3" build - Dual Deploy and glass practice prior to L3

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Dustin Lobner

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Just got recertified to L2 (was back in 2004ish) and started talking with my TAPs about an L3 attempt. I haven't flown dual deploy since 2004, so I'm basically self declaring that I haven't flown dual deploy. I also haven't fiberglassed anything successfully. So, up next is a 3" diameter dual deploy with a 38mm mount. Specs:
3" dia
60something inches long
38mm mount (good for a 38/720 mount, maybe a 6gn CTI)
Cardboard tube, 1 layer medium Soller fiberglass, yellow
Eggtimer Quantum computer
Fin can, motor mount, Av Bay, and nosecone all 3D printed

Going to leave the mesh pattern from the fiberglass, so it'll have a woven appearance, like a basket...so this one is being christened "Basket Case". Glass is yellow, anything 3D printed will be blue, which ends up with a neat looking color scheme:

BasketCase Screenshot2.PNG


Other bits-
Av bay end (very PML CPR feel):
Basketcase AvBay End.PNG
Av bay:
Basketcase AvBay.PNG
Fin Can:
BasketCase Fincan.PNG


Hoping to launch at Bong in Wisconsin or with LARS folks sometime in January-March next year.
 

OverTheTop

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Consider which direction the z-axis weakness (if using FDM) is in the prints, especially for the coupler and the fin can.

You might want to have the fins thicker at the root, tapering towards the tip, too.

What material you planning on using?
 

Dustin Lobner

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Yeah, that is all the plan. I've done this on a rocket with multiple flights on a G80 with good luck. Basically, I print them "up" as if the rocket were sitting in front of me pointed upwards...makes it strongest in tension/compression. The fins are strongest in flex at that point...it's akin to having a balsawood fin with the grains of the wood pointed straight at the body of the rocket, not along the main axis of the rocket.

Fins are 6mm wide at the base, tapering to 3mm at the tip. 15mm radius fillet around all the base edges too.

Fin can, Av bay, and nosecone are eSun PLA Pro - it's their "upgraded" PLA that I use for pretty much everything. It's what flew on the G80s, so sticking with that.
Motor mount is Matterhacker's Tough PLA, which is pretty much on par with ABS in terms of thermal resistance...I use it all the time at work for mechanical test fixtures and it works well, so using that here.
 

Nytrunner

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Can't say I like PLA much in structural applications, but looking forward to seeing how this works out for you!

Do you have threaded rods putting the ebay in compression?
 

Dustin Lobner

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I think the worries about PLA are overdone, iff you get the right PLA. "Normal" PLA that prints at 180-200C or so is crap for structural, agreed. This modified stuff is tougher in general, more heat resistant (the Matterhackers Tough PLA prints at 245 on my printer, same as ABS), and has great inter-layer adhesion. If you print it right and hit it with a hammer, instead of shattering it deforms while breaking. Couple that with appropriately radius'ed corners to keep notch stresses down...should be OK.

That said, I'm not going to fly this thing with a Warp-9 propellant or something, I'll be sticking with slower burning propellants. Flies great with a G80 though.

Edit - yes, av bay has threaded rods. Three of them all the way thru in a line - one with eye nuts on the end to attach recovery harness, other two just ending in nuts to help distribute the load.
 

ECayemberg

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Cool design, Dustin!!!

Three threaded rods is a bit unconventional, but that's fine! One or two will suffice; I think a lot of people prefer two as it gets the rods out of the way for altimeter and battery mounting on the centerline of the sled. That said, with your 3D printing abilities, you can probably print enough material around the centerline rod that mounting on axis is still possible.

I'm looking forward to "fondling" the 3D printed parts. I'm still new-ish to 3D printing for structural components in HPR...so it's still a bit mysterious and exciting!!!
 

Dustin Lobner

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Cool design, Dustin!!!

Three threaded rods is a bit unconventional, but that's fine! One or two will suffice; I think a lot of people prefer two as it gets the rods out of the way for altimeter and battery mounting on the centerline of the sled. That said, with your 3D printing abilities, you can probably print enough material around the centerline rod that mounting on axis is still possible.

I'm looking forward to "fondling" the 3D printed parts. I'm still new-ish to 3D printing for structural components in HPR...so it's still a bit mysterious and exciting!!!
Tonight's mission was to determine if I could fit the Quantum and 2 batteries with 3 rods or not, if not then yes I'll end up with two or one even...if I do one, I'll end up with some alignment pins that keep the sled from rotating.

Lol - fondling the 3D parts is a thing for sure. I started out about a year ago and I'm on my 2nd printer and have burned through more filament than I can describe. Everything from rockets to wash cloth holders. The big thing is having access to a good CAD program, which I happen to be lucky enough to have.
 

Dustin Lobner

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Here's a prototype Av Bay end with a BP canister on it...Gotta open up the hole under the terminal block to give the wires space to come up and around, and looks like I need to up the extrusion multiplier a hair. Otherwise, that's 5 solid layers all around along with 80% infill. The plate part is "stout" to say the least. The canister is only 2 layers thick and will undoubtedly be a single-use component, lol.

basketcase av bay end 1.jpg basketcase av bay end 2.jpg
 

MikeyDSlagle

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Do you intend to 3d print the parts for you L3 attempt as well? Unless it changed or I am mistaken 3d printed fin cans can't be used for L3 attempts. It was only recently implemented, IIRC.
 

Dustin Lobner

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Do you intend to 3d print the parts for you L3 attempt as well? Unless it changed or I am mistaken 3d printed fin cans can't be used for L3 attempts. It was only recently implemented, IIRC.
Not nearly this extensive. Maybe the ends of the av bay, but it'll still have plywood underneath it. Sticking to more traditional methods there.
 

OverTheTop

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Basically, I print them "up" as if the rocket were sitting in front of me pointed upwards...makes it strongest in tension/compression. The fins are strongest in flex at that point...it's akin to having a balsawood fin with the grains of the wood pointed straight at the body of the rocket, not along the main axis of the rocket.
Vertical is good for the fins, and the only way that probably makes sense. Consider printing the coupler horizontal. That gives it greater strength when subjected to bending forces (tension on one side, compression on the other), which is the more likely direction during flight. If you run an allthread, or similar, from one end of the bay to the other and secure the ends to harnesses, then even if it breaks the rocket stays together for a lower risk recovery. The allthread works a bit like pre or post-stressed reinforcing in concrete, keeping it more in tension where the material works better. Don't rely on the structural strength for off-nominal recovery scenarios. Have a plan-b in place for a safe recovery ;).
 

Dustin Lobner

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Consider printing the coupler horizontal.
Have a plan-b in place for a safe recovery ;).
Makes sense. What I might end up doing is printing it both ways and seeing how it turns out. I'd be afraid that the printed horizontal version doesn't quite turn out round...usually the very bottom of the print sags a bit, this is just a Creality CR-10 with Simplify3D for slicer...it's has good support design, but it's not a dual extruder, so printing round parts sideways sometimes doesn't go well. I just printed a piece here at work that turned out poorly for that exact reason, I'll see if it's still around and hasn't been tossed yet...
 

Dustin Lobner

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Just reread your first reply - yes, there will be allthread, and yes that's where the harness will attach, so it will stay together in some form. Managed to get pics of what I'm worried about:

Horizontal print:
Horizontal print.jpg


Vertical print:
Vertical print.jpg
 

Dustin Lobner

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Took another swing on the Av Bay end, this time with only one rod in it. It came together well, only change I have to make is changing the bolts from 8-32s to 6-32s for the terminal block.

Side 1:
Av Bay End Side 1.jpg

Side 2:
Av Bay End side 2.jpg

I also printed out the last inch or so of the Av Bay as it's designed to check for fitment with the end. Here they are apart:
AvBay End with Av Bay Segment.jpg

And finally assembled:
Av Bay assembled.jpg
 

Dustin Lobner

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Progress tonight on CAD related items.

The body tubes will be held onto the 3D printed av bay section with 4 screws. I originally had them all in the same plane, but moved them to 2 in one plane and 2 in another plane half an inch higher, so that one layer of print doesn't have 4 screws worth of tension trying to rip it apart.

aAv Bay.PNG

Got something of a first effort done on the motor mount and a revision to the fin can to match it. The holes in the fin can will have #10 bolts through them, through holes in the body tube, and then into the matching holes in the motor mount.

Pretty sure I'm going to end up using zero epoxy or other adhesives (other than glassing the body) for this entire rocket...it should all just bolt together.

aBasket Case Fin Can.PNG
aBasket Case Motor Mount.PNG




Tomorrow night or perhaps Sunday night I'm hopefully going to get to take a crack at glassing the tubes using glass sleeve and shrink tube from Soller. Can't finish off some parts of the design until I know the final OD of the glassed tubes, so want to get that in motion so I can finish the designs and start printing the rest of the parts.
 

Dustin Lobner

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Also got about half the Av Bay sled done.

The center will have the 1/4-20 all thread running through it. Big rectangular part for the Eggtimer Quantum. The 2 posts at each end go into holes on the backside of the av bay end caps and prevent the whole sled from rotating...not that that's really needed, but I figured I might as well.

aAv Bay Sled.PNG

EDIT: batteries and terminal blocks will go on the side opposite the square part, I haven't drawn that in yet.
 
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This is looking awesome...which 3D program are you using?

ToughPLA is pretty damn good too, but certainly a lot heavier. At least the Ultimaker stuff is.
 

Dustin Lobner

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This is looking awesome...which 3D program are you using?

ToughPLA is pretty damn good too, but certainly a lot heavier. At least the Ultimaker stuff is.
Solidworks. I've tried a few of the "free" programs, but my biggest complaint with them tends to be the user interface is crap. And since I'm entirely self-taught, having a clear/easy interface is important because half the time I don't know what I'm even looking for, lol.

Yeah, only the motor mount will be the Tough PLA, and yes that's the Matterhackers stuff. Printed the second end cap to the av bay, and let me tell you with "normal" PLA Pro it's quite heavy...when running 4 solid layers plus 80% infill! :eek: We'll see what the final weight comes in at, I might end up reprinting a few parts with a lower infill. That said, I have 100% confidence that it'll survive!
 

Steve Shannon

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Just reread your first reply - yes, there will be allthread, and yes that's where the harness will attach, so it will stay together in some form. Managed to get pics of what I'm worried about:

Horizontal print:
View attachment 396003


Vertical print:
View attachment 396004
Please do some destructive testing at several angles of pull and let us know the force at which that harvest connection fails. I would suggest maybe a drop test with a weighted section being dropped. My concern, as alway is safety.
 

Dustin Lobner

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Please do some destructive testing at several angles of pull and let us know the force at which that harvest connection fails. I would suggest maybe a drop test with a weighted section being dropped. My concern, as alway is safety.
Hi Steve,

Those parts won't actually be on the rocket, those were some parts that I printed for something else at work, showed them to ilustrate the difference between printing cylinders horizontal vs vertical. The av bay will be 1/4"-20 all thread with lifting eyes at the end, all 500 pounds or better working load.

I actually might have to do that testing regardless, I have access to a "proper" mechanical test lab.

Dustin
 

Steve Shannon

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Hi Steve,

Those parts won't actually be on the rocket, those were some parts that I printed for something else at work, showed them to ilustrate the difference between printing cylinders horizontal vs vertical. The av bay will be 1/4"-20 all thread with lifting eyes at the end, all 500 pounds or better working load.

I actually might have to do that testing regardless, I have access to a "proper" mechanical test lab.

Dustin
Thanks! I really appreciate it.
 

Dustin Lobner

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Got a first piece glassed with the Soller shrink tube system. Went OK (pic below), so glassed the first section last night. Went not as good but pretty obviously because of lack of experience, so I'm confident it'll get better.

My little sample thing did give me a critical dimension though - the final OD. Measured that, got my models updated, and was ready to start printing only to find my printer is having an issue (pretty sure a worn out extruder gear). Replacing that tonight, hopefully ready to go later tonight.

Fiberglass attempt.jpg
 

Dustin Lobner

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First pieces of "flight" hardware are done, av bay ends with the barrier terminal connectors installed. Only thing to change is the holes that the wires go through will eventually be filled with hot glue to seal the bay against gasses coming through.
IMG_20191107_213122952.jpg
IMG_20191107_213152383.jpg

The av bay itself is printing presently, about a 60 hour print or so. Hoping it stays stuck to the printer and doesn't fall over with half an hour left...

IMG_20191107_213108638_MP.jpg

Currently designing the av bay sled, which is turning out ugly visually but I'm hoping that it goes together nicely. That's kinda TBD.

Also - glassed my first actual tube with the Soller stuff and messed it up bigtime. Basically overheated the crap out of the shrink tube and it melted to the tube. Will try reglassing that eventually. Slowly coming together.
 

Dustin Lobner

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Av bay turned out well, the adhesion was better than expected and it didn't tip over, so that was good. Ends fit in perfectly, and it fits in a body tube perfectly. Just the av bay and the ends (no rod through the middle, or the sled) weighs 14 oz though...going to need a bigger motor than I first expected. :eek::eek:



IMG_20191108_172857738_MP.jpg IMG_20191108_172854009.jpg IMG_20191108_172907187.jpg
 

Dustin Lobner

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Av bay is mechanically done, need to do some wiring and actually assemble the Eggtimer yet.

The sled is done with a large collection of terminal/barrier strip connectors on the bac. Here's the sled assembled, minus the outside part. The other connectors will be used to attach the second battery (which will go in the hole opposite the one that is there now), attach the switches, etc.
IMG_20191111_220215835.jpg IMG_20191111_220207766.jpg



The av bay "assembled" without the exterior on it to see how the ends go on:
IMG_20191111_220703868.jpg IMG_20191111_220708933.jpg


Then put is all in the shell. Being assembled:
IMG_20191111_221114577.jpg


And fully assembled:
IMG_20191111_221332876.jpg IMG_20191111_221314198.jpg IMG_20191111_221325397.jpg


The keyed switches (2) will disconnect the + terminal of each battery. The all-thread will be trimmed a bit and then will have an eye nut (https://www.mcmaster.com/3019T15) on each end and the 5/16-18 rod will take all the loads. The idea is that this whole thing can be assembled at home, minus the powder charges. Get to the field, attach the charges via the 8-32 cross screw and wire the charge to the connector, and away you go.

It's tighter inside than I'd really like, but that is a result of how overbuilt this whole thing is. If I'm going to fix anything, it'll be moving the batteries inward as that's the tightest spot.

Deer hunting season coming up here in Wisconsin, probably won't make much progress till December.
 

David Schwantz

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Hi Dustin, I have never printed anything, but your stuff sure looks nice! I am in MN, just got back this weekend from deer hunting, good luck to you.
 

David Schwantz

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8 pt on Friday morn with bow. My son used my firearms tag for his doe, so yes. Thanks. Hope yours goes as well.
 
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