Rick Its a belt and braces attitude that is used to ensure release, if you have ever had a part or worse still, your plug stick in your mould you may understand this reasoning.
As and release agent, wax or pva is essentialy a fragile film on the mould surface, it is easy to damage during a layup so if we use 2 layers of mould release we have a better chance. Also pva can help to hide imperfections in the mould surface, tends to release with the part, offering a protective layer while we trim the flash off the finished part and you can easily spray most paints both over pva in the mould, as a gel coat, and over the part after moulding as there should be no wax contamination on the surface as it was sealed off by the pva. I would never hesitate not to use pva in most cases. Its got too much going for it! Mike Reynell [EMAIL PROTECTED] Right way up, Upside down......who cares, I'm still flying... ----- Original Message ----- From: "Rick and Jill" <[EMAIL PROTECTED]> To: "Mike Reynell" <[EMAIL PROTECTED]>; "yclui_hk" <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Sent: Tuesday, November 12, 2002 12:00 AM Subject: Why use PVA??? > I'm curious? When and why should PVA be used. > > I've always had great results using wax alone on the couple of fuse and > canopy molds that I've made. A bunch (10-12) of initial coats of the wax > before the first layup and then a light coat of wax before each use. I've > know others that have had sticking problems but the parts I've laid up have > literally popped out of the molds with a slight twisting of the mold to free > the part. > > Are there specific reasons or applications that require the use of PVA??? > > RB > > ----- Original Message ----- > From: "Mike Reynell" <[EMAIL PROTECTED]> > To: "yclui_hk" <[EMAIL PROTECTED]> > Cc: <[EMAIL PROTECTED]> > Sent: Monday, November 11, 2002 3:28 AM > Subject: Re: [RCSE] Applying PVA after waxing ? It doesn't work > > > > Hi > > > > Your problem is a common one that most have fallen into, and that is that > > the wax you are using is formulated with silicone for use in production > > environments where they can't wait for PVA to dry. > > > > You will need to strip the wax off your mould and then re-apply an non > > silicone wax from your local fibreglass supplies store. The should be able > > to guide you to the correct wax, its their job. Just tell them what you > need > > to use it for. > > > > I use several different waxes but my favourites would be Ceara J-1(a paste > > that is easy to apply and buff) and T R 108 (a wax that is more durable > but > > harder to remove). > > > > Note also that PVA quality varies a lot, with some that dont go on very > well > > unless sprayed. My current favorite is is called Partall Coverall film. > > > > Hope this helps. PS if wour local storeman wont or cant help you.....go > > elsewhere!! > > > > Mike Reynell > > [EMAIL PROTECTED] > > Right way up, Upside down......who cares, I'm still flying... > > ----- Original Message ----- > > From: "yclui_hk" <[EMAIL PROTECTED]> > > To: <[EMAIL PROTECTED]> > > Sent: Monday, November 11, 2002 12:48 AM > > Subject: [RCSE] Applying PVA after waxing ? It doesn't work > > > > > > > Hello everybody, > > > > > > I have been told by many that the correct procedure to prepare the > > > mold surface is to apply wax followed by PVA but so far all my > > > attempts have been unsuccessful. The PVA just won't stick to the > > > waxed surface but form seperate beads of liquids. I have tried to > > > thicken the PVA but it didn't help. May I know what I might have > > > done wrong ? > > > > > > Any advices will be well appreciated. > > > > > > Y C Lui > > > > > > RCSE-List facilities provided by Model Airplane News. Send "subscribe" > > and "unsubscribe" requests to [EMAIL PROTECTED] Please note > that > > subscribe and unsubscribe messages must be sent in text only format with > > MIME turned off. > > > > > > > RCSE-List facilities provided by Model Airplane News. Send "subscribe" > and "unsubscribe" requests to [EMAIL PROTECTED] Please note that > subscribe and unsubscribe messages must be sent in text only format with > MIME turned off. > > > RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off.
