Little more depth on adding nose weight

Off Grid Gecko

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Hey guys, of course I've read a bunch of threads on this but reading is one thing and doing is something else.

My OpenRocket simulation says I'm getting 0.8 cal stability on my current L2 build. Rocket is a 4in Madcow DX-3.

I've been checking weights as I go and adjusting the proper parts for weight as I add epoxy and primer. I knew the nose weight would come in close but now it's looking like 2oz of nose weight to get me over 1cal... As far as I can tell by balancing parts, the CoG is coming out right to well within 1/2 an inch. I don't have the motor yet so can't check everything (and of course paint has not been applied yet).

I've never had to add weight, but I have plenty of shotgun shells I can open up to get enough lead. Trap loads mostly and I don't really shoot them very often, just have a bunch that I inherited. I think I can get the epoxy and lead mixture in there without making a mess, just going to be a lot of spot measuring and weighing as I inject each amount to make sure and get it right. Dipping in water is also not a problem... my problem is securing it.

I can drive to town and get a dowel rod, I've just never had to use this method as I almost exclusively bash kits or build from scratch. This is my first high-power kit and been saying since I got it that it needs a longer forward tube, but I'm a little late in the game now to order a 24" tube and redo everything, and honestly don't feel like waiting on it to ship. I have some aluminum heavy-gauge fence wire I guess I could use, I'm just not thrilled about the prospect of cutting and sanding it close to the tip of my nose cone (but who is I suppose).

I've read in some of the posts about this Gorilla Glue trick with making foam by adding some water. Curious how that works. Exactly which bottle of GG I need to get, and how much I need to fill. This is a 4x16in nose cone so it's a lot of space in there. I'm not overly concerned about adding too much weight as this whole build is primarily for an L2 launch and that's about it, unless I find something fun to do with it in the future, at which time I'm fine buying another nose cone and maybe extending the upper tube or adding a payload bay behind the nose cone for fun science.

Can anyone give me like, step by step gorilla glue method for filling the nose with foam. I can get normal crack filler foam but not sure about two part foam in my part of the world. Local supply is pretty limited on a lot of things, though I could check the hardware stores and see what they carry I suppose. Will be a trip to town either way (the gas cost alone gives me a stomach ache, lol).

I also have not added any electronics, battery, or anything else to the payload bay, but it's already pretty heavy so I don't see weight there doing too much to help me.

I also realize that the 1 cal thing is a rule of thumb and not set in stone, but it's one less question to answer for at the RSO table. I have not done a stability test as again, I don't have the motor yet. Plan to order it near the end of the month.
 

mikec

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There are many ways to solve this problem. I wouldn't mess with expanding foam though some people love it. You can use almost anything to retain a mass of epoxy -- nails filed off would work too. For my DX3, I have a bunch of fender washers the base of the cone retained by an expanding bolt, that way you can adjust as needed for different motors.

Whatever you do, if you are not using dual deploy, make sure the cone is retained by rivets or something. It's hard to friction fit cones well enough to keep them from coming off at ejection. Using a backup shock cord is a good idea also if you're not sure.
 

Off Grid Gecko

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There are many ways to solve this problem. I wouldn't mess with expanding foam though some people love it. You can use almost anything to retain a mass of epoxy -- nails filed off would work too. For my DX3, I have a bunch of fender washers the base of the cone retained by an expanding bolt, that way you can adjust as needed for different motors.

Whatever you do, if you are not using dual deploy, make sure the cone is retained by rivets or something. It's hard to friction fit cones well enough to keep them from coming off at ejection. Using a backup shock cord is a good idea also if you're not sure.
Thank you for the tips. Planning to DD but yes even if I maiden on a G or a small H I plan to have everything tethered up front. This nose cone likes to change sizes on me. In the sun it's a nice tight fit but in my house it falls out without provocation. Did you cut out the base of the nose cone to get the stuff inside or expand the hole? Curious about the method for getting that all in there and secure.
Oh wait... at the base of the NC?? hmmm, that might be an idea worth looking at.
 

Off Grid Gecko

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on the sim 3oz at the base of the nose cone gets me right to 1 cal... okay, I think I have a mission next time I go to town. haha. Thanks for the idea.
 

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If you have some plastic prescription pill bottles, fill them with enough lead shot to match the weight of the motor you intend to use. Place them in your motor mount tube with the rocket horizontal and all recovery gear installed. At this point you can start hanging weight from the nose cone tip until you achieve at least the desired 1 caliber plus CG forward of CP. If I recall my DX 3 needed around 4 ounces of shot in the nose cone. Mixing shot with epoxy is pretty messy. On my most recent build I cut a 1 inch round window in the aft side of the cone and poured in the shot. With the nose pointed down, drill a bunch of small holes evenly spaced to form little nubs on the inside sufficient to hold in place an epoxy dam. Apply masking tape to the outer nose cone tip to keep epoxy from leaking out of the holes you drilled. Do your epoxy pour and leave the cone hanging nose down to cure. When you peel off the masking tape, you'll be surprised at how little extra sanding you have to do to smooth it out for paint. Worked great for me - No Muss - No Fuss!
 

Off Grid Gecko

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If you have some plastic prescription pill bottles, fill them with enough lead shot to match the weight of the motor you intend to use. Place them in your motor mount tube with the rocket horizontal and all recovery gear installed. At this point you can start hanging weight from the nose cone tip until you achieve at least the desired 1 caliber plus CG forward of CP. If I recall my DX 3 needed around 4 ounces of shot in the nose cone. Mixing shot with epoxy is pretty messy. On my most recent build I cut a 1 inch round window in the aft side of the cone and poured in the shot. With the nose pointed down, drill a bunch of small holes evenly spaced to form little nubs on the inside sufficient to hold in place an epoxy dam. Apply masking tape to the outer nose cone tip to keep epoxy from leaking out of the holes you drilled. Do your epoxy pour and leave the cone hanging nose down to cure. When you peel off the masking tape, you'll be surprised at how little extra sanding you have to do to smooth it out for paint. Worked great for me - No Muss - No Fuss!
Nother incredible idea! Keep this up and someone gonna have to sticky this post, lol.
 

Off Grid Gecko

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Just thought of another idea also, would probably have to add a lot more weight, but when I designed the E-bay I put the sled on 2 1/4in threaded rods that run the length. I never glued one end yet cause I can't make up my mind, but I could leave it without glue and tension fitted and stack quite a few hex nuts on either side to weight down the electronics bay. It's so far back though I'm not sure how much weight would need to be added.

nm bad idea, would require 11oz on the sim I'm not sure those little hex nuts weight that much, lol.
 

T-Rex

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I use BB's embedded in epoxy with bamboo skewers to retain it in the nose.
Adjustable weight is handy if you will be flying the rocket with different motors. I did my L1 with a cardboard Madcow Little John. I cut a hole in the side of the nose shoulder. The eye bolt goes through the bottom and I can stack fender washers on the shank of the eye inside the nose and secure them with a nut. I figure it provides a surface to prevent the eye bolt from pulling through the base of the nose.
 

Off Grid Gecko

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I use BB's embedded in epoxy with bamboo skewers to retain it in the nose.
Adjustable weight is handy if you will be flying the rocket with different motors. I did my L1 with a cardboard Madcow Little John. I cut a hole in the side of the nose shoulder. The eye bolt goes through the bottom and I can stack fender washers on the shank of the eye inside the nose and secure them with a nut. I figure it provides a surface to prevent the eye bolt from pulling through the base of the nose.
I'm thinking the same. 3oz isn't a whole lot more and sounds much less of a mess and no drilling holes in things. I'm not great at body work can still see faint spirals when I push my face against the tube, lol. And it drives me INSANE!

I have a piece of 5/16 threaded rod and there's a little tube at the bottom of the nosecone, maybe 3/4" long, rod fits pretty snug inside of it. Thinking washer inside with a nylon-insert lock nut then stack washers on the outside like mikec suggested. Or perhaps simply a long 5/16 bolt with the head inside the nosecone. My only worry is the end of the threads ripping my chute while the laundary is on the way out, so might need to put a tape cap at the end of it, or an extra lock nut flush with the end just to remove any possibility of a sharp edge there. All this and I'm still showing over 1100 meters on a J285. My L1 went WAY up there and I don't want to go through that again so trying to keep this guy low.
This talk about adding weight has me also wondering about a longer shank eye-bolt at the front of the electronics bay that I could load down with some heavy stuff also just to tame the lil monster down a bit.
 

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In my experience, securing lead shot in LPR nose cones, Gorilla polyurethane glue is the s___. Damp Q-tip on the surface then add glue.

Estes Goblin:

IMG_0476.JPG

[edit] Nevermind ! Talking high power here. Bamboo skewers and epoxy. Note to self: "Read the whole thread".
 
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Off Grid Gecko

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In my experience, securing lead shot in LPR nose cones, Gorilla polyurethane glue is the s___. Damp Q-tip on the surface then add glue.

Estes Goblin:

View attachment 527404

[edit] Nevermind ! Talking high power here. Bamboo skewers and epoxy. Note to self: "Read the whole thread".
Perfectly alright, I'm still interested in this. Is there a certain kind of gorilla glue (they make like 18000 products these days)? You just pour some on the damp plastic and it foams up like that? About how much do you add. You pretty well need to fill it or does it expand approx 2x/3x?
 

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samb

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Perfectly alright, I'm still interested in this. Is there a certain kind of gorilla glue (they make like 18000 products these days)? You just pour some on the damp plastic and it foams up like that? About how much do you add. You pretty well need to fill it or does it expand approx 2x/3x?
1657660671441.png
Don't fill the space with glue, it will expand. I don't know the exact rate so you'll have to experiment and wing it like all good rocket scientists. Maybe a nice pea sized dollop in the model shown.
 

Off Grid Gecko

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View attachment 527412
Don't fill the space with glue, it will expand. I don't know the exact rate so you'll have to experiment and wing it like all good rocket scientists. Maybe a nice pea sized dollop in the model shown.
That definitely gives me a better understanding, I didn't know what kind of ratio to expect so thinking do I need a whole tub of the stuff? lol. Cool. I may try this. I have a couple of lil bt-20 - bt-50 nose cones laying about. Might give it a shot just to see.
 

Off Grid Gecko

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For adjustable weight, you may want to take a look at a thread I posted a while back.

Thread 'DigBaddy's Big Daddy Nose Weight Mod' https://www.rocketryforum.com/threads/digbaddys-big-daddy-nose-weight-mod.173177/
bloody brilliant.. I'll have to remember that when I get into fiberglass rockets cause all those ones are open at the end like that. The madcow nc they send is blow molded type with the little angled loop. I decided not to cut it wide open because it was having trouble holding shape in storage as it was. I had to put it on the dashboard of my truck to let it heat up and then bend and tinker with it to get it straight. Still not perfect but a lot better than how I received it. The constant expanison and contraction I thought would be a problem if I opened it up and stuck a baffle in there, but in general, love your brilliant idea.... just have one question.

Where the bloody hell did you find a cream bottle with that size cap?? lol. I've cut the tops off so many bottles over the years looking for those perfect fits and usually end up having to hollow out the middle with sandpaper for hours for the application at hand. I think my last was a gatorade bottle to fit over a 38mm motor mount. Maybe it was a 29, can't remember.

But I don't buy a lot of cream, so I guess I never looked there. Anyway, fantastic idea. I'm kind of sold on this threaded washer holder idea I think but definitely worth taking note of. Thank you.
 

dbpeirce

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I like to cut a hole in the side of a cone shoulder and then putting a piece of all thread all the way to the tip of the cone and securing with nuts and an eyebolt. (or do this before adding a bulkhead on an open cone)
I can then mix epoxy and lead and pour into the hole and it secures itself to the threaded rod. No need to punch dowels or nails through the nose tip this way.
But like mentioned before, I would take a motor case or tube and fill it with the weight of the biggest motor you imagine using with this rocket and load the rocket as it would be ready on the pad and check your CP/CG relationship. From here you can add weight to the nose tip to test for balance. I always do this actual physical check no matter what the sim program data is.
 

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DigBaddy

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bloody brilliant.. I'll have to remember that when I get into fiberglass rockets cause all those ones are open at the end like that. The madcow nc they send is blow molded type with the little angled loop. I decided not to cut it wide open because it was having trouble holding shape in storage as it was. I had to put it on the dashboard of my truck to let it heat up and then bend and tinker with it to get it straight. Still not perfect but a lot better than how I received it. The constant expanison and contraction I thought would be a problem if I opened it up and stuck a baffle in there, but in general, love your brilliant idea.... just have one question.

Where the bloody hell did you find a cream bottle with that size cap?? lol. I've cut the tops off so many bottles over the years looking for those perfect fits and usually end up having to hollow out the middle with sandpaper for hours for the application at hand. I think my last was a gatorade bottle to fit over a 38mm motor mount. Maybe it was a 29, can't remember.

But I don't buy a lot of cream, so I guess I never looked there. Anyway, fantastic idea. I'm kind of sold on this threaded washer holder idea I think but definitely worth taking note of. Thank you.

The cream container is a paper quart one from Aldi, but others are the same. Just look for a paper quart/pint with the plastic cap on it.
 

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KenECoyote

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Only real difference for me is using 1/8" brass rod instead of chop sticks, and I run one through at right angles to the other (+ shape).
Yup, for my previous heavy nose build I used decking screws cross style for more security, but that one had more weight and the nose was fg.

Stated for the mass: Like anything else rocketry and especially hp, we have to account for the loads and stresses.

In my case, I felt this was enough and it was much easier. Given the material is a bit flexible and weight being added near the tip which was thicker, I felt bigger diameter object would help more and bamboo along with the surface adhesion of the epoxy mix was enough for a 4" cardboard build, but with anything it can fail so use judgement, build according to the max motor you plan and inspect regularly.

Along that same line, I was actually considering that creamer/milk cap example for my next "modular-ish" build (a Polecat Pershing II like yours! 😍) , but personally I would use a motor retainer for more strength.

So in the epoxied weight case originally stated, I felt dowels is sufficient, but in the other I'd a prefer stronger retainer.

YMMV
 
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Off Grid Gecko

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I like to cut a hole in the side of a cone shoulder and then putting a piece of all thread all the way to the tip of the cone and securing with nuts and an eyebolt. (or do this before adding a bulkhead on an open cone)
I can then mix epoxy and lead and pour into the hole and it secures itself to the threaded rod. No need to punch dowels or nails through the nose tip this way.
But like mentioned before, I would take a motor case or tube and fill it with the weight of the biggest motor you imagine using with this rocket and load the rocket as it would be ready on the pad and check your CP/CG relationship. From here you can add weight to the nose tip to test for balance. I always do this actual physical check no matter what the sim program data is.
It's an idea, I definitely have enough rod to reach up in there. The piece I found is 23inches long but I'll prolly end up going with a bolt instead, but maybe put the washers inside the nose.

On balancing before, yes always for sure on a new motor or something that was outside my original design constraints. When I scratch build I usually set up the bird in such a way that this doesn't ever become an issue to begin with, that's why I haven't had to mess around with nose weights before. My rockets tend to be 2cal or more and I don't launch in heavy wind (mostly because I don't want all the extra walking when it's hot out, haha)
 

Off Grid Gecko

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Had to remove 5 washers to get her in there. about 220g added to the base of the NC which puts me at 1.8 calibers for the smallest motor I will run on this bird and around 1.3 with my targeted L2 motor. Dry weight on the rocket rn is right at 2kg and I'm sure it will be over by the time I've finished the paint. Gonna need a bigger chute!

1970 rn on the kitchen scale, and I still need to add launch lugs and the drogue stuff, charge cups, electronics, battery, etc etc. Actual balance point without motor is about 1/2 in forward of what the sim is calculating, right on the little electronics bay band, how bout that? haha.

I think this solution is going to work really well for me and will probably use it again in the future. It's just so clean and so fast. My hole saw cut right through the plastic material like butter without binding up at all. Pretty impressive. Installed a nut on the inside over the washers, then a dab of loctite and a jam nut to lock the first one in place.

Thanks everyone for all the cool ideas and help. Now I'm just waiting on the rest of my parts and for primer to dry so I can continue with the sanding.
 

bobbyg23

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Hey guys, of course I've read a bunch of threads on this but reading is one thing and doing is something else.

My OpenRocket simulation says I'm getting 0.8 cal stability on my current L2 build. Rocket is a 4in Madcow DX-3.

I've been checking weights as I go and adjusting the proper parts for weight as I add epoxy and primer. I knew the nose weight would come in close but now it's looking like 2oz of nose weight to get me over 1cal... As far as I can tell by balancing parts, the CoG is coming out right to well within 1/2 an inch. I don't have the motor yet so can't check everything (and of course paint has not been applied yet).

I've never had to add weight, but I have plenty of shotgun shells I can open up to get enough lead. Trap loads mostly and I don't really shoot them very often, just have a bunch that I inherited. I think I can get the epoxy and lead mixture in there without making a mess, just going to be a lot of spot measuring and weighing as I inject each amount to make sure and get it right. Dipping in water is also not a problem... my problem is securing it.

I can drive to town and get a dowel rod, I've just never had to use this method as I almost exclusively bash kits or build from scratch. This is my first high-power kit and been saying since I got it that it needs a longer forward tube, but I'm a little late in the game now to order a 24" tube and redo everything, and honestly don't feel like waiting on it to ship. I have some aluminum heavy-gauge fence wire I guess I could use, I'm just not thrilled about the prospect of cutting and sanding it close to the tip of my nose cone (but who is I suppose).

I've read in some of the posts about this Gorilla Glue trick with making foam by adding some water. Curious how that works. Exactly which bottle of GG I need to get, and how much I need to fill. This is a 4x16in nose cone so it's a lot of space in there. I'm not overly concerned about adding too much weight as this whole build is primarily for an L2 launch and that's about it, unless I find something fun to do with it in the future, at which time I'm fine buying another nose cone and maybe extending the upper tube or adding a payload bay behind the nose cone for fun science.

Can anyone give me like, step by step gorilla glue method for filling the nose with foam. I can get normal crack filler foam but not sure about two part foam in my part of the world. Local supply is pretty limited on a lot of things, though I could check the hardware stores and see what they carry I suppose. Will be a trip to town either way (the gas cost alone gives me a stomach ache, lol).

I also have not added any electronics, battery, or anything else to the payload bay, but it's already pretty heavy so I don't see weight there doing too much to help me.

I also realize that the 1 cal thing is a rule of thumb and not set in stone, but it's one less question to answer for at the RSO table. I have not done a stability test as again, I don't have the motor yet. Plan to order it near the end of the month.
.
 

Off Grid Gecko

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Sorry to revive this thread, but how did you attach that assembly? Pic?
Sorry I've been away for a minute. The bottom of the madcow nosecones have a bit of tube extending from them and after cleaning the hole with a drill the bolt slid right in there. I cut a hole in the shoulder area with a holesaw giving just enough room to slip the washers on inside a few at a time, then secured with nuts. So it's at the base of the NC rather than the front. I'll see if I can dig up a pic of it here in a minute.
 

gdjsky01

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Nope... Now I get it. It's the access hole part that I was missing. Thank you.

Someone else talked about an expanding bolt. I can't see how once it is expanded how you are gonna get any washers on or off. They don't 'unexpand' do they? At least not what I found with a quick search.
 

Off Grid Gecko

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Nope... Now I get it. It's the access hole part that I was missing. Thank you.

Someone else talked about an expanding bolt. I can't see how once it is expanded how you are gonna get any washers on or off. They don't 'unexpand' do they? At least not what I found with a quick search.
Yeah, definitely requires being a little clever and we all have different skillsets. I think my ideal situation would be a threaded tip with a rather large diameter thread at the front and washers that will fit through the opening attached to a threaded rod on the tip.

Not sure if that makes sense the way I worded it, but basically ring threads where the tip attaches to the nosecone. Might be a bit of work to manufacture such a thing though.

Usually those expanding bolts are basically some rubber bits between washers and when you tighten the bolt the rubber squishes and expands to lock it in place. So they should be able to unlock as well, but I'd imagine you'd wear out the rubber if you messed with it a lot. I dunno. Lots of that kind of stuff at the hardware store for setting anchors in drywall or concrete you could look at. Question usually is how much fabrication will it take to secure everything inside of the nose.

I'm probably going to be focusing on larger fiberglass builds in the future and my scheme will probably involve anchoring interchangeable weights at the front of the nosecone avionics bay. Just not sure 100% what it will look like till I'm in the middle of designing it. First thing's first. L2 attempt this Saturday at the TripoliMoKan launch site :)
 
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