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Old Nov 27, 2012, 04:09 PM
BME 102 For Sale, PM me!
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Question about vacuum forming

Hello everyone,

I've got a little design I'm working on for a multi-rotor helicopter. My heli needs a dome and I've made a plug, molded a female mold with fiberglass, and now I'm ready to pour a final plug for pulling canopies. I'd like to use Dura-Bond, a setting type spackle product that cures very hard and doesn't shrink much.

Has anyone ever tried this? THe original plug was from a mix of Dura-Bond and pink foam so it wouldn't have lasted long as a plug for pulling hot plastic.

Any suggestions for a liquid molding material would be appreciated.

Bart
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Old Nov 27, 2012, 09:18 PM
KE your cub.
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in the gutter, again....
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Please have a look at the other posts before asking a question that's currently being discussed here.

Helps keep info relevant, as there's a lot of it!
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Old Nov 28, 2012, 06:50 AM
BME 102 For Sale, PM me!
USA, NJ, Milford
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Curare,

How about if you don't know an answer you don't post anything and let someone who does know just answer the question.

Who assigned you the role of board nazi to tell people what they can and can't ask? Is it really any wonder young people don't find the hobby attractive? How many people have you turned off by telling them what they can or can't do?

If nobody knows the answer then that's not a problem, I'll find it somewhere else.
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Old Nov 28, 2012, 11:46 AM
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Barchiola,

How about if you get a response you don't find helpful, you stay quiet and wait for a better answer, instead of posting a snappy response? Being rude isn't going to help you get more results, and I very much doubt anyone is going to be able to provide more information than Curare did.

After all, he provided you with a link to a thread with lots of information on the subject, including a link to detailed, step-by-step instructions for what you're looking to do, with pictures! He might have scolded you unnecessarily, but it's hard to get much more helpful than that.
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Old Nov 28, 2012, 11:52 AM
BME 102 For Sale, PM me!
USA, NJ, Milford
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i was asking about Dura Bond as a plug material. if he couldn't answer a yes/no question then he shouldn't have typed anything. i've been on this forums site almost as long as he has yet I have one tenth the posts, i think i know how to use the search function.

he assumed i didn't do a search which was wrong to do. fwiw, i own a forums site and i NEVER tell people to not ask questions. most of the forums software search functions actually suck and result in a huge waste of time plus the "search first" mentality doesn't make for a very warm and welcoming atmosphere for new people. if turning off new people is Curare's goal then he's fine to keep doing what he's doing.

Having been building models since I was about 7 (37 years that makes it), and having already done a thorough search, i asked a question.

after i asked, I went ahead and poured a Dura Bond plug in my mold and it worked out great. it popped right out and will only need minor work to start pulling plastic. for the next person that might find this post i'll update the results after the first pieces have been molded.
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Old Nov 28, 2012, 11:54 AM
BME 102 For Sale, PM me!
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Quote:
Originally Posted by machinate View Post
How about if you get a response you don't find helpful, you stay quiet and wait for a better answer
how about if you come across a topic that you have nothing to contribute to, you stay quiet? how does that sound?
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Old Nov 28, 2012, 12:11 PM
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Quote:
Originally Posted by barchiola View Post
how about if you come across a topic that you have nothing to contribute to, you stay quiet? how does that sound?
It sounds good! In fact, that's how most of my interactions on this forum go.

I clicked on this one because I did have something to contribute. I've done vacuforming, and mostly used foam, balsa, and bondo for forms. I've never tried dura-bond, but based on your description I would have guessed it to work reasonably well as long as it was strong enough to hold its shape. But I probably would have suggested spray foam, because I know that will work and I'm not sure about dura-bond.

I elected to reply like a jerk instead of being helpful because I didn't like the way you reacted to that earlier response.
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Old Nov 28, 2012, 12:14 PM
BME 102 For Sale, PM me!
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it's interesting that you were a jerk to me but didn't think to give an opinion to the guy who gave the less than helpful response to me.

i've used foam and Dura Bond for a mold but the foam gave out too easily under the heat of the plastic.
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Old Nov 28, 2012, 12:23 PM
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I try not to get worked up about unhelpful responses, because the forum is completely full of them and sooner or later, someone will turn up with a more helpful response. I get irritated by arrogant or inflammatory posts because they're completely unnecessary and just make the forum a less pleasant place to be. I realize I'm guilty as well, but in this case it seemed like the thing to do.

Anyway, when I say foam I'm not thinking of pink foam or Styrofoam - that stuff loses structure with heat and doesn't work for more than maybe one use. After all, it's basically the same material you're forming over it. I'm thinking of spray insulating foam sealant - the aerosol cans you get at hardware stores, like Great Stuff. That stuff is polyurethane, not polystyrene. It sets rock-hard and doesn't react much to heat. The only trick is getting it to release from your mold in the first place. Depending on how tidy the mold is, that could be helped with plastic wrap or paste wax.
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Old Nov 28, 2012, 12:26 PM
BME 102 For Sale, PM me!
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ok, so the useless posts aside, the spray foam will last for how many pulls? I'm using paste wax and the green spray release stuff (can't think of the name at the moment) to prep the mold. spray foam to make the shell with Dura-Bond to fill in behind it might make a better molding surface than the Dura Bond alone.

THanks for the help.
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Old Nov 28, 2012, 01:37 PM
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I've never had to make more than two of something, so I'm really not sure how long the spray foam will last. It's more likely to die from rough handling than from any part of the forming process, so if you treat it well it should hold up for a while. If you haven't encountered the stuff before, you might be surprised - it's very similar to dried Gorilla Glue. It cures to a very hard foam with a smooth surface made of very fine bubbles, with a core of much bigger bubbles.

Be careful; a little bit goes a long way, and if you seal it into a cavity it'll just break its container.
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Old Nov 28, 2012, 08:07 PM
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I have used Hornady "One Shot" case lube as a form release agent. It works surprisingly well, and it's little pricey but takes a very small amount on dense surface. Probably not as well on something like an open cell foam, though.

Hope this helps.

Bill
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Old Nov 29, 2012, 02:33 AM
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try dry lining adhesive and washing up liquid

i form my plugs from foam pull one and then pour a mix of adhesive in to make a more stable plug


Quote:
Originally Posted by barchiola View Post
Hello everyone,

I've got a little design I'm working on for a multi-rotor helicopter. My heli needs a dome and I've made a plug, molded a female mold with fiberglass, and now I'm ready to pour a final plug for pulling canopies. I'd like to use Dura-Bond, a setting type spackle product that cures very hard and doesn't shrink much.

Has anyone ever tried this? THe original plug was from a mix of Dura-Bond and pink foam so it wouldn't have lasted long as a plug for pulling hot plastic.

Any suggestions for a liquid molding material would be appreciated.

Bart
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Last edited by dpot; Nov 29, 2012 at 02:55 AM.
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Old Nov 29, 2012, 04:01 AM
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Quote:
Originally Posted by dpot View Post
try dry lining adhesive and washing up liquid

i form my plugs from foam pull one and then pour a mix of adhesive in to make a more stable plug
That's interesting.I've been casting around
(sorry about that)for something to use to copy a canopy.
Are you using the wash liquid to get a more 'plastic' mix(an old dodge when mixing cement mortar)
Stuart
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Old Nov 29, 2012, 12:17 PM
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Foam

Quote:
Originally Posted by machinate View Post
I've never had to make more than two of something, so I'm really not sure how long the spray foam will last. It's more likely to die from rough handling than from any part of the forming process, so if you treat it well it should hold up for a while. If you haven't encountered the stuff before, you might be surprised - it's very similar to dried Gorilla Glue. It cures to a very hard foam with a smooth surface made of very fine bubbles, with a core of much bigger bubbles.

Be careful; a little bit goes a long way, and if you seal it into a cavity it'll just break its container.
There's a small kit (makes a lot of foam though) here:
http://www.rcgroups.com/forums/showthread.php?t=1779168
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