PVA Application Issues - Page 10 - RC Groups
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Jan 27, 2013, 01:38 AM
608 km/h!
josh18's Avatar
Thats pretty much how I do it too. No issues yet but I do get swirls.
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Jan 27, 2013, 02:08 AM
2012 NZ Speedcup - 231 MPH
DownUnderPilot's Avatar
I always do a couple of coats of wax on my seasoned moulds and then I brush on watered down PVA. I found the full thickness PVA way too unforgiving, but when I watered it down it became a totally different beast!

I noticed a marked improvement if I leave the wax for at least an hour after bufffing off, then I give it another buff to shine the surface. This seems to let the PVA go on and dry like a mirror.
Jan 27, 2013, 02:29 AM
Entropy is happening!
Jim.Thompson's Avatar

Why use PVA on seasoned moulds.


Quote:
Originally Posted by DownUnderPilot
I always do a couple of coats of wax on my seasoned moulds and then I brush on watered down PVA. I found the full thickness PVA way too unforgiving, but when I watered it down it became a totally different beast!

............................
Why are you still using PVA if the moulds are seasoned?
See my post #507 here with reference to a paper that Adam of WWWorks originally posted a link to:

https://www.rcgroups.com/forums/show...339865&page=34
Jan 27, 2013, 03:45 AM
2012 NZ Speedcup - 231 MPH
DownUnderPilot's Avatar
Dunno, just my routine...
Jan 27, 2013, 04:27 AM
608 km/h!
josh18's Avatar
Ive never been brave enough to use wax only either.
Jan 27, 2013, 06:55 AM
Entropy is happening!
Jim.Thompson's Avatar
Do a test strip first, like I described on my thread.
Jan 27, 2013, 07:50 AM
Life begins at transition
Quote:
Originally Posted by Jim.Thompson
Why are you still using PVA if the moulds are seasoned?
See my post #507 here with reference to a paper that Adam of WWWorks originally posted a link to:

https://www.rcgroups.com/forums/show...339865&page=34
Does the same apply to epoxy? That reference is for polyester - significantly different cure methods. I tried wax-only with epoxy once. Lost the plug, so stuck with PVA ever since.

Does the mould surface end up with the sheen, or shiny like normal PVA?
Jan 27, 2013, 05:07 PM
Entropy is happening!
Jim.Thompson's Avatar

Seasoned moulds only.


Quote:
Originally Posted by Odysis
Does the same apply to epoxy? That reference is for polyester - significantly different cure methods. I tried wax-only with epoxy once. Lost the plug, so stuck with PVA ever since.

Does the mould surface end up with the sheen, or shiny like normal PVA?
I suggest you read the article. Here it is again: https://www.rcgroups.com/forums/showt...339865&page=34

Wax only is not recommended for mould production. It is for seasoned moulds when producing parts from them.

Epoxy/vinyester/polyester moulds can be considered similar in terms of seasoning, so it seems.
Jan 27, 2013, 05:24 PM
608 km/h!
josh18's Avatar
Thats it Jim, time for me to man up! I will do some test strips to make sure, but next wing I will do with wax only! Here I come crisp masked paint lines!
Jan 27, 2013, 05:38 PM
Entropy is happening!
Jim.Thompson's Avatar
Quote:
Originally Posted by josh18
Thats it Jim, time for me to man up! I will do some test strips to make sure, but next wing I will do with wax only! Here I come crisp masked paint lines!
The second set of wings for my moulded plank are in the moulds ready for spars, servo wires and such detail before joining.
I treated the moulds with wax only. No PVA. However, I did a small test strip first, which pulled off very easily (see my blog). I did this on the second pull (used wax only), because of their age. They must be close to a year old.

edit: I'll post the results after I pull them. I've no reason to expect problems though.
Last edited by Jim.Thompson; Jan 27, 2013 at 05:40 PM. Reason: see edit.
Jan 27, 2013, 05:52 PM
Just fly it!
wyowindworks's Avatar
If there is no paint then epoxy on epoxy can be a stubborn release even on a seasoned mold.
Jan 27, 2013, 07:32 PM
608 km/h!
josh18's Avatar
Thanks Adam, I'll make sure I do plenty of tests before I commit to moulding. Does it make it better that the mould and the part are made of the same resin? Either way I'll do some tests, maybe some ith paint and some without is a good idea.
Cheers- I havn't done any building for a while, I hope I remember how to do it!
Jan 27, 2013, 07:34 PM
Just fly it!
wyowindworks's Avatar
I have done heaps of operations that used the same resin in the mold and part and had no problems. That may not be true with every resin though.
Jan 27, 2013, 08:13 PM
Entropy is happening!
Jim.Thompson's Avatar
Quote:
Originally Posted by wyowindworks
If there is no paint then epoxy on epoxy can be a stubborn release even on a seasoned mold.
Is that with wax only Adam? Or with a semi-permanent? How seasoned?

Gives me cause for concern about my epoxy wing moulds.
Although, the test almost fell off.

edit:
Also, one of the skins started to lift off the mould slightly when I was removing the peel ply even though I tore it off in narrow strips. It sprang back onto the mould though. I'm not too concerned really.
Last edited by Jim.Thompson; Jan 27, 2013 at 10:04 PM. Reason: see edit.
Jan 27, 2013, 09:29 PM
Just fly it!
wyowindworks's Avatar
Jim, I'm talking about using wax only. Semi's with the right resin/paint release better than anything that I have ever tried.


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