Laminating problem ?

Hi Guys,

Yesterday I laminated a plug with 2 x 245 gsm layers carbon twill and using Latex, this evening I peeled off the latex to find what looks like a gas bubbles trapped between the layers in only one area of the hull :confused: rest of the hull was fine.

The plug is 6 months old and was primed after final sanding, few months ago it was painted by professional car painter, 2 days ago applied 8 or 9 layers of wax that was buffed between coats, as I run out of PVA.

After laying Latex over the wetted-out carbon I spent about 30 mins rolling out small air bubbles and gave the plug one last critical look over before putting in the loft to go off, looked good, temp in workshop loft has been 25 degrees C.

Any ideas what would have caused this problem ?

Cheers Alan

Hi Alan,

Are the voids between the laminate, or have they appeared against the plug surface?

My immediate guess is that you moved the plug to a place that was warmer for curing after laminating.
Even though you were meticulous with roiling out the bubbles, there will still be some gases & air trapped.
The increase in temp results in an increased volume of air.
With the nature of the latex method, you are not guaranteed an even pressure over the entire job. As a result, the smaller pockets of air tracked to a lower pressure zone, helped by the reduced viscosity of the resin, and grouped together. Forming a bigger bubble with enough pressure to lift the laminate and overcome the latex tension.
The best way to avoid this problem is laminate in a moderately warmer environment that is cooling down or do not change the curing conditions and use the preferred ‘post cure’ method. 40 - 50 degrees for at least 4 hrs, the longer the better!

Mull it over and see if my guess fits the facts!

Cheers, Jim

Hi Jim,

I have not taken the hull off the plug yet, waiting for complete cure as did not want to stress the carbon if the wax does not release easily (precaution) but after reading your excellent explanation, I’m now certain that I don’t need to look to know that it has happen at plug surface.

The facts do fit the problem, the only reason I laminated when I did was because the weather was sunny & warm, after rolling out as much air as possible I put the plug outside in the sun while I was cleaning out the workshop.

When I picked-up the plug to store it away the latex surface was very hot to touch, being in the sun and also checked with surplus epoxy and felt temp pot was warm coming from the chemical reaction, never thought much about it and stored it in the loft where the temperature was considerably lower.

The problem happened in the area around the rudder location, this is where the latex has lowest tension pressure compared the more curved areas of the hull hence, your explanation fits the problem exactly…another crate of beer I owe you !

I will now lay-up small area of carbon on the plug (to have same hull shape) and cut out bubbles section and graft in the new piece.

Cheers Alan :zbeer:

Hi Alan,

I can’t guarantee this will work, but I have a inside tip.

I have Manipulated and thermo set thin laminates… You will need a mains powered hot air gun, like you would use for stripping paint, you use this to locally heat up the laminate and it will momentarily soften the epoxy, enough to re form it. You may be able to re-set it in the right profile. I wouldn’t recommend doing it on your nicely finished plug, so perhaps it would not be possible to achieive perfection…However, you will be able to turn a ‘positive’ proud bump into a ‘negative’ hollow which could be filled and faired.
Wear gloves as you don’t want to burn your fingers.
This is quicker, and you do not have to effect a repair on a new hull!
Try it on some scrap laminate first maybe…
Cheers, Jim

Hi Jim,

Good idea, I have thermo controlled hot air gun, what sort of temp would you recommend ?

Other way would be to fill the hollows from inside the hull (loaded epoxy) and then sand-off the proud bump on outside of the hull, it is going to be painted anyway, whatya reckon ?

Cheers Alan

The idea is you use quite a high heat but only for a couple of moments. This ‘breaks’ the Tg and the resin becomes soft again, obviously you do not want to burn the resin, and because it is so thin, it will heat up almost instantly, but cool down almost as fast. The trick is to be quick and confident, so practice a little first to get a feel for the technique.
Your idea is equally as valid, but it does mean a repaired hull.
There would be an equal weight penalty, either in filler for the first method or in extra laminate (the patch would require an overlap, minimum 10 -15 mm) for the second.
Really the choice is yours but I’d start with the first methods and try to get it as perfect as I could, meaning the least amount of filling. If that turns to custard, you have plan B!


This may not apply as I use West Systems but I use hot water right out of the tap to re-shape parts. Not hulls mind you but just where things don’t quite line up. Clamp them lightly in place, pour hot water on them, push them around a bit and pour cold water on them. Seems to work. No danger of burning the parts.


I tried the hot air trick on few off-cut samples and works perfectly, thanks…but I have another problem, I can’t get the hull off the plug :pissed: spent whole afternoon tried everything max air gun pressure, long thin hardwood sticks etc …managed to separate the free-board, only midships along the keel won’t release.

I will leave the hull for couple weeks to let the carbon fully cure before getting brutal with it.

Cheers Alan

That’s weird, you have a couple of options.

Mark the fin position and make a hole to inject air from the top.
Water also helps, using the Hydraulic action. Pour water into any gaps you can and pump it further with the air gun…

I’m thinking that even though the mould may have been painted a while ago, when it got hot, it gassed out and has affected the wax.
Always post cure your tooling;-)

Hi Alan,
I’m sorry for your troubles, but the painted plugs are nothing to do with polyurethane paints ?
According to what I was reading on several wax data sheet, wax are often reacting with polyurethane surface and generate the typical ‘sticking conditions’.
Hope is not the case !

Oh what a nightmare ! could not sleep thinking about it and had to have another go at it, tried water then vinegar (break down the wax) 6 bar air pressure with drinking straws between the plug and hull, where I could get them in … nothing would get it to release, was just about to cut keel slot in the hull when saw hack-saw …ah ha :rolleyes: thin spring steel that bends nicely to follow hull curves, without breaking.

Ground off the hack saw blade teeth and smoothed edges and then slide between hull / plug and with few taps with hammer it finally popped off !

Looking closely at the area that would not release along the keel line, the first layer of carbon has quite number of irregular shaped craters (not regular smooth air bubble shape) which is not normal using latex from previous lay-ups, looks like the wax kind of exploded under high temps and epoxy bonded to directly plug painted surface as Jim suggests together, with latex pressure (see weave pattern in the paint) is highest in this area of the plug that only accentuated the problem. You can see free-boards was not affected same as bottom of the hull.

The proud bump in the rudder area Jim was nice curved shape (expanded air) exactly as you indicated and came out perfectly with hot air gun.

Claudio, I don’t know what type of paint it was, I only assumed it was enamel as it was extremely hard, you can see that the paint has lifted some filler off the plug, don’t think polyurethane would do this?. Worst of all this is the BM-7C hull that I wanted to be perfect, can’t think of a worse start. One major lesson learnt, for release I will only use good old plastic packing tape in future!!!

Ok now for next challenge, how to get paint off the carbon … does paint stripper work ok without affecting the carbon … Jim ?

Cheers Alan

NO! Absolutely no paint stripper!

I’d scrape it of with a curved Bahco scraper…

I’ve used laquer thinner to strip off old paint with no problem. I drape a rag over the area, pour a little thinner on it, cover it with a plastic bag and let it sit for a half hour or so. The paint bubbles right off. I haven’t tried it on CF. Is there a chance it’s weakening the epoxy?

[QUOTE=Astute Composites;64242I’d scrape it of with a curved Bahco scraper…[/QUOTE]

Works a treat :jump4: excepting hard to get at section at the bow, I’m back on track, thanks again Jim !

Cheers Alan

Yes, a very high risk operation. The strongest solvent I’d run with is Acetone, and not for too long if your laminate is still a bit green.

No Problemo. Jim.

It’s me again with another laminating problem :indiffere

After my previous problem with waxed plug so 2 days ago I prepared 2nd plug for laminating, this time using plastic packing tape as release agent, late afternoon when temp was around 25 C and cooling.

Hand laminated 245 gsm CF to plug & 105 gsm FBG Aero as outer hull layer to have matte finish (playing around with hull friction so boundary layer flow remains laminar) anyway, after lamination overnight temp cooled to around 16 C and next morning trimmed hull off to plug sheer line and put back plug back in the loft and during the day temp increased to 35 C ambient.

When got home last night (48 hrs after lamination) wanted to pop the hull off the mould … after 3 hours the freeboard finally came away from the plug and cannot see any damage on plastic tape surface and the inside of the lamination looks like very high polish finish, but the hull will still not come off the plug !!!

I have the impression the hull has shrunk onto the plug, is this possible ? hull is very tight all around the plug.

As next step, I’m thinking of now pouring acetone into the areas where I can separate the hull from the plug, it will make a mess of the plastic tape & may even increase the adhesion as the adhesive turns to liquid coming from the plastic tape after the acetone hits it …but cannot think of what else to do, any other suggestions ?

Problems now with 2 hulls and still have 3rd one to go ! … problems come in 3’s don"t they !?

Cheers Alan

Hi Alan,

It does seem like a little run of bad luck, sorry to hear.

The shrinkage should not present a problem. We calculate for 0.02% at 120 deg C so you shouldn’t have any problems there.
I assuming you waxed the packing tape prior to laminating?
Second assumption is that the wax is high temperature mould release?

The only time this has happened to me is when I’ve waxed the brown tape, and then spray tacked on a dry layer of peel ply before laminating. Even though it was a mist coat, it was enough to destroy the wax and the thing stuck like the proverbial…
So I avoid packing tape with wax unless it’s for a one off so that I can wreck the tooling instead - Foam plugs, etc.

If you have waxed and so on, and not applied any other products before laminating, I’m going to have to admit to being a bit baffled… Technically it should present no release issues at all.

Your solution of Acetone to melt the adhesive is valid, as long as your plug is okay with that.

If you have any other ideas feel free to jot them down and we can get to the bottom of this!


As I finished this, I’m wondering if there may be a problem with the release wax now…

Wax ? :blkeye:

What’s that quote you have as foot note with your Avatar :dunce: … I’ll wear that hat today. Now where is that acetone & lighter !

Hi Alan,

So, I’m not alone with sticky problems ! but at least I know why !

Your case is the second time in few days and what I see is a common point : the Paint
I do not know what could happen with that paint, even not in direct contact, when exposed to polymerization temperature.

In my opinion you should get rid of the paint first and start again.
In the past my wooded plugs were laminated with glass to protect the plug and then waxed directly after careful sanding and polishing, the laminated stuff was getting out almost alone !