Fiberglass help needed

[Wynand N]

Whilst hand laminating with CSM, some bubble like dry spots appear that refuses to be wetted or lay down - what can the cause of this be?
The problem is isolated to a few places (on flat areas) and it is laid down on gelcoat. Now that it is set, can it be repaired by injecting resin into the void between the gelcoat and the CSM with a syringe to fill it solid before laying the next layer of mat?
Or how do one repair that without serious surgery....

[MarboMan]

Did you get anything on the CSM before using it?

What about storage...kept in a relatively cool, dry environment?

Syringe might be a good idea! Do it as soon as possible to get best chemical bond to surrounding resin.

[Manie B]

sorry i only saw this post now after i posted my previous reply

i had similar problems with my epoxy ( which is very different ) but in my case it was surface contamination = not clean enough

after all the shit we had on the mine with the fibreglass spirals = mineral benefication plant i firmly believe that a surface must be clean and either acidic or alkaline depending on your application

i realise that you are probably applying wet on wet - what we did was mix short chopped fibres 20mm (sold by Harveys) into the polyester resin mix to make a thin light paste = porridge

it worked very well as our outer surface on the spirals was shit anyway

i am sure that if you rolled it out well you could get excellent results

[Wynand N]

Manie, the surface is clean - the plug was gelcoated this afternoon and I let the gelcoat cured past the finger pull scream test, about 3 hours total. Then a barrier coat of clean laminating resin applied and waited until it kicked, followed by the first CSM coat giving the problems now.
The CSM is kept in a cool dry place on its roller with the plastic bag/wrapper pulled over after use.

[Manie B]

before panic

how big are the bubbles

[Manie B]

it could be that you waited a bit too long and the first blush was surfacing

dont worry about small bubbles

fill with syringe - common practice

[AndrewK]

Once the resin has set the only way is to grind out or fill with a syringe that I know of.
How big are they, send a photo.
These bubbles, were you able at first to roll them out and then they reappeared? or were they not be able to be rolled out in the first place?

[fiberglass jack]

did you wear gloves while you were cutting the fiberglass, i see this problem with guys waxing moulds and not properly washing the wax off there hands and you end up with areas that the resin wont wet out. also what resin are you using u said you are using csm which has a binder to hold it together needs the syrine to disolve, also a drop of sweat can do something simalar, best thing to do is carefully grind the area out with a diegrinder and make a paste from the gelcoat and fill and carry on with the layup. if you dont fix the area will bubble and blister in the hot sun

[Wynand N]

No gloves were used, but hands were clean at the time. The problem manifested itself at the aft flange when we started the CSM. Then it went well till about midships and shit hit the fan. Funny, the problems are at the same place both sides of the hull....

Will start filling those that did not bubbled out with a syringe and the bad ones that popped out be we grind out carefully and patched before the next layer goes on.
The mat at places refused to be wet out and some of the bigger spots (two the size of my hands) did wet out and bond as the steel roller went over and then just lifted off again - no matter how much you roll it down.

Decided to use woven roving for the next layer as it wet out easier to get things back on an even keel before putting the next CSM down.

[Manie B]

Wynand your pics look very similar to the problems we had on the mine with the "spirals"

we were never 100% sure but put most of it down to contamination - sweat - slight grease on hands or clothing

that is why i have different gloves for different usage
sweat plays havoc in our hot climate
i have a constant battle with it here

i now wash everything with vinegar
i have had massive success with white vinegar
all the other stuff - meths - alcohol - acetone dont even come a close second

i am not saying this will work for you but its worth a try - if a drop of sweat gets wiped up with a vinegar cloth it dries quickly and you can proceed - it really goes fast

and dont "barbeque" any where near your work piece - we were even worried about that fatty smoke

i know it sounds like madness - but in our exteremely hot and dry climate at a very high altitude - things are different - and i solved many of my problems by working "cleaner"?

even your beautifull table in the back must ONLY be used for cutting fibre - build another table to pack things on - that table must be spotless, and cover your rolls with plastic so that no dust and sh1t can blow on it

sorry, just trying to help sport - not critisizing

[Wynand N]

Decided what the hell and let the apprentice and helper loose with small grinders fitted with sanding discs. Smoothed down the whole hull down and removed the "cancer" spots altogether rather than injecting resin and do battle that way. Now there are no voids between gel coat and glass that may cause mayhem later.

Will blow the plug clean, wipe down with acetone and lay down the woven roving and hopefully will end up with a smooth and solid surface to laminate onto further...

[ondarvr]

If these spots refused to saturate with resin and returned immediately after rolling, then it's an issue with the mat. It may be the binder was applied incorrectly (uneven), or from handling it you contaminated the surface with catalyzed resin that gelled creating stiff spots that spring back.

It's best to not apply roving directly over any cured laminate, the bond will not be as good as when mat is used as the first layer. the next layup should be a layer of mat then a layer of roving, if the part needs to thicker you can add more glass at a time though, you're not limited to one or two layers at a time. If you do plan to use more layers of glass be sure to catalyze the resin at the lower end of the recommended range so you have enough time and the layup doesn't get too hot.

[Wynand N]

ondarvr, it must have been the binder in the mat as no contamination was cause on my side, and the fact that most of the serious damage was on the one strip over the midship area and to a lesser amount elsewhere.

Nevertheless, all the spots were sanded out and in fact the whole laminated sanded smooth. I laid down a cloth instead of wr and all went well and the plug is now evenly covered with a rather fair and smooth surface to build upon.
My next rum would be CSM again - but 300g/m sq instead of the 450g/m sq used - from a new roll, followed by 2mm Coremat and another two coats CSM.

All layups will go on singular up to the CoreMat, but the last two CSM's will go on together the prevent heat buildup close to the gelcoat and to prevent warping of the mould.

[ondarvr]

I must not have paid attention the making a mold part, I was thinking you were making a part.

The same holds true for cloth, layers of cloth and/or roving alone don't bond as well when used without mat, even a thin mat helps a great deal.

For making molds one layer at a time the resin needs to be of the correct type, skin resins are promoted so they cure better in a thin laminate resulting in less post cure. What frequently happens with the slow build method is each layer never cures completely, so after the mold is complete and a few parts are built it starts to change shape. The amount of change depends on how thoroughly cured it was to start with and the temperatures reached by the parts being made, this post cure can continue for a very long time. It starts a as a pattern in the mold surface, the pattern can be from the glass used in making the tool, or from the part being made. Sometimes reworking the surface eliminates the pattern for good, but it may continue to return.

[AndrewK]

Looking at the photos it does look like contamination problem, I am guessing not a binder issue but some other contamination that could have happened during the mat manufacturing.
As ondarvr mentioned you most frequently see this happen as a result of contamination with gelled resin.
Is this going to be a female mold that you will use with infusion? if so I recommend larger flanges say 200mm.

[Fanie]

Hi Wynand,

Sorry I missed your post. I have seen those bubbles before, but only in the free state :D

That is a not-bond problem you have there. If the previous layer, ie gelcoat has dried some, paint with resin before applying the glass. The problem is not the fiberglass.

Water or wetness will also isolate the wetted glass and pevent it from proper bonding.

If the resin get to gel before it is rolled onto the previous layer properly then that can also happen. If some resin got spilled on the glass and it gelled and the glass is then applied it is what you may get.

Polyester resin in general is not full of nonsense, and I have found you must make some really bad mistakes for it to come out improper. One thing though, do not allow the resin to gel before the glass was worked over completely.

I made a couple of experiments this week. One thing I found that worked well was to cool the resin down. This prolongs your pot life from about 8 to 10 mins to about 30 mins, but the applied resin wants to gel fairly quickly since it heats up once applied.

Looking at those pictures it looks to me like the resin started gelling before it was wetted out onto the bottom glass or gelcoat. The gelled glass was at a different angle and so lifts up to form those bubbles. I would grind it down and just apply small patches of chop to get the thickness even again.

One experiment I did was to check the amount of layers vs thickness. The resin cooled down, I applied the next layer of glass before the previous one started gelling. This caused the excess resin to be taken up by the fresh glass when you roll it on 'dry', and less resin is required for fully wetting the glass out then. I must say I was impressed with the compactness I got with 12 layers.

On your boat - I would precut the glass and all the layers. Roll the glass up, just the first layer lies in place. Then start at the transom and wet the first 1m of bottom layer, then the second, then third. Then do the next half a meter, roll the 2nd layer out a bit and wet that, then the third. This way all the layers gets applied while they are all wet, and you never struggle with dried spots. You will need some hands to hold the layers.

Some more advantages are better bonding between layers, they develop better heat when the layup is thick and when you are finished with the keel the transom should already have gelled. You should never get those bubbles again.

Also, when I do large layups, I use the minimum hardner for max pot life. To apply the resin I use about a 300mm paint roller, one can do quite a big layup in a relative short span of time. They also hold more resin which gets released more by pressing down on the roller, and excess resin gets picked up by it again and spread to elsewhere.

You can wash the roller thoroughly afterwards with washing powder. I use a plastic basin so one can rotate the roller easily in it. Wet the roller properly in the stromg mix washing powder, then shake the water out some and squeeze the resin out of the roller by clamping you hand around it hard and stroke. I know what you're thinking, but this is different ;) The white stuff that comes out is resin that you can discard of. Spin the roller in the washing powder untill the hairs stand out properly and repeat. To rinse the roller I hold it under strong tap water that spins the roller. Dry by spinning it against a wall or flat surface. The hair should be soft and fluffy again. Hang it up to dry, if you put it down that part of the roller will go flat.

Best here in SA is to do glassing at night in the winter. You can work at your leisure and have enough time to do all the layups. The concoction cures the next day only.

[MikeJohns]

Wynand
CSM is a pain particulalry 450.
I just built a heavy 12 foot knockabout boat and had similar problems. I found that I could eliminate all the voids by covering the hull with clear thin polythene sheet stretching it slightly over the hull and clipping it down. Then I used a sponge to smooth down on the polythene, you can see exactly whats going on and you dont pull the fibre by trying to roll partly cured mat. Even if you don't clip the edges it seems to work just smoothing out from the centre. Leave the sheet on till the resin has set. For awkward bits with a sharper return I found I coult put polythene then a car wash sponge clamped over the top which worked a treat.

Current thinking is that the principle reasons for the bad blistering of many GRP hulls is the voids left in CSM layup.

[Wynand N]

Thanks to all for the input thus far.

Yes Andrew, this is going to be the female mold for the infusion boat. The flange is only 70mm wide with location pins (half ping pong balls) spaced evenly around the perimeter of the hull flange.
But, this flange is only the base to which the hull sheer to deck mold screws to. The hull has a continuous radius sheer flange inwards and with a slight recess about 60mm from radius edge to which the deck fits into flush. This mold is small and easier to make and fit than to fabricate a split hull mold. On this mold I will leave enough "meat" to attach the envelope snot tape, vacuum and feed lines:cool: