Resin Casting

For the cost of the rubber / resin, the pressure chamber, and the learning curve that will go along with it to make the multi-part mold needed to mold the aircraft you would be better off just buying the additional kits you want.  The kits are all over ebay.  Search for the Pit-Road kit also it is a re-release of the Skywave kit.

It seems like an obvious suggestion, but have you tried eBay? That's always my "go-to" place when I'm looking for kits, parts, etc. I'm inclined to agree that casting an entire kit may well be more time, trouble, and expense than its worth in the long run.

Bronto and blacksmith make very good points. But at 1/350 ,resin copy's are very doable,that is, small enough.there is a bit of initial investment though. Bronto,what is a pressure chamber?

I've tried casting a bit, but not two part molds, only simple things like seats, wheels, prop blades.  Just remember you'll need RTV rubber for the molds, two part casting resin, and mold release agent for making the two part molds.  And lots of legos!  Legos make great bases and walls for making your molds, and you can use them to make alignment marks for two part molds.  

One technique I'd like to try is vacuum molding.  If you reduce the pressure while casting, it can lead to fewer air bubbles trapped in the castings.

A pressure chamber is an air chamber hooked to a compressor that maintains an "over-pressure" to force the resin into the tiny details of the molds while the resin cures.  It can also be used as a vacuum chamber to "de-air"  the RTV before poring it, or air bubbles in the rubber will make the mold of such small parts about unusable.

Plaster of Paris is always an alternative it works very well.  

A vacuum pump is not really necessary for resin molding.  Biggest problem is mold design.  I like to have considerable vertical extent to my molds, so I can get a little hydrostatic pressure.  Then, I use a J-shaped pour sprue, entering mold cavity from bottom.  That way the incoming resin does not fight with air trying to escape mold, but pushes air to top of cavity.  Then, vent tubes at very cavity high-spot allows air to escape unhindered.

My advice when laying out the mold is, "think like an air bubble.  If you are getting trapped in a cavity, what would you wish for to allow easy escape."

I resin cast a 1/32nd Hercules engine in one piece without a pressure /vacuum pump/worked so well the guys here had trouble telling the master and copy apart!             

They had trouble telling it apart because the picture is too blurry to see anything.  (I'm not saying the recast didn't turn out well - just that in the picture you can't tell)

Yeah the fact that they are black could be an issue,I used the macro high detail setting but they are essentially identical and the casting process was a complete success.

Dons point about venting is very useful.fortunately in rtv rubber it's very easy.I general just cut  a vee shaped goove in the rubber,usually to the top of the mold.as don said think like an bubble trying to escape a flooded mine shaft. Mike

Yes it is useful in larger molds.

Trying to cast an entire kit would be a pretty tall order, but making molds of individual parts is pretty easy. Probably not worth it unless you're planning on cranking out quite a few, though.