BDB
Absent Minded Professor
- Joined
- Aug 22, 2015
- Messages
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I am planning to build a 150% upscale of a Binder Design Velociraptor for my L3 project. The rocket will be made of 6" Blue Tube and will use a hand-laid fiberglass nosecone and tailcone (PML). I have started working with my TAP, but I'd like to crowdsource an idea to see if anyone has done something similar.
The key question that I have is how to transfer the thrust from the motor's aft thrust ring to the airframe for a rocket with a boat tail. Surely, the fiberglass tail cone is not sufficient for the thrust of L3 motors, and I'm a little nervous about only trusting the glue holding the motor mount to the centering rings. For inspiration, I looked to the mother of all boat tail designs, the V2. Interestingly, it was designed with a "hard point" directly in front of the boat tail (highlighted).
I think I'd like to also install a thrust ring/hardpoint in my design directly in front of the boat tail and attach it to the airframe with both wood glue and screws. I would then like to create a sort of fin pocket that would abut the motor retainer and run continuously to the forward hard point.
I'm bored at work today (and my CAD skills suck), so I tried to sketch something up so you could see what I mean (I do not claim to be an artist, either):
The fin pocket would follow the shape of the boat tail, but it would have grooves to allow for interlocking centering rings. I could make it out of solid 1/4" ply, but it might also be interesting to try to cut out some of the material to reduce the weight.
So...two questions: 1) Has anyone tried something like this before? 2) If so, is there a pattern that I could cut into the fin pocket that would reduce its weight but retain its strength (think bridge design)?
The key question that I have is how to transfer the thrust from the motor's aft thrust ring to the airframe for a rocket with a boat tail. Surely, the fiberglass tail cone is not sufficient for the thrust of L3 motors, and I'm a little nervous about only trusting the glue holding the motor mount to the centering rings. For inspiration, I looked to the mother of all boat tail designs, the V2. Interestingly, it was designed with a "hard point" directly in front of the boat tail (highlighted).
I think I'd like to also install a thrust ring/hardpoint in my design directly in front of the boat tail and attach it to the airframe with both wood glue and screws. I would then like to create a sort of fin pocket that would abut the motor retainer and run continuously to the forward hard point.
I'm bored at work today (and my CAD skills suck), so I tried to sketch something up so you could see what I mean (I do not claim to be an artist, either):
The fin pocket would follow the shape of the boat tail, but it would have grooves to allow for interlocking centering rings. I could make it out of solid 1/4" ply, but it might also be interesting to try to cut out some of the material to reduce the weight.
So...two questions: 1) Has anyone tried something like this before? 2) If so, is there a pattern that I could cut into the fin pocket that would reduce its weight but retain its strength (think bridge design)?