You really know how to encourage people NOT to answer your question! You should remember, you get the best response if you ask for advice not demand it!

Anyway here goes.

I havent done this on a large scale, but have done lots of smaller moulds & experiments so here is my take on what has been said.

Protection - Whatever you do, be it epoxy or paper mache you have to protect the surface from whatever you place ontop of it. In the case of a normal mould this is usually a wax finish that the mould will not stick to. It is rubbed onto the surface & buffed to a shine so that the panel pulled from the mould has a good finish and the surface is not rough i.e. the resin or whatever will not stick to it.
You can also use a water soluable release agent which you brush onto the surface. This initially has a solvent based solution which evaporates quickly to leave a dry skin over the mould kind of like you have stretched a really thin layer of cling film over the whole surface. Once you have layed up your mould (dont worry I will come to this later) this skin layer can be dissolved using water to seperate the panel and mould. You do need to be aware that this release agent has a SOLVENT in it when you first apply it so if it is applied to certain plastics it can damage the surface (but I have used it on paint no probs).
All the other methods i.e. cling film, masking tape etc are all variations on protecting the surface that people have found work well and in the case of masking tape - works quickly efficiently and with little mess.

Split lines
If you just lay up directly onto your prepared and protected surface you will end up not being able to remove the covering you have just applied. You need to VERY carefully work out exactly where your joint lines should be so that the outer skin will not get stuck. This can be very tricky & once you have moulded you will never split off a mould with returns without damaging it. The best way to look at it is that the original manufacturer had to pull the panel from a press or mould so if they could pull it out then so can you. The thing to be wary of is that if the panel is moulded originally they are likely to have already removed the moulding lines so you have to guess where the joints were. Also if you have bridged a gap using masking tape then you will need to look at this area carefully to make sure you havent created a trap.

Lay up
You then need to lay up onto this surface. Start with gel coat then the matting. The grade of matting and amount depends on the size/shape of your mould. There are loads of books and articles about this including info on how to strengthen the mould and how much matting what timings to use etc. You need to learn this bit so do some research. Its the same for any type of fibreglass mould so there is loads of info out there.

Once you have made your joints, layed up your covering & let it go off, you split it form the original very carefully & if you are very lucky you have a mould ready for cleaning up & making your panels from.

Epoxy resin is the more expensive resin. It doesnt dissolve foam & is usually considered the better quality resin. It is used for thin fibreglass panels usually with cloth rather than matting.
Polyester resin is much cheaper. It dissolves foam and is usually used with all grades of matting.

The other option you have if you are not experianced with moulding and do not have much time with the car to be moulded is laser scanning.

This does sound an expensive method, but if you can spare the initial outlay it can be worth it & pay for itself. The scanners do not touch the surface of the car so you dont have the worry at all. Any half decent scan company will be insured anyway so it takes the worry away from you. They will usually come to you to scan or if you want to save a bit you can take the car to them. The scan of the whole car can take less than a day so you could simply hire the car. The files they produce can be used to later run a cnc multi axis milling machine that can cut you a mould out directly into a resin block ready for you to take moulds from directly.

Once you get to this stage you can sell a couple of sets of outer skin rough panels for people to work with and put onto whatever car/tube chassis they wish & if you were wise with the choice of supercar you can easily recoup the costs of the scanning/milling process & have a set of panels to work with yourself.

If the supercar being moulded wasnt mine I would use the scanning method since the cost of repairs and respray would be way more than scanning. If the supercar was mine then I would take my time and carefully mould it a panel at a time with it stripped down as far as possible.

Hope this helped, thats my ten minutes worth, please correct me if anything i said above is innacurate ...........Any more questions Goyal??    

The files they produce can be used to later run a cnc multi axis milling machine that can cut you a mould out directly into a resin block ready for you to take moulds from directly.
It is a common misconception that a scan produces code for a cnc machine but that is not the case. It produces some sort of point cloud that then has to be imported into a modeling program and made into a model. Then that model is imported into a cam software that produces the code for the cnc machine. There are cnc machines that can probe a surface and create code from those points, but trust me, the cost for that service would be huge considering that most of the points will only be .002-.005" apart and the complete surface has to be probed. Even at .025" there would be 1600 points per sq in.

Thank you for the detailed explanation Drew....That's exactly what me and others were looking for...Don't you feel better about it now?  Don't you feel that you actually contributed something good to this community today?

I didn't mean to sound "demanding" but you know sometimes you have to tell people what is needed and why it's needed...Someone asked a vailid question about molding and what's the best way to do it...Now why does it have to take 3 pages worth of one liners before someone like you, who's done this process a zillion times, can come up with a simple explanation for the rest of us....I like to educate myself when I read this forum, not feel like trying to solve a puzzle! 

Sorry if my brain works in a simplistic way and sometimes I have trouble visualizing what others are trying to say...I need to see photos of what's been done and that's the way I learn quickly - I'm a visual person....One-liner like "use epoxy resin to mold" is not a good explanation to me simply because it does not explain anything; it's just a statement.

So if my way of asking for a good explanantion seems "demanding", then so be it!   That's the way I do things...No apologies from me at this time just a BIG thank you for your time and effort!

Vasilis K.

BTW, Laser scanning seems like a great option for someone for has the money to spare for doing CNC molding of foam....But we're all trying to make el-cheapo molds of panels so this option is nice to know for me but out of my price range....

That should have been stated more nicely.  You are sounding like no one contributes anything useful to this board.  That's absolutely wrong!  Drew355... great explanation.

Just a heads up... Next time, just say you don't know how to mold anything and would like some details on how it's done.  You may find a lot more help.  Kindness is appreciated here. 

If you are going to try to do some molding, please keep us up to date on how it goes.

drew355

I hope you didn't think I was slamming you...not the case at all. It's just that there is a lot of misunderstanding out there about the ease of doing a project like this. Just for an example, I know a company that digitized a rifle stock, made the model and generated the gcode for the cnc machine. $8,000....and that was 10 years ago. I called them last year about doing something similar and the price had gone up to $10,000+ and he would not give me a firm price.  Now after doing a lot of research I have found prices much better than that, but that is the only example I could give. The stock was 30" long, 7" deep and a max of 2.25" wide. Mulitpling that out to something the size of a car would be outrageous.

You are correct too that a lazer scan would be much less espensive that a probe scan.

Mike

I am now sure I'll never let my buddy borrow my Enzo again.

Yeah no problem!
I put some pics of a damaged 406 that I have been looking at as a donor in an album on your site last night.

You may be able to help me with something too, I will PM you.