Create mold from existing boat

[nachoman]

Disclaimer: the existing boat is a custom build. This is not duplicating an existing design that is owned by anybody but me. No designs or property are being infringed upon. That being said...

I did find articles about 'splashing' and such on here. Is there any advice for creating a new mold from an existing boat? Primarily what I'm worried about is getting the new mold to release from the existing hull design. Save for spraying lots and lots of release agent on the existing boat, are there any other tips/tricks to doing this? I realize the mold will have to be at least 3X as thick as the parts it produces which is no problem. Just want to make sure it will release from the boat when it is completed.

Again, this is a 100% legit case where the original mold and plug were destroyed years ago, and just wanting to create a new mold from an existing setup without re-measuring, attempting to cut a new plug, and so on - but also without wrecking the final boat I have left over from it.

[CTMD]

From experience about 1 in 5 "plugs" end up at the tip. Beyond that its all in the prep work.

Good (non porous) surface finish and lots of coats of release agent.

[Wynand N]

polish with a water base polish until you have a smooth high gloss. Polish about 7 - 9 coats of ram wax (silicon free) on the hull - do not use polishing buff, but hand rubbing only. Then apply a PVA release agent with a sponge from the centreline to sheer in even spreads.
Now you can start with your tooling gelcoat and whatever follows.

The beauty with this is that should the mold in the unlikely event get stuck to the hull, it can be taken off by injecting water between the hull and mold as the PVA release is soluble with water. But do not take shortcuts when applying the ram wax coats.

good luck

[Herman]

Most release agents have one problem: Too good release properties...

Take any good release agent, which carries a sealer in its range. Sealing the (inevitable) porous surface is the major step in mold release. After sealing, use the release. Follow the instructions of the manufacturer.

I would not recommend a PVA, as you will end up polishing and buffing the mould, which can be a tedious job.

Can you turn the boat up-side-down? If so, you will save a lot of effort.

Also important: All holes and cut-outs in the boat should be filled. Do this as such, that you do not "lock" the mould around the boat. No dimples, in other words. (this is harder than it looks)

[nachoman]

Good info, thanks! Do you have a preferred brand of ram wax? The products I've used as of late were Partall high temp wax and Partall #10 film as the release agent. Any downside to spraying the #10 on in a ton of very thin coats, as I've done in the past?