Wing skins for vacuum bagging

[oipigface]

I am about to start making my first set of vacuum bagged wings. I have some experience of vacuum bagging, and I am following Mark Drela’s Supra plans as to structure, although the plane I’m making is a bit larger than Supra. I am intending to make a set of skins from carbon/kevlar cloth and straight kevlar cloth which I will fit to prepared foam cores. I haven’t been able to find much in the way of guidance so far, and I am looking for tips as to how to prefabricate the skins. 
One question I don’t know the answer to is whether I should prepare the skins in the wing-beds so that they are ready-shaped before bagging.

If you have anything to offer about painting that would be helpful as well.

[Marc RC pilot]

No experience here I'm afraid oipigface, but I do remembered a post by ThermalBoy who seems to have taken it to a very high level with there Proglide Home Build F5J gliders....Amazing stuff

Might be worth a shout.

Link: https://www.barcs.co.uk/gallery/album/7-proglide-f5j-update/

Cheers

 

Marc 

 

 

[paul w]

In brief- cut the cloth slightly over size, wet up with epoxy on mylar sheets (cut to size and waxed), lay these on the

foam core and then put in the bag with breather layer to evenly distribute the vacuum. Heat for cure as per

epoxy manufacturer's guidance.

 

You can spray the mylars first, effectively gluing the paint to the skins, but I've never tried this myself.

 

See if you can hunt down a copy of Phil Barnes' DVD 'Vacuum Bagging Made easy'. It's a great resource

and shows the whole process really clearly.

[Jerry Lunt]

John, have you reviewed the instructions videos at EasyComposit's??

[oipigface]

2 hours ago, Scram said:

John, have you reviewed the instructions videos at EasyComposit's??

 

Yes, I have, Jerry, but I haven’t found one that features mylars. I’ve found a number of other videos which outline the process, but they all leave many questions unanswered. For instance the first one below is very useful for details of the layup, but doesn’t show the actual bagging! The second one does show the bagging, but I find it hard to believe that putting a one brick directly on top of the prepared wing half is good way of producing a straight result! On small projects, I’m happy to screw up a few times in pursuit of the truth, but for the current one, I’d be very upset if, after having prepared cores with spars, airbrakes, hinges and so forth, the effort went to waste because I had done something stupid. There’s another question that has come up while I’ve been watching this material. No one seems to specify what weight of mylar it is best to use. 
On decoration: these show contrasting approaches. The first guy has painted the mylar before starting the layup, (he doesn’t say what paint he uses) leaving clear the parts where he wants the weave to show through; in the second the mylar is unpainted and the first two elements of the layup are lightweight glasscloth followed by complex airbrushed artwork on paper.
I was going to build the tailplane using a different technique from the wing, but I’m wondering if I shouldn’t try vacuum bagging it, just because the costs of making a mess of it are lower, and it would be an opportunity to practise!

 

[oipigface]

On 25/11/2020 at 15:28, paul w said:

See if you can hunt down a copy of Phil Barnes' DVD 'Vacuum Bagging Made easy'. It's a great resource

and shows the whole process really clearly.

Thanks for this, Paul. The video seems to have been well received by lots of people, but I can’t find a copy that is available from anywhere.

[paul w]

Definitely practice on something like a tailplane first. I did have a copy of the DVD, if I can

track down who I lent it to (and reclaim it) I'm sure we can come to some kind of loan arrangement!

[oipigface]

That would be great, Paul! PM me when and if you track it down. 

[Graham Woods]

Here's my web page from 20 years ago on the construction of my Rumour aerobatic model languishing in my garage.

http://www.favonius.com/soaring/bagging/bagging.htm

[oipigface]

Thanks, Graham. I’ve seen the part about the AMT pivot before, but not the actual bagging. It answers some of my questions. Do I remember an article of yours from one of the magazines many years ago?

[Graham Woods]

I honestly don't remember, maybe. As it happens my next aerobatic model will use 0,4mm ply very lightly vacuumed, and pressed as well, between outers, over white foam.

[Wayne B]

 

You could check this vid out, in German but does show a lot. There is a series if interested. Hope it helps.

[oipigface]

First stage successfully completed! There's an account on the thread called 'Danosa Danopren TR' on this forum. The Barnes video was very helpful.

Thanks to all for your advice and suggestions.