waxing new mould

im almost at the stage of building the first boat out of my new moulds.

once i have finished polishing them all up i give them a coat of wax to seal them up and wrap them up to keep them clean.

now when i get to make each part how many waxes should i apply?

i have used pva in the past but it leaves marks in the gelcoat.

i don't want to use pva as i don't want to have to wet flat and polish the finished job.

would 5 or 6 coats of mirror glaze 88 be enough or should i do more?

all tips etc much appreciated

 

the coats of wax by number seems about right I have always used 7 as the target number of coats the wax must haze and allow some time between coats , typically no more that two coats per day PVA applied correctly is a good Idea until the mold " breaks in" in short mix PVA with 50% cold water set the spray gun needle to allow only a fine mist of material to be released when the gun is triggered and hit the mold with three coats making sure to let the pva to dry between coats. when the part is pulled you can always buff the part to the gloss you would likes

search PVA here on the BB and read the very detailed explanation written by member Tuneles its very good info,, here I found it for you !

!http://www.boatdesign.net/forums/fiberglass-composite-boat-building/pva-mess-41668.html

 

i know how to use pva but i don't want the hassle of having to polish the finished job as i need to get the boat built as quickly as possible and don't want to have to go round polishing everything up when the parts are made.

do you reckon i'll get away with out using pva?

i have a spray gun but im not 100% confident enough to do it how tunnels explained.

 

Personally, I think I'd try a test piece to check it will come out. If you are moulding with epoxy, you will need PVA or another barrier to get release. If you are doing a polyester layup, you have a good chance of popping that out. It also depends on how 'vertical' the sides are and whether you can either pop air or water into the mould to pop the moulding out. Mirror Glaze 8 is pretty good with gelcoat and polyester systems but epoxy is a different beast especially with no gelcoat.....

BTW any test piece should be made in the most difficult part of the mould and bulked up with scrap stiffeners. If it comes out, most likely the whole thing will. If it does not, cut out the stiffeners and flex the test/scarp moulding so it does come out. For the cost of a littlegelcoat, CSM and a bit of timber it may well be worth it.

 

Pva

Garrybull, before reading the thread I liked you to I had no use for the stuff. when I read and re read his dir ections I had to try it again. man what a difference it made my boats come out of a 4 pcs mold and it is really not an issue to buff them up! once you cut or reduce the pVA with cold water and set the fluid needle to just break open ever so slightly you get an undetectable mist! allow that to dry and hit it two more times, I am spraying this with a 3M PPS plastic gun and it works very well!

 

im using polyester materials to build the boat.

epoxy over here is very expensive.

im going to see some one tomorrow and ask them the best way to go with it.

i don't mind using pva but i don't want the hassle of wet flatting the finished job and polishing it up.

if i can get away with just waxing the moulds thats the way i will go.

 

i will have a try with how tunnels explained how to do it on a smaller mould but im pretty confident that most of the moulds will be fine just waxed.

my main worry is on the hull and gunnel moulds as they are quite big and if it all goes wrong and the jobs don't come out it could be game over.

 

I would still go with the magic number of seven coats of wax, let all coats flash then apply the PVA

 

I used to put on PVA with a sponge and never had to even buff the finished part, I can't see any reason to have to "wet flatting" (wet sanding?) and then polishing (buffing).

A big buffing wheel and compound will make the dullest boat shine, maintenance wise.

Some things that you might see in the finished part, 99.639 % of regular people will never notice and after a few weeks outside being used, you probably wouldn't see it anymore.

The heat from the first few pulls drives the wax into the mold and "breaks it in" as far as I can tell. Eventually you can skip the PVA and even the wax, and get multiple pulls doing nothing, but I wouldn't risk a new mold that is still kind of vaguely chemically active and just looking to link up with the polyester from the first few parts.

 

You need a very, very fine mist of PVA over Mirrorglaze No 8, no other way of applying it without getting beading or run off. Keep with a carnauba wax, the Beeswax some places sell is terrible (with epoxy which sticks straight through it) but takes PVA better! It should be so fine that there is almost no discernible roughness to the surface of the mould/plug just a very slight dullness. SamSam is right, worst case would be a quick buff over the moulding to restore v high gloss.

As I'm about 25 mins drive from you Gary, I know about epoxy prices!. Good quality polyester resins are fine and reasonable price wise as you know. Better price performance for the type of craft you are building, good work, I have followed the project for some while.

Remember the moulding will help you in a way as it will shrink slightly away from the mould.

 

Putting it on with a damp sponge was a terrific pain in the ***, as you have to keep a wet edge, difficult to do with an alcohol based product, but when done the pva was shiny, never dull.

Years ago, in Professional Boat Builder, I read a production method of applying it. The problem is the surface tension of the PVA breaks away from the wax and leaves fisheyes, like tiny donut puddles all over. The guy in the article would hold the spray gun 4-5 feet off the surface and apply a light mist that left the mold looking real rough or dusty looking. After that dried, he would come back and apply a little bit heavier wet coat. The previous dust like mist coat gave the new PVA something to hold onto, preventing the fisheyes, while the new wet coat dissolved the dusty mist coat and left the mold completely shiny, just like the mold itself.

But that was a long time ago. I believe they have new release systems now that may eliminate all kinds of problems. Multiple releases, no PVA. Of course sometimes new problems are introduced, like release transfer to the new part which prevents/increases the difficulty of future painting or laminating.

 

Use PVA on the first parts, a little buffing is far cheaper, easier and quicker that building new molds because they stuck.

I know too many fabricators that felt PVA was too much trouble and after skipping it destroyed their molds trying to get the first parts off.

Using a rag or sponge leaves a pretty good surface, so does the correct spray method. I've had good results thinning it with water and not thinning it, but it takes a little practice.

 

We never use Pva as a general rule that is not to say there isn't a gallon in the shop for the odd occasion when some may be wiped on plugs and new moulds here and there in the extremely tight areas but as I say it is rare. Initially, at least 6 coats of honey wax are applied the solid one not the liquid and then one after every pull for the first few then one may get missed every now and then, plugs benefit from a couple more especially on top of durabuild.
Steve.

 

This may not translate to your part of the world but we used four coats of "TR" wax which is a soft white wax easy to apply and rub off. I believe it is American. The problem with TR however is it's prone to fisheyes so we finished with a hard Carnauba wax called PLP, hard to rub on and wipe off but brilliant on a new mould.
The trick is patience, too many people put on four coats in a day virtually one after the other and the previous coat doesn't get a chance to dry, end result is really you have only applied one coat 4 times !
And use lots of clean rags, a bulk removal rag and a polish rag, when the bulk rag gets loaded up chuck it and use the polish rag for the bulk and get a clean polisher.
Good Luck.

 

Oh one more thing, if you do go to pva put a splash of metho in your water before you dilute the pva, it helps to dry it off quicker.