Help! Casting Resin Wings

[Brad Cancian]

Hi everyone - I am hoping that someone can help me with casting resin components, namely some wings.

 

I scratch built some wings a while back for a BE12a project:

 

https://forum.ww1aircraftmodels.com/index.php?topic=7721.0

 

 

These wings are fairly 'generic', and were used on other aircraft such as RE8s and some BE2s, and as such I would like to cast some copies (in case I try some more scratchbuilding or conversions). Can someone point me to how I might do so? I've experimented with resin casting some years back, but only for small components. I would be worried about warping and air bubbles for such long and thin casts.

 

Is anyone able to help?  Failing that, does someone on the forum have the expertise and generosity to cast a few copies for me?

 

Many thanks!

 

BC 

Edited June 17, 2019 by Brad Cancian

[Schwarz-Brot]

To oppose Warping it helps to cast in some rods into the mould to prevent it from twisting. Alternatively you can give it a stiff surrounding. For the wings I'd try to lay some brass or stainless steel rod in there, so the final pieces have a robust component inside. Though I Never tried this myself, I know it is a way to make cast spoke-wheels a lot more durable. So should work on any other fragile part. As a bonus you get some mounting pins, if needed.

[spruecutter96]

Would 3D printing be an option? I would suspect that you'll find more folks with a printer than folks who could cast them for you. Good luck in your search, my friend.

 

Cheers.

 

Chris. 

[Army_Air_Force]

I cast all the components on my scratch built 1/72 scale Broussard model. Here's the patterns for the wings, fin/rudder, prop and tail wheel. The wings are attached into the mould by their leading edges by thin styrene sheet on a wider runner.. 

 

 

The silicone was mixed by hand and the mixing pot then given a shake by an orbital sander to shake out air bubbles.

 

 

The wing mould can be seen in the middle of this selection filled with resin. I used a piece of thin wire to brush along the trailing edge of the wing inside the mould to remove any bubbles in the resin from sticking in the narrowest part of the casting. I also used slow set resin which gave around ten minutes of working time.



The final castings, removed from the moulds and ready to be cleaned up. The leading edges needed the runners cut free, sanding and some micro air bubbles filled. Vacuuming the resin before pouring would of course remove the micro bubbles. With practice, gentle stirring of the resin minimised the introduction of air bubbles.

 

The finished model.

[Brad Cancian]

Thanks for the responses everyone - this seems more difficult than i'd hoped... 

 

Stephen -that's some wonderful scratch building! With the wings, it looks like these were cast with a one piece mould - did you have trouble removing the originals and the cast from the silicon mould, or was it flexible enough? Did you experience any warping using this method?

 

Cheers,

 

BC 

[Army_Air_Force]

Once fully cured, a bit of a twist of the mould brings the parts out no problem. Wings are simple shapes to extract. The mould had around a 1/2 to 5/8 inch wall of rubber around the outside of the wing surface and was easily able to support itself and the wing cavity straight. I usually lay the model on a small board with short legs, so that once poured, I can get my fingers under the board and lift the whole mould and resin, undisturbed to the curing cabinet where it is left to bake.

[Brad Cancian]

Thanks Stephen! Can you explain your curing cabinet to me? It sounds like some kind of oven...?  I've seen descriptions of vacuums being used to pull air bubbles from the resin, and some description of heat application, but i'd be interested to see what you use as your castings look great.

 

Thanks again,

 

BC

[Army_Air_Force]

The cabinet is basically a wooden cupboard, lined with foam backed insulation foil. In the roof of the cabinet is a 60watt filament light bulb to create heat. Once the door is shut, it brings the temperature to around 27 degrees centigrade in about 8 to 10 minutes. I use slow set resin, and stir the pot slowly to minimise the introduction of bubbles. You could of course make a vacuum chamber to extract any air, but for limited quantities of casting, it's probably not worth it.