So F-ing pissed! Part 3!

General Composites Discussions Composites Talk
#1

OK, hybridracers must have jinxed me with his alligatoring gelcoat!

I’m not sure if this is alligatoring or some sorta chemical reaction. The paint and clearcoat was actually pulled off the hood. Not even my paint stripper could do that with as much ease! The paint/clear is a couple of years old.

Tooling GC was sprayed on. 1st two coats were lightly dusted, about a minute or two between coats. Then progessively heavier coats were put on. Mold release wax was used, tooling GC was less than a couple of months old. MEKP was 1 to 1.5%.

The problem started as soon as I began to lay down the veil, I noticed it at the other end of the plug. I knew it was F-ed already but just decided to continue on. Maybe some Duratec can fix the mold?




I still need to do the other hood vent…but am gun shy now, don’t wanna F-it up. Just what I need, it’s gonna take me a while to repair the hood too. I think I’ll just overlay it in CF.

#2

Would that be caused by some seeerious shrinkage?

#3

That’s what it looks like. But the first couple of coats were already curing by the time I finished cleaning out the gun. The upper layer of GC must have been damn hot! Even with 1-1.5% MEKP.

I don’t know what the thickness was, my barrel-type mil gauge starts at 40mil and never came close to that mark.

This sucks. And spraying gelcoat sux, I’m constantly cleaning the gun in between coats, no time to rest!

#4

Rez dont get down hearted M8 i should think most of us have been through the learning curve. After you waxed did you not use a mold release agent like pva or ptfe, really needed especially on paint where your maybe unsure what it is. I would start again with a new mold, youll be ther forever trying to bring that back and i wouldnt think you`ll be happy with it.

Baz

#5

So PVA would help? The wax I used was Kleen Kare Mold Release Wax or something like that. I’ve read a lot about PVA causing surface texture problems etc.

Couldn’t I just spray the mold with Duratec surfacing primer?

#6

Rez, the problem was you had a paint of unknown type or at least you didnt know how the gel would react with it plus all the time invested in prepping the plug for the mold, so in this case it might have been prudent to do a test patch with the gel coat on the plug or PVA the plug or even both. I rarely take a chance on a new plug so most of the time and especially on a complicated mold i will use PVA or PTFE mold release agent, i will wipe it on with a lint free cloth or sponge but only lightly, you dont really need too much. And as for a texture on the mold surface from using one of these release agents no way in fact it will not be a texture unless you spray it on. Most of the time you are going to inspect the mold and do some finishing work anyway. On uncomplicated plugs where i have used a polyurethane or polyester to coat them with and the finish is like glass then yes ill wax them and mold from that without additional release agents.

Yes you could use surfacing primer on the mold but the hours you`d spend getting as good a finish as you could a plug, is it worth it i would cut my losses use the surfacing primer on sorting the plug and make a new mold.

Baz

#7

Yeah, I should’ve tested it…:mad:
I think I will redo the mold, it’d be easier to release if it were a 2piece one anyway. For the other side of the hood, I’ll use the PVA.

Well, now I know…
http://compositeforum.werksberg.com/showthread.php?t=211&highlight=clear+coating+question

Thanks for your help.

#8

Rez, if your going to pull carbon parts from this mold only make it 2 part if it really needs to be otherwise you will run into problems with the parting line showing in the finished part. That is unless the parting line is so good that when bolted together you can hardly see the join and definately not feel it at all. Have you seen my dash mold, well that was a three parter, i ended up joining two of the main parts together permanently. As you know any small imperfection be it a parting line or even a dust nib from spraying the clear gelcoat in the mold will show up as an imperfection on the weave surface. I, sad person that i am inspect the surface with a lamp prior to laying in the carbon and knocking down any nibs with 400 wet or dry used dry.

Best of luck.

Baz

#9

If you’re spraying gelcoat on a small part like this, you should be applying it in one shot.

#10

your initial coverage was too thin.

You need to lay that crap down like its going out of style…I dont think you can be too thick.

I know I had it happen again…Im wondering if the tooling gel I got is not for brushing…

I couldnt get it to stay thick enough in areas…so Im doomed to find ways to glob it on thick.

#11

Hmm, so how thick do I initially lay it on??? More than a dust but less than a medium wet pass? Now that’s a vague description!

I picked up some PVA at lunch, how far in advance should I apply it? I won’t be ready to spray til, say, the end of the week.

Baz, yes, I saw your dash mold, great stuff. The vents I’m doing have about an inch to inch & a half 90degree verticals. It was time consuming to pull the ruined mold, and I plan to make at least 20 of these. Maybe be PVA will make it easier…?

#12

Rez, just make sure its dry, youll be able to tell, obviously depends on the temp your working in. When you put it on just check it to make sure it doesnt pool, remember you dont need too much just a thin film to cover. Also watch out for it (for want of a better description) fish eying if you havn`t buffed all the wax off. The PVA if applied thin will still give you a glossy part.

Baz

#13

Rez you could also add an airline attachment to the mold but be careful if you do dont give it full tank pressure just ease the air in and she`ll pop right out. Maybe i am getting a bit commercial here were only talking small parts, heres me removing a 20 metre yacht.

Baz

#14

Thick or thin?!? Brain overload! Does not compute!:smiley:

I know, I know, it’s experience and trial and error…I’ll keep at it.

Yeah, the airline thing is a great idea. If seen the wedges with air hoses attached to them, thought it was a good idea but was too cheap to buy one. Why buy it for $50 if I can make my own for $75?:rolleyes:

Again, thanks for everyones help.

Oh yeah, how far in advance should the PVA go on?

#15

Rez, if the PVA is dry then you can start, some people like to leave it overnight. All my molds are heated so within an hour im ready but give it a couple of hours, touch it if its dry your ready. Sorry i cant be specific but it depends on the temperature where your working. If your unsure leave it overnight and it`ll be fine. For an airline attachment all you need is to drill a 1/4 inch hole in the mold, somewhere where your going to cut out excess material, obviously not near the edge of the mold. Then get a male or female threaded fitting to take an airline fitting and a ball valve to control the air and stop any vac escaping. Then just glass it in on the back side of the mold and put a small piece of electrical tape over the hole on the inside. All done for less than 10$.

Baz

#16

Good idea on the air hole, I’ll definitely plan that in somewhere!

#17

Turns out that my gelcoat wasnt a “brushable” tooling gelcoat.

I called them and asked what the hell the deal was with it being so thin…

They sat in silence.

I know Ive told my rep at least 15 times I dont like spray tooling gel cause I dont like using a cup gun. (its messy and wastefull) I use an HVLP with a 2.2 tip on it for “production” gelcoat the tooling would clog my gun.

So he says “use some cabasil”…I wanted to strangle him.

Ill have to use some but man…I guess Im not buying anything from them for tooling gelcoat.

#18

Man this PVA is hard to apply…now I remember why I don’t like it. Too little and the cloth drags and creates crap like gummed up sandpaper. Too much and it gets all bumpy.

What do you think, too thick?


No matter what, I get streaks. A light mist of water spread it around, but is that getting rid of the PVA? Or just spreading it thinner?

#19

can i ask, why are you brushing!?

use a HVLP mini gun from Harbor freight. .8? tip? or .6 i believe. water it down a TAD! … i didnt water it but sometimes i hear it helps. spray the sucker on, wait, spray, wait, spray, wait, spray! 3-4 coats till u see nice film. DO NOT apply heat or air. the faster it flashs off, the more lines ull have!!! if u let it dry by itself, it will smooth out. :wink:

#20

Be interested to know what advantages PVA has over a good release wax? Seems from posts here that its pretty difficult to apply, and results sometimes not that good.