Baffle Distance

[Bruiser]

I am working on a design in OR and I am wondering how much space do I need to leave between the end of the motor tube and the ejection baffle. The rocket design is using Estes PSII 2.5 body tube and a 29mm mount. Proposed motors are F and G, maybe H motors if I decide to go level one.

I am planning on using a baffle deign similar to this one by Semroc. I believe I can use two pieces of 29mm motor mount tubing that will squeeze into 2.5 coupler that is 4 inches long. I am thinking of leaving 1 inch of free space between the tubes and the bulkheads.



Thanks,
-Bob

 

[dhbarr]

Cross section of that tube is only ~660mm^2 , so an inch away is probably pretty good.

 

[kuririn]

Position the baffle as far forward as possible while still leaving enough room for your recovery gear. The baffle will double as a parachute ledge and keep it from slipping all the way down the tube.
This will keep your CG further forward and aid stability.
Also possibly reduce the need for nose weight.
Excellent Apogee Peak of Flight article here:
https://www.apogeerockets.com/education/downloads/Newsletter366.pdf

"Finally, I would recommend positioning the aft bulkhead disk of the baffle at least one body tube diameter in front of the engine mount tube. This will allow some space for the gasses to cool before having to go through the lower bulkhead disk. Further is better, but you don’t always have the extra room."