Looking for a light, porable material!!!

[DexterLB]

So, I'm almost ready with my ARC downscale scratch-shark. I am looking for a light material, which could be pored in a mold to make a nose cone. I've already excluced epoxy, because it's too heavy and and polystyrol because it needs to be melted and is very toxic. Do you have any suggestions?

 

[FROB]

2-part pourable foam might do it, its pretty easy to find.

Thee are also various grades and densities of casting urethane compounds, some are quite light.

 

[jderimig]

You can also try epoxy with a very large amount of microballoons (q-cells) mixed in. You can probably reduce the epoxy density to 1/4 or less in this way.

 

[MaxQ]

So, I'm almost ready with my ARC downscale scratch-shark. I am looking for a light material, which could be pored in a mold to make a nose cone. I've already excluced epoxy, because it's too heavy and and polystyrol because it needs to be melted and is very toxic. Do you have any suggestions?

How big is the nose cone?

Would you not want to glue some foam blocks together and rotate it on a lathe (or electric drill on a fixed stand) and sand the nose cone to shape.
It would be lght weight.


Gets messy with foam dust while sanding it to shape, but less steps than a making a plug and a mold ...

https://www.vatsaas.org/rtv/arsenal/bradrocs/napkin/napkinrocket.aspx

 

[DexterLB]

The nose cone is 20mm in diameter and 35mm long. That's really small - I don't know how to secure it on my drill stand!

 

[FROB]

I didn't realize it was going to be that small-
Why not just take some 1"x1" balsa, drill a 1/4" hole 3/4" down the center, glue in some 1/4 hardwood dowel, leaving 1" or so sticking out - chuck that in your drill press, and shape it with a sanding block as it spins. Start with coarse paper, when its getting close to final shape, switch to medium then fine.

 

[Peartree]

Have you thought about casting it in epoxy (mixed with microballoons) and then drilling out the center? An epoxy shell shouldn't be that heavy.

 

[DexterLB]

I didn't realize it was going to be that small-
Why not just take some 1"x1" balsa, drill a 1/4" hole 3/4" down the center, glue in some 1/4 hardwood dowel, leaving 1" or so sticking out - chuck that in your drill press, and shape it with a sanding block as it spins. Start with coarse paper, when its getting close to final shape, switch to medium then fine.

Excellent idea!! I could even make it with polystyrol using that method! Of course, balsa would be better. Wouldn't it?

Have you thought about casting it in epoxy (mixed with microballoons) and then drilling out the center? An epoxy shell shouldn't be that heavy.

Hmm that should also do it, but it will be heavier than a polystyrol or a balsa nose cone. If the first two don't work - I'll try this one.

Everyone, thanks for the replies!

 

[DexterLB]

I tried the balsa method with the drill stand, but there is one problem. when it rotates and I sand it, the sandpaper moves back and forth and at the end I get an eliptical profile. Have you got any ideas how to avoid this?

 

[FROB]

I tried the balsa method with the drill stand, but there is one problem. when it rotates and I sand it, the sandpaper moves back and forth and at the end I get an eliptical profile. Have you got any ideas how to avoid this?

Some suggestions:
Wrap the sandpaper around a large sanding block- using contact cement helps.
Next bring up the table and lock it just below/beside the balsa, and rest your sanding block on that as your sanding so it doesn't vibrate. use *very* light sanding pressure and go slow.
Most cheap drill presses use cheap spindle bearings with a lot of play, which can cause or amplify this problem. Try a different speed as well, usually the highest speed is best for this, you want the rpm to be above the natural resonance frequency of the setup to avoid oscillation.

 

[gpoehlein]

I tried the balsa method with the drill stand, but there is one problem. when it rotates and I sand it, the sandpaper moves back and forth and at the end I get an eliptical profile. Have you got any ideas how to avoid this?

According to several experts on turning balsa/foam nose cones, you're pressing too hard with your sandpaper. Try emery boards (like the wife or girlfriend uses on her nails) and just hold it lightly against the balsa. Go slow and it should be round.

 

[DexterLB]

Ok. I'll keep these two things in mind and will try again.

Thanks for the replies!

 

[Meat]

I just shaped a nose cone for my scratch sidewinder this way yeah it sound slike your pressing too hard. I started out using strips of sand paper and found I didnt have the control I wanted so switched to those sanding sponge things you find now days . they worked perfectly

 

[DexterLB]

I found out that i've run out of thick balsa, I'll go and buy some next week. Meanwhile, i made a smaller version of the cone to check. Indeed, i was pressing tooooo hard. When i did it more gently - it became a perfect cone. When i get more balsa supplies i'll make the original cone.