Nose Weight

[jetra2]

Hi all,

For this crazy cluster rocket that I'm planning to build, Rsim v5 says it's going to need about 6 ounces of nose weight. I did a calculation using BB's and epoxy as the weight, and it says I'd need 512 BB's. I don't know if my calculations are wrong, but I wanted to know if someone could propose alternatives to this - I don't know if I have 512 BB's... !!!

Thanks,
Jason

 

[jetra2]

By the way, here's a Rsim picture of the rocket I'm planning!!!

Mwa-ha-ha-ha-ha! :kill:

Jason

 

[DPatell]

Bahhhh, go 29mm

Looks and sounds crazy...

you should still go 29mm

 

[rstaff3]

29mm is the only way to go on a Fatboy Unless you are REALLY crazy and go for 38 or 54mm of course.

Oh back to the question. Lead shot is the only way to go for this kind of nose weight.

Only my opinions of course.

 

[teflonrocketry1]

What static margin are you using for a stable flight on the Fat Boy? You sould read the article by Robert Galjes at:

https://www.cmass.org/member/Robert.Galejs/sentinel39-galejs.pdf

You will find you need less than the one caliber of stability RockSim wants for stable flight. I am working on this problem trying to make the RockSim program give accurate simulations for cases like this.

Bruce S. Levison, NAR #69055

 

[powderburner]

If your project has not yet progressed beyond paper, you should take a look at moving the motor mounts forward. Even just a half inch of forward shift would help reduce the ballast.

I agree with rstaff3's idea to use lead. On a short rocket like the FB this really can make a difference. The lower density of the steel BBs means greater volume, which effectively moves the centroid of your ballast aft. Lead is higher density, and you can get the same weight into a smaller volume, which will install at a location farther forward, which will reduce the amount of ballast required. Did you follow all that?

 

[Marxi]

Hi !

(I opened a Thread at: https://www.raketenmodellbau.org/showthread.php?threadid=2958 - ok, it`s in German language, but the pics may help.. )

When building my FatBoy (for 29mm Motors) I had the same problems. SpaceCad said identical things about the stability of the FatBoy and the necessary noseweight.

Because of this fact, I "hollowed" the Nosecone to:
1. Get more room for the parachute (, the 29mm motor tube is 6" long to allow the G80T for example)
2. To have a little space above a selfmade bulkhead, where to do the Noseweight.

A pic:

 

[Marxi]

I then flew it at ALRS 4 (Switzerland) on a AT F20-7W with around 0,5/0,7 caliber of stability, which really sufficed. All worked GREAT *lol*

When flying your FatBoy on this cluster, make sure, you have at least 0,5 caliber of stability and I would really use a flashpan for ignition.
Then it can only work just fine.

Marxi

Oh, you want a launch pic ?

 

[Austin]

**** is right on with the lead shot. It is much heavier than copper or steel BB's . Unfortunately, I don't know if you can buy small quantities of it; my last purchase was a 25lb sack. But you could use sinkers found at department stores in the fishing dept...they are sold in small quantities.

Carl

 

[rstaff3]

Carl's idea of using sinkers is a good one and will most likely work just as well for this and other apps. I've hade the need, however, to fill small skinny spaces with a relatively large amount of weight. Here, small lead shot is the most efficient. One thing about a 25 lb bag...you will have a lifetime supply (at least most of us will). I actually had a devil of a time finding it locally. And I think the range that I bought it at has closed after it was found they were polluting the neighboring forest areas.

For a 29mm upgrade you gotta cut the end off the cone. I put in ballast, epoxy, and a wooden plug to hold an eye-bolt.

 

[wwattles]

If you were epoxying in the shot for the nose, why not just hang the eye hook with the screw threads in the epoxy while it's still wet, and eliminate the wood plug? You could probably suspend it with something simple like a paperclip to keep it from sinking into the wet epoxy/shot slurry... Would it work?

WW

 

[rstaff3]

Actually I mixed my examples, sorry. I didn't use lead shot in the Fat Boy. Actually, I don't even remember what I used, but I know it was built long before I got the shot.

I'd have to dry-fit the shot to answer your question. Kinda depends on how deep the slurry is. It may be ok with only some of the threads in the slurry, but I'd like an attached nut to be buried. I might change my story once I eyeballed the process.

 

[sandman]

Another source of lead is a tire shop.

You will have to melt it into more usable shapes but a cheap propane torch and an old coffee can works fine for that.

Careful...it's hot!

sandman

 

[rstaff3]

But wouldn't the molten lead burn thru a plastic nose cone

 

[powderburner]

If you pour molten lead into a plastic nose cone, yes, it will melt the nose cone.
So you pour it into something else to mold the lead into a form you can use.
Router a 1/4 inch deep & wide track into a piece of 2x4 and pour lead into that to make a lead 'rope' or choose a similar shape.
After the lead cools, push the pieces into the nose cone and epoxy.

 

[Neil]

Just go to W-mart, but a 1,500 pack of BBs for 2 bucks and be done with it! I may have to buy another Fatboy soon.... And some 29MM motor tubing... Or 38... THAT would be cool... Probly 29, though. Lets see.... How much does a fatboy cost....

 

[rstaff3]

Originally posted by powderburner
If you pour molten lead into a plastic nose cone, yes, it will melt the nose cone.
So you pour it into something else to mold the lead into a form you can use.
Router a 1/4 inch deep & wide track into a piece of 2x4 and pour lead into that to make a lead 'rope' or choose a similar shape.
After the lead cools, push the pieces into the nose cone and epoxy.

I thought the 'stick out the tongue smiley' would have avoided the need to say duh.

 

[rstaff3]

Originally posted by Neil
Just go to W-mart, but a 1,500 pack of BBs for 2 bucks and be done with it! I may have to buy another Fatboy soon.... And some 29MM motor tubing... Or 38... THAT would be cool... Probly 29, though. Lets see.... How much does a fatboy cost....

Small sized shot is still heavier and is more efficient. Especially in those tight spaces (a FB cone isn't exactly in that category). But then I have literally used rocks for nose weight And an occasional fishing weight.

 

[Rocketmaniac]

Originally posted by powderburner
If you pour molten lead into a plastic nose cone, yes, it will melt the nose cone.
So you pour it into something else to mold the lead into a form you can use.
Router a 1/4 inch deep & wide track into a piece of 2x4 and pour lead into that to make a lead 'rope' or choose a similar shape.
After the lead cools, push the pieces into the nose cone and epoxy.

What is melting temp of lead? Would a small propane torch be enough heat to melt it?

 

[Neil]

What if you stuck the cone in ice water while you were pouring it in? Besides, how much does the shape of the tip of the cone matter, anyway?

 

[rstaff3]

Hehehe, might come up with an interesting shape. Someone should try it and report back. You could always figure some way to rework the cone should the experiemnt fail

 

[Austin]

Rocket...yea, a small tourch is enough to melt lead. It would be most beneficial if you had a "melting pot" for it, as used in reloading.

 

[Austin]

Neil,

Using ice in a sink is a good way to keep plastic nosecones cool while epoxy cures, but for most plastic nosecones, lead is just way too hot. Unless you litterally dripped it in, it would melt the nosecone. The only way that works is when adding melted lead to a fiberglass nosecone and it also needs to be on ice or it will catch fire, weaken/burn.

You can experiment by coating the inside of the nosecone with a layer or two of epoxy, thn drip the lead in...since the nosecone would be eopxy lined, that may, and I say may, prevent it from distorting.

Carl

 

[Neil]

Well then, just use the BBs

 

[rstaff3]

Or the lead shot But if you have a BB gun then BBs serve a dual purpose

 

[Neil]

Yeah, but now that I am a big fan of pellets, I dont have much use for my BBs anymore, besides for my little gun (that shoots 285FPS), I only use em for noseweight! I dont wanna wreck the rifling on my 650FPS big gun... So I have about 10 thousand BBs for noseweight...

 

[powderburner]

Originally posted by rstaff3
I thought the 'stick out the tongue smiley' would have avoided the need to say duh.

Sorry about that, rstaff3, I just couldn't pass that one up. I will try to behave better now.

 

[rstaff3]

No problemo powder, just didn't want anyone to think I really thought pouring molten lead in a cone wouldn't melt it

Your idea for pouring the molten lead into a form was a good one for them who want to recyle tire weights and the like.

 

[sandman]

Melted lead into a nose cone!

Router a hole in a chunk of wood!

Guys, guys!! Try this.

Get a good sized slab of modeling clay...push the nose cone down into it.

Pour your lead into the depression in the clay.

Glue that into the inside tip of the nose cone with epoxy. The shape should be pretty close.

sandman