Rocketeer rocketpack from a 3D model build thread/questions

Hello RPF,

I have been tweaking this old pep file of the Rocketeer’s rocketpack in Sketchup for some time now (I believe the original creator was a someone named Torsoboy, circa 2008 or 9). The proportions are now generally to scale, give or take several centimeters/maybe an inch or two in some areas; places that can be fixed later on. Either way it’s close. Opposed to the original, it’s a little smoother and now separated into individual components. All in all it isn’t perfect, but I’m hoping it will serve as a great foundation for the build I have planned!





The Plan:

- CNC mill the model in 4 slices (red shapes in the image) along its length using 3” urethane foam sheet.

- Glue shapes with 4 slices back together with temporary adhesive

- use plaster/bondo/magic sculp to make all necessary proportion changes and additions, then smooth the model planes down. The rocket at this stage will just be the nacelles and a suggestion of the central section, as illustrated in red in the attached image. I will not include surface details or vents/radiator/flaps/rivets /interior engines at this stage as those will be built separately and added later.

- vacuum form (probably a large blister form) the main body in two separate halves, lengthwise. In other words the front and back of the rocket will be pulled separately. I am hoping to use 3/16” or ¼” plastic. One side may have an undercut lip that will help key it in place with the other half.

- vacuum form the central section separately with the intention that it will be removable later on. (thanks Valor for the idea!)

- all other surface details and components will be fabricated from styrene, sheet plastic, clay sculpted/molded/resin cast, and miscellaneous hardware

Questions for you guys!

1.) Would you recommend ABS or Styrene or Pet-G (Vivak) to vacuum form this? I am mostly familiar with Pet-G, as I work in the prosthetics industry and we use it frequently for sockets. Pet-G is cheap, sandable, paintable, drillable, and will accept glues and epoxies given the appropriate surface abrasion. I’m open to suggestions regarding the benefits of ABS for a pull this large and curvaceous.

2.) Anyone have any ideas or recommendations for other build methods I could take to vacuum form this? I’m not really sold on the two halves method because that’s quite a LARGE seamline, and I’m not quite sure how to join the two halves, outside of bondo or epoxy and days of sanding.


I truly appreciate any feedback, and I’m really looking forward to sharing this build with you folks!

Can't help with vaccuforming. However, could you make a mold of the finished pieces instead of vaccuforming? Resin? Fiberglass? Etc...

Interested in seeing what you come up with.

-Eric

hdtheater,

Thanks for your response - I have considered breaking this down into different sections and creating molds using Smooth-On's Rebound 25, and later slush casting each section with Smoothcast 300 or some variant. In fact that's the backup plan! I don't have a clue how I'd slushcast the visible tube portion at the bottom of the nacelle, though. I'd have to include a large core, and then have a 3/16 - 1/4" thick slushable area. Never tried something like that; I'd imagine the thickness would be inconsistent?

my main aversion to molding and casting this project is cost. Trying to keep everything under an umbrella budget of $300- $350 is tough when I'd be spending ~$180 on molding/casting supplies alone! Anybody have an idea how much cheaper/easier fiberglass mother molds might be as opposed to Smooth-On's Plastipaste?

Update from the weekend:

I went back into the models and manually smoothed a majority of the surface planes out. The software I'm using is pretty simple for a CNC program but it has a smooth tool.
Remodeled the flaps to the correct measurements as well. I won't be using the foam versions but I thought it would be wise to have a physical reference.
Started milling the first sheet and noticed something was very off; this thing was way too wide. Width of the pack was 20.5 inches - I'm making a rocketpack, not a hang glider!
I realized I had forgotten to scale it back down after I had changed a few items, so I scaled it down 12% to the correct size. You can see the outlines of the cones from the first milling mistake, haha

~6 hours total using a .25" ball nose router bit:



Another ~6 hours, same bit:


ready for contact cementing:


Such a difference seeing the physical objects in person - bewildering and exciting at the same time. For the time being I'm going to leave the two halves separate, as well as the central section. I'm still not entirely sure how I want to tackle this:

~ Build up the pack to a finished state on top of the urethane foam and then rubber mold and resin slush-cast it in sections
or
~ vacuum form the pack in two halves lengthwise, and the central section will be pulled separately, add details and accessories afterward.

I'll post the 3D model files for you guys once I work out the kinks, as well as other items that I've compiled, added to, and some that are tough to find!
I just updated a thread started by Valor that includes a graphic with nearly all the measurements for the pack: http://www.therpf.com/f9/help-rocketeer-193832/?highlight=rocketeer+help

Is that HDU foam you are using? Or something else?

nice to see it coming along.

-Eric

panicindetroit said:

The software I'm using is pretty simple for a CNC program but it has a smooth tool.

Click to expand...

May I ask which software you use? Looking for simple and hence hopefully cheap program...

looks like a great start for a great prop! :thumbsup

hdtheater said:

Is that HDU foam you are using? Or something else?

Click to expand...

Yes, although it is only 4 lb. density. It's lightweight, quite easy to sand and make corrections, wet sands much finer, and it takes plaster very well.

SciFiPropFreak said:

May I ask which software you use? Looking for simple and hence hopefully cheap program...

Click to expand...

Thanks! I used the word "simple" and probably should have used the word "limited." The program I used to import the .stl models from Google Sketchup, and then to slice them and lay them out for milling is called Aspire, by Vectric. I believe it's primarily a sign making program, and it is both as useful and easy as it is quirky. And expensive. A retail license for the software is $2,000, but if you can find a copy of a previous version and a license somehow, the upgrade is $400. Damn CNC software companies really have a strangehold on the pricing for this stuff. http://www.vectric.com/products/aspire.html