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  1. #1
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    5th February 2009
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    Montreal, Qweebec
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    Madcow Super DX3 & Patriot - a build thread -

    A build thread!

    Featuring not one, but two rockets! The Madcow Super DX3 and the 4" Patriot. I got them both over Christmas, and figured I might as well build them both at the same time. They are, essentially, the same kit: one extra fin on one, and a longer AV bay tube on the other. All the rest is the same.

    The plan: make them both dual deploy, and both share the same altimeter (use a swappable sled). I have an Eggtimer Quantum for that.. The AV bays will not have a vent band, but be secured to the upper tube with screws. Interconnection will be a single 1/4-20 threaded shaft with eye nuts, no 'U' bolts. (Both these ideas were discussed in another thread a few moths ago..) And, to have them (one at least!) ready for NYPower!

    I've decided to add a third CR to the motor tube, for a bit of added structure.

    One note, as I discussed in yet another thread, Madcow's use of CG and CP in therms of balancing. One kits give the CP location, which I think we all prefer, and the other give a recommended CG point..

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    -paul

    NAR# 101258 - L1
    www.CRMRC.org
    I don't know the same things you don't know..

  2. #2
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    I've cut new centering rings and new inner bulk plates. I have the tools, so why not!
    I ended up cutting 3 CR, and 2 bulk plates if I recall.. (more a re planned for another night!)

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    -paul

    NAR# 101258 - L1
    www.CRMRC.org
    I don't know the same things you don't know..

  3. #3
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    Let the gluing begin!

    first up, the inner bulk plates to the outer bulk plates. And the inner bulk plates to the inside of the AV bays. They are shallow enough that I fee I can get away with one fixed, one removable end.. And the nice shiny eye nuts that'll go on each end!
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    -paul

    NAR# 101258 - L1
    www.CRMRC.org
    I don't know the same things you don't know..

  4. #4
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    Next up, the first CR, the upper CRs glued in place.. I'm using the regular Bob Smith epoxy for the gluing task. it's wood & paper, so not too worried. Tubes are sanded for extra boinding power.

    I've added the drips of epoxy to the lower nut on the eye bolts, and they are set aside to cure..

    And then secured in place with the top epoxy bead added to the MMNT & CR.
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    -paul

    NAR# 101258 - L1
    www.CRMRC.org
    I don't know the same things you don't know..

  5. #5
    Join Date
    4th July 2015
    Location
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    294
    Quote Originally Posted by dr wogz View Post
    Let the gluing begin!

    first up, the inner bulk plates to the outer bulk plates. And the inner bulk plates to the inside of the AV bays. They are shallow enough that I fee I can get away with one fixed, one removable end.. And the nice shiny eye nuts that'll go on each end!
    Looking good - subscribed! Presumably at least one of the eye nuts will be removable to allow access to the AV bay, so what method will you use to stop it/them spinning off if the attached shock cord twists during descent?
    UKRA #1895
    EARS #1329
    L1 6/9/15 Custom built LOC Fantom 438 CTI H125
    L2 3/4/16 Same custom built LOC Fantom w/ DD EXL configuration CTI J410

  6. #6
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    One thing I've learned from using rail buttons: trying to get a screw dead center in the edge of the CR is no easy feat! So, I planned ahead this time, and I've added a small chunk of ply to the upper side to the bottom CR. This way, when I go to screw my button in place, I've got a 1/2" to aim for, not the usual 1/4"!

    A bit of sanding to remove the points, to make it round, and all done! I usually glue the bottom CR in place once the fins are glued, and internal fillets added.. A mark on the back-side of this CR will help align it when the time comes.
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    -paul

    NAR# 101258 - L1
    www.CRMRC.org
    I don't know the same things you don't know..

  7. #7
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    Quote Originally Posted by Tim51 View Post
    Looking good - subscribed! Presumably at least one of the eye nuts will be removable to allow access to the AV bay, so what method will you use to stop it/them spinning off if the attached shock cord twists during descent?
    Yes, both will be, at least at this point.. I plan to double-nut them to lock them in place.
    -paul

    NAR# 101258 - L1
    www.CRMRC.org
    I don't know the same things you don't know..

  8. #8
    Join Date
    2nd January 2013
    Posts
    138
    Quote Originally Posted by dr wogz View Post
    One thing I've learned from using rail buttons: trying to get a screw dead center in the edge of the CR is no easy feat! So, I planned ahead this time, and I've added a small chunk of ply to the upper side to the bottom CR. This way, when I go to screw my button in place, I've got a 1/2" to aim for, not the usual 1/4"!

    A bit of sanding to remove the points, to make it round, and all done! I usually glue the bottom CR in place once the fins are glued, and internal fillets added.. A mark on the back-side of this CR will help align it when the time comes.
    Excellent idea! Im gonna do this also on future builds.

  9. #9
    Join Date
    4th July 2015
    Location
    London, UK
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    Quote Originally Posted by dr wogz View Post
    Yes, both will be, at least at this point.. I plan to double-nut them to lock them in place.
    Good idea. I came up with a similar (albeit smaller) single all thread + 2 eye nut Av bay design, but given the size the eye nut loops were too small to take another nut. In the end I 'tethered' the loop to an anchor point with a cable tie, fresh tie for each flight. It works fine, but then the rocket's relatively light. Build thread here: <<http://www.rocketryforum.com/showthread.php?131906-Back-in-Black-2-26-quot-57mm-semi-scratch-build&highlight=57mm+2.26++Back+in+Black>>
    UKRA #1895
    EARS #1329
    L1 6/9/15 Custom built LOC Fantom 438 CTI H125
    L2 3/4/16 Same custom built LOC Fantom w/ DD EXL configuration CTI J410

  10. #10
    Join Date
    20th June 2015
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    Nice work Paul, I'm subscribed.

    Looking forward to seeing these two down by the bay this summer.
    Jim V

    Champlain Region Model Rocket Club
    CRMRC
    Facebook
    NAR #101467
    L1 - 5/21/16 Estes Mega Der Red Max H128W to 1,021'


  11. #11
    Join Date
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    And a bit more..

    I've glued the center CR to the MMNts, and started sanding the fins.

    Let me take a moment to thank my sponsors.. Two of my favorite local micro breweries.. (Although one isn't as small as it once was, and the other boasts it's own line of "hopped" vodka..)

    Last year was apples, the year before what lime, and there was a year with raspberries... This year seems to be grapefruit.. Grapefruit in a beer?! I had to try, and ya know, it's actually pretty good! I'd have to say, it is a pleasant surprise! The other is the smaller of the two, from the east end of the city. "Oshlag" always come up with unique brews and are equally a pleasure to drink. Small batches, unique ingredients, superb tastes!

    (and yes, it's the same glass, but washed between two nights of building...)
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    -paul

    NAR# 101258 - L1
    www.CRMRC.org
    I don't know the same things you don't know..

  12. #12
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    Montreal, Qweebec
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    Fin sanding..

    Plywood find sanding... I'd take advantage of modern day power tools, but my belt sander is broken. Looks like the power switch finally gave up. Broke into little pieces..

    So, first break the edges with a plane, get the basic shape. one pass, check.. pass again, check.. I usually carve off a 45 chunk off each side, then sand & round one by one. And yes, planning ply is a pain, and can lead to a disaster pretty fast.

    Do I count my strokes? Generally no.

    Do I have a special technique? Somewhat. I run my ring finger (of the hand holding the sanding block) against the edge of my bench to ensure my strokes are even. I rotate along the axis of the curve to try and maintain a constant curve. I then will sand across the curve to even it out. I then flip the fin over to do the other side. Its' usually pretty even.. I do wish I was more ambidextrous, so that I can sand one side with one hand, then sand the other side with the other hand.. Somehow I feel this would make things more even..

    Anyways, preliminary sanding & shaping done. A quick final sand later..
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    -paul

    NAR# 101258 - L1
    www.CRMRC.org
    I don't know the same things you don't know..

  13. #13
    Join Date
    20th June 2015
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    Paul,

    I use this Dremel accessory with a router bit to do my fin edges. Not perfect but gets them down to where there is less sanding involved.

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    We'll have to hit one of the microbreweries in town sometime after a launch.

    Have a great weekend

    Jim

    Jim V

    Champlain Region Model Rocket Club
    CRMRC
    Facebook
    NAR #101467
    L1 - 5/21/16 Estes Mega Der Red Max H128W to 1,021'


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