Loc Precision BIG NUKE 3E Kit

Discussion in 'High Power Rocketry (HPR)' started by Steven88, Sep 9, 2019.

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  1. Oct 29, 2019 #121

    Steven88

    Steven88

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    These instructions for the 3E call for gluing the forward and mid centering rings over the mmt and then gluing inside the main airframe. Then the way I understand the instructions, the fins are glued in and then they suggest applying additional fillets to where the fins meet the mmt and the mmt rings. Well, I can’t get my hands between the 75mm mmt and the 5.38” Loc airframe to apply fillets inside there. Not sure if these instructions were copied over from the Nuke with the 54mm tube or what but I’m wondering if I should cut the slots on the main airframe all the way down as I’ve seen some do or what the best course of action would be. A person could then glue the fins into the mmt and rings outside of the airframe and then slide the main airframe on last. When it is done that way, how do you hide those slots at the bottom that we’re cut out and make it look nice?
     
  2. Oct 29, 2019 #122

    mikec

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    You can do that but it's harder to fill the slots afterward. On a cardboard rocket, I usually leave the bottom centering ring off temporarily and make the fillets by pouring the epoxy in or guiding it with a stick or the like.
     
  3. Dec 26, 2019 #123

    Steven88

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    What are your thoughts on using these 4-40 fasteners on my Loc 3E to prevent premature separation of the NC as well as the bottom section? The fasteners come with 4-40 sheer pins/screws as well as metal screws incase you want to hold a section together and not sheer. There are only two drawbacks I see to these fasteners. The first one is minimal, but the fastener on the OD tube will protrude and leave a bump, not really a big deal if you’re not into aerodynamics. However, the main concern I had is that the combined inner part of the fasteners (the part that protrudes into the tubes) isn’t as thick as the tubes combined is. There will be a gap, please see attached photo. Will that cause the 4-40 sheer pins to bind or will they sheer properly without the fasteners butted tightly
    against each other? Apogee also sells a 2-56 fasteners but I thought for this heavy and big of a rocket the 4-40 sheer pins might be better.
     

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  4. Dec 26, 2019 #124

    Steven88

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    I taped the fasteners to the sides of the tubes just to give you the idea
     
  5. Dec 26, 2019 #125

    mikec

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    I used two 2-56 screws on mine, with brass strips epoxied to the nose cone shoulder for shear. These fasteners may work but I'm not sure.
     
  6. Dec 26, 2019 #126

    Steven88

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    Yes, on my last build, the Madcow Torrent, I used brass shim stock epoxied into the tubes for my sheer pins to thread into. After doing nine of those, six on the booster section and three on the main where the nose cone slides in (well actually, used two blind nuts on the inside of the ebay and used a dremel to smooth whatever protruded through) which also seemed to work, I thought maybe this would be a faster alternative and Apogee says you can use them as sheer pins. I was just worried if they could bind if the fasteners don’t butt each other but maybe that’s of no concern since it’s metal on both sides it’ll still sheer the screw. Loc's 3.9” paper tubes are aren’t as thickly walled as their 5.38” paper tubes and maybe the fasteners would work better on the thinner walled tubes as they would have less clearance between each other
     
  7. Dec 26, 2019 #127

    mikec

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    Always hard to say what will happen without trying it.
     
  8. Dec 26, 2019 #128

    Steven88

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    Yes, ground testing is always your best friend. I think I’m going to stick with the shim stock. I proved it worked on my last build and then no redoing my work!
     
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  9. Dec 27, 2019 #129

    Steven88

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    This is probably a controversial subject, but in which locations should install the rail buttons on my Loc 3E. The instructions don’t seem like the correct ones
     
  10. Dec 27, 2019 #130

    Steven88

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    as it talks about installing launch lugs on a ten lb rocket! Anyway, I figured I’d install them in the bottom centering ring and then if I install the other one in the top centering ring, they’ll only be about 17” apart.
     
  11. Dec 27, 2019 #131

    Steven88

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    Is the old rule of installing the heaviest motor intended to fly and placing one above and below the CG applicable or is that only on small rockets?
     
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  12. Dec 28, 2019 #132

    mikec

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    That's what I did and it's been fine. I think people tend to apply rules of thumb to button placement that don't really make much sense and certainly aren't absolute requirements.

    Since the rocket is relatively short, you probably need to use additional nose weight for the larger motors, at least I always have. I use a setup with fender washers and a molly bolt at the base of the nose cone.
     
  13. Dec 28, 2019 #133

    Steven88

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    Yeah, especially since I’m putting a thrust plate on the bottom from Apogee which adds even more weight. Do you rock sim it then to see how much weight is required?
     
  14. Dec 28, 2019 #134

    mikec

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    I built a spreadsheet that had the empty CG, used the motor mass and length as an input, and computed the weight required at the base of the nose cone to get to 1 caliber of stability. It said I could fly without weight for motors up to 3-grain 54mm, I needed 4 oz for a 4-grain, and 6 oz for an L1000 (I have a 54mm MMT on mine so that's as big as I can go.) Probably simpler just to sim it or add nose weight for the largest motor you plan to fly and take a slight performance hit for smaller motors. Just make sure to override the empty CG and weight to account for your as-built properties.

    Probably flying with less than 1 caliber of stability would be OK since this is a fairly squat rocket, but I've opted to be conservative.
     
  15. Dec 28, 2019 #135

    cbrarick

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    I have the big nuke 3e. Flown it bone stock without any weight on 54-4 grain motors and up. Ditch the thrust plate, it's not needed and just adds weight where you don't want it.
     
  16. Dec 29, 2019 #136

    Steven88

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    I was all stoked about using the flanged retainer on the bottom, love the looks of it and the way the body tube takes the force on a hard landing, but don’t like the idea of it adding half a lb to the bottom of rocket if it means I have to add that much more weight to the top
     
  17. Dec 29, 2019 #137

    mikec

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    It's a tradeoff. With the fin shape, the BT is going to take the landing force with or without the thrust plate, though the thrust plate might spread it out somewhat. My BT is a little kinked from multiple hard landings, the stock chute is a little small. I'd personally suggest ditching the thrust plate and using a larger chute, but much depends on what motors you're planning to use. If you plan to use big 75mm motors you might want to keep the thrust plate.

    This is not really intended to be a high-performance rocket so an extra pound one way or the other shouldn't matter much.
     
  18. Dec 29, 2019 #138

    Steven88

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    Yeah, will be flying mostly 75’s in it. Another thing I could do for added stability is purchase a 42” Loc tube and add that to the main section on top instead of the stock tube with the kit. That would make it quite a bit taller and should stabilize it but I think maybe it would look off balance with such a tall top section
     
  19. Jan 5, 2020 #139

    Steven88

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    On large high power plastic nose cones like the Loc 3E or which ever rocket, do you guys use the stock plastic shock loop on the nose cone shock cord mount or do cut the plastic mount off and somehow glue an eye bolt or something similar in there for better securement? It also would be nice to have a two in one shock cord mount and nose weight thing of some sort that washers could be added to for nose weight if needed.
     
  20. Jan 5, 2020 #140

    rharshberger

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    Most of us ditch the molded loop and either cut two holes on either side of the sloped section and tie the shock cord through those, or modify it one of several ways for an eyebolt.
     
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  21. Jan 5, 2020 #141

    mikec

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    If you use that loop on a rocket the size of the Big Nuke, it will eventually break, pretty much guaranteed.

    I used a toggle bolt and a screw eye that allows me to attach a variable number of fender washers to the base of the nose cone.
     
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  22. Jan 13, 2020 #142

    Steven88

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    I have a question here on my Loc Nuke 3E. I will attach a photo. I have added fillets on the interior of rocket along the MMT, and of course will add them on the exterior of the main body tube. Would it be recommended to add them on the bottom side of the main body tube as well, or is three sets of fillets not neceassary? I did not fiberglass and I won’t be flying over a baby M at the biggest in this build if I ever get L3 certified. I also plan to add two zip ties through the fins in the interior of rocket for some added holding.
     

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  23. Jan 13, 2020 #143

    jd2cylman

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    More weight at the wrong end...
     
  24. Jan 13, 2020 #144

    Steven88

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    Hadn’t thought of that, good point
     
  25. Jan 13, 2020 #145

    jbsommerfeldt

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  26. Jan 13, 2020 #146

    Steven88

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    That’s an awesome rocket. How much length did you actually add to your Big Nuke? I want to add around a foot to bottom section of mine sometime but building it stock for now.
     
  27. Jan 14, 2020 at 12:59 AM #147

    jbsommerfeldt

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    16.5". Stiffy tube coupler epoxied into the extra 16.5" but held into lower with nylon screws. Ebay fits on top of that. Three reasons I did that, 1st-ease of transportation (3 smaller pieces to fit in car instead of two longer), 2nd-flights on smaller motor config can take that piece off & 3rd-easier to get at the bottom for the shock cord or if I have to beat a motor out of it (which did happen twice).

    Why 16.5"?, I dont remember. Probably a combination of what Rocksim said and aesthetics.
     
  28. Jan 15, 2020 at 4:48 AM #148

    Steven88

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    Is it ok to place the bottom rail button on my Loc 3E in the bottom centering rings? That would place it about 3/4” up from the bottom. I doubled up on the centering rings on the very bottom so I’d have more strength and twice the thickness. Is there such a thing as getting the rail button too low?
     
  29. Jan 15, 2020 at 5:36 AM #149

    PatD

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    Shouldn't be a problem. The real issue is how much rail you have above the top button. Once it leaves the rail you no longer have rail guidance on the rocket. You do need to make sure the bottom button doesn't bind on something that low.
    Edit: you also need to ensure there is enough space between the buttons to provide positive guidance.
     
  30. Jan 15, 2020 at 5:08 PM #150

    Steven88

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    I’m thinking about either going with three rail buttons or moving the bottom one 5” up from the bottom. Is there any harm in having three rail buttons? You don’t normally see it but what could be the harm as long as they all line up?
     

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