Little Joe II Model Rocket (BT-80)

cults3d

This model is mostly 3D printed parts with a small section (95mm) of BT-80 Body Tube. For more information about the original rocket: https://en.wikipedia.org/wiki/Little_Joe_II One fun part of this model is that it is designed for a swappable cluster engine mount setup. I included a 24mm single engine mount, 3x 24mm cluster engine, a 7x 18mm setup, and a 6x 13mm canted cluster with central 18mm motor. I will add other configurations upon request. Cluster is setup for 70mm long engines. There is also a centering ring and BT-80 to BT-50 block if you want to use a stuffer tube or longer engine mount. I launch with a C11-3 w/ 35g of weight in nose spike (the long nose spike is hollow so you can add weight far forward on the model). Based on some exploratory OpenRocket simulations, it looks like you would need 3-4oz or so of nose weight if you used 7x18mm engines. I did a swing test with my model with the cluster of 6x A10 mini engines and C6-5 central engine and it flew stable. You can see a video of my flight on the C11-3 here: https://www.youtube.com/shorts/JsQ6Ara5c7o I included lug options for rod-based launch, makerbeam, and a generic slotted design for other rail buttons/lugs (1.2mm x 7.5mm slot). I included rail buttons for 20mm rail that fit in the slots (you can use them as a guide to create other rail buttons). I recommend plywood for the fins but you should be able to use a wide range of materials. The main body is slotted and has options for fin slots of 1.5mm, 2mm, and 3mm. It is easy enough to increase the size of the 1.5mm slots if you need a different size. I included templates for the fins in both STL as well as SVG format in case you use a CNC. The model has holes for Kevlar line shock chord but you can use elastic if you prefer. I also included a replacement nose spike in case you have a hard landing or something and do not want to print the whole nose cone again. Model has lots of base drag which increases stability. Compare the OpenRocket simulation which suggests .657 cal of stability to the video which shows how stable this rocket is. I recommend a simulation and swing test for your build, especially when modifying motor configurations. NOTE: This was designed from scratch but inspired by multiple models and images of the real rocket.