I had some ups and downs this weekend. From my last post, I was finishing up the prep on my DRM Extreme BT60 29mm scratch build. That rocket was printed a while back in PLA+ with the fins upright on the build plate. Well, the floor decided it wanted a closer look at my work and the rocket hit the ground, snapping one of the fins. It took be a couple minutes to recover as I was in the process of moving upstairs to put color on it. RIP.
This morning, I woke up determined to make this rocket work. I redesigned the fin can, fins, and retainer in Fusion and printed it in PETG, with the fins laying flat. The finish wasn't as nice and required about 30mins of post-processing, but the result turned out pretty nice. I need to do some tuning work on my printer to the the first layer adhesion dialed in.
I cut the MMT and body tube and mocked it up with a previously printed DRM nosecone:
The fin tabs fit snuggly with just a hair (maybe a thick 1mm) of gap between the root edge and the fin can. The MMT inserted perfect, with just a hint of friction and the retaining ring and cap also assembled nicely. My only concern was if I allowed enough clearance for the AT 29mm thrust ring. I grabbed a spent H135 motor and stuffed it in there and put the cap on. It sits nice and tight.
I finished it off by gluing: The shock cord through the channel between the BT and MMT, the MMT, body tube, and fins to the fin can, retaining ring to MMT. Finally, 3 coats of primer after lots of filling and sanding.
I am one sanding session away from being back to where I was last night. Tomorrow, I'll finish sanding the primer, touch up any problems, and hopefully start getting color on this little monster. All in all, I think this is a better overall rocket. Running with PETG vs PLA+, better fin can design, and the retainer fits AT disposable motors like a glove. I am not flying an H135 in this, but a G80? maaaaaybe.
Oh, and the Goblin Extreme BT60 29mm design is almost ready as well!
