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LOC Lil' Nuke Build Thread

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  1. #1
    Join Date
    27th July 2010
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    Indiana
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    672

    LOC Lil' Nuke Build Thread

    I gave into temptation and opened the package a couple of days ago and started it. I had planned to take my time on it, but it's a pretty straight forward kit and I think it will go pretty quickly. Most reviews I've read on this one are good and have not had any modifications. I have read a few that say the parachute is too small, so I'll have to research that some more, and I read one where the person said they added some additional nose cone weight. Maybe I better run some OpenRocket on this one just to see if I want/need to mess with either of those things.

    I sanded the seams on the nose cone down and then used some filler on the BT spirals first. The filler had dried out some, and even after adding water, it still didn't seem to do the job really well. I gave it two attempts and got most of the spirals out, though it looks like there is a spot or two that aren't perfect, hoepfully I can fix that in the priming/sanding phase. I guess it's time for some new stuff to fill in spirals.

    The next step was assembling the motor mount. This is the first time I've used epoxy in a build, so it's not the neatest work in the world. Good thing I started with the motor mount that won't be as visible. I had to do a little sanding on both the inside and outside of the centering rings to get everything to slide in place, but not much. I strayed from the instructions a bit here. Where it says to insert the mm until the end is flush with the end of the BT, I installed the lower centering ring about 1/4" higher on the mount and left about 1/4" of the mount tube sticking out beyond the BT. I did this so that it will be easier to secure the motors in place. If I end up getting a retention ring, I have room to mount it, and if I don't, I have some tube for tape so the motor doesn't pop out from the ejection charge (this came from some of the Apogee hints and tips).

    Fillets are in place on the motor mount and it is dried. Next up is sanding and attaching the fins. We're heading out today for some New Year festivities, so I probably won't be doing anything today or tomorrow. Sunday I have to watch the Colts secure the AFC South Championship,

    but after that I may do a little more work. Until then, here are a few shots...
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    Dandelion Preservation and Appreciation Association

  2. #2
    I think you will like this bird, I know I like mine. Pretty straight forward build. I built mine stock and it flies great. I did add a second parachute, but on windy days I only use one from now on(had to walk a good distance and drifted a little too far on the farm next to the launch area). I wish I would have done like you and left some room for motor retention. I retrofitted some threaded inserts into the aft centering ring and just use washers and bolts to keep the motors in. Good luck with your build and happy flying when you get it done.
    Matt

  3. #3
    Join Date
    18th January 2009
    Location
    Behind enemy lines in Socialist California
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    4,711
    I went with the Aero Pack retainers on my LOC Onyx. Between the retainers and the parachute, I have more dollars invested in this rocket than I paid for the kit.

    Yesterday at the LHS, I found some small metric (3mm) threaded T-nuts, matching hex socket head 3mm bolts, and a Dubro 3mm ball "wrench" (more of a screwdriver if you ask me). I plan to use this equipment to make my own motor retention systems. Just need some screen/z-clips to complete the package.

    As to the size of the parachute included in the kit, weigh the completed model before you start looking for a bigger chute. If the model is heavier than expected you may need a larger chute. If you're launching on grass, you may not need a larger chute. If you're launching on a concrete runway (Ames/NASA, etc.), a larger chute may be needed. In any event, the larger the chute, the longer the chase so keep that in mind.
    Kit (AKA Cranky Kong)
    Total Total Impulse as BAR (2010): 8,466.69 Ns (Equivalent to a 65% M motor.)

    On any number of government watch lists...

  4. #4
    Join Date
    27th July 2010
    Location
    Indiana
    Posts
    672
    Well, it's been a few days and the Colts won the AFC South. After spending 5 minutes here, 20 minutes there, I think I've gotten far enough to post an updated pic. I ended up grabbing some of the bondo stuff some have used for spiral filling, and boy was that a much better alternative to what I had been using. I weighed the individual pieces (except the mm, which was already installed) and started messing around some in OpenRocket. Everything seems to make sense, and the weights match what I measured, but it's not coming out quite the same as the rkt file I downloaded for the Lil Nuke from EMRR. Some of the component weights are off (but not by much), and the CG is in a different location. When adding a G64-10 motor (the max recommended) my stability caliber drops to 0.5 (the file I downloaded is around 1). The CP is really close between the two, the main difference is the CG. So I'll wait until it's done and just physically measure the CG and make any adjustments accordingly. The altitudes between the two files are really close, with a little over 2600 on the G64 (far cry from the 4200 stated on the instructions).

    Anyway, back to the build. After filling the spirals (right this time), I sanded the fins, rounding the leading and trailing edges, and mounted them with epoxy. Instead of having one 4 inch long launch lug, I cut it into shorter sections and epoxied one between the fins, and the second further up closer to the CG (or where it should be anyway). It's getting late, so I'll work on the fillets another day, and then that will just leave the shock cord (and priming/painting). Here's a pic of it at this stage.
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    Dandelion Preservation and Appreciation Association

  5. #5
    Join Date
    27th July 2010
    Location
    Indiana
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    672
    Well, the construction is done. No new pictures as the outside looks the same as it did the last post.

    I went through my open rocket file, and checked to make sure my actual final weight and CG matched the model, which it did, surprisingly enough. I did a detailed comparison with the file I downloaded from EMRR and there are some differences. Mine is only 11.1 oz, while the EMRR model was 14.4 (and the instructions say 13 oz. As I mentioned before, I have a small amount of the mm sticking out the back, so I have a bit more length. Without a motor, mine shows CG at 15.9", CP at 21.0", and stability at 2.25 cal. The model from EMRR shows CG at 15.6", CP at 21.4", and stability at 2.56 cal. There are only two differences as far as I can tell from the builds, mine is lighter overall, and mine has the mm sticking out .25". I figure one, or both of those are accounting for the differences in CG and CP.

    I ran a sim with the G64 (highest one the instructions recommend) to see what the motor did to the CG and stability. My CG moved to 19.6 and stability dropped to 0.63, which makes me nervous. The model I downloaded had stability of 1.19 with the same motor.

    So based on that, I think to be safe I'm going to add a couple of ounces to the nose. I figure I'll put enough in to bring it up to the 13 oz. the instructions indicate. Adding that to my OpenRocket file and that brings my stability up to 1.47 cal with the motor. Oddly enough, the 2 extra ounces only dropped the altitude in the simulation by 40 feet (and max velocity by 47 ft/sec.).

    I'm starting to get concerned about the parachute size though. It came with a 14" nylon chute (a nice one too). OpenRocket is showing the ground hit velocity at 31.5 ft/sec. That seems mighty fast to me, and I know TFR recommends 17-22 ft/sec. I suppose with the design of the fins, they won't be as likely to strike the ground first, and the BT is pretty thick, but I'm definitely using clips on the chute so I can quickly change it out for a larger one depending on the conditions.

    I just have to wait for it to heat up some so I can prime and paint it. I guess that'll give me time to come up with a paint scheme of some sort.

    Dandelion Preservation and Appreciation Association

  6. #6
    Join Date
    18th January 2009
    Location
    Behind enemy lines in Socialist California
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    As to the sim results, I've gotta wonder about the wisdom in mounting the fins 1" up from the bottom of the airframe. That basically moves the center of pressure up about 1" as well and puts the motor weight behind the CP. Looks like you'll need to add some weight to the nose cone to get that sorted out. No big deal, just slows the launch speed down a little and takes a little altitude off the top. Better that than an unstable bird.

    With tube fins stability isn't usually a worry. Tubers normally have a center of pressure down inside the tube can which puts the motor weight ahead of the CP.

    Now get painting that bird of yours...oh, snow headed your way, right? Never mind.
    Kit (AKA Cranky Kong)
    Total Total Impulse as BAR (2010): 8,466.69 Ns (Equivalent to a 65% M motor.)

    On any number of government watch lists...

  7. #7
    A stock built Lil' Nuke will fly fine on any motor that will fit. Long ago, I flew one on a H500 and you can reach nearly a mile on a 29/360 I200. Unless your field is concrete, the 14" chute is enough as the rocket lands on the motor.

  8. #8
    Join Date
    23rd January 2009
    Location
    Ballston Lake, NY
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    3,019
    Quote Originally Posted by Rocketjunkie View Post
    A stock built Lil' Nuke will fly fine on any motor that will fit. Long ago, I flew one on a H500 and you can reach nearly a mile on a 29/360 I200. Unless your field is concrete, the 14" chute is enough as the rocket lands on the motor.
    I second that. We have one that has close to 30 flights, on everything from a 24-40 D9W to a 29-240 H220T. Haven't thrown an H238T at it yet, but have another H220T sitting in the magazine, waiting for the Nuke...
    Dan Patell
    TRA 10904 L3

    2014: 29,290 Ns (sort of...)
    2013: 19,505 Ns

  9. #9
    Join Date
    18th January 2009
    Location
    Behind enemy lines in Socialist California
    Posts
    4,711
    A long motor moves the CG further forward, right?

    There's your solution. Don't go small, go WILDMAN!!
    Kit (AKA Cranky Kong)
    Total Total Impulse as BAR (2010): 8,466.69 Ns (Equivalent to a 65% M motor.)

    On any number of government watch lists...

  10. #10
    Join Date
    27th July 2010
    Location
    Indiana
    Posts
    672
    Since I last posted I got a couple of the Madcow Rocketry motor retainers and installed one on my Lil' Nuke.

    It warmed up a little, so I got it painted. I have printed out some stickers (on clear shipping labels) that will likely go on tonight or tomorrow night with some clear coat to keep them safe and secure. Nuke warning symbols for each fin (in black) and a stenciled "Lil' Nuke" in yellow for the Body.

    Here it is with just the paint along side my daughter's scratch build "Flower Power" rocket (also going to get some serious sticker treatment) and my Madcow Batray. I got some bleeding under the masking at the fin joints, which I'm a little disappointed with. But otherwise, I'm please with how it turned out. I was worried about the yellow, it seems yellow often comes out either too bright and stark, or too pale. I think I got just the shade I was looking for out of it. The other color is actually a dark blue, in the fluorescent light in a night time garage, it's kind of hard to tell.
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    Dandelion Preservation and Appreciation Association

  11. #11
    Join Date
    27th July 2010
    Location
    Indiana
    Posts
    672
    It finally flew this past Saturday on a G40-10. It was a bit windy so I didn't even think of going with a larger chute (even though we do have asphalt at our launch site). I was pleasantly surprised that there was barely any weathercocking even though wind was about 10+mph all day. It was a decent walk for me though. No damage.

    Here's the video, I knew it was too high up to be visible on the video, so I stopped recording after we confirmed deployment.


    http://www.youtube.com/watch?v=oInCxMm5n0s

    Dandelion Preservation and Appreciation Association

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