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Tuesday, December 2, 2008

Finishing for first class results

Hi There,
With Johann currently tackling his second attempt at a moldable plug I thought I would post some pictures of my method , which is by no means the only way of doing things, but works for me.
Although 2k paint sometimes sticks in the molding of the plug , this is most likely due to problems with the release agent and not the paint. B.T.W. this type of paint 2k has been very successfully used in all the team built Shongololo's of Evans building groups, and is still my favorite when spraying a plug and polishing it, or the mold surfaces of a hollow molded glider.

After the blue foam plug is nicely sanded to shape and layed up ,with in this case 3 x 163 gr cloth layers, I sand it smooth with 180grit paper, especially glass cloth join lines.
Then the whole plug is layed up with a layer of 104 or 86gram fine cloth, I add a small amount of micro balloons to this resin layup , this aids in filling pinholes. You will see that although the foam is blue the resin/balloons make it look whiteish.

The plug is now wet sanded with 220grit , the surface becomes smoother and any imperfections are filled and repaired.
The product shown left is an epoxy based finishing resin , it is a two part and seals the surface well and is easy to sand.
Its available in most good hobby shops.
I make a mix of this and add microballoons , this finishing layer is screeded onto the plug and gives a high build smooth coat , as you can see, this is then waterpapered with 480 grit wet and a few drops of dishwashing liquid in the water.
This surface seals the foam from any solvents and provides a good surface onto which you can spray.
My larger plugs were finished in a similar way
but instead of the ZAP finishing resin I finish with a 2 part polyester spray filler (but care is needed as this stuff eats the foam , if it's exposed.)
I trust this may be of help to modellers out there.
Note 2K paint contains ISOCYANATE (a Cyanide derivative) in the harderner which is bad for you, so always wear a respirator and protective clothing.
Happy building.

Monday, December 1, 2008

Thanks for all the support and guidance especially from Evan and Mike. It seems like this has turned into a bit of a process....
I have not had a chance to respond to your e-mails, but I'll get there!
Evan, we managed to get the coating that you recommended for the plug. We tried several places and between only selling the paint in 5l tins at R1600.00 we finally managed to get a litre. I hope it is the correct one! the trade name is SIGMAGUARD HS which is described as a two component high solids polyamine cured epoxy coating and comes in a green grey colour.
The curing times seem to be a bit of an issue as it is described as 20 hours min between coats and 10 days for final cure.....
That means we will only cast our moulds in January......
Vic has given up on us and has proceeded to build a fuse out of balsa. (He has the time and it's his preferred building technique anyway) It may be a blessing in disguise as we can use the prototype to iron out all the gremlins. We'll post some pictures as he progresses.

Meanwhile Daron and I can dream about our future composite plane and colour schemes whilst we wait!

Mmmmm Daron likes black and yellow....