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Old May 05, 2014, 03:10 AM
Registered User
Australia, QLD, Flinders View
Joined Feb 2008
121 Posts
Question
Vac bagging a fuselage

Is it possible to Vacuum Bag a Blue Foam Fuselage core?
How would I do this?
I have vacuumed a prototype wing. My First attempted. Now I need a Fuse, I have looked at the lost foam technique. Too much messing around for my likings but it is an option; a mould would be the way to go if I had one.

Any help Is Good help

Cheers
Jason
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Old May 05, 2014, 09:35 PM
Registered User
Joined Dec 2012
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I have done a few pods with just a bag, no mylar. If you are looking for a quick robust fuse or pod that doesnt have to be a beauty queen then go for it. Leave the foam in if you dont have to worry about weight and itll be solid as a tank. I just made sure my wing saddle area didnt have any wrinkles and just did my best pulling the rest of them out as the bag sucked down.
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Old May 06, 2014, 12:13 PM
Little Red Plane
United States, TN, Knoxville
Joined Dec 2012
496 Posts
I've made several fuses using PVA bags. The process is the same as they use to make a prosthetic leg.
Google prosthetic PVA bags and you will find a ton of information on the process.
It is a much different technique than what most plane builders use, but it works quite well for single fuses and the lost foam technique.
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Old May 06, 2014, 12:51 PM
Red Merle ALES
Curtis Suter's Avatar
United States, Mt, Helena
Joined Apr 2002
5,314 Posts
You can make nice fuselages as you describe. The inside will be smooth and shiny but not so much on the outside. All that means is a little more filling and sanding then prime and paint and you can't tell the difference. For one off models it is much simpler than making a female mold as required in making a hundred.

Here is one that I recently did using a piece of wood as the male mold. I cut it off the mold, reseamed it, used lightweight sparkling compound to fill the weave, sanded, primed, sanded and painted.

Best of luck.

Curtis
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Old May 06, 2014, 03:58 PM
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Australia, QLD, Flinders View
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Cheers guys for the info. Would wrapping it in peelply help?
I have also thought of doing an infusion might be easier?
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Last edited by jason riddell; May 06, 2014 at 04:09 PM.
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Old May 06, 2014, 10:22 PM
Entropy is happening!
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Bellingen NSW Australia
Joined Aug 2008
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Jason,
If you want to mould a fuse, I suggest start with a casting plaster or proper "HydroCal" for your first mould. It makes a mould suitable for a few parts. There are several threads on these forums that describe the process. I've done them using Bunnings Casting Plaster. Not the strongest, but did the job and easy to obtain.
The plug can be made from wood, foam, MDF etc. MDF sanded and finished with several coats of epoxy is possibly the easiest. Laminated layers afford indication of symmetry.
Otherwise for a one off, use the methods decribed above - without Peel Ply I suggest. That will only give you a stippled rough finish to sand and fill.

edit: Your first wing looks good. What is the slight crazing? Is that part of the design of the decoration?
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Last edited by Jim.Thompson; May 06, 2014 at 10:23 PM. Reason: see edit.
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Old May 07, 2014, 12:15 AM
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Gday Jim,

The crazing happened when I sprayed the paint on it. I think it has had a reaction to Mold Release I'm using Carnauda Wax. Was a bit upset with the finish but the crazing has growen on me. It kind a stands out to most things. No it's just odd. lol.
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Old May 07, 2014, 01:59 AM
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Jim.Thompson's Avatar
Bellingen NSW Australia
Joined Aug 2008
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Quote:
Originally Posted by jason riddell View Post
Gday Jim,

The crazing happened when I sprayed the paint on it. I think it has had a reaction to Mold Release I'm using Carnauda Wax. Was a bit upset with the finish but the crazing has growen on me. It kind a stands out to most things. No it's just odd. lol.
Yes, it looks Ok, like you planned it.
To avoid it in future (if you want to), start with a light mist coat of paint on the wax and let it dry. Then a second slightly heavier coat, allow to dry again. Then a final wet coat.
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Old May 08, 2014, 07:48 PM
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gold coast australia
Joined Aug 2008
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After we spoke about this project a while ago great to see you getting it done
BTW the crazing is caused by to much paint to soon. Just leave more time between coats to let the fumes out , and lighter coats as Jim said. Replicate what you did on the orange stripes as there perfect ha ha.
BUT I do like the crocodile skin look
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Old May 09, 2014, 05:13 AM
Arrarrar!
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Australia, NSW, Wagga Wagga
Joined Jan 2010
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Hi Jason, you can definitely bag a blue foam plug! It works well, and if you use thicker style film (I was using builders clear plastic then) the finish is pretty good. You have to watch that the cloth doesn't get sucked/ squeezed into the bag seams but other than that it is pretty simple. You should look into carbon sock- you slide it over your plug and zip tie one end. You pull it length wise and it tightens perfectly around the shape, then you zip tie the other end. Next, wet it out and either bag it or use some special release agent treated heat shrink tube from Soller Composites and there you have a bullet proof and light fuse. I did my first couple of homebrews this way and highly recommend it. Bagging is probably best, as you risk melting the foam with the heat shrink, just watch those seams.
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Old May 09, 2014, 07:10 AM
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That looks realy good Josh.

well I have taken the fuse out of the bag. It has turened out pretty good, a couple of imperfections nothing a little sanding and some fill carn't fix. Might rebage it with a carbon finish just to make it a bit stronger. with the wing and tail it comes in at 450g
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