Skelenaut Redux

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gfunk

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Thanks to CoyoteNumber2 for the original Skelenaut inspiration in 2015 and sharing his lessons learned!

I successfully flew my own Skelenaut this Christmas. The local clubs weren't sure they wanted to let this one fly untested, luckily I have my own FAA CoA on some private Midwest farmland for a maiden flight.

With a loaded/pad weight of about 14lbs the AT K185W took it to ~1,300' AGL and 160 mph. Spoiler alert: Skeletons are draggy!

Build details:
  • I used most of a full length of MAC canvas phenolic 54mm air frame, creating essentially a goofy minimum diameter rocket.
  • Fins are huge, probably too big, and made from 1/4" birch ply. Generous fillets and 1.5 layers of T-T 2x2 twill CF cloth over the wood made sure they stayed put. I was willing to accept over-stability and weather cocking to make sure this didn't go unstable and turn into 7 seconds of long burn undead terror.
  • I flew an RRC3 to get the apogee event timing right. The required delay would be really short, like a few seconds.
  • True "Head End Deployment" fired a 72" Spherachute main at apogee. I had a 18" chute on the skull just in case the main needed help getting out. It didn't need the help, ground testing was spot on.
  • I utilized rail buttons and a square hole through the skull to allow the optimal guidance offered by a 1010 rail.
  • Walgreens seems to have the highest quality plastic skeletons around, better than either HD or Lowes.

Skelenaut video:
Video Link

Damage report:
He broke a distal phalanx off his second toe upon landing. This toe proved hard to locate amidst a harvested soybean field, so he's a battle scarred toe amputee now.

Also has minor zipper repair required due to a somewhat horizontal/high-speed deployment. I think this was due to weather cocking and then gravity turning on the long burn low thrust motor. A K550 or K456 might be a better choice for the next flight, but that long burn thunder at low altitude sure was cool. Regardless, he will be ready to fly again in October.

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Nytrunner

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Quite a unique....rocket?,...you have there!

What did you do with your leading edges for the tip to tip? They look really smooth
 

gfunk

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Quite a unique....rocket?,...you have there!

What did you do with your leading edges for the tip to tip? They look really smooth
Thanks!

I beveled the plywood edges, leaving the middle ply square. Then T-T doing one fin set at a time in a huge V-block, using my son's play sand in a trash bag for compression over parchment paper. The CF under compression did a nice job forming over the bevels.

Once all the fin sets were done I sanded all the edges smooth. At this point the wood's middle ply was very visible, so I buttered on a bead of black rocketpoxy down the tip chords and leading/trailing edges. I sanded this smooth, sanded the fin faces some more, and then foam rollered on a "finish coat" of US composites 635.

It's pretty good, but not perfect. More sanding and epoxy would have filled in some pin holes on the faces, but wasn't worth the effort for this application. Good enough to fly a skeleton on! Probably not the solution for Mach busting flights, but that wasn't a concern here.
 

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CoyoteNumber2

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Nice work! This is a flying skeleton done right.
 

BABAR

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Congrats, very nice.

The post deployment ground picture with the skull off to one side definitely ranks as one of the most macabre model rocket pics ever!
 

BABAR

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He was definitely on his toes for the ascent, but his phalanges relaxed post Deployment!

Very nice!
 

gfunk

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What is the retainer/rail-button used here?
Custom made, goofy, 54mm minimum diameter retainer with integral button attachment.

Pretty draggy solution for most min diameter applications, but not nearly as draggy as a life size skeleton. [emoji6]

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