Wet Lay Laminating Advice

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#1

Hi chaps, I’ve just got over my first stumbling block where I was trashing moulds from poor release… Thanks to Hanaldo and Elitec for that! So now I’m on to the proper job of actually starting to make some parts… if you can offer advice on how to improve my laminating from the below photos and layup description that’d be really appreciated!

PRF epoxy compatible gel coat
3 plys 200g twill carbon
PRF epoxy
Peelply
Bread wrap
Breather
Vac bagged 28.5in after drop test to find big leak

Damage to mould from poor release after buffing off semiperm like a wax:

Gel coat not wetting out as release agent working very well:

Gel coat released slightly before laminating:

Overview of moulded part:

Detail of air between carbon weave and bridging on external radii (ignore blotches in the middle from gelcoat needing to be brushed out again whilst tacky):

So my requests are for advice on how to achieve a better visual part using wet lay -

What can I do to get rid of the air between the weave?

  • I brushed a layer of resin onto the tacked off gel coat, and wetted the Carbon between release film using a filler spreader before putting it in the mould. But despite this the carbon looks quite dry on the inner surface. Breather is quite wet, 2:1 resin to carbon ratio so plenty of the stuff slopping about, 3rd layer went in dry to wetted second layer.

What can I do to stop the bridging?

  • I was quite careful putting the carbon into the mould, and after bagging I also went around with a plastic tool to push it into the mould. There is one tiny spot (less than 1cm2) that shows the peel ply bridged, otherwise it is carbon away from the gelcoat, like the top of the last photo. Should I conciously push excess carbon into the recesses of mould? Or should my peel ply be put in several strips to not pull the carbon away from the mould face?

What suggestions do you have to improve my layup process in general?

  • am I using the right kit? Should I use a non perforated or less perforated release film like this rather than bread wrap?

Thanks very much for any suggestions!

#2

im roughly at the same stage of making parts as you and have came across some of the same problems so very keen to see the answers.

On my last part i was able to get less bridging by putting the part under vac but stopping before it was 100% under pressure. I would then push in all the corners and then continue to remove the air. still had some issues but a lot less.

#3

Hi Jonty,

I bet on the positive side it’s nice to have a new set of problems instead of the same old thing!

Im an just curious - when you pulled vacuum, did you simply pull full vacuum right away or did you gently place the bag into position as vacuum was pulled down gradually?

Phill
www.elitecomposites.com.au

#4

I think there might have been to much gel coat before the cloth went on so that the vacuum could not pull the cloth down. Just an idea.
-Shawn

#5

Hi Phil, yes it sure is nice to be working on a new issue - if every part I make I fix just 1 single issue and get closer to a perfect part I’ll be a happy man!

Initially we pulled a full vacuum to check for leaks, then once we isolated that we pulled it down pretty quickly - in hindsight that’s pretty obvious to be a cause of some of the bridging - to be fair, we were just hoping to get the thing to release without tearing the mould to bits!

Anyway, would you normally put most of your time into consolidating the part once a partial vacuum is pulled, rather than (still being careful of course) when the laminate is first layed up? And would the way consolidation is done, either when initially being laminated or once the vacuum is pulled, be a factor in the air between the weave? I am a bit unsure of why the breather is so wet yet the bottom of the laminate so dry, hence me question about bleeder materials.

Hi Shawn, you’re right there was a lot of gel coat - I couldn’t stay at my workshop to brush out once it started to tack off, so ended up making 2 additional stabs at it! But since the gelcoat was essentially cured when I laminated this basically makes the new mould face, so I don’t think this would have any bearing on whether the carbon was pulled into contact or not. Thanks for the input though!

#6

air between weave: use different type of weave in the backing layers, my choice is biaxial.
bridging: pull vacuum gradually as suggested and for complex shape parts use multiple smaller pieces of peelply, breather etc. to cover the surface for example separate pieces for the “humps” and for the perimeter overlapping themselves rather than one uniform piece for the entire part. that way you will eliminate the chances to have any bridging due to the tension in these layers.
these tricks worked for me.

#7

Hi Jim, thanks for the suggestions! Biaxial carbon as a backing layer I guess helps prevent the resin being pulled out through the laminate stack I guess? I’ll give that a try if there are no other options, but I’m currently running on fumes finiancially at the moment, so if I didn’t need to invest in additional reinforcement that would be a help - are there other things I can do to achieve the same effect of reducing resin flow to the breather?

Thanks!

#8

i’m guessing you can use perforated film with less holes and try to lay up the layers in 45 degrees, that should reduce that effects significantly.

#9

Ah yeah good idea, I’ll see if I can lay up at 45deg for my middle ply.

Bearing in mind I’m doing cosmetic parts at the moment and perfect surface condition is much more desirable than saving every last bit of weight, is it ill-advised to use an unperforated release film? In a way I’d prefer to go to an extreme and then move back to a workable middle ground, rather than tickling my way towards the optimum from this poor surface condition!

#10

Latest progress is I gelcoated last night; basically kept brushing out every 10-15mins using only 20g of gelcoat over both parts initially, and then about 45mins later added about another 10-15g. I need to find the right time where the gelcoat is viscous enough to wet out fully without waxing away into puddles like my photo in the first post. Is it just a case of finding the right time to brush out again, or can I use an additive?

This afternoon I’ll laminate with the following changes:

3 plys of 200g at 0, 45, 0deg instead of all 0deg
Peelply applied in strips to high/low areas to prevent bridging
double layer of breadwrap to reduce resin flow
more careful consolidation under partial vacuum

Hopefully we’ll get a part that looks a bit more pro this time…

#11

Hi chaps, I haven’t got photos available just yet of my latest effort, but essentially the parts I made this weekend look very similar to the photos above; bridging is marginally improved but not eliminated, and the resin has still been pulled out of the laminate stack leaving the air between the weave.

Initially the double layer of breadwrap looked to be working, but actually it just slowed down the movement of resin into the breather, but did not prevent it; there was some pooling of resin in the breather towards the vacuum fitting.

I did one piece with a 200g twill at 0 deg, then 400g twill at 45 deg, and the other part was 200g 3 plys at 0, 45, 0 deg. they both look the same as each other and the same as before so unfortunately changing the orientation and using a heavier fabric hasn’t helped - I think these ideas are not wrong, just I’ve got another more fundamental problem. With the consolidation I struggled to get the carbon to stay in place over the edges before bagging, and then even with only partial vacuum it was a real struggle to move the laminate into the corners using fingers or a nylon tool. Maybe this will come with practice? However the air between the weave seems directly linked to the resin being pulled out the back, and feels like a hardware/setup problem, not a technique issue.

Any suggestions for what direction I should head for the next parts?

Thanks!

#12

Perhaps you might try a simpler part first. Maybe something small and flat to get a handle on your air issues then move to the more complex part to deal with the bridging. That should separate the two major issues and make it slightly less complicated. (and cheaper)

#13

Hi AVT, thanks for the suggestion. I do have a flat panel I can use, and since I want some flat sheet for some other projects I could look at using this. However, the depth of this part is only about 1cm, and the mould shape is not too complex - essentially just 2 blisters standing out of a rectangle. It’s about 30cm long and 12cm wide, so not that big - basically mixing the gelcoat in a smaller quantity is difficult as I am using less than 2g of MEKP anyway!

Do you think air between the weave is related to the the bridging? And if so what could the mechanism be? If the air between the weave is caused by the bridging I’ll move to the flat panel again, otherwise my gut feel is to stick with the small mould since it at least gives me some practice at laiminating and consolidating.

#14

I didn’t notice any discussion about how much vacuum your pulling?Maybe try dropping that and see?

#15

Hi Mike, we’re pulling about 28.5in. So you’d suggest we back it off? And if so, what would you aim for?

#16

I would drop that in half so less then 50% or even lower and see,maybe try using just fiberglass to keep costs down until you have it right.

#17

Ok thanks mate, I’ll have a try at that for my next attempt… gel coat tomorrow and then laminate friday afternoon I think.

#18

You could also try letting your resin kick a little so it doesn’t bleed so easy. What kind of perf release film are you using?P3?

#19

I’m using this from Easy composites. I just searched P3 film and came up with this from their store as well. This states ~8mm spacing for P3 - I’d guess the breadwrap is about twice that frequency.

One of my queries earlier in the thread was whether people think I should use a less perforated release film (or even non perforated) but unfortunately no one was able to offer any guidance. Have you got experience of ‘breadwrap’ or a similarly high perforation release film, or have you always used P3?

EDIT

I realised I had been speaking to Easy Composites about the mould release problem I was having previously, but hadn’t called them about these issues; I just spoke to one of the guys who suggested dropping the vacuum down to “about 15-20%” so 4-6in for wet lay. He also said that the release film perforation won’t make much difference - I could just get rid of it if I wanted, however I’ve found it makes removing the breather much easier, so it’ll stay for now.

I think part of the problem with the bridging may be that I am going heavy with the resin and so this pools next to the surface and keeps the carbon away, then when I leave my pump on the resin is wicked away, leaving the bridged area as well as the air between the weave.

Soooo… my plan will be to go less resin rich, wind the pump right down to 5in, and have another try.

#20

I also use p3 seams to work. Not sure if you can get anything smaller or bigger spacing. I think the reduced vacuum alone will give you a better looking

What is bread wrap ?