Iain Posted March 10, 2018 Author Share Posted March 10, 2018 Firstly - apologies for delayed update - had a bad case of Flu in Feb - absolutely wiped out... Have made further progress on cockpit and engine - pics tomorrow hopefully - but this afternoon I finally had time/space to make the moulds to copy a couple of the kit transparencies so that I can cast copies in resin and make new masters for the central tunnel - and rear canopy. I thought some folks here might be interested in how I go about this - so... Back to childhood - Lego and Plasticene The parts I want to copy from the Tamiya kit - have left the mould seam on the top of the canopy - this will help me align the two resin castings I'll bond together to make the extended rear-canopy master: Lego 'well' - with 80 thou styrene base cut to fit tightly inside: Kit parts with Plasticene inner plugs: And ready to drop in the well: Plasticene 'sausage' that will form a seal for the base: And in place: Placed in situ - with plastic baking spatula use to press down in place evenly: Next - rubber! Iain Whitey, LSP_Kevin, Greg W and 2 others 5 Link to comment Share on other sites More sharing options...
Iain Posted March 10, 2018 Author Share Posted March 10, 2018 Using RTV silicone rubber - rubber to catalyst ratio 100:1.5 Cheap digital cooking scales I bought from Aldi a couple of years back - sensitive enough for this work: Rubber and catalyst mixed thoroughly - and ready to be de-gassed. It's amazing how much air gets into the rubber when mixing - if we don't remove we may end up with voids in the mould. Vacuum pump at left - vacuum pot at right - clear top worth it's weight in, well, clear acrylic! With a vacuum applied - the rubber mix expands like a mad thing as the gas expands. I usually need to cycle several times to remove as much air as possible: With the rubber mix poured into the moulding well - it's time for another few vacuum cycles. After pour: And, with vacuum applied: And the degassed rubber - ready to solidify overnight: Hopefully more of an update tomorrow - thanks for looking in! Iain LSP_Kevin, MikeC, KiwiZac and 7 others 10 Link to comment Share on other sites More sharing options...
alaninaustria Posted March 10, 2018 Share Posted March 10, 2018 Hi Iain, glad you are back on the mend mate! This looks really neat - will you be using this to cast male plugs for vac canopies? Cheers Alan Link to comment Share on other sites More sharing options...
Iain Posted March 10, 2018 Author Share Posted March 10, 2018 Hi Iain, glad you are back on the mend mate! This looks really neat - will you be using this to cast male plugs for vac canopies? Cheers Alan Yes - resin copies that will then form basis of pattern for vacuum forming in UV Stabilised PETG on my machine. One thing causing concern is properly capturing the 'blown' effect on the rear canopy - we'll see. BTW - this is 4 inches longer on the real aeroplane than the front section - so obtaining a spare kit canopy wouldn't have helped. Blue skies! Iain LSP_Kevin 1 Link to comment Share on other sites More sharing options...
Trak-Tor Posted March 10, 2018 Share Posted March 10, 2018 Great report! Should be useful sooner or later over here. Glad to see you back in form. Thanks, Iain! Juraj Link to comment Share on other sites More sharing options...
themongoose Posted March 11, 2018 Share Posted March 11, 2018 Super informative! I'll have to try this method out next. Link to comment Share on other sites More sharing options...
Iain Posted March 11, 2018 Author Share Posted March 11, 2018 Thanks guys - never quite sure what's of interest, and what isn't! Iain Harold 1 Link to comment Share on other sites More sharing options...
Kagemusha Posted March 11, 2018 Share Posted March 11, 2018 Very interesting for sure, nice work on the plasticine sausage especially. Link to comment Share on other sites More sharing options...
dennismcc Posted March 11, 2018 Share Posted March 11, 2018 Modelling magic at it's best, I was surprised by the amount of air trapped in the mix, I wouldn't have thought that there would be so much. Cheers Dennis Link to comment Share on other sites More sharing options...
Iain Posted March 11, 2018 Author Share Posted March 11, 2018 First time I degassed a cup of mixed RTV Rubber I was absolutely shocked - the air bubbles just kept coming! From previous experience of having more complex moulds end up with bubbles in the final moulds (engines for my Constellation project) I de-gas every time now. Iain alaninaustria 1 Link to comment Share on other sites More sharing options...
Iain Posted March 11, 2018 Author Share Posted March 11, 2018 Mould unpacked and all good - ready to cast next. Iain KiwiZac and alaninaustria 2 Link to comment Share on other sites More sharing options...
dsahling1 Posted March 11, 2018 Share Posted March 11, 2018 To each their own (and this is most impressive), but Tamiya does sell replacement sprues... :-) Can't wait to see how this turns out Link to comment Share on other sites More sharing options...
Iain Posted March 11, 2018 Author Share Posted March 11, 2018 See earlier in thread - the rear canopy is longer than standard - and the connecting tunnel between the 'pits is new - so spare Tamiya clear parts would be absolutely useless. New clear mouldings are a necessity, not a nicety As soon as I've cast copies of the Tamiya parts and started making new patterns from them, you'll see why I'm going this route... Iain Harold and KiwiZac 2 Link to comment Share on other sites More sharing options...
alaninaustria Posted March 11, 2018 Share Posted March 11, 2018 Really interesting to see this all come together Iain! Cheers Alan Link to comment Share on other sites More sharing options...
Tony C Posted March 11, 2018 Share Posted March 11, 2018 Vacuum pump at left - vacuum pot at right - clear top worth it's weight in, well, clear acrylic! Iain Quick question Iain, is the clear acrylic cover simply resting on the vacuum pot? I'd have thought that the cover would not have enough weight to provide a seal! Link to comment Share on other sites More sharing options...
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