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[funtimefrankie]

I need to make six lifeboats for my Manxman. I have made one out of DAS to use as a plug.

I'm thinking of using plaster of paris for the mould and P38 pressed in to make the boats. There are no under cuts so it should come out OK.
I had thought of using RTV  for the  mould but comes a bit expensive to make just the one mould.
Using P38 I can make them hollow to keep the weight down.

The boats are about 10cm long.

Any thoughts anyone?

[DickyD]

You might find P40 a better proposition.

[funtimefrankie]

You might find P40 a better proposition.

Is that a "softer" version?

[DickyD]

Thats the version with the chopped fibre glass in it. Wont be so brittle.

[nemesis]

Hi, Plaster of Paris, unless vaccumed, is very porous. you may find that the material you are going to use to make the L/Boats will bond to the mould, giving you a lot of work. I found that PVAcetate is no good either. What you want is Plaster Coating Solution as used by Dental Technicians. Paint it on a warm mould & let it dry, when dry it forms a thin tough skin. It comes off when the mould is opened & then you can start again. It works, I have used it all my working life, so go to your local dental lab & get a wee bottleful. If you are going to use a brush to apply please make sure you wash it out after application to avoid cross contamination, or you may set off the rest of the bottle. Any problems, give me a call.
                                                     Nemesis

[funtimefrankie]

Made my six boats now.
The first mould was no good because I did not mix enough plaster and when I added more, it come out with some voids.
The second one is OK.
Using P38 the first three came out fine, no4 brought a bit of the mould with it, so the last 2 were a bit rougher, but useable.
I gave the inside a good wipe with vaseline, the P38 seamed to shrink a whisker when it set so the boats all came out easily.
The picture shows the green painted plug, the mould, which would have been better in a bit bigger box, one end was a near the edge, so chipped a bit.
The boats are first out on the left the last one on the right.
They all need some work, but feel strong and I think I could clean enough out of the inside to put detail in there, I had planned to have them sheeted up.