1/4A or MMX 1/25 RIM 2 Terrier?

[dakota196]

Which one? I have never flown MMX, but 1/4A way in the past. Say 1970’s. Just looking for opinions on motor. No motor mount installed yet, or recovery system.

 

[kuririn]

From your other thread it appears to be a BT-5 to BT-20?
Might be too heavy for MMX.
I would go with 13mm mini motors.

 

[tooth]

Great looking rocket, your design? I've flown several on MMX motors and am always surprised at their boost. Might be good to model it in OR or Rocksim to see for sure.

 

[mh9162013]

I concur that a 13mm engine is probably your best bet. Might even need 1/2A impulse to get a flight above 50 feet with that thing (which is a really cool design, by the way).

Curious about where the CG will be in relation to the CP, though.

 

[dakota196]

I don’t have a way to find this out. I don’t have OR or Rocksim. As of now, the cg is right at the forward edge of the stage coupler.

 

[dakota196]

I mainly build just for building and for static display, but every model can fly. I just choose not to at this time. This one I just might. Easy to build in an hour. i am curious also.

 

[dakota196]

From your other thread it appears to be a BT-5 to BT-20?
Might be too heavy for MMX.
I would go with 13mm mini motors.

Yea it is. I want a very low impulse. It weighs 11 grams naked.

 

[dakota196]

Great looking rocket, your design? I've flown several on MMX motors and am always surprised at their boost. Might be good to model it in OR or Rocksim to see for sure.

Scratched from Alway drawings. I also have a 2.6” booster version for 2 stage G/D power.

 

[mh9162013]

Yea it is. I want a very low impulse. It weighs 11 grams naked.

Yeah, definitely go at least 1/4A impulse.

 

[kuririn]

I don’t have a way to find this out. I don’t have OR or Rocksim. As of now, the cg is right at the forward edge of the stage coupler.

Do the string test for stability.
On your finished rocket:
Load the heaviest motor you intend to fly.
Find the center of gravity (CG) by balancing the rocket on your finger and marking it.
Tie a string to that mark and tape it down securely.
Swing the rocket in a circle over your head and observe how it flies.
If it flies nose first then it's stable.
Anything else then you need to increase the distance between the CG and CP (center of pressure).
Two ways to do this.
Easy way: add more nose weight.
Harder way: replace main fins with larger ones.
Good luck.

 

[dakota196]

This with an all up bird, yes? Motor mount, motor, and recovery system?

 

[kuririn]

This with an all up bird, yes? Motor mount, motor, and recovery system?

Yes, a finished rocket.

 

[kuririn]

Posted on You Tube by our own lakeroadster:

 

[cls]

I like the transition, did you make it?

 

[dakota196]

I like the transition, did you make it?

Yes. It is a centering ring sanded to shape.