Nike Smoke Scratch Build with 3D Printed Parts

[Kane]

Next project is 3" diameter scratch-built Nike Smoke. I've been experimenting with 3D printed airframe parts (nosecones and fins). The Nike Smoke's long nosecone and thick, airfoiled fins seemed like a fun challenge. I'm not really a scale modeler so that's not the intent of this project. Regardless, I have endeavored to adhere as closely as possible to the dimensions recorded by Harry Stine without getting too caught up in any of the finer details. I've recently come to appreciate the minimalism of the Nike Smoke design, but I am tempted to add a tail cone to it (it really seems to want one). We'll see what happens.

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The body tube and motor mount will just be LOC cardboard tubes and the motor mount centering rings standard plywood. The nosecone, avionics trays, and fins will primarily be 3D printed. I'm still working out the weights of the various 3D printed parts.

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The nosecone will be printed in 3 parts due to print volume limitations. The nose tip will be printed solid. The mid section and base/shoulder are mostly hollow tubes so are technically printed solid as well. The parts will be epoxied together and then covered with laminating epoxy and sanded smooth. An M4 threaded rod will be epoxied into the nose tip to secure the avionics tray / bulkhead and act as the recovery anchor.

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For the fins, I plan to print two outside layers to create the thick airfoil. These will be laminated to a 1/16" G10 fiberglass interlayer. I'll drill a grid of holes in the interlayer to promote epoxy adhesion "through" all three layers. Each assembly will be covered in laminating epoxy and sanded smooth. The G10 interlayer includes the TTW mounting tab.

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The avionics package will include redundant Eggtimer Quantum altimeters and an Eggfinder Mini GPS tracker. The bulkhead and avionics tray are one piece. An M5 eye nut (recovery anchor point) holds the whole thing closed (and can be unscrewed for access to the avionics compartment).

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Depending on how the 3D printed part weights shake out, she should be able to fly on a pretty wide range of motors. The solid printed nose tip, threaded rod, and nosecone avionics compartment should push the CG forward and the sizeable fins keep the CP fairly aft.

 

[Glasspack]

Nice

 

[cwbullet]

Consider sharing the STL files once you get it built. People would love to build it.

 

[Kane]

Consider sharing the STL files once you get it built. People would love to build it.

Will do. Made some slight modifications - including sending the nose cone tip out to be CNC'd aluminum. I'm sure there will be some more iterations as I print, assemble, weigh, and adjust for stability.

 

[Kane]

Just arrived today from JLCPCB. Aluminum nose cone tip. Anodized and threaded for an M5 threaded rod to connect it to the rest of the nose cone and the avionics bay.

 

[Kane]

Aluminum tip and first section of PETG nose cone completed.

 

[ShadowSpire48]

Consider sharing the STL files once you get it built. People would love to build it.

Agree on this. I found a 3" Nike nose cone file somewhere online and printed it but holy cow the geometry that they exported it with was horrendous, very low-poly for most of the lower section with a few high poly smooth areas.

 

[Kane]

Got the bottom section of the nose cone printed. Next I'll epoxy the base and mid section together and then coat with laminating epoxy to smooth.

 

[tfish]

cool..
I see one point of concern..
Your 1/16 G10 inner layer is pretty lite weight. I realize you're adding an other layers of airfoil..which adds some thickness to the fins. But 80% of the workload will be done by that 1/16 G10 through the wall.

Nike smoke fin shape is not the best anti flutter profiles (short root to span ratio)

I did not see what size motor tube you're going with ..if it's 29mm and H reloads...it will probably be OK..

still a cool project.

Tony

 

[Kane]

cool..
I see one point of concern..
Your 1/16 G10 inner layer is pretty lite weight. I realize you're adding an other layers of airfoil..which adds some thickness to the fins. But 80% of the workload will be done by that 1/16 G10 through the wall.

Nike smoke fin shape is not the best anti flutter profiles (short root to span ratio)

I did not see what size motor tube you're going with ..if it's 29mm and H reloads...it will probably be OK..

still a cool project.

Tony

I am anticipating some added resistance to flutter from the printed airfoil layers (printing on a diagonal so none of the layers are orthogonal to the flight vector and the lamination will add some stiffness), but that's not calculable (at least, not by me) so I've left it out of the flutter calcs. I'm glad you pointed this out though. I do actually check flutter for all my scratch builds and did so for this one. However, after reading your comment I went back and looked at my spreadsheet and realized I hadn't considered flying anything larger than an I motor. I had originally started this project thinking it would just fly H and I motors. Upon further reflection, a J340M or J340W could be a killer flight. Those motors definitely put the speeds above what that 1/16" G10 can handle. Looks like bumping the thickness up to 3/32" will do the trick. This bumps the "safe" velocity up to 990 ft/s which is about the speed predicted on a J340M.

Thanks for the heads up!

 

[ZeroGPrints]

View attachment 673570
Just arrived today from JLCPCB. Aluminum nose cone tip. Anodized and threaded for an M5 threaded rod to connect it to the rest of the nose cone and the avionics bay.

Is this long of an aluminum tip necessary or is it just decoration?

 

[Kane]

Probably not necessary unless one wanted to push it over mach (even then, probably not necessary). I've been itching to try this service and it was relatively inexpensive.
I have a separate configuration that can be printed that's omits the aluminum tip for a printed one.

 

[Kane]

Started printing one of the fin layers today. Printed with no bottom layers so the 40% infill is exposed on the surface that will get laminated to the G10 fin layer. The idea here is that this will promote greater adhesion between the PETG and G10. Also note the print angle on the bed at 45 degrees so the cubic infill grids and the subsequent top skin layers are not orthogonal to the direction flight.

 

[Kane]

Made some progress on the Smoke.
Cut out the 3/32" G10 fin layers and have all the PETG airfoils printed. Drilled holes in the G10 around the perimeter to promote through-adhesion across all three layers. Sanded and cleaned all G10 surfaces with acetone. Going to print a jig so I can lay these up accurately.


Nose cone fully printed, coated with laminating epoxy, and sanded smooth.


Tail cone printed. I'll likely coat this with a laminating epoxy after attaching to the rear of the airframe.


Avionics nose cone sled printed. Added all the heat set inserts for electronics standoffs. Completed the Eggfinder TX Mini and one of the Quantum altimeters.

 

[ShadowSpire48]

Tail cone printed. I'll likely coat this with a laminating epoxy after attaching to the rear of the airframe.
View attachment 683591

Why a tail cone? The Nike didn’t have one

 

[Kane]

Why a tail cone? The Nike didn’t have one

'Cause I like it better with.
As noted in my OP, I'm not really interested in "historical accuracy." I was more interested in the design per se as it relates to some of the building techniques I'm developing.

 

[Kane]

Little bit of a hiatus with work stuff taking priority. Tonight I got all the 3D printed airfoils laminated to their G10 cores.

The exposed infill on the laminating side of each airfoil really used a fair amount of epoxy so I suspect these will end up a little heavier than anticipated.
Once these dry, I'll sand the leading edges of the G10 to match the angle of the 3D printed airfoils. Then I'll layer on some laminating epoxy to smooth the transition from the 3D printed part to the G10.

 

[PhxRocketeer]

Little bit of a hiatus with work stuff taking priority. Tonight I got all the 3D printed airfoils laminated to their G10 cores.
View attachment 687165
The exposed infill on the laminating side of each airfoil really used a fair amount of epoxy so I suspect these will end up a little heavier than anticipated.
Once these dry, I'll sand the leading edges of the G10 to match the angle of the 3D printed airfoils. Then I'll layer on some laminating epoxy to smooth the transition from the 3D printed part to the G10.

Definitely recommend trying dynamic layer height in the slicer next time for those fins. It can keep the infill areas thick and then step down to 0.08 for the airfoiled sections to give a smoother appearance. But I like the approach you used for print angle and infill, may have to give that a try.

 

[Kane]

Definitely recommend trying dynamic layer height in the slicer next time for those fins. It can keep the infill areas thick and then step down to 0.08 for the airfoiled sections to give a smoother appearance. But I like the approach you used for print angle and infill, may have to give that a try.

How did I not know about this? Thanks for the tip. I'll be covering these with self-leveling epoxy to smooth everything, but the dynamic layer height would have been nice to give a smoothe substrate to begin with. Will definitely look into it.

 

[Kane]

Progress over the weekend:
Airframe slotted.


Motor mount built with epoxy dams. Also assembled the recovery tether with zipper guard.


Beveled the leading and trailing edges of the G10 layer of fins. Next step will be self-leveling laminating epoxy.

 

[Kane]

First layer of self-leveling laminating epoxy applied and sanded. Still have a few low spots so these get another coat and round of sanding.

 

[Kane]

I had the tail cone that I originally printed in PETG printed in SLS Nylon by JLCPCB. It has a higher heat resistance than PETG.
Also printed the fin alignment jig. Dry fit all the parts. Looking pretty good.

 

[Kane]

Next coat of self-leveling laminating epoxy applied to the fins.

 

[PhxRocketeer]

I love the G10 core with printed airfoils. Will have to try that soon!

 

[bad_idea]

I had the tail cone that I originally printed in PETG printed in SLS Nylon by JLCPCB. It has a higher heat resistance than PETG.

If you don't mind my asking, what did it cost to have those printed and what was the surface finish like as received? I've been curious if farming out SLS nylon printing would be an affordable way to get higher quality parts than I'm able to print at home with FDM.

 

[Kane]

If you don't mind my asking, what did it cost to have those printed and what was the surface finish like as received? I've been curious if farming out SLS nylon printing would be an affordable way to get higher quality parts than I'm able to print at home with FDM.

The tail cone was only about $4.50 (plus shipping which was actually more than the part itself - about $13 but that was to ship the tail cone and a fin jig).

 

[Kane]

If you don't mind my asking, what did it cost to have those printed and what was the surface finish like as received? I've been curious if farming out SLS nylon printing would be an affordable way to get higher quality parts than I'm able to print at home with FDM.

And the finish is nice. They actually sandblast it so it has a slightly textured finish.

 

[bad_idea]

The tail cone was only about $4.50 (plus shipping which was actually more than the part itself - about $13 but that was to ship the tail cone and a fin jig).

And the finish is nice. They actually sandblast it so it has a slightly textured finish.

Thanks. That sounds very reasonable. Good to know about the finish. That might not work for what I'm thinking of, but maybe I'll have some test parts made to see.