Tooling gelcoat

Discussion in 'Fiberglass and Composite Boat Building' started by RTM, Jun 19, 2013.

  1. RTM
    Joined: Jun 2013
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    Location: Central Florida

    RTM Junior Member

    I built a plug for a small center console to be used in my 15 ft. Whaler. The plug is built from plywood covered with gloss Formica with radiused corners. I put the required draft in the sides so the plug should release from the mold. I degreased the plug and have mold release waxed it about five times. Next step is to spray the PVA on the plug and it should be ready to laminate. I have done alot of fiberglass repair work over the years, but never worked with gelcoat. The garage where I am working is 85 degrees+. My question pertains to the tooling gelcoat which I plan to roll on and tip off with a brush. Mixing it with 2% MEKP is the norm. Should I reduce it to about 1% becuase of the hot garage. How about cooling the can of gelcoat in the fridge before I use it. Any help is appreciated.
    Rich
     
  2. garrybull
    Joined: Nov 2010
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    Location: portsmouth england

    garrybull Senior Member

    cooling the gelcoat down will make it quite thick and hard to apply.

    i would store it indoors at a more reasonable temp.

    i apply most gelcoats with a 2 or 3" brush on the first coat and second coat with a roller on small moulds but other people will do it the opposite way.

    if your worried the gelcoat may go off before you can use it all just mix up small amounts at a time with 1.5-2% catalyst.

    that way you won't have any problems.

    axing the plug 5 times and a coat of pva should be plenty for the mould to release from the plug.

    you could always put a bolt flange right through the centre of the plug so that the mould then becomes 2 pieces which will help with the release process but you end up with a line that will need to be sanded and polished out once released from the mould.
     
  3. tunnels

    tunnels Previous Member

    Ok lets get to basics again !!
    If you working in a hot place you could work early morning when its the coolest time of the day ! Playing with catalyst ratios and dropping it beyond the lower acceptable level then the gell will never reach its full potential hardness . so you tooling gel is a waste of time and could evne be softer than ordinary gel coat . So instead of thinking 2.0% 1.5 is the normal percentage is any country ive worked in !! do a small test sample and test the gel time !!
    NOW ALL THIS HAS TO BE DONE ACCURATELY use a proper measure not a spoon or counting drops !! that's no good at all !! but people do it !!
    KNOW WHAT THE TEMPRATURE IS !!
    KNOW WHAT THE HUMIDITY LEVEL IS !!
    KNOW WHAT THE CATALYST RATIO IS !!
    THEN YOU WILL KNOW THE GEL TIME !!

    If you check with your supplier and make sure you have the right catalyst for gel coat !! most times its different to what's used in resin !!
    Why ?? because it produces less gas and means less porosity and less pin-holing if you have to do any sanding at anytime later !!
    Once you get the gel time then you will know hoe long you have to work with it . the clock is ticking from the moment the catalyst comes in contact with the gel so don't waste time !!
    It will be best to give a second coat so now ,yes you should be able to up the catalyst to 2.0 % and to make that coat go on quicker !!, mix a little resin with the catalysed gel to thin it and make it flow better and be more brush-able and get it on quickly :D:p
     
  4. RTM
    Joined: Jun 2013
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    Location: Central Florida

    RTM Junior Member

    Tunnels, thanks for your reply. That is good advice. I'll also take your advice when it comes to the PVA also. One other thing though. When I bought the tooling gel, one qt, and the hardener, MEKP, they gave me a chart on quanities mixing but is seems to have disappeared. I have one qt. of tooling gel coat, 32 oz., how much hardener for the entire qt. at 2% and 1.5%. I can break it down from there.
    thanks, rich
     
  5. RTM
    Joined: Jun 2013
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    Location: Central Florida

    RTM Junior Member

    Tunnels, I guess I had a brain fade when I made that post. I figured it out on my calculator. I plan to mix one pint 8 oz gelcoat at a time. My console is only about 14 aq feet. At 1.5 percent I need .12 oz of hardener. That's not much. You say to measure accurately.
    What can I use to do this?

    rich
     
  6. tunnels

    tunnels Previous Member

    Im a metrics man and that's absolutely simple 1 litre @ 1.5 % =15mils for resin and gel goats !!
    1 litre of resin is just over 900 grams
    1 litre gel coat a little heavier very close to 1 kg because of the pigment's in them but its near enough !!
    Glass is measured in Metres and comes in Grams measured per sq. mtr 300,450 600, 820,900,1200, etc etc those are some of the most common sizes used every day and I don't have to even think about it
    speed o in the car is kilometres per hour and 50ks is normal or 100ks on the open road
    and that's the way it should be !!
    Imperial I forgotten 25 years ago
    years , months and days will never change but I do remember a time clock in one place I worked that had 100 minutes to every hour, not 60 and that was just to much to think about but still only 24 hours in a day so I guess there're always be some things that are impossible to change .
     
  7. tunnels

    tunnels Previous Member

    for small quantities a big plastic syringe (no needles required ) a lot of people use all the time .
    But your supplier is bound to have a small squeeze bottle that has a measure on top with a scale down the side !! in your case could be marked off in oz or mils and need a set of scales to work by weight , kitchen scales for smaller weights or bigger quantities bathroom scales and these days come in digital so are pretty accurate ,again possibly marked in pounds or kilos or even both !! some plastic buckets and containers have a scale marked inside down the side ,
    Make sure the plastic is styrene resistant or it could dissolve or melt away into a gooey blob !! there's a zillion different types of plastics out there
    good luck :):D:p
     
  8. RTM
    Joined: Jun 2013
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    Location: Central Florida

    RTM Junior Member

    I have made absolutely no progress on my center console mold since I brushed on a coat of orange tooling gel on the plug over a week ago. Its been raining every day and almost all day. Humidity is through the roof. Am shooting for Thursday, with very low prediction of rain. I wiped down the plug with lacquer thinner to get rid of the tackiness, and supplier says to sand the tooling gel with 120 grit paper on my orbital sander, paint on another coat of gel, wait about an hour and a half, and then laminate the mold. does this sound about right???

    rich
     
  9. tunnels

    tunnels Previous Member

    Back to basics again

    Gel coats when they are applied go to the sit and gel stage . at that stage of sitting the catalyst is producing gas bubbles and with added agents built in the gel coat like all of them this allows bubbles to surface until the gel becomes so solidified and the bubbles can not move so that's where porosity comes from . the second stage after the initial gel is a stage that is crumbly and its most vulnerable to damages if you touch and it sticks to your finger and you can lift it off the mould and tear it !! so never touch ever !! not with anything !!
    Ok now its hardened but not cured !!, gel and hardened is quiet different to cure , cure takes place over time 12 hours is pretty close depended on temperature and of course humidity . humidity inhibits cure more that you think . oh yes its hard but no where near its full potential hardness. At this stage also the surface is tacky and should always be tacky !! this is a good thing because the un-gel-ed surface is ripe for a second layer of gel to be applied or the resin and the first skin of glass so there by you have the perfect chemical bond between the two !!
    Gel coat manufactures are very ,very clever people and there chemists are magicians to be able to make such a complex material such as gel coat !!!

    My answer is do not wipe thinners or acetone or even touch the sticky surface because you could totally stuff the gel coat and cause the dreaded alligators as the thinners etches into ,softens and captivates the partially hardened gel coat you already have on now ,remember the next coat of what ever you put over it the gel time needs to be short and quick because it to could activate the gel that's there .

    I ask also what were you thinking to leave it so long before doing the next stage ?? if you cant do a job within a specified time frame DONT START IT !! :confused:
    I couldn't not post what I wrote the first time so this is my watered down version !! :eek:
     
  10. RTM
    Joined: Jun 2013
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    Location: Central Florida

    RTM Junior Member

    I ask also what were you thinking to leave it so long before doing the next stage ?? if you cant do a job within a specified time frame DONT START IT !!

    I didn't have enough gelcoat to do the second coat. Like I said my experience with gel coat is lacking. I picked up another qt the next day and then the daily rains started, and haven't stopped yet. Not hard rain all day but in spurts and then the sun comes out for an hour and the humidity shoots up and more rain comes.
    Thing is, I could have done this job 4 months ago when it was 70 and dry.

    rich

    rich
     
  11. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    Just as a matter of interest, ratios are by WEIGHT, not VOLUME, it means bugger all in most practice, but it DOES need to be understood.
     
  12. tunnels

    tunnels Previous Member


    Why ?? weight for the gel coat and volume for the catalyst !!! so its both !! Now don't get to confused its not worth loosing sleep over I promise!!
    In 25 years i never even thought about such a thing !!
     
  13. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    Well Tunnels, you now have the next 25 years to think about it.......
     
  14. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    One other thing: 1 liter of resin is some 1,12 kgs, not 0,9 kgs. But as the topicstarter is imperial, he should not care.

    If you are not experienced, follow the instructions of the supplier to the letter. You CAN go lower on peroxide levels, but without a barcol impressor you have no clue of the effect it has (other than geltime)

    For newcomers:
    -follow the instructions given
    -make a small test panel
    -check gelcoat thickness with a wet film gauge. Gelcoat thickness is critical. If you do not measure, you do not know. (these gauges are ultra cheap and can usually be obtained for free at your supplier)

    [​IMG]
    [​IMG]
     

  15. RTM
    Joined: Jun 2013
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    Location: Central Florida

    RTM Junior Member

    I sanded the first coat of tooling resin which sat on the plug for a week or so due to humid weather, then brushed on two more heavy coats, 1 1/2 hours between coats. No alligatoring, looks good. Waited another 1 1/2 hours, gelcoat tacky but fairly hard, and started laminating. Got about 3/4 finished, quit for the day, late afternoon in low 90's temp. Finished the next morning. Looks good.

    Temps were about 80 degrees when first start at 7am, climbed to low 90's in afternoon. I was worried about doing this job with these high temps, but supplier said to put the gel coat and the resin in refrig, and use normal amount of MEK. I did this and had no problems. I mixed up a pint of resin at a time, and kept the refrigerated gelcoat and resin in a bucket of ice water as I worked. Temp of the resin and gelcoat were 54 degrees when laid on the plug. Now have to glass on some reinforcements and I will let cure and seperate this weekend.
     
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