How to add nosecone weight?

[burritoman1]

I'm currently building a Madcow Super DX3 and since I added quite a bit of weight to the back, the sim calls for about a pound of nose weight in order to hit 2 cals of stability. The method I usually use is to drill a hole into the nosecone and fill it with lead weights and epoxy. However, the DX3 instructions explicitly state that the epoxy alone will not stick to the nose cone, and that i must add screws through the nosecone into the weights to secure them, and then grind down the heads of the screws so they are flush with the surface of the nose cone. The whole thing seems a bit convoluted, especially since the weights I use are fishing weights which are far too small to screw into. My alternate solution is to add the weights and then fill the remaining volume with expanding foam. However I don't have any experience with that method so I'd like to hear some other people's ideas before continuing.

 

[sharkbait]

I'm currently building a Madcow Super DX3 and since I added quite a bit of weight to the back, the sim calls for about a pound of nose weight in order to hit 2 cals of stability. The method I usually use is to drill a hole into the nosecone and fill it with lead weights and epoxy. However, the DX3 instructions explicitly state that the epoxy alone will not stick to the nose cone, and that i must add screws through the nosecone into the weights to secure them, and then grind down the heads of the screws so they are flush with the surface of the nose cone. The whole thing seems a bit convoluted, especially since the weights I use are fishing weights which are far too small to screw into. My alternate solution is to add the weights and then fill the remaining volume with expanding foam. However I don't have any experience with that method so I'd like to hear some other people's ideas before continuing.

The screws din’t have to be in the individual lead weights, the are creating anchor points to hold the epoxy + lead mass in place, I would not foam it if you ever intend to to put a tracker bay in the NC

 

[burritoman1]

The screws din’t have to be in the individual lead weights, the are creating anchor points to hold the epoxy + lead mass in place, I would not foam it if you ever intend to to put a tracker bay in the NC

That makes more sense. However, I realized that I may want to vary the nose weight for different flights so I may use another method altogether. I saw a thread where someone used a threaded rod screwed into the NC with many nuts fastened onto it, which makes the weight both removable and easily adjustable. I will experiment with this method and post the results here. If anyone has any other ideas for removable nose weight systems I would like to hear them.

 

[Rschub]

Loc has a nose weight system that's pretty slick, you can buy the parts separately without having to get another nosecone.

https://locprecision.com/collections/rocket-components/products/rnws?variant=44181190279401

Someone makes a 3D printed avbays that install in plastic nose cones. You could use it for weight instead.

https://www.rocketryforum.com/threads/4in-nose-cone-ebay.181970/#post-2485916

 

[mtnmanak]

That makes more sense. However, I realized that I may want to vary the nose weight for different flights so I may use another method altogether. I saw a thread where someone used a threaded rod screwed into the NC with many nuts fastened onto it, which makes the weight both removable and easily adjustable. I will experiment with this method and post the results here. If anyone has any other ideas for removable nose weight systems I would like to hear them.

If you are going to use some kind of epoxy/weight in the nosecone tip, use BBs instead of fishing weights. BBs more evenly distribute and are easier to form into a nice mass. If you want to anchor the mass, put two relatively thin brass rods through the nosecone at 90 degree angles from each other, pour in your BBs and epoxy and, after it cures, clip the brass rods on the outside of the NC flush and sand until they are flat to the surface.

If you want to have a removeable system, make your life easier and use LOCs removeable nosecone weight system: https://locprecision.com/products/rnws?_pos=1&_sid=2e3409274&_ss=r&variant=39778648096959

 

[thzero]

I'm currently building a Madcow Super DX3 and since I added quite a bit of weight to the back, the sim calls for about a pound of nose weight in order to hit 2 cals of stability. The method I usually use is to drill a hole into the nosecone and fill it with lead weights and epoxy. However, the DX3 instructions explicitly state that the epoxy alone will not stick to the nose cone, and that i must add screws through the nosecone into the weights to secure them, and then grind down the heads of the screws so they are flush with the surface of the nose cone. The whole thing seems a bit convoluted, especially since the weights I use are fishing weights which are far too small to screw into. My alternate solution is to add the weights and then fill the remaining volume with expanding foam. However I don't have any experience with that method so I'd like to hear some other people's ideas before continuing.

All you need is 1...

You are screwing into the epoxy. Or use a brass rod, or screws I guess could work too, pour in epoxy then your weights and more epoxy.

Done.

 

[JimByrne]

I use lead bullets in epoxy with a nail through the nose cone---it all locks in when the epoxy sets up. I use a Demel tool with an abrasive disk to cut off the nail & grind it even with the sides of the nose cone.

 

[terryg]

I use BB's that I moisten with a little bit of water. I then add polyurethane glue and rotate and shake until they are all covered and there is no rattleing. The glue foams up as it cures and is very sticky and adhered strongly. I have not had any issues with it coming loose.

 

[BABAR]

Not a HPR guy but done some nose cones weights that had me nervous, and read some stuff here.

Apologies I don’t know about your particular cone, whether it is two piece and allows ready access to interior or not.

Issues.

1. Epoxy doesn’t always adhere well to smooth plastic. Wash out the inside (and outside, for paint adhesion) of cone, I think soapy water will work.

2. epoxy can heat up as it cures. I have read that it can deform plastic nose cones, although I don’t know if your model’s cone is thick or tough enough to resist the heat. I have read that having the tip nose down in a cup of water doesn’t hurt.

3. Rough up the inside surface as much as possible with coarse sandpaper or just scrape it a bunch with some metal.

4. Cross bars of some sort are strong added security. I just used wooden dowels, one ventral-dorsal, one right-left.
Drill holes so the just barely fit, once everything is in place cut as close to outer surface as you can, sand until flush with surface. It’s a lot easier to do than it sounds. If it’s a LOT of weight, metal rods would be stronger.

5. Again depends on the cone. But weight put into the cone tip is NOT directly connected to the nose cone attachment to shock cord )I have seen plastic nose cone attachments “built in” loops break, especially when good bit of weight is glued to forward tip of cone. Wouldn’t hurt to have a threaded rod sticking out through the base that is glued into your nose cone mass, which could both be a source to add weight with washers later AND serve as a shock cord attachment point. So your shock cord is attached to a strong metal threaded rod which is attached to a heavy mass which is attached to a plastic (weaker but lower intrinsic mass)nose cone. This is inherently stronger than shock cord attached to (lighter but weaker) nose cone attached to a heavy weight. In latter case the cone or molded cone attachment loop is a potential failure point.

I’ll go back in my hole now.

 

[MikeT]

 

[conneryc]

In the past I've always done the lead-shot/epoxy followed up with expanding foam for my L1/L2 rockets and it has worked well. I was planning on doing the same with my L3 build, but I think I'm going to go with the LOC removeable nosecone weight system since the kit I'm building is one of theirs. That way I have much more control to be able to compensate for difference size motors. My initial flight for certification will be on a 75mm but it has a 98mm mount, so using the RNWS seems like the better option.

 

[Capt. Eric]

I have used expanding epoxy foam. Also small crimp style fishing weights. If you need to add weight later on you could screw in some screws or lag bolts. All simple and effective. Or you can make your nose cone a separate project by itself and follow some of the above suggestions. Works well too and I suppose looks more "engineered". Whatever works for you, but I'm a believer in K.I.S.S.

 

[Rob Campbell]

I recently added weight with BB gun shot I bought at Walmart. I secured it with crossed brass rods ands three bottles of Gorilla Glue. Gorilla glue is as strong as epoxy and foams up like expending form. If I ever use Gorilla Glue again for this, I will seal the holes for the rods with medium CA. That Gorilla Glue found the small gaps and leaked out, making a mess on the outside of the nose cone.

 

[JimByrne]

Above someone mentioned epoxy heating up the plastic nose cone while curing--my solution is to put the tip of the nosecone in a can of water to absorb some of the heat

 

[atestani]

I came up with a nose cone weight system that uses interchangeable "weight tubes" which can be quickly changed in the field. I have flown this multiple times with different motors and different weights.

The aft end of the nose cone is cut off so two different diameter centering rings which hold a 29mm engine tube can be epoxied in. The nose cone stays on during deployment with this design but it should be adaptable to adding an eyebolt for nose cone deployment. The aft end of the 29mm engine tube has a motor retainer. BT-50 tubes with end caps make up the weight tubes which are filled with the appropriate amount of epoxy and then lead shot or BBs poured in. The capped end of the BT-50 weight tubes is inserted first which puts the weight as far forward as possible. There are centering rings on the BT-50 tubes so they are centered in the 29mm engine tube and secured by the motor retainer.

All of the plastic parts are 3D printed. If anyone is interested in the STL files for these parts, let me know.

Multiple images are attached to show how I did this.

 

[Titan II]

That makes more sense. However, I realized that I may want to vary the nose weight for different flights so I may use another method altogether. I saw a thread where someone used a threaded rod screwed into the NC with many nuts fastened onto it, which makes the weight both removable and easily adjustable. I will experiment with this method and post the results here. If anyone has any other ideas for removable nose weight systems I would like to hear them.

I used a cast all thread eye bolt on my DX3. Weight was adjustable and it had the eye for attaching the shock cord.

 

[BABAR]

Yeah, that’s what I was afraid of. That plastic attachment molded loop/thingie is a serious weak point if you add nose weight.

I’d consider cutting of the caudal base of the shoulder, about where that caudal step off is. The opens up the base to stick in weights of choice, glue of choice (epoxy or polyurethane, latter is messy, good idea from @Rob Campbell on sealing inside of any cross rods if you go this route.)

Still thinking a threaded rod with some washers and maybe three nuts to forward end glued in would give you a shock cord attachment point and an ability to add more weight.

Crazy idea, do it with a large screw eye BOLT (the full solid case ring? Not the bend one that isn’t contiguous at both ends.) Put Vaseline on the BOLT. Glue it in with for washers and at least three bolts.

After glue dries you maaaaay be able to unscrew the screw bolt, leaving the nuts solidly glued with supporting cross dowels or rods. You now have a secure attachment to the heavy nose weight (more important than the nose cone itself.). AND you can use it to add washers if you need more weight later.

heads up, I haven’t actually done this, but I think it would work.

 

[Art Upton]

I have never heard of needing 1 pound of nose weight in any rocket large and small I have built.

Only time I heard of nose weight was people trying to fly insane motors in Mini - Maggs

 

[MikeT]

I have never heard of needing 1 pound of nose weight in any rocket large and small I have built.

Only time I heard of nose weight was people trying to fly insane motors in Mini - Maggs

Only one I needed weight in is my 4 inch LOC V2 and it was a bunch.

 

[sharkbait]

In the past I've always done the lead-shot/epoxy followed up with expanding foam for my L1/L2 rockets and it has worked well. I was planning on doing the same with my L3 build, but I think I'm going to go with the LOC removeable nosecone weight system since the kit I'm building is one of theirs. That way I have much more control to be able to compensate for difference size motors. My initial flight for certification will be on a 75mm but it has a 98mm mount, so using the RNWS seems like the better option.

For 75 & 98’s adjustable weight systems make sense, if you’re talking 29 & 38 then just set up weight for the biggest motor and be done, the approximate loaded weight difference between a 29-2g and 6g is around 5ozs so just add the extra weight and forget about it, same goes for 38’s with a difference between 2g & 6g of about 14 ozs, unless you’re an altitude junkie or going for a record that’s the simplest. 54’s are an either way IMHO with about 2lbs difference between a 2g and a 6g motor.

 

[Donnager]

For 75 & 98’s adjustable weight systems make sense, if you’re talking 29 & 38 then just set up weight for the biggest motor and be done, the approximate loaded weight difference between a 29-2g and 6g is around 5ozs so just add the extra weight and forget about it, same goes for 38’s with a difference between 2g & 6g of about 14 ozs, unless you’re an altitude junkie or going for a record that’s the simplest. 54’s are an either way IMHO with about 2lbs difference between a 2g and a 6g motor.

This is generally the way I look at it. My stubby rockets are far from high performers. I will not shy away from putting in all the nose weight required for stability/reliability.

I have a Big Daddy that has flown an H-550, and another that does 54mm J250's. I have a 6" fiberglass Stinger that has a ridiculous amount of weight in it due to the odd combinations I had for it, and a LOC Mega Magg that has a good bit of lead as well.

I really don't understand those that brag that they didn't follow the caliber rule of thumb, but were successful (I only had 0.25 caliber but mine flew great!). This, especially for heavy rockets, is not a rule I tend to tempt.

I don't like 1.6" dia skywriters. When they get big (4" 5.5") I REALLY don't like them, and don't intend to be the cause. I tend to go for stable to overstable, generally by the book, or well developed experience, not base drag hacks or other crutches that make you NOT want to add at least a little weight. It does make the world a little less exciting, though.

 

[thzero]

This is generally the way I look at it. My stubby rockets are far from high performers. I will not shy away from putting in all the nose weight required for stability/reliability.

So what is your solution for adding weight to a nose cone?

 

[Donnager]

So what is your solution for adding weight to a nose cone?

Usually two pieces of 1/8" stainless tig wire. I drill the holes, thread a loop around the crossed wires (if I'm using a loop for retention), and pour in lead shot and either epoxy or slightly activated polyurethane glue.

The stainless wire will stick out a little. I tape over them and invert it to cure, usually in front of a blower to keep cool. Then grind the wire flush after the adhesive cures. Then back to bodywork. Be careful on how fast you grind them because they can get hot and soften epoxy/glue/plastic nose right at the edge.

 

[T-Rex]

I'm in the "BBs and epoxy" group. I always use bamboo skewers or wood dowels for cross bracing. Cheap, readily available , and easy to sand.

 

[Donnager]

I'm in the "BBs and epoxy" group. I always use bamboo skewers or wood dowels for cross bracing. Cheap, readily available , and easy to sand.

Wood dowels don't get the heat buildup when doing bodywork/smoothing/grinding. A great option, and better in some ways than wire. They definitely smooth better.

 

[rcktnut]

I use BB's that I moisten with a little bit of water. I then add polyurethane glue and rotate and shake until they are all covered and there is no rattleing. The glue foams up as it cures and is very sticky and adhered strongly. I have not had any issues with it coming loose.

+1 Never had a problem with this method. No need to add skewers, nails, etc. through the side of nosecone.

 

[sharkbait]

+1 Never had a problem with this method. No need to add skewers, nails, etc. through the side of nosecone.

There’s a lot of different ways to add weight to the NC, it kinda depends on the situation as to which technique is best, ie is it a plastic cone or fiberglass, are you going to have a tracker bay or e-bay in there, are you adding 6ozs or 20lbs ect ect

 

[techrat]

I saw someone else (this is not my idea, but I thought it was pretty slick); glue in a wooden bulkhead into the nosecone. He then cut a hole and glued in a prescription drug plastic bottle. He could then vary the inserted weight, and then seal it up with the bottle's cap. I think this was for a Big Daddy, but for your purposes, you might have to scale it up. Although I think even the biggest fishing weights might fit in the larger prescription drug bottles.

 

[techrat]

Here you go: check this genius solution.
https://www.rocketryforum.com/threads/digbaddys-big-daddy-nose-weight-mod.173177/

 

[techrat]

And FYI: When the instructions say that Epoxy won't stick to the inside of the nose cone -- use original Gorilla Glue, the one that foams up as it dries. That sticks to everything.