Nose weights?

[Mushtang]

I'm building my first scratch rocket and have a hollow plastic nosecone from Estes that I'm using. The bottom of the nosecone has a small hole in it but otherwise it's not open.

In a previous kit I had a similar nose cone and some clay was provided for me to roll up, stuff into the hole, and using a dowel press the clay into the front of the nose. That worked well and I thought of doing the same here.

Instead of clay I went to use Play-Doh (I didn't have any clay but my 6 year old son has more Play-Doh than he'll ever need) but it didn't stick to the front of the cone. I had a devil of a time getting it back out of that little hole.

What is the best way to add weight to this type of nosecone? Should I head to Hobby Lobby after work today and pick up some clay and expect that to work?

[Rex R]

#4 or #6 lead shot mixed with epoxy works...(sigh) I know, where to find. for my jayhawk I used pelletgun ammo & epoxy. note epoxy runs about 1.1 g/cm^3. depending on how much weight you need...you might be able to get by with just epoxy .
rex

[fyrwrxz]

BB's work just fine too! A word of caution about using epoxy. On the thin shell nosecones in LPR you may want to use a cold bath (ice cubes in a bowl) and keep the tip submerged as it heats up and cures out. This keeps the nose cone from deforming. This may be overkill for a small amount of epoxy, but safer than sorry.

[kjohnson]

Plasticine modeling clay is what you're looking for.

If you want something denser, head to Cabella's or Bass Pro shops for some shot gun pellets, these can be encased in epoxy like Rex mentions.

kj

[Mushtang]

Plasticine modeling clay is what you're looking for.

Perfect! Thanks!!

[MarkII]

Add weight if the rocket needs it to enhance stability. Otherwise, why make more work for the motor?

If I am reading the original post correctly, the author seems to be saying that since the nose cone is hollow and plastic, it therefore needs to be weighted. In fact, though, the one factor has nothing at all to do with the other. The previous rocket needed to have clay packed into its nose cone because the rocket's overall design required it in order to give it sufficient stability in flight. The fact that the nose cone consisted of hollow molded plastic was entirely coincidental. If the design of the rocket that he is building now is stable without extra nose weight (unless it is very oddly shaped or can only use tiny fins due to scale modeling constraints, it should be), then he doesn't need to do anything to the nose cone. Packing the nose cone in this situation will simply increase the amount of mass that the rocket's motor has to lift without adding any improvement. If this is a scratch design, then the author should design more stability into the rocket rather than resort to using a weighted nose cone to get it to fly straight. Properly designed rockets rarely need to have weight added to the nose. You can fly a rocket with nothing for a nose cone but a piece of card stock rolled into a conical shape if the rocket's design is otherwise stable. (In fact, you can fly a properly designed rocket successfully with no nose cone at all.) The author needs to first check the stability of his design with the plain, unweighted nose cone. Adding nose cone weight is normally a last resort. It is only done when there is absolutely no other option.

[fyrwrxz]

See, Mark? That's why we missed you. Everybody 'solved the problem' but didn't eliminate it. I jumped on the trolley thinking the nose weight was a given factor Mushtang had already resigned himself to. Shoulda read 'scratchbuild' as 'untested design'. "Unfettered by logic" my a$$....

[Mushtang]

Add weight if the rocket needs it to enhance stability. Otherwise, why make more work for the motor?

If I am reading the original post correctly, the author seems to be saying that since the nose cone is hollow and plastic, it therefore needs to be weighted. In fact, though, the one factor has nothing at all to do with the other. The previous rocket needed to have clay packed into its nose cone because the rocket's overall design required it in order to give it sufficient stability in flight. The fact that the nose cone consisted of hollow molded plastic was entirely coincidental. If the design of the rocket that he is building now is stable without extra nose weight (unless it is very oddly shaped or can only use tiny fins due to scale modeling constraints, it should be), then he doesn't need to do anything to the nose cone. Packing the nose cone in this situation will simply increase the amount of mass that the rocket's motor has to lift without adding any improvement. If this is a scratch design, then the author should design more stability into the rocket rather than resort to using a weighted nose cone to get it to fly straight. Properly designed rockets rarely need to have weight added to the nose. You can fly a rocket with nothing for a nose cone but a piece of card stock rolled into a conical shape if the rocket's design is otherwise stable. (In fact, you can fly a properly designed rocket successfully with no nose cone at all.) The author needs to first check the stability of his design with the plain, unweighted nose cone. Adding nose cone weight is normally a last resort. It is only done when there is absolutely no other option.

I didn't state in the OP that I've decided that the rocket will likely need nose weight to be stable. I haven't done a computer simulation to know for sure, nor have I swing tested it. I balanced it on my finger and the CG is slightly forward of the fins and the need to add weight is totally a guess on my part. This rocket isn't going to be a super high flyer so if the weight wasn't necessary I don't think I'd care. I'd rather have it and not need it, than to need it and not have it and watch my rocket spiral crazily after launch.

But starting there, if someone IS going to add weight, and they have a hollow plastic nosecone....

[GaryT]

Another trick I've done is drill small holes around the NC tip as high up at the epoxy/weight will be, Then cover those holes with tape, Once you pour in your mixture the epoxy will fill the holes acting as barbs to keep it secured!

When you pull off the tape the epoxy will be nice and flush with the outside of the NC.

[qquake2k]

I usually drill through and use bamboo skewers to hold the resin in place.

http://www.rocketryforum.com/showthr...t=32926&page=2

[GaryT]

I usually drill through and use bamboo skewers to hold the resin in place.

http://www.rocketryforum.com/showthr...t=32926&page=2

Yes that can also be done but your not really gaining anything and its a hell of allot more work to make them flush, Its still only going to be holding on by the thickness of the NC wall.

[qquake2k]

Yes that can also be done but your not really gaining anything and its a hell of allot more work to make them flush, Its still only going to be holding on by the thickness of the NC wall.

I would definitely use skewers or dowels through if you're adding a lot of nose weight. In my case, I added 5 ounces. For an ounce or less, you could probably get away with just drilling holes and taping them. I do know from experience that you need some mechanical means of holding the resin in place. It won't stick to the plastic. I've even tried epoxy putty, and that didn't even stick.

[GaryT]

Like I said though its still only holding by the same depth whether it be wood or epoxy, I've held in 3lbs on a plastic NC with multiple flights on K's and L's with no Issue, But to each his own.

However I do recommend you douche the inside of the NC with acetone before adding the epoxy.

[LW Bercini]

...However I do recommend you douche the inside of the NC with acetone before adding the epoxy.

Hang on a sec. That may be a fine practice for a large, thick plastic nose cone destined for an HPR bird, but if the OP is about a thinner, lighter LPR nose cone (especially a QCR nose), acetone may be the recipe for problems.

[GaryT]

Hang on a sec. That may be a fine practice for a large, thick plastic nose cone destined for an HPR bird, but if the OP is about a thinner, lighter LPR nose cone (especially a QCR nose), acetone may be the recipe for problems.

It'll be fine, Just a quick rinse is all thats needed.

[Mushtang]

The one I'm using is the one pictured here:
https://www.discountrocketry.com/nos...one-p-638.html

I stopped by my local hobby shop today and picked up some modeling clay. I'll put some of that in and let it dry. If I drop it onto the table and it doesn't pop lose I'm sure I'll be fine. Otherwise I'll drip a little CA in there and see if that makes it stick. It's only going to fly on a C engine - nothing too powerful.

[MarkII]

I didn't state in the OP that I've decided that the rocket will likely need nose weight to be stable. I haven't done a computer simulation to know for sure, nor have I swing tested it. I balanced it on my finger and the CG is slightly forward of the fins and the need to add weight is totally a guess on my part. This rocket isn't going to be a super high flyer so if the weight wasn't necessary I don't think I'd care. I'd rather have it and not need it, than to need it and not have it and watch my rocket spiral crazily after launch.

But starting there, if someone IS going to add weight, and they have a hollow plastic nosecone....

Sorry, Mushtang, but your first post didn't provide that important context. You can probably see how someone could draw the wrong conclusion if all they had to go on was what you said in post #1. I am relieved to see that you are a bit ahead of that initial impression. Adding nose weight isn't a matter of guesswork or simply a "best practice" though. You need to determine if your rocket will actually need it rather than relying on a vague impression or a guess. It isn't a choice between "having it and not needing it" versus "not having it and needing it." You need to calculate the actual stability margin of your rocket and then, if it must be increased, you should be able to examine the pros and cons of various methods of making the rocket more stable, rather than simply adding mass to the nose cone in the blind hope that it will work. There are various ways to make a rocket more stable, starting with tweaks in the design. Understanding matters like this is what makes one a skilled rocket designer.

[qquake2k]

The one I'm using is the one pictured here:
https://www.discountrocketry.com/nos...one-p-638.html

I stopped by my local hobby shop today and picked up some modeling clay. I'll put some of that in and let it dry. If I drop it onto the table and it doesn't pop lose I'm sure I'll be fine. Otherwise I'll drip a little CA in there and see if that makes it stick. It's only going to fly on a C engine - nothing too powerful.

I've done the clay in the nose cone for certain kits that required it, but in smaller ogive nose cones, not a large elliptical. That's the same nose cone I used on my Blood Sucker that required nose weight. I did the acetone rinse on the inside, and used epoxy putty. It did come loose. I ended up filling the nose cone with canned expanding foam. That held it in place.

http://www.rocketryforum.com/showpos...1&postcount=69

[Mushtang]

Sorry, Mushtang, but your first post didn't provide that important context. You can probably see how someone could draw the wrong conclusion if all they had to go on was what you said in post #1. I am relieved to see that you are a bit ahead of that initial impression. Adding nose weight isn't a matter of guesswork or simply a "best practice" though. You need to determine if your rocket will actually need it rather than relying on a vague impression or a guess. It isn't a choice between "having it and not needing it" versus "not having it and needing it." You need to calculate the actual stability margin of your rocket and then, if it must be increased, you should be able to examine the pros and cons of various methods of making the rocket more stable, rather than simply adding mass to the nose cone in the blind hope that it will work. There are various ways to make a rocket more stable, starting with tweaks in the design. Understanding matters like this is what makes one a skilled rocket designer.

Thanks for your help! These forums are great, and I've learned a lot from them, but still have a long ways to go.

I've loaded Open Rocket onto my laptop at home but haven't input anything into it yet. I'm just getting started in this hobby and have built about a dozen kits but this is my first scratch build. So I have zero experience determining CG or CP - and the rocket I've built is probably not something easy to model in a simulation program anyway.

After I fly it once and see how well it does I'll post a thread about it.