1/48 P-38F-15-LO – Mediterranean Theatre of Operations

[Crimea_River]

Thanks guys.I left the mold over night and came home to check on it at lunch. Still not fully set! I've now stuck it directly under a lightbulb to keep it warm and hopefully I'll be able to strip it tonight.

Terry, along with busting my wallet for the silicone, I also bought some modeling clay as a potential take 3. the drawback with that method is that I'll only be able to cast the half nacelle as the air scoop fairings on both sides prevent one from removing the model part without deforming the mold.

I think I'll try that method as well tonight and see how that comes out, covering all the bases so to speak.

 

[Airframes]

Ah, of course. If there are 'sticky out bits', then it's virtually impossible to remove the master (in this case the kit part) without ruining the mould.
However, it can be done with 'Plasticine' by moulding two halves. It's been a while, but I've done this successfully when moulding wheels, and items such as drop tanks, using existing kit parts as masters.
For the wheels, for example, I made 'Plasticine' moulds of both sides of the wheel/tyre combination, cast the parts, and then joined the two halves after moulding.
Not ideal, but sometimes the only way to get around a complex shape problem.

 

[Wayne Little]

Interesting series of events while i have been off a couple of days...hope it works out Andy...

 

[Crimea_River]

Pics later but I can report that the material had finally cured with the help of the lightbulb. Obviously very temperature sensitive. The problem now is that the mold has receded below the edge of the nacelle so that if I poured the resin as is, the casting would be too squat. I'll need to build up the sides a bit.

 

[Crimea_River]

So to expand on what I said above, I learned that, despite the very viscous nature of the new mold material I used here, the stuff actually managed to become more flowable to the extent that it actually oozed through the seams of the Lego bricks which I thought would be tight enough to prevent this from happening. This, combined with the fact that some of the mold material also flowed over the nacelle wall into the inside surface (the material was removed for the pic below) caused the level of the mold compound to drop below the edge of the nacelle, which would be a problem for the piece I want to cast.

The nice thing about the material I used earlier was that it set so quickly that it had no chance to flow anywhere and I didn't need to be as worried about it flowing all over the place. The bad thing, of course, was that it shrank too much when it dried. In hindsight, I should have glued some fences to the inside of the nacelle to allow the mold compound to be poured deeper. In any event, I had to deal with what I now had and I decided to build up the level with the clay I bought:

Here is the mold with the model removed. There's no sign of shrinkage this time though there are some bubbles that formed along the bottom so I expect my casting will have warts all over it that will need to be sanded off.

For added insurance, I thought that I'd also cast a second piece, using Terry's suggested use of clay. For this method, I had to settle on making just the half nacelle because the air scoop would be destroyed when I peeled the model out of the soft material.

After I took the above picture, I had to start over as the clay was sticking so hard that there was no way of removing the mold without severely deforming it. I reset it and decided to leave it for while to cool down, thinking that this would help. It didn't. So I started again and this time coated the model with some lubricating oil. This time, I was able to remove the model.

So now we have the resin mixed and added to both forms and we now wait again for a couple of days to see what's up.

If this doesn't work, there will need to be a plan D!

 

[Wayne Little]

Good luck!

 

[fubar57]

Andy, if that doesn't work, I have a ceiling dangler that got womped by a yoga mat just recently(no, not mine). I can remove the entire nacelle back to the wing.

Geo

 

[Wurger]

 

[JKim]

I hope plan C works! Looking forward to the next installment in As The Resin Cures!

 

[Airframes]

Looking good so far Andy.
Don't know what type of clay you're using, but with kid's 'Plasticine', as opposed to real modelling or sculpting clay, all that's needed to prevent the part sticking to the 'plastic' clay is to wet it before pressing into the 'clay', or, just press it in, ease the clay free just a touch, then press the clay gently back into place.
I once tried rubbing the part with a light oil, but this just caused the colouring, or maybe the 'Plasticine' itself, to dissolve very slightly around the edges, softening the clay, causing it to move slightly off the surfaces of the part pressed into it.
When the cast resin part is removed, sometimes the 'clay' will either stick to the part anyway, or deform as the part is pulled free. This might ruin the 'mould', but the cast part should be fine, and the 'clay' can be used again anyway.

 

[Crimea_River]

Thanks Terry. Checked on the casts and they are hardening nicely so another day or so should see how they turned out.

Geo, very generous of but I'm fairly certain that I can make one of these casts work.

 

[Airframes]

Looking forward to seeing it Andy.

 

[Catch22]

Yeah, me too!

 

[Crimea_River]

SUCCESS!

The full piece is the one that I'll use as it has stripped from the form beautifully. A number of minor pock marks in the surface exist, caused by air bubbles that were trapped in the mold liquid but these will be easily filled in. The air scoops are fully formed, the panel lines and rivets showed up nicely, and there is no sign of shrinkage. A trial fit with the lower cowl shows that it should do fine.

The casting is still a bit pliable so I will let it fully cure for a few days before laying the putty on and shaping it.

 

[Catch22]

Great to see Andy!

 

[fubar57]

Well done Andy

Geo

 

[Airframes]

Excellent ! Now set up a production line for 'CR Resins' !

 

[Crimea_River]

Yeah. After costs and time spent, I'd probably end up making about 0.4 cents and hour.

 

[Airframes]

Nah, with practice and bulk purchase of materials, it's be at least 0.6 Cents per hour - given you worked a 60 hour week !

 

[Crimea_River]

0.3 after tax.....

As I now have a path forward, I'll see if I can get this model done in the next two weeks. I've decided to mostly OOB this one and today, I painted the cockpit, put it together, and added some harnesses made of tape and lead wire. The canopy will be closed so I'm not worried about what will be seen, though I do want to add some wiring to the radio equipment.