Will half inch thick Silicone Caulk harden fast enough?

I've got a project to do for the kids. They want to put a Unicorn Horn on their pony for a project. I looked all over google and ebay and found that the horns that are sold are either cheap paper cones that dont even look like a spiral horn and will fall apart, or costly ones made of hard resin, wood, or plastic.
First off, we're not going to pay $50 or more for these things, and secondly, I think the hard ones can be dangerous. Their pony is about as gentle as you can find, but all it takes is one spin of his head and some kid could get jabbed by the point.
So, the thought is to make one. Styrofoam can be gotten in cone shapes, but I think it's too weak. We dont want it to break if the pony rubs it on a tree or something, and would like to keep this for future events too. That's when I came up with an idea. Take one of those paper new years eve horns, and fill it with Great Stuff foam. After it hardens, take silicone caulk and coat the outside of it with silicone, forming the spirals with the silicone. This will create a soft horn that wont hurt anyone.
The problem I see is that the silicone might just run down the cone and not retain the spirals. Also, I wonder how long it will take for half inch thick (in spots), to harden? The plan is to use white silicone, because I know it cant be painted.
The thought did occur to put it on in thinner layers too.
Originally the thought was to make the whole thing out of Great Stuff foam, but the way that stuff runs and expands, and makes a terrible mess, I decided that was not a good idea.
Ideally, making it out of pourable latex, using a mold would be the best way, but there dont seem to be molds for this, and I have no idea where to buy the latex. Another thought was to wrap twine to form the thing, and dip it in the latex, but I'm back to finding where to buy the latex.
I think the cheapest way would be the Great Stuff foam and silicone. Under $10 for materials.
By the way, in case you're wondering how this gets attached to the pony, it will get screwed onto the pony's leather bridle. I'll probably need to stick a small piece of wood shoved into the foam at the base to hold the screw.
Thanks in advance for all suggestions & ideas.
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On Feb 23, 4:12 am, snipped-for-privacy@myplace.com wrote:

That should work for you! It shouldn't run (if its base is flat, "D" shaped to cone) and should be completely dry in a day or two at that half inch thickness.
Good Luck!
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Rather than silicone, wrap some 1/2" backer rod around the cone. Hot glue the rod to the cone.
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On Feb 23, 2:12 am, snipped-for-privacy@myplace.com wrote:

I would build on Sonny's idea.
Make your own cardboard cone out of a plastic wrap or aluminum foil cardboard tube or a wrapping paper tube.
You can from just about whatever length and angle you want. Fill with foam and embed a wooden disc (hole saw leavings) with a dowel glued into it.
Wrap the exterior with either 1/2", 3/8" or 1/4" backer rod or drip irrigation weep tubing. Secure rod to cone with pins or brads.
Use paintable caulk to seal rod to cone. Let caulk dry and prime the whole thing with a water based primer.
Paint as desired.
As cool as the silicone culk spiral sounds....... it will be very difficult to execute, an exercise in frustration. :(
good luck
cheers Bob
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On 2/23/2012 4:12 AM, snipped-for-privacy@myplace.com wrote:

No matter what you use for the horn remind the kids not to play "Leap Frog" with the pony once the horn is mounted. :-)
Don
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On Feb 23, 4:12 am, snipped-for-privacy@myplace.com wrote:

Go to SmoothOn.com and view their products for casting things. Good company, been in business for decades. They even schedule classes for molding all manner of things. Should you decide to fabricate something, polystyrene foam is easy to whittle, and can be wrapped in fiberglass cloth coated with epoxy. The result is light and rugged, commonly used in prototype shops everywhere. Caution: don't substitute polyester resins for epoxy. They will dissolve the polystyrene foam quickly.
Joe
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On 2/23/2012 5:12 AM, snipped-for-privacy@myplace.com wrote:

Newsprint and wallpaper paste make great papier mache....crumple up paper (for bulk) or use cardboard cone for basic shape. Mix up paste, dip strips of newsprint into paste and apply to form. You can form the spirals with twisted strips of newsprint dipped in paste and wound around form. Do it in steps and dry in oven between steps. Can incorporate a tie or whatever fasteners (loops to fasten to bridle?) you plan to use. Paint, throw on some glitter or whatever. Would be very lightweight but strong enough to bump or drop a time or two.
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