Fibreglass tip.

[The Pastor]

When making a fiberglass mold of a fairing, use more than 1 layer of glad wrap.

Glad wrap works ok but it will destroy your paint job. like it disovles the paint somehow.

Don't ask me how i know :(

but now ive got a good mold to make a new one :D

[imdying]

Depending on if you're making a working splash mould (i.e. a thin mould just used to take a plug from), or a mould you want to make an essentially finished part from (i.e. a quality finish), there's a few ways to approach it.

If you want to take a splash mould from a part you really don't want to damage, you can cover it in aluminum tape, and wax that.

For a good mould, then wax it and maybe some PVA, although there are other semi perm release agents you can use.

Glad wrap (Yanks call it Visqueen) will die from most resins.

[Pedrostt500]

Depending on if you're making a working splash mould (i.e. a thin mould just used to take a plug from), or a mould you want to make an essentially finished part from (i.e. a quality finish), there's a few ways to approach it.

If you want to take a splash mould from a part you really don't want to damage, you can cover it in aluminum tape, and wax that.

For a good mould, then wax it and maybe some PVA, although there are other semi perm release agents you can use.

Glad wrap (Yanks call it Visqueen) will die from most resins.

The PVA is polyvinyl Alcohol not PVA glue.
I learned this.

[imdying]

Hahahahah yep :yes:

I learned something new too... a foam brush is a great way to apply it if you can't spray it :)

[The Pastor]

I found the glad wrap to stay intact - the mold relased fairly easily just messed the paint up underneeth.

[imdying]

The paint underneath needs to be reisistant to the exothermic (http://en.wikipedia.org/wiki/Exothermic) reaction that exists when the resin or gel coat cures. I've had trouble with this myself, spray can paints won't handle it, but some of the spray can primers do.

This (http://www.duratec1.com/dp04.html) product comes highly recommended by the composite guys in the states, it's a polyester surfacing primer specifically designed for surfacing plus. A 2 pack paint will also resist, but it's an entirely unfriendly product for home use.

The Duratec products are distributed in New Zealand by Adhesive Technologies (adhesivetechnologies.co.nz) and is also obtainable from Nuplex, which is nice given they have pretty much everything you'll need for composites work. Flatheadfred is a member on here, he's also works for Nuplex as a technical support person.

I'll get some of the Duratec Surfacing Primer this week or next, see if it's as good as suggested, and report back, if it interests you.

As far as existing top coats go regarding survivability (when taking a mould from them), it appears to be hit and miss. I would be interested in hearing from composite professionals, as to whether there are techniques that can be applied to ensure the finish on existing parts (with unknown top coats) can be maintained unblemished.

In my experience, the aluminum foil tape will do this for you, but it introduces another couple of steps (taking the splash mould and making another plug from that), and every step increases the potential for shape changes (altering of lines, dimensions, and makes it easy to accidentaly sand out details.

[arj127]

Neatly put brown packing tape over the part you want to release off, then wax that a few times. Paint will only be damaged if it was a poor paint job to start with then.

[CookMySock]

Epoxy is lot less severe on existing paint/plastic than polyester is.

Steve