What would you consider as too much noseweight?

Discussion in 'High Power Rocketry (HPR)' started by Ben Martin, Oct 11, 2018.

  1. Oct 11, 2018 #1

    Ben Martin

    Ben Martin

    Ben Martin

    Well-Known Member

    Joined:
    Sep 29, 2018
    Messages:
    193
    Likes Received:
    12
    Gender:
    Male
    Location:
    Houston
    I have been working on recreating my rocket (4" Patriot) in OpenRocket, but after a few simulations, it shows that I will need nearly 800 grams of nose weight in order to be stable on a J motor (L2).

    Is this an outrageous amount or pretty reasonable?
    upload_2018-10-11_15-51-31.png
     
  2. Oct 11, 2018 #2

    Andrew_ASC

    Andrew_ASC

    Andrew_ASC

    UTC SEDS 2017 3rd

    Joined:
    Sep 22, 2017
    Messages:
    2,641
    Likes Received:
    160
    Gender:
    Male
    I had to add 488 grams of lead to my Wildman RB-05A Sport for it to fly on H-I range. The RSOs were okay with adding that much counterweight they and I just want it stable. Add as much as you want for stability. Some of the real bigger rockets need pounds of it.

    The practical problem I had was the nose and chute went projectile mode twice due to inexperience in build errors. A mentor literally used the airframe and a knot on the outside to prevent the nose from seperating with shock cord attached from all the momentum the nose had. It was breaking epoxy bonds dude.

    Make sure you got an eyebolt in centering ring or some kind of solid recovery harness point that can stand up to a 800g nose weight ejection. (Epoxy on sidewall with shock cord was a poor choice) in my noob experience. Epoxying a shock cord worked for light MD rockets but not for the Saab with heavy noseweight.

    The mentor recommended I could slit a coupler then attach epoxy cord internally later then compress another coupler on top as I had already screwed up the build by not putting an eyebolt on a CR.
     
  3. Oct 11, 2018 #3

    Bat-mite

    Bat-mite

    Bat-mite

    Rocketeer in MD

    Joined:
    Dec 5, 2013
    Messages:
    8,011
    Likes Received:
    127
    Gender:
    Male
    Location:
    Maryland
    I'm not sure I understand the question. You add as much nose weight as you need to get the rocket stable, no matter how much or how little it turns out to be. My MegaNuk has 6 pounds of nose weight. Patriots struggle with stability due to the small fins. Actual Patriot missiles have a heavy warhead in the nose.
     
  4. Oct 11, 2018 #4

    Ben Martin

    Ben Martin

    Ben Martin

    Well-Known Member

    Joined:
    Sep 29, 2018
    Messages:
    193
    Likes Received:
    12
    Gender:
    Male
    Location:
    Houston
    My concern is too much stress on my shock cord and eyebolts. It would need a solid 700 grams due to it being a 4" Patriot with those tiny fins. I had issues with the nosecone flying off with only 300grams of noseweight, so this 700 grams will be an even bigger issue. I plan on either using plastic rivets or screws to attach the nosecone to the payload bay, but I am concerned that it might cause issues with the parachute deployment or cause other issues.
     
  5. Oct 11, 2018 #5

    Ben Martin

    Ben Martin

    Ben Martin

    Well-Known Member

    Joined:
    Sep 29, 2018
    Messages:
    193
    Likes Received:
    12
    Gender:
    Male
    Location:
    Houston
    I was just wondering if there was a point where having too much nose weight would cause separation and recovery issues. It is only using nylon cord and eyebolts to hold the stages together. Attaching the nosecone to the payload bay might also be an issue too with that much weight.
     
  6. Oct 11, 2018 #6

    Andrew_ASC

    Andrew_ASC

    Andrew_ASC

    UTC SEDS 2017 3rd

    Joined:
    Sep 22, 2017
    Messages:
    2,641
    Likes Received:
    160
    Gender:
    Male
    I’d sink an eyebolt into that epoxy mass dude in the nose of lead/epoxy and put another 25 ft of Kevlar or nylon cord to absorb the energy slowly if that nose does pop off with eyebolt the top of your payload bay. My opinion there. That’s just me after seeing what heavy noses tend to do on scale rockets. Two you would be set for dual deploy. I literally failed a cert 1 twice with a stable rocket. I would sim the recovery harness and nomex mass too. Not just chute.
     
  7. Oct 11, 2018 #7

    Andrew_ASC

    Andrew_ASC

    Andrew_ASC

    UTC SEDS 2017 3rd

    Joined:
    Sep 22, 2017
    Messages:
    2,641
    Likes Received:
    160
    Gender:
    Male
    I had recovery issues due to the build techniques I used were inadequate for the noseweight added. The rocket needed the noseweight for stability. This comes down to if your build techniques survive the harsh ejection with that much added mass.
     
  8. Oct 11, 2018 #8

    Nytrunner

    Nytrunner

    Nytrunner

    Master of Rivets

    Joined:
    Oct 15, 2016
    Messages:
    2,719
    Likes Received:
    134
    Gender:
    Male
    Location:
    Huntsville AL
    When I get home, I'll post the flight validated file for my L1 Patriot so you can compare

    That just seems awfully heavy to me. I assume you've weighed the whole thing sans motor.
    What kind of adhesive, (and how much) did you use at the back?
     
    Andrew_ASC likes this.
  9. Oct 11, 2018 #9

    Ben Martin

    Ben Martin

    Ben Martin

    Well-Known Member

    Joined:
    Sep 29, 2018
    Messages:
    193
    Likes Received:
    12
    Gender:
    Male
    Location:
    Houston
    Issue is that I plan on launching in a few days.
     
  10. Oct 11, 2018 #10

    Ben Martin

    Ben Martin

    Ben Martin

    Well-Known Member

    Joined:
    Sep 29, 2018
    Messages:
    193
    Likes Received:
    12
    Gender:
    Male
    Location:
    Houston
    I have a heavy fin fillet with epoxy clay and a generous use of epoxy. It's 1670g with 300g of nose weight. With H148 it had a CG of 31in.
     
  11. Oct 11, 2018 #11

    Andrew_ASC

    Andrew_ASC

    Andrew_ASC

    UTC SEDS 2017 3rd

    Joined:
    Sep 22, 2017
    Messages:
    2,641
    Likes Received:
    160
    Gender:
    Male
    Well. You can try with what you got and see experimentally if that is adequate. And if it isn’t then you redo it. See what the experienced guys or gals say at the launch site about your rocket if you want. They may have better ideas.
     
  12. Oct 11, 2018 #12

    manixFan

    manixFan

    manixFan

    Well-Known Member

    Joined:
    Feb 15, 2009
    Messages:
    703
    Likes Received:
    21
    Bring them down on two separate chutes. The nose cone can come down a bit faster (as long as the recovery area is not hard pavement). It's a lot less likely to create a recovery issue. I did this with a big rocket that needed pounds of nose weight. It's really hard to control the motion of a heavy nosecone so in my opinion just better to let it come down on its own rather than stress the entire system and risk the entire rocket.

    Good luck,


    Tony
     
  13. Oct 11, 2018 #13

    Ben Martin

    Ben Martin

    Ben Martin

    Well-Known Member

    Joined:
    Sep 29, 2018
    Messages:
    193
    Likes Received:
    12
    Gender:
    Male
    Location:
    Houston
    I failed my L1 due to my nosecone flying off, I should have just put a parachute on it lmao.
     
  14. Oct 11, 2018 #14

    Zeus-cat

    Zeus-cat

    Zeus-cat

    Well-Known Member

    Joined:
    Mar 14, 2009
    Messages:
    3,581
    Likes Received:
    48
    A guy in my club built a Battlestar Galactica Viper and had to put a crap ton on nose weight in it. He flew it in an Aerotech H550 and had drag separation right after motor burnout. The rocket was rebuilt, but only for display as the zipper damage to the body tube was extensive. So if using a lot of nose weight you really need to secure the nose until you want it to come off.
     
  15. Oct 12, 2018 #15

    Andy Limper

    Andy Limper

    Andy Limper

    Active Member

    Joined:
    Jan 13, 2012
    Messages:
    34
    Likes Received:
    3
    Yep. Shear pin the nose on. Had heavy nose cone separate on a 5.4 inch custom AGM Rascal at Airfest this year. Things got ugly
     
  16. Oct 12, 2018 #16

    Ben Martin

    Ben Martin

    Ben Martin

    Well-Known Member

    Joined:
    Sep 29, 2018
    Messages:
    193
    Likes Received:
    12
    Gender:
    Male
    Location:
    Houston
    What about plastic rivets?
     
  17. Oct 12, 2018 #17

    seth_cooper

    seth_cooper

    seth_cooper

    Well-Known Member

    Joined:
    Apr 5, 2015
    Messages:
    87
    Likes Received:
    5
    I have 24 ounces in the nose of a Madcow Seawolf. No problems with friction fitting using masking tape. If you wanted to be safe, use a couple of shear pins.
     
  18. Oct 12, 2018 #18

    Rex R

    Rex R

    Rex R

    LV2

    Joined:
    Apr 21, 2010
    Messages:
    5,670
    Likes Received:
    18
    you're using 9/16" nylon shock cord, yes? it can handle the stress. I used approx. 500g in mine(last time I flew it on an 'I' motor I used 16 oz of cheese to compensate for the bigger motor :)), just make sure to attach the nose to the payload bay. one thing to keep in mind is that the standard av-bay is about 500g...personally I would go ahead and use a separate rocket for the L2 (bigger, longer/heavier) but that's my opinion.
    Rex
     
  19. Oct 12, 2018 #19

    Ben Martin

    Ben Martin

    Ben Martin

    Well-Known Member

    Joined:
    Sep 29, 2018
    Messages:
    193
    Likes Received:
    12
    Gender:
    Male
    Location:
    Houston
    I'm working on a 3D printed L2 project right now so I'll limit my Patriot to L1.
     
  20. Oct 12, 2018 #20

    Ben Martin

    Ben Martin

    Ben Martin

    Well-Known Member

    Joined:
    Sep 29, 2018
    Messages:
    193
    Likes Received:
    12
    Gender:
    Male
    Location:
    Houston
    What method did you use to connect the nosecone to the payload bay?
     
  21. Oct 12, 2018 #21

    Rex R

    Rex R

    Rex R

    LV2

    Joined:
    Apr 21, 2010
    Messages:
    5,670
    Likes Received:
    18
    I drilled through the airframe and the shoulder of the nose cone, then tapped the cone for 4-40 screws(2 each). button head screws work well (low profile and hold paint well). good luck.
    Rex
     
    Ben Martin likes this.
  22. Oct 12, 2018 #22

    dr wogz

    dr wogz

    dr wogz

    Fly caster

    Joined:
    Feb 5, 2009
    Messages:
    4,000
    Likes Received:
    64
    Location:
    Land of Poutine!
    I have about 22oz in mine. And I did have a drag separation incident with it last year (All part of learning)

    My MC patriot has about 16oz in it. 4" cardboard if you're wondering..
     
  23. Oct 12, 2018 #23

    Ben Martin

    Ben Martin

    Ben Martin

    Well-Known Member

    Joined:
    Sep 29, 2018
    Messages:
    193
    Likes Received:
    12
    Gender:
    Male
    Location:
    Houston
    So around 450grams? It seems like my 4" Patriot requires more or maybe OpenRocket is just being too generous.
     
  24. Oct 12, 2018 #24

    dr wogz

    dr wogz

    dr wogz

    Fly caster

    Joined:
    Feb 5, 2009
    Messages:
    4,000
    Likes Received:
    64
    Location:
    Land of Poutine!
    There, 2 holes in the bottom of the nose one. Poured the lead shot in the one of them. Tie it off with a bowling, and some tape over that to hold it tight..
     

    Attached Files:

  25. Oct 12, 2018 #25

    Ben Martin

    Ben Martin

    Ben Martin

    Well-Known Member

    Joined:
    Sep 29, 2018
    Messages:
    193
    Likes Received:
    12
    Gender:
    Male
    Location:
    Houston
    I plan on just using bbs and epoxy for nose weight and putting some screws through the payload bay to hold the nosecone on.
     
  26. Oct 12, 2018 #26

    dr wogz

    dr wogz

    dr wogz

    Fly caster

    Joined:
    Feb 5, 2009
    Messages:
    4,000
    Likes Received:
    64
    Location:
    Land of Poutine!
    I actually point out where the CP is, according to the instructions. I then placed the equivalent of a medium J in the aft end. Then, with the NC off, I tried a string around where the min CG point is to be (4" ahead of the CP) and start to add weight to the open front end. Once I got about right, I hung the NC on it too! I then knew what I was after to get it to balance right, with a honkin' motor..

    Call it the old fashioned way!
     
  27. Oct 12, 2018 #27

    dr wogz

    dr wogz

    dr wogz

    Fly caster

    Joined:
    Feb 5, 2009
    Messages:
    4,000
    Likes Received:
    64
    Location:
    Land of Poutine!
    I use wooden dowels to hold the lead shot n epoxy in place. Goes they the nose cone, supported at both ends..

    Easier to sand smooth..
     

    Attached Files:

  28. Oct 12, 2018 #28

    Ben Martin

    Ben Martin

    Ben Martin

    Well-Known Member

    Joined:
    Sep 29, 2018
    Messages:
    193
    Likes Received:
    12
    Gender:
    Male
    Location:
    Houston
    Sounds like the best way to do it. I'm still surprised that my Patriot was able to fly with my CG at 31in (300g in nosecone), RockSim showed a margin of 1.2, but OpenRocket showed a margin of just .3 cal.
     
  29. Oct 12, 2018 #29

    seth_cooper

    seth_cooper

    seth_cooper

    Well-Known Member

    Joined:
    Apr 5, 2015
    Messages:
    87
    Likes Received:
    5
    I've switched from using epoxy to hold the lead shot in place. Had too many come loose over time. Never tried the wooden dowels.

    Now I use Gorilla glue with a touch of water to get some added expansion. That stuff sticks! No dowels needed.
     
  30. Oct 12, 2018 #30

    manixFan

    manixFan

    manixFan

    Well-Known Member

    Joined:
    Feb 15, 2009
    Messages:
    703
    Likes Received:
    21
    Don’t believe everything your sim tells you. I’ve always waited to add nose weight until I have the rocket built and configured for flight with the heaviest motor I plan to use. Then I’ll add the actual weight needed to get the right stability margin. Just recently a member here posted how he added nose weight according to the sim and found he had a much larger margin than needed. That extra weight means of course a bigger chute, more stress on recovery harness, etc.

    Just something to consider.


    Tony
     
    grouch likes this.

Share This Page