4" Big Daddy

Discussion in 'High Power Rocketry (HPR)' started by wij, Sep 7, 2019.

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  1. Sep 7, 2019 #1

    wij

    wij

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    After finishing my Black fly build a couple weeks ago I got the urge to start yet another build! Being a fan of short stubby rockets the Big Daddy is one of my favorites so I have mapped out a design using standard high power components which will end up being a 4" diameter, 26" tall, 38mm replica of the Big Daddy from estes.

    Parts:
    LOC 3.9" nosecone. 12.5" long
    LOC 3.9" airframe. 12" long
    1/8" aircraft grade birch ply ttw fins (x4)
    LOC 38mm motor mount. 8" long
    3.9"-38mm 1/4" ply centering rings (x2)
    15ft of 1/2" nylon for shock cord.
    1010 rail buttons
    Eye-bolts for recovery attachments.
    24" or 30" chute? will know once I get a final weight.

    Planning on flying this with single deploy, possibly trying out a JLCR for higher flights. I will be modding the nose cone with a bit of nose weight (how much depends on where the cg is at) and also will secure a eye bolt either into a bulkhead that is up in the front of the nose cone or into the epoxy nose weight slurry itself. Either way I will have enough room to house the chute/shock cord burrito in the NC.

    For motor retention I will be using two tee-nuts in the rear CR and have screws with small metal brackets holding the motor casing in place. Simple diy solution that cost around $1 compared to other motor retainers I have used on my other builds.

    I have ordered all my components and they should be arriving Tuesday. This morning I took a trip to my favorite hobby shop in PHX, Duncan's R/C, to pick up a sheet of ply for the fins. Duncan's keeps a great selection of rocketry parts and motors on hand!

    So far I have cut out and sanded the fins so they are all uniform. I have the 38mm motor mount tubing on hand so I will be cutting an 8" section of that today as well.

    More to come soon!!
     

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  2. Sep 8, 2019 #2

    Andrew_ASC

    Andrew_ASC

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    Nice project dude.
     
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  3. Sep 8, 2019 #3

    wij

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    Thank you, I have been pondering this build for a good while. Glad to finally be bringing it to life!
     
  4. Sep 10, 2019 #4

    wij

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    Got my workbench all prepped and parts that I had on hand layed out, also beveled the leading edges of the fins. Waiting on ups to ring my doorbell with all the remaining parts for this build! Anytime now....
     

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  5. Sep 11, 2019 #5

    MikeyDSlagle

    MikeyDSlagle

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    Big Daddies are fun.
    4" stubbies are fun.
    This should be fun.
    38mm is a good choice or...put a 54mm in it and fly it on 1grain soda can motors.
    My 4" Cowabunga is one of my favorites. My Tembo has a 54mm in it.
    Put a bay in the nose cone to handle apogee deployment.
    Or just keep it simple. Either way, it should be fun.

    My Cowabunga has a 30" chute, so that will probably work for yours. I added 4oz of nose weight I think, plus whatever my bay adds.
     
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  6. Sep 11, 2019 #6

    wij

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    Parts arrived! Let the build begin. So far I have chopped the bottom of the nosecone off and I cut the body tube to length. After that I used the handy fin wrap tool from payloadbay.com to plot out the 4 fin slots. Getting started on cutting the slots out and getting the motor mount going as well currently. I really am building this rocket for the H550 dms and similar quick burning motors, Kind of mimicking a projectile rather than a rocket. I will be flying it with the 29/240 case as well with the H210, H220, and H250 reloads.

    Mikey, Im curious to see how you did your nc bay if you have any pics. I haven't decided what i'm going to do for deployment yet. Keep it simple with motor eject, or build a nosecone avbay and let the electronics handle it. Im open to both and I think it will come down to how much space I have for recovery components once the mmt is installed. I prefer electronics though for its accuracy. Btw the 54mm sounds like a very fun idea... I feel a fiberglass version 2 coming in the future lol!!
     

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  7. Sep 11, 2019 #7

    wij

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    Made some more progress this evening. Airframe is slotted and ready to accept the motormount. I drilled holes in the rear CR to tap in tee-nuts for motor retention and also drilled the fwd CR for the 1/4” eyebolt. I then roughed up the whole motor mount surface and bonded the fwd centering ring to the motor mount tube and set aside to cure.

    Once cured I proceeded to install it to the airframe. I spread some epoxy just above the fin slots and slid the motor mount assembly into place and added a healthy fillet on top side of the fwd CR. Per usual technique I installed the rear CR to keep the motor mount centered but didn’t bond it to the tube. I can use the screws that thread into the tee-nuts to pull it out after the fwd CR cures and continue with the fillet on the bottom of the fwd CR.

    After that’s cured I will remove the aft CR, then install the rail buttons and move onto the fins.
     

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  8. Sep 11, 2019 #8

    Theory

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    cool deal

    no doubt this will be a fun one, and, as a fan of the quick burning motors, i did that choice!
     
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  9. Sep 11, 2019 #9

    MikeyDSlagle

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    I have four 4" birds, all with different nose cone bay setups. The Cowabunga is the cheapest using a section of drain pipe and homemade rings. I did upgrade to a printed custom printed sled. The way I have the switch is the most inconvenient as well.
    The others are more elegant. One is a nose cone bay from MAC another is a custom made pancake.
    I recently made a bay to fit above the MMT in a 2.6 Lil Goblin. It leaves the nose cone open for the laundry. Working on one similar for the Mega Magg too. One for a 4" Big Daddy would be fairly easy to do, and still have room in the nose for laundry.
    I'll try to grab some pictures when I get home tonight.
     
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  10. Sep 11, 2019 #10

    wij

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    So after doing a few dry fits I did end up deciding I will try to go with electronics for deployment and have the avbay in the nose. I ordered a 4" to 54mm centering ring and a 4" coupler bulkhead from madcow last night. It will be very similar the how John Coker does it in his plastic nosecone mod youtube video. It should leave just enough room to stuff all the recovery gear in a kevlar wrap in the airframe. Im interested to see the avbay above the mmt that you mention, sounds like another possibility I would be open to. Pics please :D

    My other rockets all use the twist and tape method for a switch but for this one I want something really easy and clean. I have a few switches that I can mess with and decide on when the time comes to setup the NC and electronics.
     
  11. Sep 11, 2019 #11

    wij

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    More progress this morning! I filled the tube spirals and also the mold lines on the nose cone then gave it a good sanding with 150 grit followed by 320 grit. Test fit all the fins to check the alignment and we are looking spot on. After that I drilled holes for the rail buttons and installed those into the airframe. Currently i'm tacking all the fin roots to the mmt and will start on fillets Internal and external next.
     

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  12. Sep 12, 2019 at 6:43 PM #12

    wij

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    Fins are on and filleted. Rear CR is bonded to motor mount. Nose cone is up next.. I have some options I would like some opinions on if anyone wants to chime in!
     

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  13. Sep 12, 2019 at 6:57 PM #13

    wij

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    Barometer or Accelerometer? I built a sled yesterday to hold my electronics, the sled will be attached to a bulkhead that will bolt onto a centering ring above the nc shoulder.

    I have a pico AA1 accelerometer that I have used once just for data (output not used) and it provides some interesting measurements. You can configure it to fire its single output on apogee which would work in this build because i'm going single deploy. Has anyone had experience using an accelerometer for apogee deploy?

    Other option is an Eggtimer Quark which has a barometric sensor and is a simple dual deploy altimeter. Only data provided is max altitude. I use these in other builds and they work great!

    I would like to put the Pico AA1 to use if it would be applicable in this situation and also the 9v battery it requires will add some weight in the nose vs having to add permanent nose weight with the Quark setup.(still may have to add some, but not as much) Just looking for advice on one vs the other for apogee deployment capabilities.
     
  14. Sep 14, 2019 at 5:36 PM #14

    OKTurbo

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    Not a big daddy, but this is how I set up my maxi der Red Max for altimeter deploy from a nose cone electronics bay. I still haven’t flow this, so take it with a grain of salt. I’ll see how it does at Tulsa Rocketry’s High Frontier launch in a couple of weeks.

    I’m using a RRC2 barometric altimeter to deploy the main at apogee...it’ll be bundled with a chute release. Using an oversized 18” square nomex wrap to act as a pseudo streamer at apogee.

    I made a vent tunnel to get the static pressure port further down the body tube...trying to avoid to much turbulence or ram air pressure for the altimeter. I keyed the nose cone to the body tube so the port holes will always line up.

    Master power switch on the sled. Magnetic switch to turn it on at the pad.

    Now for the pics.

    C51F79A3-7E79-48B0-9E3E-1CAABE3BCA57.jpeg 7A91B947-E713-46CB-9A0D-66C1236A2A8C.jpeg AA392E2F-FC7D-4C36-B38E-B8CBCADF8DD2.jpeg 389A1C48-1889-48E8-BBBE-F91448CAD78C.jpeg 9BC5CCEC-2B74-49DE-8E2F-D2EDDDAA039F.jpeg 56287DD0-5799-4C2B-8386-2DA7A7E3008E.jpeg 85F74533-DDDD-44D7-9BA1-B023FC4F77F4.jpeg B4F7C91B-32C2-46A0-957A-C6956E54877A.jpeg
     
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  15. Sep 14, 2019 at 7:04 PM #15

    wij

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    That is a clean setup! I really like how you did the pressure vent. What is the reason for cutting the nose cone shoulder down on that one side?
     
  16. Sep 14, 2019 at 7:18 PM #16

    OKTurbo

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  17. Sep 14, 2019 at 7:59 PM #17

    SteveNeill

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    I love this build and I'm watching. I have a Bigdaddy but the idea of a larger on is something on my list now.
     
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  18. Sep 14, 2019 at 10:35 PM #18

    wij

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    Painted the airframe and the nosecone and it is looking sweet, I need to add some yellow now! I went with a rotary switch mounted externally on the nose cone. Also got the avbay sled setup and it's now mounted in the nosecone. I may switch out the Pico AA1 accelerometer for the eggtimer quark.. but ultimately i'm curious to see if an accelerometer will do fine deploying at apogee, as i've never really experimented with it.
     

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  19. Sep 14, 2019 at 10:58 PM #19

    SteveNeill

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    How about a picture with you holding it for size reference? Really like this rocket.
     
  20. Sep 14, 2019 at 11:23 PM #20

    wij

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    Heres a cool comparison shot, the green one is an Estes big daddy. the shape of them look pretty close!
     

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  21. Sep 15, 2019 at 12:25 AM #21

    SteveNeill

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    Nice. You're giving me ideas. ;)
     
  22. Sep 16, 2019 at 5:57 PM #22

    wij

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    After getting everything together the nose cone weighs about 17oz. I opted to add a set of brass shear plates to use two 2-56 shear-pins so I don't have any premature separation issues.
     

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  23. Sep 16, 2019 at 6:16 PM #23

    wij

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    Tested ejection charge last night. 1 gram of black powder makes a clean and energetic separation. These are some Screen shots from a slo-mo video.
     

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  24. Sep 17, 2019 at 1:42 PM #24

    jbr

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    shear pins in my fiberglass rockets don't need brass shear plates
    my mileage varies
     
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  25. Sep 17, 2019 at 6:20 PM #25

    wij

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    Ahhhhh that is a reason I would like to try a fiberglass build in the future. I have not built a fiberglass rocket yet. I would imagine it’s far more durable as well. I have my eyes on a few kits...

    I’ve tried many ways to break shear pins reliably with cardboard tubes and plastic nose ones and I never have gotten satisfying results not using shear plates.

    Since using brass shear plates the deployment charges shear the pins perfectly! It is a bit of extra work but I’ve found it’s definitely worth it on a cardboard airframe if your wanting to set up DD or in this case keep a heavy nose come from prematurely separating.
     
  26. Sep 17, 2019 at 7:13 PM #26

    jbr

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  27. Sep 18, 2019 at 12:26 AM #27

    wij

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    Correct this one is cardboard. I scratch built this one and dimensions came out to be pretty close to the AMW one. I wanted to build a stubby rocket that would handle the Aerotech H550. I will get around 2k with the 29/240 reloads and about 2500' with the H550. Building it cardboard kept the weight down so I still get some Nice altitude with the 29mm reloads. Current weight with no motor is 36oz compared to the AMW one which is estimated at 3.5lbs.
     
    Last edited: Sep 18, 2019 at 1:31 AM

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