What caused this, GRP that is...

Discussion in 'Fiberglass and Composite Boat Building' started by Wynand N, Jul 4, 2012.

  1. Wynand N
    Joined: Oct 2004
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    Likes: 148, Points: 73, Legacy Rep: 1806
    Location: South Africa

    Wynand N Retired Steelboatbuilder

    Gelcoat; What caused this?

    Worked with GRP for the last 6 years and never came upon this kind of problem before:confused:

    I laminated a lid - pulled about 5 dozen off from the same mold in the past without any problems - and was shocked to see the result. The gelcoat was freckled at places.
    I inspected the mold and did find some ram wax that was not fully polished off to a shine by my helper and thought that was the problem.

    Nevertheless, I then personally polished off the mold to an extremely high and smooth shine and remove any dust with a special "static" cloth I have. When mixing the MEKP into the gelcoat, I made sure it was very thoroughly mixed and used 2.5% hardener to gelcoat ratio.
    I applied the gelcoat evenly with new GRP brush and left to harden for about an hour and half in the winter sun - was solid tacky and squealed when finger was pulled over.

    I applied the first layer of 450g CSM with brush and rolled out with a ribbed roller. I then fitted a prefabricated X reinforcing (grp) with hole drilled to let any fumes escaped under it. Then I applied the second coat of 450g CSM and left to cure for about 22 hours. Btw, normal GP polyester laminating resin used.
    This second molding actually came out worse than the first one and I did everything myself to make sure it was done right....:(

    Except for the ripples in the gelcoat, some gelcoat surfaces feels "funny, waxy wet" like. In the mold is a tacky, sticky residue left after the molding was removed from it, see pictures.

    What can be the problem, as I am mystified? The gelcoat is a different brand than the laminating resin used, but have done so many times in the past without any problem.
    I just have a funny feeling that the gelcoat is at fault; my supplier repacked for me in 5 kg containers and can it be that I was actually given flow coat instead of gelcoat? What would the symptoms be if it is indeed flow coat?

    Or am I missing something...Any help and input would be greatly be appreciated.
     

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    Last edited: Jul 4, 2012
  2. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    aligatoring or elephant skin. Caused by undercure of the first layer of gelcoat. The second layer (gelcoat or resin) attacks the first layer.

    remedy: give the gelcoat a better cure, you can use all options:

    -more catalyst or cobalt
    -more heat
    -longer cure time
    -thicker layer
    -styrene blanket (styrene sinks, and gelcoat under styrene fumes will not cure properly)

    wax is not the issue here.

    Do a search for the 2 terms above, and you will get some more info. However, the above should solve your problems. With this info you will be able to troubleshoot and pinpoint a possible cause.
     
  3. tunnels

    tunnels Previous Member

    AH you got some of them to !!
    WOW You never done gel coating and glassing till you had a dose of alligators !!
    For a demo i tried to replicate a alligaters couple of times what you got and it wouldnt work !!
    Some where recently posted some pictures of what the chinese guys did on a deck a while back just looks like what you got but they had heaps of it !!.

    After re reading you post you touched on that its winter where ever you are .
    Gel coat and resins need to be warmed slightly or about 20c if possile, tins and drums sitting on concrete floors the cold comes up and be lucky if they are even i double figures maybe !!
    2.5% OF CATALYST sound a little high ??
    the catalyst you using is how old ??
    keep your catalyst in a dark ,cool place when you not using the container , light over time slowly kills it and it becomes way less potant than when it was new !!
    To much catalyst will slow the Gelcoat as well so dont over catalyse .
    Warm your mould and mix your gell coat and let it stand for 3 or 4 minutes before you apply .
    The cataylst will have start to work and warmed the gel coat in the container . if its a small mould make sure you know what the gell time is because the warming and standing will speed that up so be quick .
    The thickness you are putting on you could have thin patchs from brush strokes .
    A good idea is to mix some gel coat about 20% with the resin you use for the first glass skin also hides any marks and possible see throughs even if the gel coat didnt alligator .
    Never a dull moment and just when you think you got it some one rips the rug out from under you feet !!.. :D
     
    1 person likes this.
  4. tunnels

    tunnels Previous Member

    This is from another post . may help in the future !!

    Gel coaters check list for brushing !!!

    --------------------------------------------------------------------------------

    Moulds to be gel coated should be clean ,waxed and polished!!
    Pva has been sprayed and is ready to go ! 100% dry and dust free!
    Do you have all the essentials that you will need, could need and if there’s a breakdown tools required right at you finger tips !!.

    Ok list!!
    Gel coat that’s the right colour and has been shaken and stirred and left to stand for a few minutes !
    Is the gel coat cold from sitting on a concrete floor ,is best sat on a work bench up off the floor ,and been there for 24 hours as I could take that long to acclimatize to you workshop conditions .
    If you are brushing then your brush’s need to have been soaking in acetone for a short time and then taken out shaken and gently dried 100% . for 30 minutes . Loose hairs, and dust all needs to have been washed out.
    Plastic containers if they are new also need to be wiped with a clean rag and placed on a bench upside down, so they stay clean.
    Gelcoat even new straight from the container could have congealed or thickened lumps in it so best to strain.
    Panty hose or stockings are best ,or you can use cheese cloth !,even fine glass cloth !! These are all suitable as strainers. pull and stretch over the top of the container then pour the gel coat gently through till you get the amount you require !!,gently pick up the strainer material and drape over and inside the Gelcoat container so it can be used a second time if need be !!.
    A good set of digital scales with a 0.00 scale for accuracy and totally cover completely with plastic that you can see through and tape in place.
    Always be accurate with measuring and check and check again.
    You should already know what the temperature and the humidity is from the wall dial as you walked in your workshop when you arrived !!.
    This is what we have that hangs on the gun boom so everyone can see all the time !!,
    Its pretty accurate for what it is and have checked it against a expensive unit that we have !!
    Keep it clean and check throughout the day !!
    Temperature can remain the same but the humidity levels can fluctuate considerably for many reasons!!.

    Don't even have to think about this !!
    Gelcoat 1.5% of catalyst so if you have weighed the gel on your scales and know the kgs !! Squeezed the catalyst measuring bottle and set the required amount
    You have a battery drill with a clean painter stirrer attached you are ready to go .
    Pour the measured amount of catalyst into the middle of the gel coat and begin to stir with your drill slowly to begin with. And then slowly speed up and move round and round in the Gelcoat container to thoroughly and completely mix. Slowly down to almost stop and slowly withdraw the stirrer stop and wipe clean and lay on the clean bench . from this point the clock is ticking !!,if you have done your home work and a little testing you will have a pretty good idea of the gel time !!,so with your egg timer set it 5 minutes less and pick up your brush and go !!!.
    (Why pour the catalyst in the middle of the gel?? )
    Catalyst if not mixed properly will cling to the sides of the container and as you brush you will pick up this unmixed catalyst and I gets wiper directly onto the mould !!
    Unmixed catalyst can and does have drastic affects on the surface of the mould and can eat the wax away , can bleach the new Gelcoat and discolour it . non of these thing will be seen of noticed till the product is released from the mould and there will be a strong odour of catalyst !!
    Poor mixing happens more so when using square containers than round !! You have to be 110% on the ball 110% of the time!!
    Leave nothing to chance at any time !!!)

    __________________:D
     
  5. Wynand N
    Joined: Oct 2004
    Posts: 1,260
    Likes: 148, Points: 73, Legacy Rep: 1806
    Location: South Africa

    Wynand N Retired Steelboatbuilder

    Thanks Herman and Tunnels:cool:

    We did have a cold spell here - actually postponed the laminating job a few days until it was more bearable and only started midday then. I actually lost the box that was laminated with the first lid as well due to same symptoms.:mad:

    I did notice the gelcoat was really very thick and have to help it out of the container into the mixing bowl and spread out very "difficult" due to the thick viscosity....and the cold the reason I popped 2.5% catalyst into it to help curing within a reasonable time - usually uses about 1.5% in the summer. The catalyst is fresh and bought recently.

    Well, never to old to learn. At least I am a member of the alligator club now:D
    Will put the gel out in the sun and further heat it up with a heater since the days barely touches 20C max nowadays.
     
  6. tunnels

    tunnels Previous Member

    At least I am a member of the alligator club
    Such pretty wee things !!
    yes you have earned you wings to fly !!
    well done !!


    But if the resin comes through and it sometimes does if the resin had gelcoat in it you may never even noticed apart from being a colour differance maybe .
    Gelcoats and resins like a little warmth so warm everything specially the mould if possible . Warm not hot or you will have another whole set of problems .

    Location: South Africa so what part of the country ??

    I just relooked at the pictures you sent . those marks on the mould are possibly just just the very edge of the aligaters and parts where it could have started to pre release .If it soft and stick styrene should take it off and do the whole mould let it completely 110 % dry and rewax 3 times after and then re-gelcoat again Or catalyze some resin pretty high and pour over the surface give it a good brush, round and round and up and down and when its completely hard blow it off with compressed air should come out absolutley clean dont forget to wax the mould again !!
    .
     
  7. Wynand N
    Joined: Oct 2004
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    Location: South Africa

    Wynand N Retired Steelboatbuilder

    Quite far inland at a town called Welkom in the Free State province - see map. We are now smack in the middle of our winter :)

    [​IMG]
     
  8. Herman
    Joined: Oct 2004
    Posts: 1,618
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    Location: The Netherlands

    Herman Senior Member

    There are waxes available that dissolve uncured resin. These are ideal for cleaning up a mould if there are small uncured resin drops. Whatever the worker does, he cannot ****-up the release properties of the mould, which is quite re-assuring.

    Ferro FR17L is one of them.

    When doing VARTM, you regularly see a thin line of uncured resin at the inner seal, where the resin thickness is running to zero. This Ferro FR17L wax cleans up the flange nicely.
     

  9. Angélique
    Joined: Feb 2009
    Posts: 3,003
    Likes: 336, Points: 83, Legacy Rep: 1632
    Location: Belgium ⇄ The Netherlands

    Angélique aka Angel (only by name)

    For resin warming and warm ready to use storage this guy converted a broken fridge into a warm cabinet with an old fashioned light bulb as heat source controlled by an ordinary (also old fashioned) room thermostat.

    Broken fridge as a cheap and already insulated cabinet with light bulb heating controlled by room thermostat.

    _conversion_fridge_to_warm_resin_cabinet_1_.jpg - _conversion_fridge_to_warm_resin_cabinet_2_.jpg - _conversion_fridge_to_warm_resin_cabinet_3_.jpg
    - click pics to enlarge a bit

    Such a thing in SA is only useful during mid winter, but for others it might be a warm resin ready to use storage solution for a longer period of the year . . . :idea:

    All thanks for the info & tips here [​IMG]

    Good luck !
    Angel
     
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