Need build opinion, 2 or 3 centering rings...

[threelapfancy]

Hi guys, just looking for opinion. One of the rockets I am building right now is a 6" scratch build using hawk mountain tubing. Height is 116" (just over 9.5') that will be flying on a motor configuration of 3 - 54mm motor cluster. The length of the motor tubes I am using is 16" and the fin length is 10". I certainly plan on using 1 centering ring right above and right below the fins so there will be about 5.5" above the fin that would not have a centering ring if I used only 2. The centering rings are 1/2" Baltic Birch.

I am sure that the rocket would be fine with just 2, but what do you guys think about adding another at the top of the motor tubes? What advantages/disadvantages would this create on this type of rocket.

Just trying to get some opinions.
Thanks
Steve

 

[AndyC]

If you have the motor tubes extra long already, I'd add the extra ring. It ensures that anything in the booster tube sits higher and does not get twisted (or cooked?) between the motor tubes. This moves Cg forward as well (presuming you don't add lots of weight with excess threaded rod, etc..).

One of my mentors suggested I cut a LOC type 54mm motor tube at the top ring as well of a project I built, suggesting it could get damaged by the recovery system, and was not necessary anyway. Its likely less of a worry with with fiberglass tubing, but it is a point. Why have extra motor tube if there is no ring at the end?

 

[dave carver]

Put in an upper ring. If nothing else it would reduce the volume of space you have to fill with ejection charge gasses to blow the cone off.

 

[JDcluster]

You only need 2 rings for the outboards. The older Magnum only had 1 CR with holes for the outboards. The stock Magnum had 8-9" long motor tubes.


JD

 

[threelapfancy]

There are no outboards. The motor tubes are arranged at 0, 120, & 240 degrees otherwise 3 54mm motors would not fit. Does this change any opinions?

 

[Handeman]

I would add the third ring and put a long kevlar loop across it as an anchor for the recovery system. It probably wouldn't make any difference, but it would give a little more stiffness against unbalanced torque if one of the motors didn't lite.

 

[Pantherjon]

I would go ahead and use the 3rd centering ring right at the top of the motor tubes..Good place to mount your recovery device.