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  1. #31
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    17th December 2013
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    Add a boattail, that'll lower stability as well.
    But then it wouldn't exactly be a true upacale.

    Nothing is foolproof to a sufficiently talented fool.
    TRA #16513
    Level 1: Danger Close ---AT H123W to 1240'--- 29 OCT 2016
    Level 2: Binder Design Tyrannosaur ---AT J315R to 2148'--- 30 SEP 2017

  2. #32
    Join Date
    17th November 2015
    Posts
    1,054
    Soliciting opinions:
    1. Rail buttons: 1010 should be enough for this, right? It's not like I'm sticking K motors in it... I'm thinking I'll use the Apogee-style rail buttons with weld nuts inside the tube, mostly because 1. I've used them before and 2. I like them. Conformal guides are cool, but you can't really replace them easily.

    2. Beveling the fins... I'm thinking something like a 60 degree angle for the leading edge, 45 degree for the trailing edge.... Beyond "a sharp edge goes through the air better than a dull one", is there a particular formula/reason/place to learn on why I should go with a particular angle? And if I glass or carbon the fins, should I bevel them first and then clean them up after the reinforcement? Or just glass them then bevel them?

    Thanks for any suggestions....


  3. #33
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    17th December 2013
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    Slagle, La
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    1010 buttons shuold be plenty sufficient. I have only seen the big boys fly on 1515. I've seen 4 inch Frenzies and a Stealth use 1010s, so yours should be fine.
    Nothing is foolproof to a sufficiently talented fool.
    TRA #16513
    Level 1: Danger Close ---AT H123W to 1240'--- 29 OCT 2016
    Level 2: Binder Design Tyrannosaur ---AT J315R to 2148'--- 30 SEP 2017

  4. #34
    Join Date
    30th January 2016
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    US > OK > NE
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    3,740
    Quote Originally Posted by ActingLikeAKid View Post
    Soliciting opinions:
    1. Rail buttons: 1010 should be enough for this, right? It's not like I'm sticking K motors in it... I'm thinking I'll use the Apogee-style rail buttons with weld nuts inside the tube, mostly because 1. I've used them before and 2. I like them. Conformal guides are cool, but you can't really replace them easily.

    2. Beveling the fins... I'm thinking something like a 60 degree angle for the leading edge, 45 degree for the trailing edge.... Beyond "a sharp edge goes through the air better than a dull one", is there a particular formula/reason/place to learn on why I should go with a particular angle? And if I glass or carbon the fins, should I bevel them first and then clean them up after the reinforcement? Or just glass them then bevel them?

    Thanks for any suggestions....
    Somewhere in the 7-12 range is more typical, I think?

  5. #35
    Join Date
    28th June 2016
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    PA
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    662
    Quote Originally Posted by ActingLikeAKid View Post
    Soliciting opinions:
    1. Rail buttons: 1010 should be enough for this, right? It's not like I'm sticking K motors in it... I'm thinking I'll use the Apogee-style rail buttons with weld nuts inside the tube, mostly because 1. I've used them before and 2. I like them. Conformal guides are cool, but you can't really replace them easily.

    2. Beveling the fins... I'm thinking something like a 60 degree angle for the leading edge, 45 degree for the trailing edge.... Beyond "a sharp edge goes through the air better than a dull one", is there a particular formula/reason/place to learn on why I should go with a particular angle? And if I glass or carbon the fins, should I bevel them first and then clean them up after the reinforcement? Or just glass them then bevel them?

    Thanks for any suggestions....
    My rules of thumb: 1010 rail buttons are good for rockets up to 50 lbs. 1515 are good for rockets up to 200 lbs. As you approach the upper end of either range it's a good idea to make sure the rail has some support behind it.

    I always bevel at 10 degrees and try to leave 0.030" thickness in the center. Bevel the main piece of G10 before you T2T. If you T2T the fins, I would trim the T2T material to either the back edge of the bevel or to the middle of the bevel. Then, coat the edge in epoxy to seal it.
    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

  6. #36
    Join Date
    17th November 2015
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    1,054
    Quote Originally Posted by NateLowrie View Post
    My rules of thumb: 1010 rail buttons are good for rockets up to 50 lbs. 1515 are good for rockets up to 200 lbs. As you approach the upper end of either range it's a good idea to make sure the rail has some support behind it.
    Awesome. 1010 is good enough for me

    Quote Originally Posted by NateLowrie View Post
    I always bevel at 10 degrees and try to leave 0.030" thickness in the center. Bevel the main piece of G10 before you T2T. If you T2T the fins, I would trim the T2T material to either the back edge of the bevel or to the middle of the bevel. Then, coat the edge in epoxy to seal it.
    10 degrees doesn't seem like a lot, so it's more like "gently rounded"? Also this is birch plywood (which is one of the reasons I'm glassing in the first place) ... Your suggestion kind of echoes what I was thinking: that glassing T2T is going to be a lot like a "grownup" version of papering fins.

    Thanks

  7. #37
    Join Date
    17th November 2015
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    Also: What do y'all think of this?

    My design will be fine for most motors, unless I put a really big J in there. And for that, I'm ... squished. There is scant room between the top of the motor and the bulkhead. IF I decide to do a big screamin' J in it, would this work:
    1. Drill 3 holes in the coupler on the upper section. Screw a short (like 8 inch) section of body tube to that, with 3 inches of coupler glued to the body tube (1.5" in the BT, 1.5" exposed). Everything else works as normal, but all the recovery laundry gets stuffed in the section I added. It's reversible (I just unscrew the screws and take the additional section out) and shouldn't affect the stability of the rocket....

    ...thoughts?

  8. #38
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    17th November 2015
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    Here's what it looks like with the motor getting perilously close. No way I can stuff everything in:
    Click image for larger version. 

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    Here's what happens if I add my extender:
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  9. #39
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    10 degrees is common. See the fins below on my Patriot for reference.Click image for larger version. 

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    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

  10. #40
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    17th December 2013
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    Slagle, La
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    Adding an extension should work. I have seen some rockets where the entire booster is pinned, riveted, or screwed so it can be easily removed to service the shock cord or shock cord mount. There won't be much stress from recovery on that section.
    And you could build a baffle into the coupler.
    Nothing is foolproof to a sufficiently talented fool.
    TRA #16513
    Level 1: Danger Close ---AT H123W to 1240'--- 29 OCT 2016
    Level 2: Binder Design Tyrannosaur ---AT J315R to 2148'--- 30 SEP 2017

  11. #41
    Join Date
    15th March 2016
    Posts
    370
    You could also drill holes in your transition and sink screws through the airframes into it, then move the chute into the next section of airframe.

    Also, airfoil guides can be attached removable like you described for the 1010s you are planning, you just need different size nuts for backing. I use T-nuts, they are like the weld nuts, but with little spikes for sticking them in wood. You can cut the spikes off and use them the same as the weld nuts.

  12. #42
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    17th November 2015
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    Thanks for your comments everyone! Got some pictures and a progress report coming...

  13. #43
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    17th November 2015
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    Progress report!

    DONE! Sand holes to fit fins
    DONE! Sand one end of 38mm tube to fit retainer
    DONE! Take deep breath and cut BTs to length (38mm both for motor mount & lower-upper)

    This was tough. My first idea was to get a coping saw and use that; a lack of experience and the wrong tool conspired to give me a pretty chewed-up tube end. MUCH better results with a Dremel cutting wheel. Only problem with that is that the wheel is small enough that the tube end isn't square (it was mostly square across the tube but sort of very-slightly tapered). The solution to all my problems was to tape a piece of 60 grit sandpaper to my workbench and, holding the BT vertical, sand the rough end. (then repeat with smoother grit until I had a nice square end) [see footnote]
    DONE! Sand ends of BTs nice & smooth
    DONE! Sand-seal all tubes (but only inside of mmt)

    I ended up sealing the inside & outside of all tubes (the sealer doesn't add noticeable thickness, and where it got gloppy, it's easily knocked down).

    Lots of information to share here.
    Bluetube is ... interesting to work with. Very strong, very light. With the sealer on it actually feels a lot like fiberglass - smooth and light.
    The sanding sealer was a recommendation from Dave at ARR. This is NOT Aerogloss "dope" sealer; he recommended Cabot but said any high-quality non-water-based sanding sealer would work (go to Lowe's, not your local hobby shop). Here are some tips:
    1 WEAR GLOVES. The sealer is sticky and nasty and you don't want it anywhere but where you want it to go (NB: it's really easy to get it where you don't want it to go.
    2 Do the inside of the tubes first. Inside and outside need to be sealed and a little whoopsie on the inside is 100% not visible; a whoopsie on the outside may be.
    3. To do the insides of the tubes, here's the best method I found: Tape up the outside of the tube so it doesn't get dripped on. For small/short tubes you can wrap with masking tape; for bigger tubes, a combination of grocery bags & masking tape seemed to work fine. You'll need paper towels, a low wide container and a rod that's longer than your body tube. Pour about a half-cup of sanding sealer into a low wide container. Prepare your paper towels. You'll need four pieces per tube. For 29mm, each piece is a quarter-sheet, 38mm each piece is a half-sheet, 54mm each piece is 3/4 of a sheet. Don't worry about being exact. Soak three paper towel pieces in the sanding sealer and stuff them into the body tube, one at a time (like LPR wadding). Stuff one dry piece in behind them. This will wipe down the sealer and smooth it out. Slowly push the towels through the tube with the rod, back into the container of sealer. Look down the tube for dry spots inside. If you see some, repeat.
    4. Outsides of the tubes were a lot easier - just used a paintbrush.

    And now, pictures!
    Click image for larger version. 

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    Tubes drying. The sanding sealer turns the pale blue cardboard-looking tubes a dark beautiful bluish green. If I'd been more careful, I think this could have been a really pretty "naked" build. But I wasn't, so this will all get covered in primer and shiny, shiny paint. Tubes are being held up with some bamboo skewers jammed into an Amazon box. There's a small sledgehammer stuffed in the end to keep it all stable.
    Click image for larger version. 

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    Tube insides drying. Taping up the outsides was about as much fun as you'd think.

    Click image for larger version. 

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    First dry-fit of everything, sitting next to the original.


    [footnote] I messaged the late Dave Bucher and told him he'd probably laugh at my terrible use of a coping saw; he suggested that using a box-cutter and a lot of patience would have been a better idea. He was a smart man and I'm sad I didn't get to know him better.

  14. #44
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    17th December 2013
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    So does blue tube have to be sealed inside and out? Never even seen the stuff but have been thinking about trying it.
    Nothing is foolproof to a sufficiently talented fool.
    TRA #16513
    Level 1: Danger Close ---AT H123W to 1240'--- 29 OCT 2016
    Level 2: Binder Design Tyrannosaur ---AT J315R to 2148'--- 30 SEP 2017

  15. #45
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    17th November 2015
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    Quote Originally Posted by MikeyDSlagle View Post
    So does blue tube have to be sealed inside and out? Never even seen the stuff but have been thinking about trying it.
    That's what Dave at ARR said. I'm not certain, but I believe it helps keep it resistant to moisture.

  16. #46
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    Ahh okay. Good to know. Thanks. I wouldn't even have asked. I have sealer I've used on a few paper rocketfs so it won't be first. I didn't get good results then, but the rockets had glassine and I would imagine that had a lot to do with it.
    Nothing is foolproof to a sufficiently talented fool.
    TRA #16513
    Level 1: Danger Close ---AT H123W to 1240'--- 29 OCT 2016
    Level 2: Binder Design Tyrannosaur ---AT J315R to 2148'--- 30 SEP 2017

  17. #47
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    17th November 2015
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    yep. Also BT is a lot beefier in terms of being able to sand it -- with paper, once you're through the sealer, it's like 'OH WELL, I'VE MADE A HOLE IN IT NOW"....In terms of abrasion resistance, BT seems to be almost as hard as PVC.

    Current status is: hand sanding the BTs with some of that awesome 3m flexible sandpaper. I don't care about how the insides look, but I like a smooth finish on the exterior. I'll probably use filling primer, but I'd like to get it as smooth as possible before I do. Right now, you can see little "valleys" from the brush strokes where I applied the sealer. Trying to get the tube worked down, debating using a power sander to do it more quickly/evenly. I think I'll stick to hand work though.

  18. #48
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    22nd August 2015
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    Quote Originally Posted by ActingLikeAKid View Post
    Current status is: hand sanding the BTs with some of that awesome 3m flexible sandpaper.
    I love that stuff, but it is crazy expensive.
    NAR #100940, RIMRA & CMASS
    L1 - 4/17/16, Tyrannosaur (by Binder Design), Loki H144
    L2 - 8/19/17, Terrordactyl (by Binder Design), CTI J250

  19. #49
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    17th November 2015
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    Quote Originally Posted by BDB View Post
    I love that stuff, but it is crazy expensive.
    ...Relatively speaking. I got a roll of 220 for $12 last year sometime and I am in zero danger of running out. One of the things that I love about it is how long it lasts: Normal paper sandpaper gets gummed up and you chuck it. This stuff you can rinse and wash and dry and it's good to go.

  20. #50
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    22nd August 2015
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    Quote Originally Posted by ActingLikeAKid View Post
    ...Relatively speaking. I got a roll of 220 for $12 last year sometime and I am in zero danger of running out. One of the things that I love about it is how long it lasts: Normal paper sandpaper gets gummed up and you chuck it. This stuff you can rinse and wash and dry and it's good to go.
    That is a good deal. It looks like I'm just getting ripped off by Home Depot. They are selling it for >2x the price you paid.
    NAR #100940, RIMRA & CMASS
    L1 - 4/17/16, Tyrannosaur (by Binder Design), Loki H144
    L2 - 8/19/17, Terrordactyl (by Binder Design), CTI J250

  21. #51
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    17th November 2015
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    Update: My attempt to sand it smooth has gone through the sealer. ANOTHER coat coming soon. This time I'll use a nicer brush in an attempt to get a smooth finish

  22. #52
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    17th December 2013
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    Slagle, La
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    I always used the foam brushes. Don't know if that will help.
    Nothing is foolproof to a sufficiently talented fool.
    TRA #16513
    Level 1: Danger Close ---AT H123W to 1240'--- 29 OCT 2016
    Level 2: Binder Design Tyrannosaur ---AT J315R to 2148'--- 30 SEP 2017

  23. #53
    Join Date
    26th June 2014
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    124
    Quote Originally Posted by ActingLikeAKid View Post
    Question for anyone following: Is too much stability a bad thing? According to my initial forays, this thing will have stability of 4-5 cal with a motor in it. Obviously, that means it's prone to weathercocking in a good wind, but other than that, is a super-stable rocket a bad thing?
    On a rocket with transitions and different diameter airframes, which diameter does the simulation use to determine the correct cal to use for stability? If I have a rocket with 98mm, 54mm and 38 mm airframes connected with transitions, is 1 cal 98mm, 54mm or 38 mm? Or does it average the different diameters?
    Level 1. Fiberglass scratch built on an Aero Tech H123
    Level 2. Fiberglass scratch built 4 inch diameter 8 lb rocket on an Aerotech J540r at Midwest Power
    Mile high. Level 2 rocket on an Aero Tech k695 to 7334 feet at CIA launch Monticello Il.
    Max altitude 10411 on an Aerotech L1090

  24. #54
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    17th November 2015
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    Quote Originally Posted by SDramstad View Post
    On a rocket with transitions and different diameter airframes, which diameter does the simulation use to determine the correct cal to use for stability? If I have a rocket with 98mm, 54mm and 38 mm airframes connected with transitions, is 1 cal 98mm, 54mm or 38 mm? Or does it average the different diameters?
    Huh. That's a really interesting question. Just checked with OpenRocket and it was pretty straightforward to figure out. Stability is based upon the thickest tube. My rocket's biggest tubing is 54mm Blue Tube with an OD of 57.5mm. With an AT I motor, stability is 4.43 cal; CG at 949mm, CP at 1203mm. Delta is 254mm. 254/4.43 = 57.33, close enough to the max tube size. Wonder if the flight calculations "shortcut" to the biggest tube.

  25. #55
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    17th November 2015
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    Update:
    1. Sand holes to fit fins
    2. Sand one end of 38mm tube to fit retainer
    3. Take deep breath and cut BTs to length (38mm both for motor mount & lower-upper)
    4. Sand ends of BTs nice & smooth
    5. Cut CRs to let Kevlar fit through Cut 2 slots

    7. Sand-seal all tubes (but only inside of mmt) (still in progress)

    CRs have been cut. Not as pretty as I would have liked, but there's plenty of room for the kevlar. I realized after I did this that I didn't need to do slots on the bottom CR, but oh well. Good news is that I can easily fill that hole with epoxy.

    After sealing the tubes twice and then sanding, I realized a few things:
    1. This sanding sealer (Cabot's Quick Dry) dries in and hour IF YOU GIVE IT A THIN EVEN COAT. If there are ANY runs, drips, or blobs, that can increase to much, much longer.
    2. Don't even THINK of painting over this stuff for 24 hours.

    It looks like after 24-72 hours, primer can be applied without issue. Not sure what I'm doing for a paint scheme yet - I'm leaning toward a simple black with white fins - but I cut a section of blue tube as a tester so that I can try different paint combinations. Last thing I want is to get all the way done and then discover I have to sand back down through everything and start with fresh primer or something.

    Anyway, here's a shot of the CRs on the mmt with the kevlar. Going to use the "encapsulate in epoxy" method to hold both sides in. (and no, this isn't final positioning, this is just to make sure that I can get the kevlar through them.)
    Click image for larger version. 

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    Still to do! Adjusting this list to be more "build heavy" and "finishing light" .... it's currently 20 degrees and snowing, so I'm likely not painting much in the near future.

    9. CA top CR in place on mmt.
    10. Test fit with top fins MARK MMT FOR ALIGNMENT. Adjust CR if necessary.
    11. CA mid CR in place
    12. Test fit with all fins Should be snug. Adjust CR if necessary.
    13. retest fit with all fins
    14. Score mmt all over. Put swivel on Kevlar, install Kevlar harness with swivel on it. Encapsulate with epoxy. Let cure. Whip top of Kevlar to make loop.
    15. Retest fit with all fins
    16. Epoxy CRs in place with good fillets on non-fin sides, "spot" fillets on fin-sides
    8. Bondo tubes
    xx. Draw line & drill upper hole for rail button. Install & glue in rail button (just above top CR)
    23. Build Eggfinder tx
    24. Build Eggfinder rx
    25. Test Eggfinders
    17. Install mmt, Test fins while curing.
    18. Install lower fins with alignment jig. Double-butter for internal fillets.
    19. Install upper fins One at a time, clamp w/straightedges
    20. Install rear CR and let dry.
    xx. Drill hole for lower RB through rear CR, and install.
    21. Fillet upper & lower fins
    22. Glass fins

    26. Install eggfinders and assemble upper-upper (pins to hold in place)
    27. Assemble lower-upper
    28. Primer
    29. Sand, fill.
    30. Primer
    31. color coat
    32. Contrast coat
    33. Clear coat
    34. Polish
    35. Install recovery system
    36. Fly!
    Last edited by ActingLikeAKid; 3rd December 2016 at 12:35 AM. Reason: made a note to put on rail buttons

  26. #56
    Join Date
    17th November 2015
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    Update on sealing the Blue Tube. (Bluetube?): As I think I mentioned, the sealer is REALLY finicky. If you apply a perfect smooth even coat, it dries in an hour. If you have THE TINIEST drip or run, it can be several times that. Sanded the Blue Tube, knocked down the visible runs, and finally put on a new coat of sealer. Currently drying in my kitchen on a tarp with the window cracked and the exhaust fan on (it's 40F outside, this is as close as I'm going to get to "painting weather" for a while.). Once it's dry I should be able to forget about finishing stuff for a while. Up next is assembling the motor mount.

  27. #57
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    17th November 2015
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    Actually I'm waiting on a swivel -- I ordered some nice welded ones with ball-bearings from Amazon. And I can't move forward much til they arrive, so ... I'm going to build a fin-beveling jig. I figure if I stick some sandpaper on a board , screw on a guide wall, then put a half-inch block about 3" away, that should give me a 10 degree (ish?) bevel, if my math is right. Pictures to come!

  28. #58
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    Update! Been busy around here, but I've managed to make some progress!

    1. Sand holes to fit fins
    2. Sand one end of 38mm tube to fit retainer
    3. Take deep breath and cut BTs to length (38mm both for motor mount & lower-upper)
    4. Sand ends of BTs nice & smooth
    5. Cut CRs to let Kevlar fit through Cut 2 slots

    7. Sand-seal all tubes (but only inside of mmt)
    9. CA top CR in place on mmt.
    10. Test fit with top fins MARK MMT FOR ALIGNMENT. Adjust CR if necessary.
    11. CA mid CR in place
    12. Test fit with all fins Should be snug. Adjust CR if necessary.
    13. retest fit with all fins
    14. Score mmt all over. Put swivel on Kevlar, install Kevlar harness with swivel on it. Encapsulate with epoxy. Let cure. Whip top of Kevlar to make loop.
    15. Retest fit with all fins
    16. Epoxy CRs in place with good fillets on non-fin sides, "spot" fillets on fin-sides.
    xx. Draw line for rail buttons.

    OKAY! We're making good progress. I'm realizing that there's a decent chance that I won't launch for a few months, so I'm taking my time. The motor mount is assembled. Kevlar Y Harness is on. Nice thick fillets between the CRs and the mmt. I've checked the fit and the fins fit SNUGLY - when the mmt and fins are installed, there is zero play, exactly as I'd hoped.

    With the mmt installed, you can see the CR at the top and bottom of the upper fin slot and the top of the bottom fin slot (bottom CR goes on after the fins are in)
    Click image for larger version. 

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    To make it easy to get a good alignment spot where the kevlar isn't interfering, I marked some alignment spots at the bottom of the rocket:
    Click image for larger version. 

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    Centering Ring fillets and shock cord installed:
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    In other news, the Eggfinder arrived, I got my soldering iron and.... I realized that I need more soldering practice. First project was a dud, operator error. Picked up three small projects from Amazon so that I can keep practicing so the Eggfinder is a breeze. It'll be something to keep me occupied on these cold dark winter nights.

    Re-numbering the to-do list!


    17. Bondo tubes (note: Filling primer does a great job on the 29mm tube, we'll see if I need to fill the spirals on 38. I probably will.)
    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. Work on solder practice projects
    21. Bevel fins.
    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!

  29. #59
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    17th November 2015
    Posts
    1,054
    (note that this isn't the "shock cord" per se - this is the Kevlar Y-harness part. There's a swivel on the Kevlar that I'll attach to about 12 feet of 1/2" nylon.)

  30. #60
    Join Date
    17th November 2015
    Posts
    1,054
    Merry Christmas, Happy New Year, and a small update!

    I got a few Velleman kits to put together to hone my soldering skills and what a great idea that was! The kits are fun, relatively easy to put together, and not too expensive. By the third, I had a MUCH better "feel" for getting the solder to flow into a joint. I also discovered that soldering is fun and I may have a new hobby. Oops!

    Done in this round:
    20. Work on solder practice projects (see above! So much fun.)
    21. Bevel fins. I spent a bunch of time figuring out a decent way to do this. In the past, I've always just eyeballed this, but since this may break Mach, I want the fins to be evenly beveled with a nice low-profile bevel - something like 10 degrees. I went through a few iterations (Dremel was a TERRIBLE idea) and eventually came up with this, which seemed to work really well:
    1. Clamp piece of wood stock to edge of workbench.
    2. Slide fin around until appropriate angle is achieved. Obviously, if you can't get the angle you need, find a piece of thicker or thinner stock. When the right angle is achieved, mark the point where the fin touches the stock. Draw a line parallel to the leading edge of the fin there, then recreate that line on both sides of all fins. Borrow a cheap silicone mat from the kitchen and carefully lay it over the workbench and the block. Line up each fin and sand the leading edge using an orbital sander. The sander stays flat, the fin is held at the right angle. I used 100 grit and feather-weight pressure. Here's how it came out:

    The general setup. The fin is just laying on the block, and isn't straight, but you get the idea.
    Click image for larger version. 

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    Finished result. This was a practice fin so the edge isn't quite as even as I'd like, but now that I've done it, I'm pretty confident that I have a repeatable process. Also the silicone mat isn't shown but made a HUGE difference in keeping the work piece still. If you don't have a silicone mat, they're like 7 bucks on Amazon, or you could also cut a piece of some of that anti-slip stuff you put under rugs.
    Click image for larger version. 

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    17. Bondo tubes ... Actually used CWF on this one, per Always Ready Rocketry. Lots of sanding but that's ok.

    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!


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