A few questions about the Apogee Mini-Copter and Gyro Chaser Rockets

[mh9162013]

I'm thinking about trying out helicopter rockets and I was watching the assembly videos for the above referenced rockets and have a few questions I hope some of you might be able to answer.

First, the aft disc that's near where the CF/graphite shaft attaches to the shock cord has holes in it. Why? I can see how putting holes might save some weight, but might you get a more reliable ejection if the holes weren't there (or were smaller)?

Second, the shock cord (at least for the Gyro Chaser) has an odd attachment point, ie it goes through the main body tube and is glued to the root area of one of the fins. Why? Why can't you just tie it to the top of the motor mount tube?

Third, if I installed a baffle in one of these rockets, it shouldn't affect the functionality of the rocket, right? I get how it adds weight and might force me to make the rocket longer (assuming I don't shorten the blades), but are there any other considerations I'm not aware of?

Fourth, if I installed a baffle and instead of lengthening the main body tube, I shortened the blades a bit, what's the drawback besides a faster descent and extra work while building?

I know these are competition rockets, so many of the answers to my questions might be, "because of weight," but I want to make sure I'm not missing anything from a structural or functional perspective. Thanks!

 

[dpower]

I built the mini-copter a few years ago, and crashed it after a few flights, don't recall what happened.

IIRC, the disc is to reduce force on the rotor system, since it's quite fragile. Some ejection charges are quite strong, that's probably why the shock cord attaches the way it does.

It was an enjoyable build, though. I seem to recall getting better times on the Estes mini-A-heli, even though it weighs more, the large blades more than make up for it, and I achieved more reliable operation.

Adding a baffle certainly will decrease performance from weight, though more importantly increases the possibility of kicking the motor instead of ejecting the rotor system. Don't expect to get many flights on either of these models, they're tough to get to fly well, so I don't think a baffle will increase the life. By all means, though, build and fly them - helicopters are great fun!

 

[mh9162013]

I built the mini-copter a few years ago, and crashed it after a few flights, don't recall what happened.

IIRC, the disc is to reduce force on the rotor system, since it's quite fragile. Some ejection charges are quite strong, that's probably why the shock cord attaches the way it does.

It was an enjoyable build, though. I seem to recall getting better times on the Estes mini-A-heli, even though it weighs more, the large blades more than make up for it, and I achieved more reliable operation.

Adding a baffle certainly will decrease performance from weight, though more importantly increases the possibility of kicking the motor instead of ejecting the rotor system. Don't expect to get many flights on either of these models, they're tough to get to fly well, so I don't think a baffle will increase the life. By all means, though, build and fly them - helicopters are great fun!

Thank you for your insights and answers to my questions.

If I used a baffle, I'd also use a motor retainer to prevent motor ejection. And the reason I'd use a baffle is to reduce the soot thrown onto the rotor blades and hub.

Your comment about having difficulty getting these rockets to fly well and their short lifespans gives me pause, as I'm not big on "disposable" rockets. But I do think helicopter model rocket recovery is really cool and I'd like to experience it in-person sometime.

 

[kjohnson]

If this is your 1st heli recovery rocket, I would recommend the Heli-Roc kit over either the Mini-Copter or the Gyro Chaser as it is just as much fun but with way less hassle.

As to your questions, they are mostly answered in the video instructions:
1. Holes in the lower disc- to allow some of the ejection gasses to pass through so you eject the rotors, but don't blow them out too hard
2. Shock cord mount to the fin- it's a very strong attachment technique
3 and 4. Baffles. They really aren't needed. You will make the model heavier and may change the ejection behavior of the kit. Do it if you want, but expect issues.

kj