Hi I bought a mould for IOM from a friend who only pulled a couple of hulls and decks - it is in perfect condition and I intend to keeping it that way.
So I am seeking your advices before using it as I never made a hull from a female mould
I bought this release agent so the hull doesn’t stick on the mould - Formula Five® Mold release wax
Don’t know if any of you have used this release agent or similar - based on the instructions it recommends 3 layers with a buff at the end to a shiny state
Once I get to that state can I start laying the resin ? will use West Epoxy system 105 and 205.
I won’t use a gelcoat but will paint the boat once assembled for a better finish so should I lay a coat of epoxy first in mould then apply the first layer of fibreglass cloth to soak on, then apply the second layer on top which I’ll wet with epoxy and so on - or lay the fibreglass cloth in then wet it in the mould and so on ? I guess the later option will increase the chance of pinholes on the outside of the hull but since I will paint the hull does it matter ?
I intend to do wet on wet with a layer of peel-ply to finish.
If the mold has had a couple of hulls pulled out of it you really just have to freshen the wax with a single coat. That said there is no harm in using PVA although some people have had difficulty applying it. It tends to bead up on the wax. Very light sprayed on coats works best for me. You will get a better finish on the part without PVA but since you’re going to paint you have to sand it anyway and the better finish becomes moot.
Don
I had another thought. Since you don’t really know the history of the mold I would give it the full wax treatment. I use six coats, one every half hour, buff between coats. I do it in front of the TV. During a commercial I apply a coat, next commercial I buff it, wait two more commercials and apply the next coat. Repeat six times. Let cure overnight. Just before layup apply another coat, wait 15 min, buff it and start your layup. This my be a bit of overkill but I’m a belt and suspenders kind of guy.
Thank you all for your valuable input - very useful indeed.
From what I read and marks comment here it seems PVA release agents is used a lot with great success - is it better then the wax I got ? or just different. What is it with the PVA ? easier to de-mould and preserve the mould ?
i would do both… PVA and Wax… better safe than sorry… but as other has said the pva can leave marks on the finish side of the hull
the PVA is essentially like a nonstick cooking spray…but as other has said the pva can leave marks on the finish side of the hull but since you are going to spray paint it you’ll have to sand… I have had success using a foam brush to apply.
TF, I have never heard about spraying primer on a mold… can you elaborate on your process…
Gilbert, if you wee stateside I’d send you some of my PVA…
Thanks Marc, I get it now I might order some cos they seem to have a decent price
any idea of the difference btw these 2 ? film release Agent PVA and this Partall PVA film which one should I use with my wax ? checked the specs and can’t find much difference ?
There is some great info in the “composites” forum on rcgroups.com. I would use both wax and PVA, unless you want to change horses midstream and go with something like the Frekote like of mold treatment. I have had great results with wax and PVA, but have also had some sticking problems. I have not used the Frekote 700NC but a few times, but have had excellent results with it. It also does not leave any film on the mold that would show up in your layup.
Wax is the “release” agent and the PVA is a barrier coat to keep the unreacted molecules in the mold from reacting with, and bonding to the epoxy (or polyester) layup. Once the mold has been used a number of times, you should be able to get by with a waxing every few pulls. Most model boat builders never really get to that point! So use the PVA!
I have also sprayed primer in molds and layup on top of that. It is like another barrier coat to protect the mold, and saves that sanding step after demold, before primer.
I’ve been molding our 2mAC hulls for the past 2 years. You can see some pictures under the America’s Cup forum. I would agree that protecting the mold is the primary concern. I’ve pulled 6 hulls so far from our tooling using wax only. 6-7 coats seems to provide easy release even for the more difficult areas like the molded in hull/deck flange. I’ve used both Ampreg 22 and currently Proset 125 systems. Since our hulls are carbon in twill and uni, everything gets vacuum bagged. It’s hard to explain just how much this improves the process but peeling off the breather and peel ply loaded with excess resin kind of says it all. You might also consider the West System suggestion of aerosol hairspray as a supplemental release agent. It’s water soluble much like PVA, cheap and simple to apply after waxing. However, unless you have a difficult to demold shape (unlikely) wax is tried and true and really all you’ll need IMO.
Here’s a picture of the fun in action…
(click image for big view)
It’s always exciting pulling the part from the mold even after dozens of hulls, fins etc.
I think I will order the PVA release to be sure to be sure cos I’m quite a newbie when I comes to moulding and as a few of you have said my priority is to keep the moulds safe so wax and PVA it will be.
I can only imagine the improvements by doing a strat vaccum bagged as I see it already by using a peel-ply. I have started using peelply when doing my test hull see one of my previous post here. where I learned a lot in the process. Hi Bill I will check you posts cos I think your boats are fantastic - nowhere near your experience but learning.
Now I am working on a hull that has already been moulded from this mould from a guy in scotland - with a coloured gelcoat. this is the subject of a new thread to come on this forum.
It is amazing how much there is to know in building these boats ! but it is great experience and learning lots so thank you all for sharing your views and experience.
The wax acts to fill the microscopic scratches in the mold surface that you cannot see, so the more you can make the mold shine before waxing, the better it will release. Use non-silicone based polishes (the bottles say “paint shop safe” or something similar). If the mold is in good condition, then machine buff with a foam pad or hand buff with something like Nu-Finish #2 (motor cycle shops carry it to polish chrome and some auto parts stores like Kragen have it in the car wax section). A final buff with a swirl mark remover (in the car wax section) can make it reflect like a mirror. I have purchased a 3" polisher http://www.griotsgarage.com/product/professional+3+inch+random+orbital.do?sortby=ourPicks that works great on hull plugs. Their polishes are a little expensive, but they are a proven system so you know it works.
You generally start a new mold, after letting it sit for a week or so, with 8 to 10 coats of wax. Not to build the wax up to any thickness, but to make sure nothing is missed. Be sure to let each coat dry to a full haze before buffing and use a clean section of cloth each time. Second pull has less coats and after the five you say the mold has had, one coat should be plenty between each pull.
As far as PVA, think of it as insurance. Properly applied PVA (one mist coat and then a wet but not dripping coat) is only a few mils thick and is just there to be a chemical barrier between the new epoxy and any unreacted open links links in the mold epoxy. What you think is solid and fully cured epoxy still has 3 to 5% unreacted molecular sites with which the new epoxy can react and stick. I have let a mold sit for 6 months and used just wax.
There are also semi-permanent release systems that don’t use wax or PVA - Freecoat is probably the most well known - with their own mold sealer and they work great, but they go bad quickly even unopened on the shelf so they are generally not for the DYI’er. I have used it once and the hull just dropped out of the inverted mold
If you are going to paint in the mold to act like a light weight gelcoat, then test the paint/wax/mold material/epoxy on a flat sheet of the material FIRST. Only certain combinations work and others make a mess of the mold. There is a good thread about which combinations people have found to work on the Composits forum of RC Groups.
