Level III Build - Cert Attempt - Aeschylus (5" WM Punisher)

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MrPoopyPants

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Hi Everyone,

So I am starting my L3 project which I am planning to Launch later this summer or in the fall. The reason I am posting the thread is to share a little bit, maybe get some constructive feedback/ideas/don't do that!s/mockery and also so my TA's can keep up with it as well. I get long winded sometimes so I'll try to keep this all reasonably short.

I am building this project with a Wildman 5" Punisher with a few minor modifications. I really like this rocket and have flown the 3" and 4" versions. It's really just the fin shape and overall look of it that does it for me. This will be well overbuilt on purpose - It needs to get the cert but I also want to fly it for a long time. I'm not going to add heft just because - but I'm not going to sacrifice any robustness for the sake of weight savings. This is also going to be a build that I won't make any exceptions on. No matter the time it takes or cost - no cut corners.

Minor Mods:
  1. Longer Motor Tube - For the Cert - I'll be flying an AT M1600R (gotta love that red!)v but want to really push it after the certification and the longer tube makes me feel a little better - the 98/15360 (Later Flight) will come above the 36" tube I am using but it allows me to add a 3rd centering ring - which really makes me happy. It's double the length of the regular MMT.
  2. OAL - My other punisher projects are around 12/1 body tube. I cut my 3" down so it was a little closer to 10/1. I'd like to go 10/1 with project. So it means - I'll be cutting about 10" of the 60" BT. My sim is attached - which has the OEM 60" tube - but that will be changing. I only want to cut it once and really don't want to cut too much by mistake - so I will make the final decision on how much to cut once I have it almost finished and can really dial the sim in. I think they look better and fly better a bit shorter.
  3. Nose Cone (Not being done) - I wanted to go to a 6/1 nose cone but can't really find one - after mocking it up, I think the 5:1 looks better - Wildman doesn't make one and I don't want plastic - I've looked around and don't have any good ideas on sourcing a longer nose - open to ideas possibly but I think I'm set on the 5/1
  4. Ejection - More on that below
Hardware/Avionics:
  1. Flanged AeroPack Motor Retainer
  2. FW Blue Raven - Primary Alt
  3. MW RRC3 - Backup Alt
  4. FW GPS and Backup RDF
  5. Possible second FW GPS for back up but I am really unsure about this. If I do it, I'll use the Inverted Pursuits system and attach to the shock cord. I'm worried that two of the same GPS units in such close proximity may interfere with each other and not sure how/if my ground station can have two connections - possibly an email to Adrian or a second ground station is in order. I don't know why I am considering this... I've never had any issues with FW GPS - so this may (likely) be a dumb idea I am having.
  6. Avionics Sled - I am planning to 3D print my own sled - I want to make it specific to this rocket and the electronics I am flying - Really like the idea of having solid built in attachments for everything - this is probably the biggest hurdle for me. I am new to 3D printing and I'm well into my 40s - learning new software is like expecting my mother to know how to handle a google maps pin.
Glue!:
  1. Proline 4500 - This will be used for the fin roots, centering rings and to attach a Y harness to the MMT. I will use the epoxy/knot method for the harness.
  2. West Systems 105/205 - All other locations.
  3. All epoxy will be vacuumed to limit air bubbles.
Fins and Fillets: WM does not have a sim for the 5" Punisher - I think they are 26% larger in all dimensions from the 4" which is 26% larger than the 3" fin set but I didn't want to take any chances. So I plotted them out and input them manually.
  1. Internal Fillets - Unthickened West Systems using the injection method. I am really considering double internals - basically a fillet at the fin/mmt and then also the fin to the interior of the airframe. Unsure on this but for the 30G weight penalty - It sure will make me feel good.
  2. Externals - Thickened West/406. I usually mix this stuff up super thick - more like playdough consistency than peanut butter - I'm aware that some strength is lost (or at least I've heard that and it makes sense) so I will be thickening as little as possible - May figure out a slick way to keep the epoxy from running off the fins and then shape the forward fillet once it sets up a bit. I'm gonna make these pretty big - Probably a .75" Radius or bigger. I'll then go over them with West/410 for sandability or use my favorite spot putty. Really depends on how well the lay down.
  3. I'm considering to really sharpen up the airfoil on these - but I don't think there's any benefit to that on this project - Just potential for them to be damaged.
  4. Centering Rings - Will also be injected with West.
Finish:
  1. I've already laid down filler primer on the nose cone and wet sanded (future coat before paint goes on. The FWFG cones really need filler to get them smooth. Sanding seams to pull glass fiber out. I was considering body filler but the sandable primers do pretty darn good.
  2. I've named the project "Aschylus" and will have vinyl decals and graphics made up. Not sure on the color but I am leaning towards a light color - probably not white but... actually - I have no idea - I want metallic flake paint so bad but don't want any radio interference with the tracking.
  3. My intention is to have this look amazing - at least for it's first flight.
Final Thoughts:

I am thinking of doing true head end deploy and incorporating line cutters but I want to be able to use different motor hardware - I haven't been able to wrap my head around how to accomplish this and it's not a MD project - I'll probably keep it traditional HED with a drogue in the main BT. I also bought the ejection wells from Tinder - so that will be a trick little deal. For HED I like to put my charges way up in the nose to force the main out so I may only use the charge wells at apogee.

Drogue - I usually upsize my drogues - We have super thin air in Colorado and it's hard to pack in an oversized chute in the nose cone so I've made up for that with a little extra drogue diameter - I feel like I've been dodging a bullet maybe. My DD flights are usually too high (and too far away - big drifty drogue) for me to see what's going on but I have a feeling my nose cone is pointed straight down at the main deployment. There's plenty of room in this big padonkadonk 5" nose cone for almost anything. the drogue for this cert attempt will probably only be big enough to keep it as close to 100fps as I am comfortable with - would love peoples thoughts on this subject.

A note on the attached Sim File - Its very not complete. All of the inputs are from measurements and weights I took off the physical parts. I have not accounted for any hardware, flight laundry, avionics, motor retainers or epoxies - just the glass. I will be sure to upload sims as I progress with this thread.

Thanks everyone - especially Wildman, Will Bussell (TAP), Big Pete Ekstrom (TAP) and the Anti-Gravity Group guys.

Cheers
 

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This looks like an awesome build. Good luck on the L3 cert.

I don't think you need the longer motor tube. It's absolutely fine if the casing sticks out the top, as long as the tube is centered and retained well. The fins add so much bonding area that you don't need to add a third centering ring for extra strength.

If you want a different shape nosecone, I have been developing a pretty good method. Soller composites fiberglass sleeves laid up over a 3D printed male plug with condoms for mold release has worked quite well for me. At 5", you'd probably need to get some novelty extra large condoms. For the nosecone tip, you could cast one out of expoxy, with a 3D printed mold, or get one machined. JLCPCB has an incredibly affordable machining service, they made an aluminum nosecone tip for my 75mm submin for $30 shipped. Admittedly, I've only used this technique for up to 3" nosecones. @Brainstormz123 has done it for larger ones.
 
This looks like an awesome build. Good luck on the L3 cert.

I don't think you need the longer motor tube. It's absolutely fine if the casing sticks out the top, as long as the tube is centered and retained well. The fins add so much bonding area that you don't need to add a third centering ring for extra strength.

If you want a different shape nosecone, I have been developing a pretty good method. Soller composites fiberglass sleeves laid up over a 3D printed male plug with condoms for mold release has worked quite well for me. At 5", you'd probably need to get some novelty extra large condoms. For the nosecone tip, you could cast one out of expoxy, with a 3D printed mold, or get one machined. JLCPCB has an incredibly affordable machining service, they made an aluminum nosecone tip for my 75mm submin for $30 shipped. Admittedly, I've only used this technique for up to 3" nosecones. @Brainstormz123 has done it for larger ones.
Thanks @Neutronium95

You had me at extra large novelty condoms :)

I agree the motor tube is a bit overkill - But, well you know - peace of mind and what not - I'm not built yet so I may go back on this decision. So long as I don't have a weird offcenter thrust - it's just not needed. But I have some "N" plans for this rocket and don't want to feel like I should second guess the build - either way point well taken.

I've heard about the custom nose cone layups! Pretty wild what can be done in the age of 3D printing.
 
Noticed that you are opting to go with a longer MMT. I do the same thing on my builds, know its not necessary and many dislike it, but its my style, so I second your choice!
Thank you! I agree that it's just not necessary - but I just like it. Haha

My only concern is that punishers seem to have their CG aft a bit by design. I've never had to add nose weight but considering that I'm cutting this down a little it'll make the CG a little more of something for me to pay close attention to. It'll be supersonic - I think I'll be okay if I can get somewhere around 1.25 - 1.5 cal. Static Margin.

Thanks for the input and for following along.
 
Thank you! I agree that it's just not necessary - but I just like it. Haha

My only concern is that punishers seem to have their CG aft a bit by design. I've never had to add nose weight but considering that I'm cutting this down a little it'll make the CG a little more of something for me to pay close attention to. It'll be supersonic - I think I'll be okay if I can get somewhere around 1.25 - 1.5 cal. Static Margin.

Thanks for the input and for following along.

Adding nose weight isn't an issue. you have a built in "hard point" of sorts with the tip of the nose cone. You also have the electronics bay in the base of the nose cone, lots of options.

Remember, your CP will move around as you go through Mach.
 
Adding nose weight isn't an issue. you have a built in "hard point" of sorts with the tip of the nose cone. You also have the electronics bay in the base of the nose cone, lots of options.

Remember, your CP will move around as you go through Mach.
Yes - that eyebolt really helps! I cram a couple of screws in the eye and then drop down fishing weights - then pour west. The screws work as a little extra support. Probably not needed. Also - I figured out to use about half a pump of west instead of a full pump. That stuff gets super hot when used like that. Braden Carlson suggested putting the tip of the nose cone in water as well. Smart man he is.

I prefer this method over adding weight lower down. More bang for the weight when its all the way at the top! haha

My supersonic flights have all had a 2.0 Cal. But I think I can get away with less... not much less but maybe a half cal. Maybe not though and I should really make sure to get 2.0. Once I have the sim complete I can see how the CG moves during the burn and compare to the CP. Considering this is a cert flight - I will probably not push it very much though.

Thanks again @Theory
 
Looks like an awesome build. I am currently working on something very similar. How are you vacuuming epoxy?
I have a 5 Gallon Vacuum Chamber. Will mix epoxy and then vacuum. I think pot life on west systems is about 15 minutes so long as it's a single pump (my preferred way of measuring west) The proline has a longer pot life and I will mix in much smaller quantities.

If you are thinking of getting a vacuum chamber you should - They're about the price of J motor.
 

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