Windmill of Desssssstiny!

[boatgeek]

I've been noodling at this project for a while, and finally have enough to start up a build thread.

This is an oddroc that has it all: Spinning, 3-D printing, burn strings, Rube Goldberg mechanics, base drag, sketchy recovery, options for gross overpowering, and a few fragile parts thrown in for good measure. It'll be a party.

The basic concept is here. On ascent, it's more or less a shuttlecock. Once the D12-0 motor in the middle's ejection charge torches the burn string(s), the booms pop up and it becomes a flat windmill.


Totally normal, Lord RSO, I promise!

Power is up to 3 24mm motors. I need a D12-0 in the middle for the burn strings, but the outboards may well be composites. I'm thinking a pair of CTI F79 SS as the top end motors. Total altitude, maybe a hundred feet. Follow on to a few more posts about the design...

 

[Aeronerd]

VERY cool!!

 

[boatgeek]

The center core is 3D printed. There are a bunch of what seemed like clever design concepts in there; we'll see how those work out in practice. Here's the top:


You can see the three motor tubes (center one is buried under the crown business in the middle) and the square that will ride over a 1010 rail. There are 6 slots for the booms, and above them are posts that will hold the rubber bands that will pull the booms up to horizontal and tension the sails at the same time. I had planned to use the hooks at the top of the posts for the rubber bands, but they may not be needed. I haven't 100% figured out the rigging and tensions system yet. If you look on the far side just below the boom carrier, you'll see a small slot. The burn string will feed through there across the top of the motor. There will be three burn strings, one for each opposing pair of booms. The string goes down off of the boom, through a little half-moon guide on the bottom of the center core, up through that slot, over the motor, and out to the boom on the other side in the reverse order.

Flipping it over to the bottom, we have:

More or less what you'd expect. I'm planning on putting cardboard tubes in as a liner for the motor mounts to insulate the PLA from the motors. I'll probably throw a pair of Estes retainers on the outboards and just tape the center.

All 3D design work is in Rhino 3D (which I have for work) and printed by my co-worker.

 

[Hobie1dog]

talented, I'm highly envious

 

[boatgeek]

I've had the center core and the carbon fiber booms on hand for a couple of months. the hangup has been sewing up the sails. I finally got on that this week, with a prototype sail earlier this week and the rest of them largely done today. Here's a few pictures of how that goes:


Start by rolling hems on the top and bottom of the sails. I double rolled with a 1/2" seam allowance since it's easier for me to cut the ripstop with scissors than a hot knife. A double roll keeps all of the fraying on the inside. You'll see a trick on this that I learned from sewing nearly a thousand masks during the pandemic. Instead of stopping and starting in between each panel, you run the next one right after the first without stopping. This saves a lot of time and thread. After you've run all the panels through, you snip them apart.


Next is pinning the leading edge. The leading edge has 1/2" folded under for fraying, then 1" folded over to leave space for the boom. I got really good at estimating a 1/2" seam with the masks, so the ruler is mainly a formality. I really like this little guy I picked up at a trade show. You set the clip at the distance you want, and it's super-easy to get the right seam allowances. When I took this picture, I hadn't fully processed the leading edge-top corner that's at the bottom of the picture. That's trimmed a little further and then tucked into the seam so it's all neat and tidy. After sewing the leading edge down, I did a double row of stitching across the top of the pocket since that sits on top of the boom.

All sewing is done on my mom's 1960's era Kenmore machine. If you're going to do any significant amount of sewing, do yourself a favor and pick up a sewing machine from no later than the early 1980's. Any more stitches than zigzag is sheer frippery, and the old machines are often (a) cheaper than what you can buy now and (b) far more durable and powerful. This machine was intended to make a family's clothing for a lifetime, and it shows.

 

[boatgeek]

OK, here's the money shot. This is more of less what the windmill will look like on descent.



I still need to sew up the trailing edge hems--I was waiting to do that until I can make sure that everything fits and that I can incorporate some hardware for tensioning the sails.

 

[boatgeek]

talented, I'm highly envious

What you don't see here is all the times I had to start pieces over because I messed them up!

Thank you!

 

[boatgeek]

One last thing for now. Ten Internet points for the person who knows the reference for the rocket's name. I thought briefly about calling it the Windmill of Death and Destruction, but I don't believe in tempting the Rocket Gods. Seeing how those fickle beings punished another rocketeer made me settle on a different name.

 

[lakeroadster]

One last thing for now. Ten Internet points for the person who knows the reference for the rocket's name. I thought briefly about calling it the Windmill of Death and Destruction, but I don't believe in tempting the Rocket Gods. Seeing how those fickle beings punished another rocketeer made me settle on a different name.

The Flying Dutchman? I mean, you are a boatgeek... and this rocket has sails... and it's got that Dutch windmill vibe going.

 

[KenECoyote]

One last thing for now. Ten Internet points for the person who knows the reference for the rocket's name. I thought briefly about calling it the Windmill of Death and Destruction, but I don't believe in tempting the Rocket Gods. Seeing how those fickle beings punished another rocketeer made me settle on a different name.

Flying Guillotine?

 

[boatgeek]

The Flying Dutchman? I mean, you are a boatgeek... and this rocket has sails... and it's got that Dutch windmill vibe going.

Flying Guillotine?

Both far off. I’ll give a hint tomorrow morning if nobody has it.

 

[dhbarr]

2008 Prince of Persia Ruined Citadel Windmills.

 

[BABAR]

May not matter, but consider elastic thread or rubber bands in place of standard string for burn strings. Standard string tends to loosen within a short time (even from field table to pad), elastic stays tight and burns through just as easily.

 

[KenECoyote]

Animal Farm?

 

[Cape Byron]

One last thing for now. Ten Internet points for the person who knows the reference for the rocket's name.

Seldom seen TRF member @Don_Quixote .

 

[boatgeek]

May not matter, but consider elastic thread or rubber bands in place of standard string for burn strings. Standard string tends to loosen within a short time (even from field table to pad), elastic stays tight and burns through just as easily.

Good thought. I was going to use regular thread but I’ll make sure to check how secure it stays.

 

[boatgeek]

2008 Prince of Persia Ruined Citadel Windmills.

Animal Farm?

Seldom seen TRF member @Don_Quixote .

All great guesses, all far away. The windmill isn’t part of the original quote. Think a classic comic strip.

 

[Daddyisabar]

That is really sick...I love it! Like the circles you will find in the windmills of your mind!

 

[Rktman]

Really impressive design work and fabrication! Subscribed!

 

[David Schwantz]

"The wooden shoe"

 

[icyclops]

Dutch Wheelly
or
Pin Wheel of Luck
or
Pandora’s Windmill

good luck on your maiden flight…

 

[rharshberger]

a play on Jack Blacks/Tenacious D
Pick of Destiny

 

[boatgeek]

a play on Jack Blacks/Tenacious D
Pick of Destiny

I have scads of alternatives if I ever decide to retcon the origin story, but also not the actual reference. I’ll post it up tomorrow if nobody has guessed.

 

[Rocket86]

BC comic, the boulder?

 

[boatgeek]

BC comic, the boulder?

Much closer, the comic is a little more recent than that.

 

[BABAR]

alternative, “Six Flags over” (whatever state you happen to be in, in my case Confusion.)

 

[boatgeek]

OK, here's the original reference. I'll probably have to provide the LCO with cymbals for my flights though.

 

[BABAR]

Hopefully it will be only cymbals that crash.

 

[mbeels]

Along with the Stage-a-saurus (and Thagomizer), I like these cartoon themed rockets.

 

[boatgeek]

After a truly ridiculous period of inactivity (3 months, really?!), I did a burst of work this weekend. The Windmill of Destiny is nearly flight ready. Progress since last time included installing motor mount tubes and retention, hemming up the sails, sewing some 200-lb-WLL split rings to the sail corners, and installing some control lines across the circumference. On the booms, I drilled through-holes and threaded bits of heavy paperclips through. Those are sealed by injecting some epoxy in from the end toward the center and then puching the epoxy up to the paperclip with a bit of masking tape.

I ended up using fixed-length lines from the outer trailing edge of the sail to the next boom. That means that the sails won't be very tight on the way up, making for a little less drag and more spin. I think it will still be a good effect, though. On the inner trailing edge, I just hooked a rubber band from the trailing edge of the sail to the next boom over. Here's what it looks like with the thread installed to hold the booms down:


From left to right, that's full stack, the top showing where the burn string threads cross over the central motor, and the business end. The center MMT will be for a D12-0; the outers can take any 24mm motors that I dare. My TARC team has a stock of F79s that turned out to be too much power, so that's a good candidate for an all-up flight.

Finally, a demo of what happens when the -0 motor fires the ejection charge and burns the threads:
View attachment IMG_4624.MOV

Looking forward to launching in a couple of weeks!