I have got some ideas for some small body modifications but I need to find a way to make a mold of the existing area that I am going to try and fill or change. Do anyone have any ideas of how to make a mold of an area of a car? What process do I need to do to make sure I do not damage (paint, plastic dis-coloration or such) of the panels I need the mold of?
Thanks
Ray

I have got some ideas for some small body modifications but I need to find a way to make a mold of the existing area that I am going to try and fill or change. Do anyone have any ideas of how to make a mold of an area of a car? What process do I need to do to make sure I do not damage (paint, plastic dis-coloration or such) of the panels I need the mold of?
Thanks
Ray

How big of an area?

One area (most likely the biggest) is 4 ft x 2 ft x 1 ft
Some of the others would probably no bigger then a headlight.

If you can find the old episodes somewhere they made some fiberglass molds for some fender flares on a couple of episodes of Musclecar.

Don

I used to own /run a fiberglass moulding company/factory...
The finish on the product that comes out of the mould depends on the preparation that goes into the plug the object you want to reproduce...right down to a finger print!
1st remove any silicones
Then source a mould release polish...these are 100% wax
Start polishing...about 5 coats, allow 4 to 5 hrs between coats Dont let anyone touch the surface without a clean polishing rag.
This stage you have 2 options which you do depends on your craftmanship above
It also determines the finish surface of the mould and amount of prep on the mould before pulling your 1st unit.
1/ you proceed with clear gel coat stage (below)
2/ use a cellelose based mould release agent, this is sprayed on with a fine paint spray gun and let dry

The 1st coat of clear moulding gelcoat canbe brushed on about a 15 to 18/1000" thickness...allow to set.
Next a black or dark brown gelcoat...clear with pigment ...this uses a very fine layer of chopstrand fiberglass it is like tissue paper.

NO air bubbles when laying up
If you have cnrs where the glass will not lay down...soak some rovings (this is the 'string fiberglass that goes thru a commerical choper gun which automatically mixes resin/hardner and feed the roving thru knife blades chopping them up and sprays everything onto the surface for rolling out...)
Allow to set.
Now comes the heavy layers of chopstrand/resin...the ratio by weight is 1:2
Lay each layer and allow to set..if you lay more than 1 layer you will generate yoo much heat and can distort the mould.
2 to 5 layers..Thickness between 3/8 and 1/2" this depends on how many units you want to pull off the mould.
Now the mould needs to be reinforced to keep its shape later on.
One can use manythings for this wood with top edges rounded off, rolled up paper (the strength is in the shape of the 'glass that goes over it) steel pipe between 1/2" x 1/2 " to 1" x 1"
These are 'glued' to the mould in place with good old fashioned body filler
Start laying more glass over the reenforcing strips and the whole of the surface ..about 2 to 4 layers again.

Allow to set for 24 hrs.
Trim the edges
Depending on the size and shape of the unit depend on how much effort needs to separate the mould from the plug
Smaller units only generally require a compressed air gun run between the edges of the mould and plug, going around many times..the compressed air forced in between thenm causes the separation.....If a bigger mould wacking with a rubber mallet around edges and over the surface while using the compressed air will pop it off
Bigger mould often require drilling 1 or a couple of small holes thru the mould in critical areas but not into the plug...then using the air gun to force air in.
General practice so as not to touch the plug when drilling the plug has a couple little bits of...think you guys call it kiddies modelling clay ..stuck to the surface of the plug before the 1st coat of gelcoat.
These holes can be left to pop the units out of the mould later...but are filled with modelling clay before putting on gelcoat.

Trick of the trade notes:
Any places where say emblens ot bolt holes need to be drilled into the final units and be marked on the plug with ting lumps of modeling clay...these tiny indentations will be transfered to the final unit
keep renforcing about 1" from edges
Before laying up coats....use 60 or 40 grit sand paper to knock off and stray stands sticking up and high spots that will stop the next layer laying down smooth with no bubbles underneath.
If anything the edges should be layed up around edges a little thicker on each coat..just a bit more 'generous' in this area.
Do not lay up gelcoats or layers on a cold day or if the unit is cold.

If cellelose mould release was used, the mould now needs to be sanded smooth using 1200 wet and dry and finished with 1600 grit.
Before laying up the 1st unit the mould needs 4 to 5 layers of polish, same as prepping the plug...and again if not confident in your craftmanship cellelose release.
After pulling 3 or 4 units the mould will just need 1 polish between units for about 5 units, then another 4 to 5 again....
This also depends on time between rolling over units , dust, storage conditions etc

Trimming units in the mould...there is a piont in the curing when triming is done with a sturdy knife...too early and you will de laminate the edges, too late triming will have to be done when cured with a mechanical hand hacksaw blade.

It all sounds complex and lot of time...it is not
most of the time is between stages.
NEVER... NEVER take a short cut.

Steps, will the multiple layers of wax and mold release protect the paint from reacting with the resin?

alan

Yes...
We used to take moulds off Mac and Foden trucks, even did a full tilt front of a '56 chev.
We had to make a full dash for a bus company and they wanted a vynl finsih, so covered the dash in vynyl.....morris mini speedo dashes...thu most was industial stuff..air con and machinery covers etc.
And when we made plugs up out of old bits of wood, filler bog, the surface was single pot undercoat, sanded very smooth and polished....that stuff would peel off if you breathed hard on it

But do not let anyone anything touch the plug after the last polish...the oil of a finger print can cause what we called a stick up....
Same goes after polishing a mould...the unit sticks inside

Like I said NEVER take a shortcut, play exactly by the 'rules' and everythin goes like clockwork...easy....do a short cut and IT WILL not might..bite you in the butt.