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Casting Nosecones From Water Bottles... Would This Work???

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K'Tesh

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I have a design I'm working on and I've found plastic water bottle that is *PERFECT* for my project (it actually inspired the design). Question is, can I use it for a NC?

Due to a mistake, I happen to have a large amount of chopped fiberglass (about 2lbs). I was thinking that I could pour some 30 minute epoxy inside the water bottle, then add the chopped FG and then rotate it until the epoxy sets up. I wouldn't put so much epoxy in it to fill it, just enough for a 1/16" or 1/18" layer (I might use multiple applications). Once it's set up completely, I can cut a slit in the side of the bottle and remove the NC. So, would this work? Or am I just dreaming?

Thanks!
 
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Donnager

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Maybe if you had a way to chuck it in a drill to spin everything heavy to the outside (bubbles to the inside)........ it might be worth a try.

I'd expect lots of hair and bubbles without a way to make them go (away), and separating the interior from the bottle might be a trick. Epoxy seems to be utterly incapable of sticking to certain things, unless you don't want it to.

Some kind of release agent may be a good idea, and you'll probably want a fan or a bowl of water to keep it cool as it cures. If it overheats the bottle, you'll probably have a mess.

Edit--If you do it, take pictures.
 
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blackjack2564

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more appropriate would be to carefully cut bottle in half,essentially making mold of each half. lay up fiberglass inside, then remove.
Depending on how stiff the bottle is u may need to support each half with something sturdy like foam.
Use glass strips along seam to put NC back together.

Just using chopped glass would be terribly brittle and would not work. Probably 2 layers of 6oz and another 2 of something much heavier. What about incorporating the shoulder?
 

Zeus-cat

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I think heat during curing is the biggest issue. I honestly don't know how hot epoxy gets as it cures, but if it is hot enough to distort the bottle it would be a problem. If it gets hot enough could you instead make a plaster impression of the bottle and then pour the epoxy into the mold. Smash the mold when the epoxy is cured and you have your nose cone.
 

PSLimo

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I've fabricated lots of nose and tail cones and never had heat issues even when fabricating over a balloon for a 5" nosecone when wetting out single layers of glass. Using large amounts of epoxy for weight in a nosecone is a different story.

nc1.JPG
nc.jpg


Phil
 

Kelly

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This is essentially how many fiberglass items (boats, e.g.) are made, in a female mold - except using glass mat or cloth instead of chopped, and putting down a gelcoat first to get a good finish. Do you have more than one bottle, for trial and error? Cloth would probably be better, if you could get it to lay flat.
 

K'Tesh

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Thanks everyone for the feedback.

Maybe if you had a way to chuck it in a drill to spin everything heavy to the outside (bubbles to the inside)........ it might be worth a try.

I'd expect lots of hair and bubbles without a way to make them go (away), and separating the interior from the bottle might be a trick. Epoxy seems to be utterly incapable of sticking to certain things, unless you don't want it to.

Some kind of release agent may be a good idea, and you'll probably want a fan or a bowl of water to keep it cool as it cures. If it overheats the bottle, you'll probably have a mess.

Edit--If you do it, take pictures.
I doubt that bubbles would be much of a problem, like Kelly mentions below, this would be much like other things that are fabricated with a FG gel coat. With the slick surface of the water bottle I don't think that the epoxy would stick to it. I was planning on rotating it, but I don't know how I'd do it where it's getting more than a single direction roll. My friend in Hollywood worked on "Enemy Mine", and said that he was able to modify a disco light fixture to rotocast the Drax skulls seen in the movie, but that would be a bit of a problem to source.

more appropriate would be to carefully cut bottle in half,essentially making mold of each half. lay up fiberglass inside, then remove.
Depending on how stiff the bottle is u may need to support each half with something sturdy like foam.
Use glass strips along seam to put NC back together.

Just using chopped glass would be terribly brittle and would not work. Probably 2 layers of 6oz and another 2 of something much heavier. What about incorporating the shoulder?
Cutting the bottle in half would be a PITA to mold the inside, it's very flimsy once cut lengthwise. However, there is the idea that it could be a gel coat that would be reinforced from the inside later with sheets of FG. Would it be really brittle? I imagine it would be kind of like OSB chip board

As to the shoulder, I was thinking that if I can get it to be about 1/16" thick, then an ordinary coupler could be inserted in it, and epoxied in place..

I think heat during curing is the biggest issue. I honestly don't know how hot epoxy gets as it cures, but if it is hot enough to distort the bottle it would be a problem. If it gets hot enough could you instead make a plaster impression of the bottle and then pour the epoxy into the mold. Smash the mold when the epoxy is cured and you have your nose cone.
I don't think that heat would be a big issue, especially if I drill a vent, build it up in thin layers, and keep things rotating while it cures. If it's a thick coating, I can see it doing that, but not with a thin skin of it. The plaster idea however... I'm liking that.


I've fabricated lots of nose and tail cones and never had heat issues even when fabricating over a balloon for a 5" nosecone when wetting out single layers of glass. Using large amounts of epoxy for weight in a nosecone is a different story.

1601340172147.png
1601340097847.png


Phil
Thats COOL!!! I like the idea of the balloon. I might be able to use it for a different project. I made a PVC pipe and brush bristle "cactus" for the local Mexican restaurant, as an advertisement. Never could figure out how to top it off though. Hmmm...


This is essentially how many fiberglass items (boats, e.g.) are made, in a female mold - except using glass mat or cloth instead of chopped, and putting down a gelcoat first to get a good finish. Do you have more than one bottle, for trial and error? Cloth would probably be better, if you could get it to lay flat.
The bottles are readily available, so trial and error is a possibility. Getting FG to lay flat would be a major PITA, as the "mold" is so thin and flimsy. But after the chopped FG and gel coat layer cures, reinforcing from the inside would be possible. Perhaps creating a reinforcing jacket of plaster would be a in order.

Again, Thanks All for the ideas.

I think I'll give it a go if I can source some local epoxy. My BSI stuff is too valuable to try with this..

All The Best!
 
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rharshberger

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Hand roto-molding is how Steve Neill (SNG Aero) made the super light nose cones for Frank Burke's 4" X-15 glider (I made the nosecone plug that Steve used). Send Steve a PM he is a master at this stuff.
 

heada

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Chopped fiber is different from milled fiber. Chopped should work but milled is too fine and won't work nearly as well. If you can't roto-mold, then a 2 part mold should be second best.
 

rokit

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I have a design I'm working on and I've found plastic water bottle that is *PERFECT* for my project (it actually inspired the design). Question is, can I use it for a NC?

Due to a mistake, I happen to have a large amount of chopped fiberglass (about 2lbs). I was thinking that I could pour some 30 minute epoxy inside the water bottle, then add the chopped FG and then rotate it until the epoxy sets up. I wouldn't put so much epoxy in it to fill it, just enough for a 1/16" or 1/18" layer (I might use multiple applications). Once it's set up completely, I can cut a slit in the side of the bottle and remove the NC. So, would this work? Or am I just dreaming?

Thanks!
Look up "DIY Rotocasting"; lots of videos on the 'tube and plenty of plans on maker-type sites.

What's the scale of the project -- model, HPR, or ?

I understand that an element of the project is to use existing materials, but . . . I'm not sure the slurry of epoxy and chopped fibers will remain consistently mixed when the mold is rotated. Depending on the scale, something like this might work better:


I tried doing a 38mm nosecone using their product, rotating the mold by hand. Regardless of what you use, if you're hand-rotating, it's hard to get a consistent material thickness if you cast in one shot. From what I read several thin layers provide more uniformity.

Looking forward to what this gets used for!

Mike
 

rokit

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(psst . . . Mike . . . it's the HPR forum)


:facepalm:

So, how about diameter/impulse level?

Mike
 

K'Tesh

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Look up "DIY Rotocasting"; lots of videos on the 'tube and plenty of plans on maker-type sites.

What's the scale of the project -- model, HPR, or ?

I understand that an element of the project is to use existing materials, but . . . I'm not sure the slurry of epoxy and chopped fibers will remain consistently mixed when the mold is rotated. Depending on the scale, something like this might work better:


I tried doing a 38mm nosecone using their product, rotating the mold by hand. Regardless of what you use, if you're hand-rotating, it's hard to get a consistent material thickness if you cast in one shot. From what I read several thin layers provide more uniformity.

Looking forward to what this gets used for!

Mike
Why do I keep forgetting to check youtube? Awesome suggestion... Here's a video with something I think lots of us will recognize... It's another use for a launch rail.


(psst . . . Mike . . . it's the HPR forum)


:facepalm:

So, how about diameter/impulse level?

Mike
The design is a 4" OD , 54mm powered rocket ~6' tall.
 

PSLimo

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I wondered how well that might work, thanks for confirming :)
Hi dhbarr,

It does work, that balloon nosecone was part of a full scale Javelin 148 build. Beautiful flight on a complex all fiberglass build, minus the balloon, lol. Take a look at the parts and first flight on a redline motor:

javelin1.JPG

javelin (2).jpg

2009_0222_121005.jpg


Very cool thinking outside the box, looking forward to seeing K'esh's build.

Phil
 

tsmith1315

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Jim, I encourage you to waste a little epoxy and a bottle to see how it responds.
Do it quick & greasy- just a dowel/centering ring and a hand drill to spin it.
 

K'Tesh

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I've been thinking about some of the responses, and one thing that I think is being confused about what I've got planned... I'm not planning on mixing the epoxy and the fg together then pouring it into the bottle. I'm thinking mix the epoxy, pour it into the bottle, give it a spin (coating the inside surfaces), then add the chopped fg, and shake/spin it to distribute it in the bottle, then after everything cures, perhaps adding more epoxy if I feel it's needed.. Another idea I have to reduce the amount of wasted epoxy is to perhaps drill a small hole in the bottom of the bottle, and insert a round balloon that I'd inflate and tie off... The balloon would prevent the epoxy from flowing far into areas that would be cut away anyway.
 
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