Help Support RocketryForum by donating using the link above or becoming a Supporting Member.


Page 3 of 5 FirstFirst 1 2 3 4 5 LastLast
Results 61 to 90 of 121
  1. #61
    Join Date
    22nd August 2015
    Location
    Rhode Island
    Posts
    1,137
    The bevel looks good. Were you just using a steady hand to keep the sander level, or did you have some sort of jig?

    NAR #100940, RIMRA & CMASS
    L1 - 4/17/16, Tyrannosaur (by Binder Design), Loki H144
    L2 - 8/19/17, Terrordactyl (by Binder Design), CTI J250

  2. #62
    Join Date
    17th November 2015
    Posts
    1,052
    Quote Originally Posted by BDB View Post
    The bevel looks good. Were you just using a steady hand to keep the sander level, or did you have some sort of jig?
    Thanks! Just a steady hand. That's why I was using really really light pressure - so that if I messed up and wasn't holding it level, I could fix it in the next pass. Even with light pressure, it was MAYBE 30 seconds of sanding per side with 100 grit. I figured if the next layer of laminate was showing up with an even line, I was in good shape.


  3. #63
    Join Date
    17th November 2015
    Posts
    1,052
    Another small update:
    Having beveled the "test" fin, I went ahead with the rest. VERY pleased with the result. Here's a shot of the setup... I had drawn lines on all the fins to align on the "pivot point", then realized I was close to just lining up the edge of the fin with the edge of the board. Much easier. Also note the borrowed silicone mat that keeps everything from sliding around.
    Click image for larger version. 

Name:	IMG_4395.jpg 
Views:	67 
Size:	63.2 KB 
ID:	309168
    Finished product:
    Click image for larger version. 

Name:	IMG_4404.jpg 
Views:	62 
Size:	95.6 KB 
ID:	309166
    And I got some biking in while I sanded the CWF off the blue tube.
    Click image for larger version. 

Name:	IMG_4402.jpg 
Views:	65 
Size:	110.1 KB 
ID:	309167
    Still need to do:

    18. drill upper hole for rail button. Install & glue in rail button (just above top CR). Drill hole for lower rail button too.

    19. Install mmt. Test fins a couple of times while epoxy cures. Be sure to cure with nose-end up so epoxy flows down onto CRs.
    20. Make alignment jig.
    21. Test-fit lower fins. Possibly do a double-alignment jig: one that slides over the BT with slots for the fins and clamp a piece of flat stock to the fins to keep them straight. Belt and suspenders!
    22.
    Install lower fins with alignment jig. Double-butter for internal fillets.
    23. Install upper fins One at a time, clamp w/straightedges
    24. Build Eggfinder tx

    25. Build Eggfinder rx
    26. Test Eggfinders
    27. Install lower RB, just above bottom CR.
    28. Install rear CR and let dry.

    29. Fillet upper & lower fins
    30. Glass fins
    31. Install eggfinders and assemble upper-upper (pins to hold in place)
    32. Assemble lower-upper
    33. Primer
    34. Sand, fill.
    35. Primer
    36. color coat
    37. Contrast coat
    38. Clear coat
    39. Polish
    40. Install recovery system
    41. Fly![/QUOTE]
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	IMG_4395.jpg 
Views:	51 
Size:	105.9 KB 
ID:	309165  

  4. #64
    Join Date
    17th November 2015
    Posts
    1,052
    So the eggfinder build was challenging but IT'S DONE AND IT WORKS, HUZZAH!
    So I can check off:
    24. Build Eggfinder tx
    25. Build Eggfinder rx
    26. Test Eggfinders
    Also got this done:
    18. drill upper hole for rail button. Install & glue in rail button (just above top CR). Drill hole for lower rail button too.

    Waiting on my 3d-printer-having friend to make up a sled for the Tx unit. He's going to re-do the upper transition with a sled. The idea will be that the sled will go all the way into the NC and the NC and upper body tube will be one piece that slides over the electronics. We'll see if that works...

    Up next:
    19. Install mmt. Test fins a couple of times while epoxy cures. Be sure to cure with nose-end up so epoxy flows down onto CRs.
    20. Make alignment jig.
    21. Test-fit lower fins. Possibly do a double-alignment jig: one that slides over the BT with slots for the fins and clamp a piece of flat stock to the fins to keep them straight. Belt and suspenders!
    22.
    Install lower fins with alignment jig. Double-butter for internal fillets.
    23. Install upper fins One at a time, clamp w/straightedges
    27. Install lower RB, just above bottom CR.
    28. Install rear CR and let dry.

    29. Fillet upper & lower fins
    30. Glass fins
    31. Install eggfinders and assemble upper-upper (pins to hold in place)
    32. Assemble lower-upper
    33. Primer
    34. Sand, fill.
    35. Primer
    36. color coat
    37. Contrast coat
    38. Clear coat
    39. Polish
    40. Install recovery system
    41. Fly!
    Last edited by ActingLikeAKid; 12th February 2017 at 04:34 PM.

  5. #65
    Join Date
    17th November 2015
    Posts
    1,052
    Crossing another one off:
    19. Install mmt. Test fins a couple of times while epoxy cures. Be sure to cure with nose-end up so epoxy flows down onto CRs.
    This was interesting.... Laid out all my parts:
    Click image for larger version. 

Name:	IMG_4622.jpg 
Views:	49 
Size:	119.1 KB 
ID:	311614

    And because I wanted a solid ring of epoxy above the top mmt, I taped a tongue depressor to a piece of angle iron. That ended up working ... okay. Mixed up a bunch of Rocketpoxy (actually measured the weight this time, as opposed to eyeballing it) on the paper plate, then scooped it onto the tongue depressor on the stick, then applied a ring of glue. Goal was to get it between the upper fin slots and I did pretty well at that. Not a great shot, but you can see some goopy epoxy way up int he tube.
    Click image for larger version. 

Name:	IMG_4623.jpg 
Views:	49 
Size:	71.7 KB 
ID:	311615
    Next step (not pictured, was working quickly and didn't want to get epoxy on my phone:
    Slide the mmt in until the upper 2 CRs were in the body tube, then smear some more epoxy into the BT. The goal was to create a second ring of epoxy above the third (from the top) CR. You can't see it without an X-ray, but it's there Did that, then slid the whole mmt in and turned it to the alignment marks I made.

    That's when I saw (as I'd kind of expected/worried) a decent amount of rocketpoxy in the fin slots (it had been pushed out as the rings slid up). I was prepared, though: A popsicle stick wrapped in paper towel dipped in rubbing alcohol cleaned that right up. I also realized I'd forgotten to cover the bottom of the mmt as I'd planned, so I used a similar method to clean up the bottom of the mmt and the inside of the bottom of the BT. Once I'd gotten rid of all the epoxy in the fin slots (there wasn't a lot, but any could make the fins not fit), I dampened a couple of fins with alcohol (just in case there was any residual epoxy) and put them in (the idea being that the fins would hold the mmt in place - the tolerances are tight, so the fins held the mmt exactly where it needs to be). This worked PERFECTLY. Every 10 to 30 minutes (or when I remembered), I'd pop the fins out and move them to a different slot. This ensured that the slots were clear and that if there was a little residual epoxy, I didn't prematurely glue a fin in. Here it is drying:
    Click image for larger version. 

Name:	IMG_4627.jpg 
Views:	47 
Size:	130.4 KB 
ID:	311611
    A shot of the epoxy sitting on top of the CR:
    Click image for larger version. 

Name:	IMG_4629.jpg 
Views:	48 
Size:	85.8 KB 
ID:	311612
    And this is what you get when you measure a LOT before you cut. Wanted the bottom of the fin flush with the bottom of the BT, and got exactly that.
    Click image for larger version. 

Name:	IMG_4630.jpg 
Views:	48 
Size:	96.1 KB 
ID:	311613

    Time to hit payload bay and print out an alignment jig or two - I have some foam core sitting waiting for exactly this. Wondering if I REALLY need fillets if I'm going to glass the fins tip-to-tip. I'm thinking not.

    Up next:
    20. Make alignment jig.
    22.
    Install lower fins with alignment jig. Double-butter for internal fillets.
    23. Install upper fins. One at a time, clamp w/straightedges
    27. Install lower RB, just above bottom CR.
    28. Install rear CR and let dry.

    29. Fillet upper & lower fins
    30. Glass fins
    31. Install eggfinders and assemble upper-upper (pins to hold in place)
    32. Assemble lower-upper
    33. Primer
    34. Sand, fill.
    35. Primer
    36. color coat
    37. Contrast coat
    38. Clear coat
    39. Polish
    40. Install recovery system
    41. Fly!

  6. #66
    Join Date
    22nd August 2015
    Location
    Rhode Island
    Posts
    1,137
    Coming along nicely! This thread is inspiring me to use blue tube for one of my upcoming scratch builds.
    NAR #100940, RIMRA & CMASS
    L1 - 4/17/16, Tyrannosaur (by Binder Design), Loki H144
    L2 - 8/19/17, Terrordactyl (by Binder Design), CTI J250

  7. #67
    Join Date
    17th November 2015
    Posts
    1,052
    Quote Originally Posted by BDB View Post
    Coming along nicely! This thread is inspiring me to use blue tube for one of my upcoming scratch builds.
    Thanks! Apart from applying the sanding sealer, I'm pretty happy with it - it's easy to drill/sand/cut and pretty lightweight.

  8. #68
    Join Date
    15th October 2016
    Location
    Huntsville AL
    Posts
    1,870
    Do any kits come in Blue-Tube, or is it just a raw material?
    "I'm at least 70% confident about whatever I say (90% of the time)"- college me

    NAR 101195
    Level 1: Big SAM, 9/10/16

  9. #69
    Join Date
    19th January 2009
    Location
    Tucson, Az
    Posts
    2,348
    Some Blue-Tube kits are available here:

    http://www.alwaysreadyrocketry.com/

    I have seen the Blue Phenix fly and it is a nice looking rocket that performs well.
    Last edited by terryg; 12th February 2017 at 10:39 PM.
    more rockets then cents

  10. #70
    Join Date
    15th October 2016
    Location
    Huntsville AL
    Posts
    1,870
    Those all look like 3FNC.

    I'll probably pass on those, but for scratch builds like this Mega Vector, it looks like a great build material.

    Speaking of which, the build is coming out really nice.

  11. #71
    Join Date
    17th November 2015
    Posts
    1,052
    Thanks!! Having them pre cut the slots was a HUGE help - not terribly expensive and 1000% easier and more precise than using my dremel

  12. #72
    Join Date
    17th November 2015
    Posts
    1,052
    So I've been busy, but not with this. I had some really troubling personal stuff happen and (it's a long story) I really, REALLY wanted to do rocket work - it lets my brain "check out" while I focus on the task at hand. And I really wanted my brain to check out for a bit. But I was out of town and I had to leave quickly so ... no rocket stuff.

    But I'm back and the day I got home I was fiddling with fiberglass. I built a little fincan out of a piece of 29mm bluetube and some basswood. This wasn't supposed to be airworthy, it was just to test all the materials (and later will be a test for finishes to make sure everything is compatible).

    First attempt at glassing was an utter failure - I spread on some epoxy, laid down the cloth, squeegeed it, and it looked good. I gave it 90 minutes, said "OK, this feels leathery, I think?" and tried to trim the glass. The whole piece of cloth moved. I pulled everything off, wiped down with alcohol and tried again.

    Pot life on the epoxy I'm using is 25-35 minutes and cure time is 8-10 hours. On the second attempt I tried at 3 hours and it went MUCH better. So it went:
    -Cut 3 pieces: two to go over the fillets and halfway out the fin, and one big tip-to-tip piece.
    -Sand the part with 220 (I am prepping the actual part with 60 as well to give the resin some good scratches to "hold on to")
    -Paint with epoxy
    -Lay down the first two small pieces, smooth with (GLOVED!) finger.
    -Lay down the big piece. Smooth with fingers.
    -Smooth everything with an old hotel room key, squeegeeing out the epoxy as much as possible (but leaving the cloth wet)
    -Wait 3 hours, trim cloth.
    -Wait for the cure (not wait for the Cure. Robert Smith was not helpful when I asked him about composite material layup)
    -Sand smooth. Wipe thoroughly.
    -Paint with a thin coat of resin.
    -Let cure.
    -Sand.

    It's ready for paint now. And here's how it looks. I only glassed one side of two fins; even with one side glassed, you can see the difference. Same pressure applied on both sides.
    Click image for larger version. 

Name:	bendyfin.jpg 
Views:	68 
Size:	39.5 KB 
ID:	313412

  13. #73
    Join Date
    22nd August 2015
    Location
    Rhode Island
    Posts
    1,137
    Very cool. I'm planning to attempt a layup like this in the near future. What weight if cloth did you use? And are you planning to extend all of the layers past the beveled edge of the fin?
    NAR #100940, RIMRA & CMASS
    L1 - 4/17/16, Tyrannosaur (by Binder Design), Loki H144
    L2 - 8/19/17, Terrordactyl (by Binder Design), CTI J250

  14. #74
    Join Date
    17th November 2015
    Posts
    1,052
    Quote Originally Posted by BDB View Post
    Very cool. I'm planning to attempt a layup like this in the near future. What weight if cloth did you use? And are you planning to extend all of the layers past the beveled edge of the fin?
    Thanks! I used 6oz cloth (I think - TopRamen sent me a bunch of cloth to try glassing with; I had a big chunk of this, weighed it, measured it, and it worked out to about 6oz per yard, so...).
    I did 2 layers - one that went from mid-fin to almost meeting in the middle of the body tube (if that makes sense) and one layer that went almost tip-to-tip. I'm not sure if I'll do the second layer on the actual project - you can kind of see a bump where it ends and I don't know if I really need the strength (and if I can skip the weight, why not).
    The tip-to-tip layer went all the way to the edge of the fin while I was letting it cure, then I cut it right around the edge of the bevel. Just seemed like it was easier to maintain the bevel without glass on it.
    Hope this helps!

  15. #75
    Join Date
    17th November 2015
    Posts
    1,052
    Fins are on and drying!! More pictures soon.

  16. #76
    Join Date
    17th November 2015
    Posts
    1,052
    More updates! First, the updated to-do list, in no small part to remind me what I have left to do. And I have some more on my to-do list.

    Done:

    20. Make alignment jig.
    22. Install lower fins with alignment jig. Double-butter for internal fillets.
    27. Install lower RB, just above bottom CR.
    28. Install rear CR and let dry.

    Up next:
    Make jig for upper fins (I was going to use an alignment jig, but realized that the upper fins are so small that the weight of the clamps and straightedges would be more of a liability than a benefit)
    23. Install upper fins.
    29. Fillet upper & lower fins
    30. Glass fins
    Fabricate Eggfinder sled
    Drill lower coupler and install eyebolt
    Epoxy couplers to 38mm section
    Make a new lid for my Eggfinder; install it.
    31. Install eggfinder and assemble upper-upper (one long screw and a side pin)

    Paint and finish.

    40. Install recovery system
    41. Fly!

    I have a ... possibly interesting plan for the Eggfinder sled. I kind of had "version one" of this in a separate thread, but I think I have an even better plan now....
    The gist: I cut a small slot in the top of the upper transition. The slot is maybe 3/4" deep but doesn't go all the way to the edges. (if it helps to visualize it, think of something like the key hole for the door of a car made in the 80s, if you're old enough )
    I make a sled out of glassed basswood that's long enough that the top corners of the sled press against the inside of the nose cone. The bottom of the sled fits into the slot in the transition and is secured either with epoxy or a small bolt.
    The nose cone and upper BT are epoxied together and slide down over the sled at flight time. Two or three pins hold the nose cone in place.
    Something like this:
    Click image for larger version. 

Name:	finalnose.png 
Views:	41 
Size:	4.8 KB 
ID:	314121
    the transition is purple, eggfinder is green, sled is brown. EF is on one side, battery is ziptied to the other side. The pins are black but wouldn't be in that configuration, it would be more like this from the top:

    Click image for larger version. 

Name:	topview.png 
Views:	37 
Size:	5.5 KB 
ID:	314123
    The dotted lines show where the tab of the sled fits into the transition. Body tube is blue, pins are black.
    Biggest challenge will be CAREFULLY cutting the slot with my Dremel. Slow deep breaths

  17. #77
    Join Date
    17th November 2015
    Posts
    1,052
    I think we're officially in the home stretch, which is good because I've got about 3 weeks before launch.

    Eggfinder sled is installed and looks good. Needs to be drilled and Eggfinder and battery installed. Need to fabricate some "stops" to keep the battery in place. Good news: The eggfinder and battery are mostly held in place by the upper section of the rocket; the clearance is tight enough that I had to trim a little bit off the posts for the jumpers....which means that there won't be a lot of lateral motion.

    My friend re-printed the lower transition with a hole in it (the old one had a fairly loose honeycomb that wouldnt' have been enough for the eyebolt to grab onto). Used a nyloc nut on the top of the eyebolt so that it can spin without undoing the nut.

    Rear CR is in and drying. This was fun: I wanted a good amount of epoxy above the CR and I also wanted it to flow down onto the CR. If I point the rocket upright while it's drying, the epoxy will flow down, but the rear CR could also slide down. So I jammed some popsicle sticks up against the CR. Now the rocket is resting on the popsicle sticks, which hold the CR in place, and the epoxy (should?) be flowing down onto the CR.

    Click image for larger version. 

Name:	hack.jpg 
Views:	48 
Size:	27.6 KB 
ID:	315938
    Up next:
    -Fillet fins
    -Glass fins
    -install motor retainer
    -Install Eggfinder and battery
    -Drill upper section and install retention bolts
    -Drill pressure relief hole
    -Assemble recovery gear
    -Prime/fill/sand
    -Paint
    -Fly

  18. #78
    Join Date
    17th November 2015
    Posts
    1,052
    Fillets done. First round of glassing started today. Slow and steady and fingers crossed.

  19. #79
    Join Date
    17th November 2015
    Posts
    1,052
    Update time!
    Got the eyebolt in the first transition. The nut is sunk deep into the top of it; I tightened it by jamming a knife next to the nut and twisting the eyebolt. Since it's a nyloc nut, it'll spin without loosening. I tightened just enough so there's a little play in it.Click image for larger version. 

Name:	IMG_5020.jpg 
Views:	41 
Size:	110.9 KB 
ID:	318256
    Fillets look ...well, really good, in my humble opinion.
    Click image for larger version. 

Name:	IMG_5037.jpg 
Views:	43 
Size:	71.6 KB 
ID:	318257
    Glass also looks good. Let it cure then sanded off the excess. Came out well.
    Click image for larger version. 

Name:	IMG_5070.jpg 
Views:	45 
Size:	141.0 KB 
ID:	318258
    After the glass cured, I painted it with a thick coat of epoxy. The result is a nice smooth finish.
    Frustrating thing happened on my upper transition -- I heard a crack and thought it was the glue holding the sled in.
    It was the actual top surface of the transition. I put in a gob of epoxy, made a slotted cover with 1/16 G10 glass, and put the sled in the slot. Looks good and is super strong:
    Click image for larger version. 

Name:	IMG_5078.jpg 
Views:	45 
Size:	66.4 KB 
ID:	318259Click image for larger version. 

Name:	IMG_5085.jpg 
Views:	44 
Size:	49.0 KB 
ID:	318260
    By the time I'd glassed the third set of fins, I remembered a recommendation: Lay down masking tape just above where you want the glass. When it's leathery but not cured, cut through the glass and peel the tape away. Nice clean lines!
    Click image for larger version. 

Name:	IMG_5086.jpg 
Views:	47 
Size:	117.2 KB 
ID:	318261
    Paint phase one - check out the low-tech paint stand. Also I bolted some tubing to the rocket where the rail buttons will be so I didn't paint the buttons.
    Click image for larger version. 

Name:	IMG_5153.jpg 
Views:	46 
Size:	340.9 KB 
ID:	318262Click image for larger version. 

Name:	IMG_5154.jpg 
Views:	45 
Size:	148.0 KB 
ID:	318263Click image for larger version. 

Name:	IMG_5155.jpg 
Views:	45 
Size:	405.3 KB 
ID:	318264
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	IMG_5018.jpg 
Views:	41 
Size:	72.3 KB 
ID:	318255  

  20. #80
    Join Date
    17th November 2015
    Posts
    1,052
    ...And after all that, tragedy struck.
    Was painting and the nose dropped and cracked.
    Attachment 318266
    It was super frustrating, but I epoxied it back on, sanded it down, and wrapped the nose in 2 layers of 2-oz glass. A couple of gentle test-whacks and it seems like it's good. PRODUCTION CONTINUES!

    The rest of the rocket looked really, really good though.

    Attachment 318267

  21. #81
    Join Date
    17th November 2015
    Posts
    1,052
    ...And that brings us to today. Had the rocket packed and ready to go. Had the Aerotech DMS in the motor mount, charge in, retainer on, electronics prepped in the nose cone. And ... I don't even remember what happened -- I dropped it or bumped it or...something. And suddenly my rocket was in many more pieces than I wanted. It's not a great picture of the failures, but both transitions failed at the narrow end of the transition (i.e. at the bottom of the top shoulder). Not sure what's causing these ABS failures; it's not usually a brittle material. The bottom transition I could theoretically epoxy back together then wrap with some glass (a LOT of glass, to be sure)and I think it would be OK. But I can't do that for the top -- both of the tubes that attach to it are designed removable. I think the solution will be some rods that run through the length of the transition to add strength.

    It was a really frustrating launch day for me.

    What really brought me joy, though, was that this was my club's first spring launch and we had over a hundred Scouts, Boys and Girls Club kids, and members of the community that came out and flew, most for the first time. Watching and hearing these kids get excited about rockets really helped soften the blow.
    Attachment 318270Attachment 318271

  22. #82
    Join Date
    17th November 2015
    Posts
    1,052
    ...and I'm kicking myself about spending SO MUCH TIME on the @$!#!#! paint. I mean, sure, it looks good. But rockets are made to fly, not gleam beautifully in a garage.

  23. #83
    Join Date
    15th October 2016
    Location
    Huntsville AL
    Posts
    1,870
    Your links aren't working for me, so without seeing the pictures, my thoughts are thus:
    -Stress concentration at the narrow end. Less material trying to take the same stresses, combined with a sharp corner that could promote fracture.
    -3D printing. Bending moments act along the Weakest axis of your prints. Layer separation gives fractures a field day.
    -Cross section geometry. Bending moments are strongest at the edges in the bend plane, but a circular tube (neglecting the low infill I see in your photos) has the very least material at those two points.

    Consider Several more shells at the exterior. Unless you change the print orientation, you may be stuck with the layer separation.
    "I'm at least 70% confident about whatever I say (90% of the time)"- college me

    NAR 101195
    Level 1: Big SAM, 9/10/16

  24. #84
    Join Date
    22nd August 2015
    Location
    Rhode Island
    Posts
    1,137
    This is painful to read. I'm assuming that the break is between the layers of the ABS. That happened to a nosecone that I printed recently. I've been thinking about epoxying it back together and then filling it with foam for reinforcement.
    NAR #100940, RIMRA & CMASS
    L1 - 4/17/16, Tyrannosaur (by Binder Design), Loki H144
    L2 - 8/19/17, Terrordactyl (by Binder Design), CTI J250

  25. #85
    Join Date
    17th November 2015
    Posts
    1,052
    Thanks, y'all. Not sure what happened to the attachment links. My friend who printed the transitions actually printed a second version of the blue one with a much tighter matrix to make it stronger. But apparently this is a tremendously weak spot, and/or ABS just isn't very strong under flexion (is that a word? I think that's a word and I'm too lazy to google). Same friend who printed these has some pultruded carbon rods. I think if I just have the carbon running down the middle & epoxy it back together, that ought to make it pretty bulletproof, especially if I glass the outside. There's no twisting forces, the ABS ought to resist compression and tension OK (especially with the carbon up the middle). The biggest weakness seems to be flexing, which would be 100% addressed with a rod up the middle.
    Attempt 2 at the pictures. The ABS failed in the same way as the nose cone - a weirdly modest tap and it just fractured. I think the gist is that 3d ABS is probably OK for filling-out HPR, but needs glass or something else to be properly strong. Again, I'm glad I found this out before launch.
    Click image for larger version. 

Name:	IMG_5256.jpg 
Views:	86 
Size:	82.6 KB 
ID:	318324Click image for larger version. 

Name:	IMG_5260.jpg 
Views:	85 
Size:	118.5 KB 
ID:	318325

  26. #86
    Join Date
    28th June 2016
    Location
    PA
    Posts
    662
    Quote Originally Posted by ActingLikeAKid View Post
    Thanks, y'all. Not sure what happened to the attachment links. My friend who printed the transitions actually printed a second version of the blue one with a much tighter matrix to make it stronger. But apparently this is a tremendously weak spot, and/or ABS just isn't very strong under flexion (is that a word? I think that's a word and I'm too lazy to google). Same friend who printed these has some pultruded carbon rods. I think if I just have the carbon running down the middle & epoxy it back together, that ought to make it pretty bulletproof, especially if I glass the outside. There's no twisting forces, the ABS ought to resist compression and tension OK (especially with the carbon up the middle). The biggest weakness seems to be flexing, which would be 100% addressed with a rod up the middle.
    Attempt 2 at the pictures. The ABS failed in the same way as the nose cone - a weirdly modest tap and it just fractured. I think the gist is that 3d ABS is probably OK for filling-out HPR, but needs glass or something else to be properly strong. Again, I'm glad I found this out before launch.
    Click image for larger version. 

Name:	IMG_5256.jpg 
Views:	86 
Size:	82.6 KB 
ID:	318324Click image for larger version. 

Name:	IMG_5260.jpg 
Views:	85 
Size:	118.5 KB 
ID:	318325
    It's not an ideal orientation to print on, but try printing the parts rotated 90 degrees on the printer. The weakest part of the 3D part is the adhesion of the layers to one another. If you flip the part orientation 90 degrees then the layer structure is running perpendicular to the shear force and should be stronger. Lastly, I would run with 25% infill but make your wall thickness 3 times thicker.
    TRA #10518 ---- MDRA #106

    L1, 6/25/2016: Modified MadCow Super Batray, CTI I236 BS
    L2, 9/17/2016: Modified RW Patriot, CTI J280 SS
    L3, 4/8/2017: RW Formula 200, CTI M1810 RL

    Max Altitude: 4,978', L3 Cert flight
    Max Speed: Mach ???, L3 Cert flight

  27. #87
    Join Date
    30th January 2016
    Location
    US > OK > NE
    Posts
    3,475
    Hrmm, side printed, identically shaped, mechanically interlocking halves. Then CF 'em with Soller sleeve & heatshrink to add tremendous hoop strength.

  28. #88
    Join Date
    15th October 2016
    Location
    Huntsville AL
    Posts
    1,870
    ABS should be pretty strong, but like Nate said, your print orientation is the weakness.
    When you bend, you're basically peeling the layers apart instead of putting tension on the filament lines themselves.

    If you could somehow embed 4 small carbon rods running top to bottom along the edges (at 12, 3, 6 and 9 o'clock), that would strengthen against bending better than a fat rod in the center.

  29. #89
    Join Date
    17th November 2015
    Posts
    1,052
    Quote Originally Posted by Nytrunner View Post
    ABS should be pretty strong, but like Nate said, your print orientation is the weakness.
    When you bend, you're basically peeling the layers apart instead of putting tension on the filament lines themselves.

    If you could somehow embed 4 small carbon rods running top to bottom along the edges (at 12, 3, 6 and 9 o'clock), that would strengthen against bending better than a fat rod in the center.
    A friend suggested arrow shafts...that might be small enough...

  30. #90
    Join Date
    17th November 2015
    Posts
    1,052
    I'VE GOT IT! I think...

    So I was turning this problem over in my head - how to strengthen the ABS, how to get a strengthening rod joined with the eyebolt so there's seamless strength.... then it hit me: THE ANSWER IS COUPLERS.

    I started thinking "well how would I make this if I didn't have a friend with a 3d printer?" and that was enough.

    I'm going to get two couplers - one that fits in the smaller tube, one that fits in the bigger tube. I'm going to use two centering rings to join them together. When done, I should have (for example) 2 inches of big coupler with 4 inches of small coupler sticking out the top. Then to make the transition smooth, I'm going to get my 3d-printer-having friend to print a sleeve that goes over the small tube, the sleeve will go from (e.g.) 0mm thickness to 5mm thickness. So the sleeve will handle the taper but be mostly cosmetic.


Similar Threads

  1. Military-look Vector Force
    By ActingLikeAKid in forum Low Power Rocketry (LPR)
    Replies: 13
    Last Post: 2nd January 2016, 09:59 PM
  2. Estes - Vector Force (#3210) gallery
    By Fishhead in forum Galleries / Photo & Video Tips
    Replies: 0
    Last Post: 7th July 2014, 10:14 PM
  3. Estes Vector Force
    By gdjsky01 in forum Low Power Rocketry (LPR)
    Replies: 29
    Last Post: 19th February 2014, 06:08 PM
  4. Estes Vector Force
    By SCIGS30 in forum Low Power Rocketry (LPR)
    Replies: 17
    Last Post: 31st August 2011, 11:40 PM
  5. Estes - Vector Force Gallery
    By SCIGS30 in forum Galleries / Photo & Video Tips
    Replies: 0
    Last Post: 24th August 2011, 05:07 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •