Carbon fibre sheet

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#1

once again im having problems making a CF sheet lol, when the layup has fully cured there is very tiny bubbles in the face of the sheet ruining the part, my method is this -

sheet of glass waxed about 20 times with honeywax +

coat of poly resin surfboard resin so its nice and clear

4 plies of 200gsm CF rolled with paddle rollers like mad

finish coat of resin with wax in so i can rub down after

the sheet needs to be a good finish on both sides,

so, is there a better way of doing it to eliminate more or less ALL the bubbles ?

Vacuuming the sheet ? but i couldnt use peel ply as it will put the finish onto the sheet, but i could layup 3 plies of CF with peel ply then when that has set layup the last ply just as normal ?

how do you guys do it ?

seems like everything i do at the moment is going wrong and i just feel like giving up lol, if it wasnt for this excellent site i dont know who i would ask for help, so a big thank you to all of you :slight_smile:

Matt

#2

How about adding another sheet of glass on top of the laminate and then vacuum bag them all together? Just a thought.

#3

use a clear gelcoat. if you want both sides with a finish make two thin sheets and glue them together. if you vacuum two glass sheets down I think you would end up breaking the top sheet when you try releasing it and also probably would trap a lot of air since it wouldnt be able to breath. Perhaps having a top caul plate and infusing would work.

#4

vacuum vacuum vacuum!!!

#5

How would you do it ? 3 plies of carbon then vacuum with peel ply and then add the fourth layer by hand afterwards ?

#6

or the 4, and then brush on another layer of resin on top of the peelply surface. Might have to sand, and put a second layer of resin…depending on your surface quality.

or infusion…aka VARTM/VIP. You can have 2 tool sides for a flat sheet, with no problem at all.

#7

i believe the pinholes on your surface are the wax’s fault. maybe they are causing the surfboard resin to bead? if your bubbles are underneath the surface coat, then its your wetting up to blame, you re trapping air or not putting enough resin. try pouring lots of resin directly from the cup to the center of the laminate, then “push” it gently towards the perimeter. this way, any air will be driven out.

#8

Are you using mold release?

#9

“4 layers of 200 gram rolled with paddle rollers like mad”

That is the problem. Your pushing the layers of carbon fiber down so much so that you are forcing the clear surface coat resin to be pushed into the carbon fiber cloth… leaving bad spots.

Rolling with a smooth or bristled roller is probably ok, but don’t push down on the roller let the roller do the work. Also let the clear surface coat on the glass get past B-stage before you lay down your fiber cloth.

Also it is best to use vacuum, BUT you can get away with using two heavy pieces of glass. Of course the backside will never be as glossy as the front side. It’s commonly accepted that one side of carbon fiber will always be kinda of rough and dull. If you don’t like the rough dull side then brush on some clear resin after the sheet is made.

If you don’t like the idea of using peel ply, use perforated release ply with a layer of breather cloth on top of the perf ply. Then vacuum it all down.

Hope that is somewhat helpful :slight_smile:

#10

STATUS UPDATE

right vacuuming the sheet works :smiley: gets rid of pretty much all of the bubbles so im chuffed to bits :wink:

however,

part of my resin surface coat stuck to the sheet of glass, now why did it do this ? the glass was waxed 20 times (i counted) with honeywax +, put the wax on and left for 5 mins, buffed off then left for at least an hour each time to fully dry / harden,

so my first part with no bubbles in it was wrecked by part of the surface coat coming off lol

anyone got any ideas or theories as to whay part of it stuck to the glass ?

thanks everyone for your help so far i feel as though im making nice progress now

Matt :smiley:

#11

how long did you let it cure for?

#12

Erm prob 2 or so hours, I tried my finger on it and none came off onto my finger so I presume it had fully cured,

#13

Possibly found the problem of it sticking to the mould there. :slight_smile:

What resin are you using btw, Polyester?

#14

Two hours isnt long enought for a cure.If its ordinary polyester I would leave it about six hours if you can unless you are post curing it with heat

#15

Glass was cleaned before waxing? probably so I would say use some NC700 or NC770 mold release. Nothing will stick with a couple coats of it.

http://cgi.ebay.com/Frekote-700-NC-Mold-Release-Carbon-Fiber-Kevlar_W0QQitemZ110428868481QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item19b612cf81&_trksid=p3286.c0.m14

#16

Ok cheers for the recomendation, just got to find someone in the uk who can supply it.

Thank you … Matt