Optimal Angle; L/D ratio for ISC

[WFWalby]

I'm scratch building a 5" to 4" 2-stage and have questions about the optimum L/D and angle of the ISC transition. This vehicle is not being designed for super performance i.e. speed/altitude but more for reliability and durability. 98mm motor in the booster and 75mm in sustainer. ISC will most likely be 3D printed using Onyx.
Constructive suggestions appreciated.
William

 

[Banzai88]

Seeing as couplers are one of the known failure points, and most folks aversion to any sort of 3D printing in stress joints like that, I'd personally do a conventional build, either cardboard and fiberglass skin, or straight fiberglass, ESPECIALLY seeing as your using 98 and 75mm motors in a 5"-to-4" HP rocket. You might have a hard time convincing an RSO that your 3D printing is gonna handle the stress, and lateral(conventional) print layers would probably 100% rule that out since there really is no way to non-destructively test layer adhesion.

Either way, one caliber of engagement on each side of the tube is normally recommended, and as for the taper section, I don't think that there are any hard/fast rules other than what looks right, but I'd start by looking at other sized commercial offerings and probably scale up from there. Here's one to maybe scale things up from: https://wildmanrocketry.com/collections/transition/products/transition-4-to-54

 

[0011001100]

Seeing as couplers are one of the known failure points, and most folks aversion to any sort of 3D printing in stress joints like that, I'd personally do a conventional build, either cardboard and fiberglass skin, or straight fiberglass, ESPECIALLY seeing as your using 98 and 75mm motors in a 5"-to-4" HP rocket. You might have a hard time convincing an RSO that your 3D printing is gonna handle the stress, and lateral(conventional) print layers would probably 100% rule that out since there really is no way to non-destructively test layer adhesion

Normally yes, but he said he would be printing it in Onyx material which is Markforged's CF-PA and if he is able to use the carbon fiber reinforcements on a Mark Two then it would be plenty strong. I have personally tested this material and it is possible to print parts that are stronger than solid aluminum.

 

[Banzai88]

Normally yes, but he said he would be printing it in Onyx material which is Markforged's CF-PA and if he is able to use the carbon fiber reinforcements on a Mark Two then it would be plenty strong. I have personally tested this material and it is possible to print parts that are stronger than solid aluminum.

Sooo many filaments, sooo little time!