Sky Shark 218- 1940s Sci Fi Build Thread for the Buck Rodgers Challenge!

[ljwilley]

So, I've thought about it, and I have decided to join the challenge. This will serve as both the build thread AND the official submission once I am done building/flying. That being said, please no 3 page arguments about waffles or glue or whatever; I don't want the judges to have to go through 6 pages of crap to get all of the information! I plan to include all information necessary for someone else to build something like this, including 3d print files, a Rocksim file, SVG files (if you want to laser cut or print templates for fins), and all the information about the build. So, here goes nothin!



I did a quick search of 1940s sci fi rockets, and I ended up with one that I really liked!
View attachment images (1).jfif
I plan on basing the rocket from a 3" dia. pringles tube and using a cluster of 2x18mm motors in the central body. (not in the fin pods.)
I will keep everyone updated!

 

[ljwilley]

I don't know why the picture came out as a download link. I converted it to JPG to here it is

 

[cwbullet]

Interesting design! subscribed.

 

[ljwilley]

So I did a a little sketch of the rocket. In the picture it looks like the fins are swept behind the rocket a bit, which would help with stability. However, I plan to keep the fins in front of the rear of the rocket, to prevent them from breaking. It wont be an exact replica of the picture, but that was not the original plan either; I just am using it as a base design.


There will be a BT60 tube running through the middle, but for now I just have the section of main body tube, which I cut to approximately 4.5" long.


For reference, this is a USA sized pringles can. I am aware that they are slightly different in size in certain other countries.

 

[ljwilley]

A better drawing I did on my CAD Software, this one includes the paint scheme idea



Still thinking about what the fins on the side parallel to the angle of the picture should be. All we have to work with is a line.

 

[ljwilley]

Also, I did some more cad design and now I have SVG files for both the inner and outer sections of the main wings. This is useful for either a laser cut OR for printing out templates. Fins will be cut out soon!

 

[ljwilley]

Got some fins cut!

 

[ljwilley]

Finished printing the tailcone! It's a bit tight on the pringles tube, and a bit loose on the BT60 tube, but it will all be glued together so that shouldn't be a problem.







I have added the .step file below!

 

[ljwilley]

As I said earlier, there is another fin in the drawing that is aligned with the drawing so as to look like a mere line. I can only assume that means there is one of each side, but we don't know what they look like. So, I decided to go simple. Here is an SVG for the other fins. I will cut them out next.

 

[ljwilley]

Ok, so all of the fins (including the side fins I just talked about) have been cut out, and now they have been sanded. Forgot to add, they were all cut from 1/8" balsa.




They next 3d print, the lower part of the nose cone (basically a transition) is printing right now.


Yes, I get a live feed from my computer!

 

[ratchet01]

Looks good!
Personally, I wasn't fond of the wingtips being broader tham the root.
Even though there is a "real life" presidence for it

 

[ljwilley]

Looks good!
Personally, I wasn't fond of the wingtips being broader tham the root.
Even though there is a "real life" presidence for it

Yes, I didn't like that either. Just makes it more likely to break.

 

[ljwilley]

The upper transition and the nose cone have been printed! I have attached the .step files below.

 

[ljwilley]

Also finished cutting out the BT60 inner tube. It cut to about 10.75", but if you make your own I recommend doing your own measurements.

 

[ljwilley]

Ok, so everything is glued together, including the central tube. I used a little epoxy to glue the central tube in, along with some CA for the tailcone and forward transition. The nose cone fits pretty well too.

 

[ljwilley]

Designed some little connections for the fin pods, and I'm printing them now. If they fit, I will post the step file.

 

[ljwilley]

Ok, so I printed the parts and they fit fine. I will print the nose cones and tail cones for the pods next.

 

[ljwilley]

Got a few fins on! Used Titebond II wood glue.

 

[pugachu]

Got a few fins on! Used Titebond II wood glue.

Is that a habenero plant in the background??

The rocket is looking pretty good, too :-D

 

[ljwilley]

Is that a habenero plant in the background??

Yep! I got the plant a couple years ago but it's only made 4 or 5 peppers a year. This year something obviously changed! I grind em up and dry em out and put em in a pepper shaker. Very spicy, but good flavor.

The rocket is looking pretty good, too :-D

Thanks!

 

[ljwilley]

 

[ljwilley]

Files for the pod noses and tail cones:

 

[ljwilley]

Printed some centering rings and now I'm going to glue them to two 18mm tubes with CA. Each tube is about 2.75" long, and I have left the file for the centering ring below.

 

[ljwilley]

Ok, so all of the balsa fins were a bit wiggly and didn't seem to adhere well to the surface of the tube using wood glue. So, I added some epoxy fillets. (very small ones). They are nice and strong now! Just wanted to add this, as for the competition I should mention all of the adhesives I use and where I use them.

 

[ljwilley]

Glued the motor mount in with Titebond II wood glue, and glued on the 3d printed pod tubes with some more CA.

 

[ljwilley]

OK, so I glued on the outer fins. I plan to do a rocksim file and probably use some nose weight. The nose cone, along with the tailcone and noses on the pods, will be painted separately from the rest. I used CA for the outer fins.

 

[billpr]

Gonna be Awesome

 

[ljwilley]

So... I'm having a bit of trouble with Rocsim. When I add the two main wings to to the design, Rocsim says that the CP is 15inches IN FRONT OF the nose tip. Only when I add the two smaller fins does it start to bring the CP back again- but only to about 7 inches behind the nose tip- not good! But, I did a swing test after adding just 1/2oz of nose wight and the rocket is stable. (With 2 b6-4 motors loaded in) The CG in the rocket is about .75" in front of the fins, and the rocket seems to be stable. So if anyone knows what's wrong with Rocsim, please tell me!

 

[ljwilley]

Even weirder, when I simulate the flight on Rocsim, the flight appears to be stable even though Rocsim says it's not! For now, all I can offer is an unstable Rocsim file (for reference of parts only) and a successful swing test. I will paint the rocket next!

 

[ljwilley]

Just as proof for the successful swing test, I have a video. Sorry about the low light, but it's definitely clear the rocket is stable!