During the NFL playoffs I clean house and watch/listen to westerns.(Wife has been gone a month and comes home tomorrow, I am shampooiing carpets right now.)
I use BB's, lead shot from reloading shotgun shells, or fishing sinkers(# 7 or 7 1/2 shot).Put how ever many you need to get the ballast and some epoxy is how I do it. In balsa nose cones on smaller stuff, I drill a hole in the apex, fill it with lead, epoxy, then body putty and resand to shape.

I have also been known to take a piece of galvanized pipe and use it for a mold, melt lead and pour it in, if it is a big piece. Of course if you could find some tungsten beads, you could use them. You cannot melt them but as a wad, they take up less space than lead because tungsten is more dense than lead, about the same as gold, but less than uranium.

Thanx Bear. I'm thinking this is the easiest approach, even if it doesn't readily allow one to dial in the weight at the launch - one can just set for worst case (largest) motor.

The large fins of the Jumanji should work in your favor, pulling the CP back. Have you done any sims to determine what kind of margin you're looking at? Just throw in a wide range of motors (light, heavy, long, and short) to see if you really need as much weight as you think. Sometimes a long motor in a short bird works in your favor!

I've only seen a few pix of the Jumanji, and never seen one fly. Post a pic of your bird. We'd love to see it.

-Ken

As I recall Adrian Adamson purchased a few hundred grams of tungsten powder via ebay for very little money. My weighted nose cones have used the smalled fishing bb-shot or lead shotgun ammo mixed into a paste with 5-30 minute epoxy.

I typically use lead shot, mixed with epoxy. This gets a lot of weight right near the tip, so the CG is affected more efficiently than with a less-dense weight.

I like to do this in pretty small batches of a couple ounces at a time. Otherwise, a large quantity of epoxy could get really hot in the nose tip and damage the cone. Once I have all the weight installed, I foam the cone so that the weight can't break loose and move rearward under abrupt acceleration or movement.

You can get tungsten powder from Amazon, but it's not all that cheap. People use it for weighting golf clubs. It's about $15 for 1/2 lb if I recall correctly. It's a pretty easy way to shave 1/2" off of the length of a 29mm record attempt bird compared to lead shot, but I wouldn't use it for larger than 38mm or 54mm or if I weren't going for all-out performance. Using some tungsten powder mixed with lead shot could be good if you want to maximize the density at a lower cost, because there are a bunch of spaces between the spheres of the lead shot that would get filled in.

Lead shot mixed with epoxy in the nose cone is the most common way. If you have space, then BBs are also an inexpensive solution (plus they are easy to find at any Walmart or sporting goods store).

Mark makes a good point about the heat from large batches of epoxy deforming a plastic nosecone. One thing you can do to prevent this is to keep the tip of the nosecone immersed in a bucket of water during the cure. He is also right on when it comes to foam-fill to keep the weight from coming loose. It is difficult to keep the weight in place after a few flights.

Scrap up the inside of the plastic cones as much as possible to improve adhesion.

You could just buy a piece of lead and turn it in the shape of a nosecone 🙂

Edward

Lead is so sticky on the tooling. My one experiment with it chattered like crazy and I gave it up.

Mold it into the shape of your nose cone? Make a male model, make the female in plaster. Fill the new mold with lead, break the plaster off, unless you want to save it. You could even make the male out of wax, which will act as your releasing agent also, and then use the lost wax method of molding metal. Done in industry all the time for investment castings. Possible, and relatively practical, but a solid lead nose cone sounds like a oversize bullet and could come with it's own set of hazards. I do not think I would recommend it.

Which hits harder - a pound of lead or a pound of steel?

Edward

If you include the kinetic energy once up to velocity, the lead will hit harder. Velocity and weight being the same, should be about the same, but we know the lead is more dense, so the energy stored will be greater, at least that is what I recall of my physics and kinetic energy vehicles.

If a pound of lead and steel are going the same speed, the energy is the same. The lead will just take up a smaller volume. I guess you could stay potential energy density is higher.

Edward