My very 1st Mold

General Composites Discussions Showcase
#1

Hi All,
A lot of you guys have helped me with my first experience with fibreglass. I have made some mess but though my progress thread would be good to see what i have learned over the past week!

So first of all i had my boot which i attempted to make into a mold, for this i just filled the holes in the boot lid with p38. i then sanded this down with 240grit wet&dry paper, followed by 600 grit w&d. Once this was all done i applied 2 layers of car wax!
The condition of the paint in the first place was bad and not clean or shiny! The filler was poorly prepped and the boot really should have been repainted.

Here are some pics of what i went through!



#2

the above pictures were for the mold, this consisted of 2 layers of tissue and 2 layers of csm(not sure on the thickness/strength) all held together with polyester resin.

Also see in the pictures that the filler is all visible!

Now below are pictures of the mold once it had been removed!!:eek:

Overall view of mold!

Paint stuck to resin

poor filling stuck to the resin!!

#3

this is the current state of the plug(boot)

the filling has been properly re-worked and all filled level and smooth upto 1200 grit. Then the layers of grey primer have been built up 3 layers so far each time being flattened to 1200 grit w&d.

I am going to get some paint tomorrow and some laquer. (not sure if i should use laquer, and if i do is there a specific type?)



#4

this one has been re-wprked again to be level and smooth!

#5



#6

after taking them pictures above i then reworked it all adding more elbow grease to make sure it is nice and flat and smooth. I find the primer really brings up the blemishes/impurities!

I will update as and when i can!!

Thanks John

#7

don’t wax it and apply polyester. wait!

first, you should get some tooling gelcoat if you re gonna make a mold.

second, its best you’d put a flange around the plug. even if you don’t use vacuum.

third, use the paint you re gonna use on the bonnet on a test panel, and when its done, wax it and apply some polyester resin or gelcoat. theres a great possibility the resin will eat through the wax and to the paint. That depends on what type of paint you use.

The most certain way to success is this. Sprayable pva. even if your resin and car paint react to each other, pva makes a barrier between them. The products i use are like this: first there is a liquid wax, which u apply with a cloth, and then polish it (not to a shine, just to remove streaks and lines). Then spray several coats of pva on it. When it dries, you can be sure that you won’t have any nasty surprises. (and because pva is shiny when it dries, you don’t even have to paint the boot. just sand it to a fine surface, and spray pva on it. saves time and money.

#8

No liquid wax.:rolleyes: It should be a paste wax specifically for mold release. About 5 coats are applied, and buffed to a shine.
Avoid PVA completely. It ruins all the hard work to make the mold smooth and shiny.

#9

Using this wax!
http://www.turtlewaxuk.com/prod.asp?Partcode=FG1678

Now that i have smoothed the boot plug, it is really smooth and shiny, i have so far applied 2 layers of wax, this has got better the more i coated it, i will keep adding coats of this until it is really shiny and buffed.

Then i will add supports to the side of the mold using cardboard and electrical foil tape.

Will get pics tomorrow or wednesday.

Thanks John

#10

at least do a test if your car paint reacts to the resin

#11

Eeeek! That’s for your car!

I highly recommend using material specifically designed for this purpose. You’ll see the difference.

#12

Is it definatley no good for a mold then? It is already looking good, should i get some new wax for mold release then? What characteristics has the release wax got that the car wax has?

Just being inquisitive not argumentative.

Thanks John

#13

ok, 2nd time round as soon as i layed the polyester resin it all reacted with the gel coat!! Is this due to not having enough gel coat down? Should i use more, if i need more is there something to use that stops it running so much or it all drips off the end of the bonnet.

I stopped using the turtle wax and used maguiers carnuba wax instead, this i heard is meant to be good for molds.

i then added a thin layer of pva(is this the problem)??

Here are pictures of the reaction i got!!




Any help greatfully received!

#14

I can see no pictures…

Did you let your gelcoat set before laying up?
What sort of gelcoat/resin - cat ratio are you using?

#15

added pictures again after moving them into a folder in photobucket.

Thanks

#16

So from what I can see the gel coat has reacted with paint on the bootlid?

#17

yeah seems to me more like polyester reacting with the paint on the plug. how thin was your layer of pva? did you spray it on? sponge it? brush it?

#18

pva was a thin layer used a rag to add it, then i added the gel coat which was left until it was tacky, tacky as in when i pressed it, it left a fingerprint but wasn’t on my hand.

Then i added a layer of polyester resin and the matting layer, then i added 300gram woven roving with more resin, then another layer of 300gm woven roving on even more resin, then one layer of 600 gram roving on more polyester resin.

So from what has been said, the reaction is from the gel coat and the paint, and to prevent this adding more layers of pva will stop this?

Quite annoying this result as i spent a lot of time waxing and prepping the plug this time!!!

What steps should i take to ensure 3rd time is lucky for me??

Thanks John

#19

How thick did you spray the gelcoat? Did it actually damage the surface of the plug?
It seems to me that you just made the gelcoat layer too thin.

#20

i didnt spray the gel coat, i dont have spraying equipment, i brushed it on, it is hard to measure the depth of the resin/gel coat. What sort of thickness should i be aiming for?

Thanks John