The British X Craft WWII Submarine

[Subculture]

For hull tooling I prefer to stick with glass matt/cloth and resin.

A thick heavy tool like this will not give at all. In some instances that can be an advantage, but a hull can very easily wind up with the odd unintentional undercut, e.g. a patch of filler that has sunk a little, and it isn't always obvious to the mark one eyeball.
A conventionally laid-up tool will flex enough to release without lock-in, whereas with a thick tool, you will almost certainly knacker the master in releasing it, and risk damaging the tool too.

In a nutshell, make sure your master is spot on before pouring that sand/resin mix!

Andy

[Kazzer]

For hull tooling I prefer to stick with glass matt/cloth and resin.

A thick heavy tool like this will not give at all. In some instances that can be an advantage, but a hull can very easily wind up with the odd unintentional undercut, e.g. a patch of filler that has sunk a little, and it isn't always obvious to the mark one eyeball.
A conventionally laid-up tool will flex enough to release without lock-in, whereas with a thick tool, you will almost certainly knacker the master in releasing it, and risk damaging the tool too.

In a nutshell, make sure your master is spot on before pouring that sand/resin mix!

Andy

I've been making molds for many years and advising customers on the like, and you're right to make the comments regarding overhangs and undercuts. The way the M1 was made, these are taken care of. On my T Class plug, I've cut off the aft torpedo tubes, and intend to glue them onto the model as part of a fittings kit.

I am going to make the final molds in 4 sections, quartering each one, but initially, I want to make sure I get one good half section, as there are no more parts to mold from. (Thanks to UPS for losing them - idiots!)

[Kazzer]

I just looked at my mold and decided to open it up!

It was still warm from the exotherm, and the MDF board just fell away from the resin.




And then - the scary part - I tried to get my precious master from the mold - it fell out! The brown strip in the middle is the hardboard keel.



I have a bubble - it's on the top edge on the right - see above. I can live with that as it's an easy mold repair.

Other than that -MISSION ACCOMPLISHED!

Below, you can see the wood and foam I placed within the GRP hull. This enabled me to screw it down to the MDF.




Yep! I reckon that's a winner!

[Kazzer]

I poured another X Craft dive plane today, and even though I had PVA sprayed the mold, I was having difficulty in removing the product from the mold. It had barely cured up and was a little flexible, but I could not get it out of the solid sand/epoxy mold. This is the disadvantage of these cheaper molds.

However, the light bulb came on, and I decided to put the entire setup into a pot of boiling water for 10 minutes. Hopefully, it would cure out the resin, and at the same time, make it very pliable and easier to remove. I was right, and the dive plane fell out of the mold.

So, I think we have a new process here.
It goes like this -

1. Make a mold using sand/epoxy.
2. 2 coats Mold wax and polish with cloth
3. Spray 2 coats of PVA
4. Pour epoxy into mold
5. Shake the mold vigorously to remove bubbles
6. Allow to set for 5-6 hours
7. Boil the mold in water for ten minutes.




Below, I'm making a mold for the rudder from the shattered parts of the rudder (thanks UPS)
I used black epoxy to make the mold, and unfortunately used the same color for the rudder, so I messed with the photo to get a better view of the part.

Note the clay placed to provide vents and pouring holes.




And while I was messed up with resin, a little more urethane foam on my hands wouldn't hurt!

Here's the M1 model. I'm making a mold for the starboard side now. I placed the dummy keel onto the original mold, to get it lined up so they match. Then I taped the dummy keel to the model hull and transferred to an MDF board.



After lining it up to match registration marks from the other mold, I pumped a load of Great Stuff Foam under the hull and whacked a 20lb bag of lead shot on top. Hopefully, the model will now be glued tight to the MDF - we'll see tomorrow!

[Subculture]

I've had good results using hairspray in place of PVA. Comes in a convenient aerosol, and a tin lasts quite a while, and it doesn't separate like PVA has a tendency to. You do end up with rather fragrant smelling castings though!

[greenman407]

Really good stuff there Mike. Heres a picture that I found of a bloke running one of these things. Didnt know if you had it.