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

[O_Pablo]

Hi Brad,
I'm afraid that without a vacuum pump it will not work. I think you can use even the simplest ones, used for vacuum packaging in the kitchen, like this https://www.amazon.com/s?k=kitchen+vacuum+pump&ref=nb_sb_noss_1 . Below is a link to the photo album of the owner of the Small Stuff company to show how he prepared the Coudron wing for the casting.
https://www.flickr.com/photos/smallstuffmodels/albums/72157635905401753
In Poland my friend cooperates with the owner of Melius Manu in  resin casting, but I'm afraid that distance between Poland and Australia would make such a cooperation  senseless.
Regards
Paul

[pepperman42]

This has caught my interest. I looked at the the build link but wasn't quite clear on where the vac pump comes in. After pouring the resin in the silicon mould does it go in one of the bags/vac pump combos?

Steve

[O_Pablo]

Of course, I gave the general link to kitchen vacuum pumps, I tried with the positive result of using rigid food storage containers with a vacuum valve, e.g. something like that:
https://www.amazon.com/TINVOO-Handheld-Cordless-included-Patented/dp/B07DDL4FBX/ref=sr_1_8?keywords=kitchen+vacuum+pump&qid=1560782933&s=gateway&sr=8-8
or that:
https://www.amazon.com/Containers-Airtight-Storage-Freshness-Proof-Set/dp/B07MW57NVS/ref=sr_1_25?keywords=kitchen+vacuum+pump&qid=1560782933&s=gateway&sr=8-25
The operation is simple - after flooding the core with silicone, place it in a container and suck air through the pump. A similar action applies to casting. After filling the silicone mold with the resin, place it in the vacuo box and suck air.
The examples of professional casting can be found on youtobe - https://www.youtube.com/watch?v=TRpc4jQdpXA from 1:40 Preparing & casting.

Regards
Paul

[krow113]

 Vacuum ( negative pressure) is used 2 ways in casting.

 One after the mixing of the silicone mould material. Air bubbles are vacuumed out of the mixture prior to pouring and after pouring as well. If a pump is not available , gentle agitation will help air bubbles to rise up and out of the silicone.

So now your mould is ready for resin. Mix the resin and vacuum that mixture if possible. Pour the resin and vacuum that as well.

 Here are some pics of a chamber made from a pressure cooker:




 This is a little fancy with the digital pressure guage but it works great. You can see the lexan viewing window bolted and epoxied on , and a DeVilbiss petcock on the top. The petcock introduces vacuum at a controllable rate, and after vacuum can be used to re-pressurize the mould with the introduction of atmosphere back into the chamber , forcing the resin into the details of the mould.

Qualifying pics of metal props , rims and hubs cast in metal and resin successfully:





 There is a LOT to the work. Mould box's must be sturdy and rigid , there must be at least 1/2" of silicone around the master to be cast , dont cheap out! This will really apply to a long thin wing casting attempt.
Mix all ingredients thouroughly!!! As per instructions. Use water to guage the amount of resin needed , fill the mould with it and add 30% to be sure.
Purchase the longest curing resin to start and work from that.
You WILL fail and fail miserably if you do not apply rigid standards to your attempt. Cutting corners is simply not possible.
I researched until I was satisfied that I could complete the procedure  tooling up followed along with some practise casting.
I have a pile of useless moulds , and crappy castings , so get ready for some material waste.
The amount of pre-planning you do will help to allieviate this.
 
 Its impossible to detail the entire procedure here, youtube and ither modellers can help.
Good luck!