How to make a 2 part mould?

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#1

Hi everyone.

Due to the shape of a part im trying to make, the mould will need to be 2 pieces. Im using gel coat backed up with layers of fibreglass for the mould.

I was wondering what is the best way to accomplish the 2 parts?
Should i make 1 half first and the other half after? If so how do i make it so that both parts are exactly the correct size to meet in the middle? How to i make a point to build up the finishing edge for the first half?

Or do I make both parts at the same time, but use something to keep them separate?

All help greatly appreciated!

#2

Send me your email and I will send photos.

#3

Here is a thread that I did on a different site. It covers how to make a two piece mold by using a curved parting board. There is a fair bit of reading but all the info is there. You can jump to post #22 to get to the parting board and such. Feel free to ask questions here.

After previewing it there are clearly some things missing… I’ll try to put together a tutorial.

Two Piece Mold

#4

Here’s a visual from a mold I did a while back. Obviously there are some layup pics missing but hopefully this should present the idea. I’m going to be pulling a part next week. I’ll get some pics.

#5

Followup pics

#6

Simple cheap way… Figure out where your parting line goes and build up a flange there with clay and sheet metal/mdf/fiberglass sheets. You will make one mould at a time so make sure the side you are going to make the first mould on has a clean edge with the clay/flange area. On your flange you will want to build up some locating pins so both moulds align once it’s completed. Next you can apply mould release to the same side and start building your mould. Once your first mould is cured pull the flanging off and cover the other side and the flange on your new first mould with release agent. Now you can lay up your second mould and the recesses that are on your first mould will now form the locating pins on the second. After this mould is cured you can demould/trim.

Ok so as I hit the preview button I see Finitetech posted some great pics of the process I was trying to describe.

#7

here is my thread about this on another board
http://www.homebuiltairplanes.com/forums/member-project-logs/7553-molds-making-thread.html#post85426

#8

As Rotorage stated…!

Side Note: Some parts like the tail piece pictured are self locating due to the nature of the shapes so locating pins weren’t needed.