Fiberglass molds?

[JeffEmbracedDC]

Hey, guys.

Here are examples of a pieces I would like to recreate: http://www3.towerhobbies.com/cgi-bin...H=proline+body Made of .030 to .060 polycarbonate/lexan.

Let's say I already have the body and I just want to duplicate it. If I were to lay the inside of the body with fiberglass cloth, vacuum bag it, and remove the fiberglass shell would it be possible to use that fiberglass shell as a male mold for polycarbonate? I understand I might need to lay more layers of fiberglass inside as reinforcement - but the main question is - could fiberglass work as a mold?

If so, how difficult would it to be to get the fiberglass ultra smooth? would gel coating take care of that?

I'm trying to think of inexpensive ways to create a reliable male mold from a female piece that already exists.

Thanks! If anyone has any thoughts suggestions let me know.

-Jeff

[High Seas]

Jeff - I tried checking out the image - sorry 403 - no access rights on the server. If you post maybe I could get you better commnmts - but so far:

Yes you can use fiberglass as a mold for thermoforming. I have done it - and it works. I did need to reinforce the insides of my mold - for fear it would collapse iunder the pressure.
I use Spray Cooking oil just to make sure it would release from the plastic. I have seen that others have tried/used baby powder, felt, etc.

To get your mold really smooth - yes, gel coat will do that - but make sure it is compatible with your "master". First wax the inside of your master - several times - polish between. Make sure you miss nothing. For good measure, spray in some PVA - you can get at a marine store - smal quantity. (Or go to McMaster and get some spray wax. Use something designed for the resin - or you might pooch the resin.
Lay it all up in layers - take your time - don't rush and make to thick a layup. , when cured - pop it - and enjoy holding you new master whle sipping a cool one.
Jim

There - that is Just a start. Sure others have ideas too - or ask for more help

[JeffEmbracedDC]

Sounds great

Not sure why the link didn't work.. here's a different one: http://www3.towerhobbies.com/cgi-bin...H=proline+body

But that sounds like about what I was thinking..

When laying the glass would you let the first layer or two cure before laying in further reinforcements or would you do all if it at the same time? I suppose you would build on a flange which would help a lot.. you could also bolt the flange to your vacuum surface and cut up some wood pieces to place inside of the finished mold as even futher reinforcing..

So do you do a layer or two first and continue with more or do it all at once? Thanks

-Jeff

[High Seas]

Well, I'd proly do 2 then let them go green (not sticky to touch, not warm - your fingerprint won't mark) then do another. If you do it all at once you could risk an exotherm and melt your model if not careful!

The wood and flange are all useful additions and make the plug stronger and then pulling the follow-on work easier too.

You know you're dealing with TM'd materials and all those ramifications - right? Like-- resale, etc. (Some would say even personal use is problematic - I'm no lawyer.)

The thermoforming materials are another issue - but there is plenty of help around here too. Notably, Dr. Crash. - You might check TK560 site too for more details on the vacuum process if you haven't already.

Jim

[JeffEmbracedDC]

Well, I'd proly do 2 then let them go green (not sticky to touch, not warm - your fingerprint won't mark) then do another. If you do it all at once you could risk an exotherm and melt your model if not careful!

The wood and flange are all useful additions and make the plug stronger and then pulling the follow-on work easier too.

You know you're dealing with TM'd materials and all those ramifications - right? Like-- resale, etc. (Some would say even personal use is problematic - I'm no lawyer.)

The thermoforming materials are another issue - but there is plenty of help around here too. Notably, Dr. Crash. - You might check TK560 site too for more details on the vacuum process if you haven't already.

Jim

Sounds great. Lots of good info.

Yeah.. for selling.. a product has to be at least 10% different so I'd have to make some tweaks. My first thought is to heat up certain areas of the body and modify them by hand.. get them how I want them, cool it back down and use that to make my fiberglass mold. If that doesn't work I'm, sure I can figure something out.

I know lexan/polycarbonate is one of the most difficult plastics to form (stubbornness with bubbling, etc) but hopefully with a little help I can get it rolling.

Thanks again

-Jeff

Thanks

[High Seas]

Make your mold - then alter it -- BONDO on a car body -- LOL - who'da thunk?! Add pics of progress - I'm sure others would be interested too. Jim

[trophy]

I am very interested to hear how you get on with this project.
I would like to know what size sheet of plastic does one use for these bodies.
As for altering your mould I would use gelcoat heavily filled with talc micro fibres etc.
Use of alloy powders greatly increases the temp the polyester will handle.
Before applying heavily sand the areas with an 80grit or coarser.

[MGDriver]

Another idea to reinforce it after the fiberglass work would be to use expanding foam. Just get a can at Home Depot or somewhere similar and fill the entire backside with it. Then just cut off an extra even with the top (bottom).

[RMDMARINE]

Jeff

I have been making fiberglass molds for a lot of years, and still doing it even after I have retired.

The instructions you have been given is a good basic way of starting but with one flaw, you have to use Epoxy. I was into RC car racing back in the late 80's early 90's and was sponsored by OPS. I too made some molds for the bodies and found out that Lexan and other Polycarbonate plastics do not like Styrene, you have to use a non Styrene base resin.

There is a lot of new technology out there today in the way of pourable molding products, one company that I use a lot is WWW.FREEMANSUPPLY.COM
they sell everything from soft to hard silicone rubber and some neat Epoxy. They even have some good video on how to use their products.

Just watch that you do not modify the body and get negitive draft in your plug.

RMD