are relaxed when it comes to the rules and as long as you can explain why it needs to be done and how you did it, they could be perfectly fine with it. Some clubs would rather you plug a zero delay booster motor rather than eject it out of the rocket. I think most RSO's will reject a motor that has had it's delay removed to turn it into a booster or reduce the delay to shorter than certified but most will be fine with plugging a booster.

I've done it in the past on D12-0 motors because I couldn't find any C11-P motors which were the only plugged 24mm at the time. I put in a few layers of wadding flat, used a dowel to push them into the motor against the BP grain and then poured in epoxy to the top of the motor case.