Adding nose weight to balsa cones

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neil_w

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Is the accepted want to add nose weight to balsa cones just to add washers under the shoulder? I'm gonna need upwards of 1/2 ounce (hopefully not more but who knows at this point) on my IRIS-T. How many washers is practical, and how do you secure them?

I was thinking about drilling into the shoulder and filling the hole with epoxy/lead shot, although given space limitations that would only cover part of my needed weight, so I figure I'll still need washers to go with it. Also, my first attempt at drilling into a balsa nose was a bit of a fraught experience, I'm a little nervous about it.
 
I use a drill press and hold the cone with my hand, applying light pressure feed the cone onto a brad point bit of whatever size hole I want, then after the weight is in place I use a dowel the diameter of the hole to mount my eyebolt into and plug the hole. The reason for using my hand to hold it is to prevent damage to the nose cone exterior since balsa is so soft.
 
I use a drill press and hold the cone with my hand, applying light pressure feed the cone onto a brad point bit of whatever size hole I want, then after the weight is in place I use a dowel the diameter of the hole to mount my eyebolt into and plug the hole. The reason for using my hand to hold it is to prevent damage to the nose cone exterior since balsa is so soft.

+1. I've done a few, and done different sizes of hole s really 'pack' in the shot. I then use epoxy to hold it all in (its heavy to begin with!)

I've also drilled nice big holes, and used nice big bolts glued in place..

I do like the idea of a hole & hardwood dowel for the eye screw. Nice touch. (I usually drill an appropriately sized hole, then epoxy & screw the eye in, then ensure it's embedded in the base of the cone, and add more epoxy to grab the bottom portion of the 'eye'..)
 
I usually drill by hand (place the bit in the vice and turn the cone on it) starting with a smaller size. If I have to add weight, I've often epoxied fishing weights into the hole, then plugged it with a hardwood dowel. If I don't need weight, I usually drill for the dowel anyway since they hold a thread for the eyelet much better than balsa. Don't forget that the dowel adds a little weight as well...
 
I start with a small pilot hole and step up to the size I really need. For me, that would be the a size to snugly fit a hardwood fluted dowel into. I keep 2-3 different widths of those. But I've had to be a little creative when a wider hole was necessary. A good practice to use also, is wrap some tape around the bit where you only want to drill to. I'll over drill one in a skinny minute if I didn't do that. Also, I find you can use 1/2 of one of those fluted dowels and pre drill a hole for the screw eye. Lastly, you don't have to use just bird shot. Fishing weights come in 1/4, 1/2 and whole oz sizes and you can even use some of the smaller ones that aren't a specified weight. Break out the scales baby!
 
I like the drilling technique as well. It allows the weight to be placed further into the nose, meaning you don't need quite as much as if you glue washers to the base of the cone. I have used a drill press and a Dremel tool to make space in the cone--both seemed to work fine.
 
I guess I should have mentioned that in this unusual case my nose cone is only going to be about an inch long, so I'm not sure how much room I'll really have there for storing lead *and* having room behind it for a dowel. One advantage I have is that it's OK if I drill all the way through the front of the nose, since it'll eventually be covered by... other stuff. I do like the idea of putting the drill bit in the vise and turning the cone onto it; that sounds like I should be able to control it nicely.

Today at HD, just for yuks, I bought some 3/16" x 1 1/4" washers and some relatively heavy and oversized eyelets, thinking one of them could contribute to the weight and also have larger threads that could hold in the balsa better (if I don't use a dowel). I'm gonna weight all the stuff tomorrow and see how much would really be needed. If I could get away with, say, 2 washers and the eyelet I'll probably go with that; if I need much more than 2 washers I'll try to figure out whether I can find room in the nose for some lead.

If I do go with the washers, what's a good way to attach them? I'm thinking some for of epoxy arrangement, but don't have a detailed picture yet.
 
Another option is to use stick on wheel weights, they are normally used to balance car tires and they have a very sticky backing already on them. they are 1/4oz each about 1/2"x3/4" in footprint.
 
Maybe youi could get someone to turn you a new nose cone out of a heavy piece of wood. Oak? Then drill that out if necessary and fill it with shot. Of course there's always the method of cracking. Split that cone down the center and carve out the inside. Then glue it back together and fill the void.
 
Maybe youi could get someone to turn you a new nose cone out of a heavy piece of wood.
"Someone"? ;)

Of course there's always the method of cracking. Split that cone down the center and carve out the inside. Then glue it back together and fill the void.
Now that is interesting. I would imagine that could work quite well, but suspect I'd be pretty scared of ruining the nose cone. But that is certainly an intriguing possible approach.
 
"Someone"? ;)


Now that is interesting. I would imagine that could work quite well, but suspect I'd be pretty scared of ruining the nose cone. But that is certainly an intriguing possible approach.

If it'll make you feel any better, I only did that twice before and both times they split perfect. You just have to start smart and cause the split to ride the wood grain. Maybe there's a video out there somewhere on it. Or just try it on a damaged cone in your bone yard.
 
I've "flown" an HPR RB-05A Sport Scale missile. Being you know scale missile and all it had negative stability stock. Unacceptable. Normally you don't want to make rockets heavy as f***, but in this extreme case its easier to add lead to a nosecone than it is to explain to an RSO why your sim rocket loops. Everyone cringes at the idea of adding a bunch of lead shot to a rocket, until you explain its so unstable its unsafe without it. Then they side with you adding more lead. It had a hollow cone so I roughed up the inside of the nose and rocketpoxied lead shot slushy into the nosecone. Then I put about a half inch more rocketpoxy in a solid layer over that. It fell 5400ft and didn't come undone. You may need 50-100 grams, check in or by adding a small diameter long bore "hole" as a mass itself then increment until it's stable, then drill it and fill it as I suggest so your stability cal is decent. It's honestly no big deal. The bigger deal on HPR is making sure the nosecone with a bunch of lead shot doesn't fall a freaking mile and well hurt somebody. In my case it stuck itself 8" into earth and couldn't kick it lose. Rocket was stable. It'll have more momentum when the ejection charge deploys than a normal cone and any shock cord weakness is known instantly.

Also the closer the mass is to the front of the nosecone, the less mass you'll need.
 
I've "flown" an HPR RB-05A Sport Scale missile. Being you know scale missile and all it had negative stability stock. Unacceptable. Normally you don't want to make rockets heavy as f***, but in this extreme case its easier to add lead to a nosecone than it is to explain to an RSO why your sim rocket loops. Everyone cringes at the idea of adding a bunch of lead shot to a rocket, until you explain its so unstable its unsafe without it. Then they side with you adding more lead. It had a hollow cone so I roughed up the inside of the nose and rocketpoxied lead shot slushy into the nosecone. Then I put about a half inch more rocketpoxy in a solid layer over that. It fell 5400ft and didn't come undone. You may need 50-100 grams, check in or by adding a small diameter long bore "hole" as a mass itself then increment until it's stable, then drill it and fill it as I suggest so your stability cal is decent. It's honestly no big deal. The bigger deal on HPR is making sure the nosecone with a bunch of lead shot doesn't fall a freaking mile and well hurt somebody. In my case it stuck itself 8" into earth and couldn't kick it lose. Rocket was stable. It'll have more momentum when the ejection charge deploys than a normal cone and any shock cord weakness is known instantly.

Also the closer the mass is to the front of the nosecone, the less mass you'll need.

Andrew,

What the ... does this have to do with the original poster's question? Either offer a suggestion or counter someone else's point. Keep it on topic. No need to go into detail about your personal endeavours (which seems to be about 2 or 3 rockets only at this point) about some unrelated issue..

Neil knows what he's doing, CP, CG, and all (go look at some of his other threads). We pretty much all do. We know we need to add weight, and that some require more than others. He's asking about adding weight to a balsa nose cone. Have you done this (added weight to a balsa nosecone)? Do you have something to offer? Something that differs from what we've posted, or a variant to what's been posted?




And stop swearing. There is absolutely no need for it. Every post you make seems to have a few words that start & end with a letter, but contain ***. This is a family forum. These are general discussions. Be polite & courteous. you might find you get a little more respect too..

rant off

(Sorry, hard day today.. )
 
BTW I misspoke earlier, I'll have 1.5" of nose cone, plus shoulder.

I weighed my eyelet and washers, and it looks like the eyelet is about 0.16 oz, and each washer is 0.25 oz. So 2 washers (total 0.66 oz) really ought to be enough. If it turns out be a bit *too* much then I can go a smaller second washer. The final weight and CG of the build at this point is hard to estimate because some of the construction is not modeled in OR.

Further odd thoughts...
- I wonder if burying the threads of the eyelet in a pool of epoxy, inside a (say) 1/4" hole would be stronger than actually screwing it into the balsa? Even if I back out the screw and fill the hole with glue before reinserting, I'd think a solid block of epoxy would still be stronger. That's not too much different from the Avalon, where I simply buried a loop of Kevlar in a hole full of epoxy rather than using an eyelet. Seems *very* strong. I would think this should be as good as a dowel.
- I was then thinking that if I bored out good-sized hole, maybe 3/4", then I could fill it with epoxy and shot and just shove the stem of the eyelet in there. I think though that I would be more comfortable just using the washers.
- The eyelet, if sufficiently well anchored into the nose, should be able to hold the washers just fine. I would probably still try to epoxy-secure the washers to the shoulder of the nose cone, but eyelet will be the ultimate insurance.
 
I'm talking about adding lead shot to a cone. Whatever epoxy and wood glue he wants to use is up to him. As long as shot isn't lose, mixed with epoxy, and it packs fine then its safer and he can seal it off with more epoxy for good measure is acceptable practice. These guys are all mentioning tire weights and using sticky peel off sticker like contact surfaces.
 
I'm talking about adding lead shot to a cone. Whatever epoxy and wood glue he wants to use is up to him. As long as shot isn't lose, mixed with epoxy, and it packs fine then its safer and he can seal it off with more epoxy for good measure is acceptable practice. These guys are all mentioning tire weights and using sticky peel off sticker like contact surfaces.
The tire weights and others are commonly ( by some) used alternatives to lead shot, sinkers, tungsten sinkers, tungsten powders etc.

@Neil, yes putting the eyelet directly into the epoxy would be stronger but also extremely difficult to remove if you needed to drill out some of the weight later, Qquake recently had an unplanned ubolt removal to repurpose a nosecone iirc, it was quite the ordeal iirc.
 
I'm talking about adding lead shot to a cone. Whatever epoxy and wood glue he wants to use is up to him. As long as shot isn't lose, mixed with epoxy, and it packs fine then its safer and he can seal it off with more epoxy for good measure is acceptable practice. These guys are all mentioning tire weights and using sticky peel off sticker like contact surfaces.
you realize balsa nose cones are usually a solid mass of wood, right?
 
FWIW, here is what I did or my BT-20 scratch build Exocet. A nut epoxied to the end of a balsa cone with a kevlar loop going through the middle. It weighs 9g(nearly 1/3oz). Many nice flights so far, held up very well.

 
I was actually thinking about a nut, seeing them jangling about in the bins next to the washers. Washers give better granularity/control, and can be held in place by the eyelet. A nut allow you embody the entire weight with a single piece, and there's probably a good enough selection of nuts out there to get close to the desired weight. Two good options I think.

How did you affix the Kevlar, and why does it look like you extended the shoulder with an additional piece of something?
 
I was actually thinking about a nut, seeing them jangling about in the bins next to the washers. Washers give better granularity/control, and can be held in place by the eyelet. A nut allow you embody the entire weight with a single piece, and there's probably a good enough selection of nuts out there to get close to the desired weight. Two good options I think.

How did you affix the Kevlar, and why does it look like you extended the shoulder with an additional piece of something?

One thing about the nut is it would be easy to mount with a proper sized wood dowel drilled and glued into the nose cone, the nut would cut its own threads on the wood, then the eyebolt could be screwed directly into the wood dowel like normal, then if you wanted to change the nut for another one that maybe had holes drilled on all six sides to lighten it you could.
 
One thing about the nut is it would be easy to mount with a proper sized wood dowel drilled and glued into the nose cone, the nut would cut its own threads on the wood, then the eyebolt could be screwed directly into the wood dowel like normal, then if you wanted to change the nut for another one that maybe had holes drilled on all six sides to lighten it you could.
That is a very nifty idea!
 
Is the accepted want to add nose weight to balsa cones just to add washers under the shoulder? I'm gonna need upwards of 1/2 ounce (hopefully not more but who knows at this point) on my IRIS-T. How many washers is practical, and how do you secure them?

I was thinking about drilling into the shoulder and filling the hole with epoxy/lead shot, although given space limitations that would only cover part of my needed weight, so I figure I'll still need washers to go with it. Also, my first attempt at drilling into a balsa nose was a bit of a fraught experience, I'm a little nervous about it.

Generally that's exactly what I like to do. Washers have always seemed to me to be further back which sometimes requires more weight to move the CG the same distance Less Shot & epoxy does in the drilled out Wood or plastic nose cone. It's been S.O.P. for over a decade now on all my micro models as mentioned it allows me to need a little less mass Further Forward in the Cone to move the CG to were I want and Mass is always the ememy with Micros:)

Drilling out basswood or balsa nosecones gets to be second nature after a couple. I do all sizes now T2 to BNC-70's using a dremel and Cutters & Fishtail burrs rather then drill bits. These Cutters cut in all directions as well as starting the hole. Really easy in balsa, a bit harder in basswood.
instead of a screw eye I use a kevlar loop imbedded in the epoxy/shot as the shock cord anchor.

MM 275f02_Assemble boattail MMT_06-25-03.jpg

MM 370uc04_Hollow out Transition_05-21-10.JPG
 
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How did you affix the Kevlar, and why does it look like you extended the shoulder with an additional piece of something?

I dug out a slot in the shoulder where I inserted the knotted ends of the cord, which were epoxied in place. The extra piece on the end was to help seal up where the kevlar was anchored, and also to extend the shoulder since it was a bit short when I turned it. Actually that nose cone was made from several layers of scrap balsa, glued into a block, which I cut and turned into shape using a cordless drill as a makeshift lathe.
 
The tire weights and others are commonly ( by some) used alternatives to lead shot, sinkers, tungsten sinkers, tungsten powders etc.

@Neil, yes putting the eyelet directly into the epoxy would be stronger but also extremely difficult to remove if you needed to drill out some of the weight later, Qquake recently had an unplanned ubolt removal to repurpose a nosecone iirc, it was quite the ordeal iirc.

Pinewood Derby Tungsten Putty.

https://www.pinewoodpro.com/p/020511.html
 
When drilling balsa cones or transistions. I like to wrap tape around the shoulder to prevent cracking from the bit tearing the wood. I drill by hand mostly, I use a spare drill chuck to mount the bit. Also for small cones, I knot the cord and set it in the hole with epoxy or wood glue and it holds fine. Hope this helps.
 
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