Hi Mike et. al.

 

There are several ways.  Release wax is pretty straight forward although  there are now wipe on mold releases that require no wiping off and the release is better for styrene based poly/vinylesters.  The stuff sometimes can be too slippery for epoxy which typically releases a lot more easily.  Anyway, you can use plaster if you don't need a lot of precision.  It is cheap and easily available.  It does shrink though so be prepared. And you must seal it before you make a part.  Another way is to build the parts in wood then use paste wax and build directly off of that.  The wood holds a lot of wax and releases easily.

 

I also would suggest using polyester and chopped strand mat, not BID fabric.  If it has large flat areas, I'd also use 18 or 24 oz woven rovings for fast build up.  TAP has it but it's expensive from them.  Our local place has it for a lot less money but I can't tell you around your area.  Also, a very simple, cheap coring that is easy to fit in complex areas that will stiffen a part up very well is called Coremat.  It comes in different thicknesses like 4mm, 6mm, 8mm and on.  It isn't very weight efficient but for splashed molds, it's a great thing.  The density is typically about 45 lbs cu. ft. which is equivilent to oak or ash.  It is very tough though so if you have a part needing to be through bolted, Coremat is very effective. 

 

Also, it is tempting to not use gelcoat against the surface and it is true that you can do it without it but it very seldom pays off.  Most of the time, the surface has a lot of pits and minor voids, so I would strongly advise using gelcoat of any kind.  It doesn't have to be tooling gel.

 

And if it is a really large panel, glassing in some stiffeners like longitudinal 2x2's or 2x4's can keep it all straight.  Be sure to make both straight and parallel so that you can flip it over and realign it if they are parallel.  Or, you can make a diagonally braced and cut plywood frame notched in the middle.

 

For really cheap stuff and for the quick and dirty, you can even take newspaper and roll sheets into a long tight roll, place it on the first laminates and then laminate a couple of layers of 1.5 oz CSM (Chopped Strand Mat) over it and it adds an amazing amount of un-elegant stiffening.  Cardboard mailing tubes also work well for straight panels.

 

Does that give you any ideas?

 

Dan Newland