Working Time, Pot Life, Open Time, Gel Time... Huh?!

Discussion in 'Materials' started by CatBuilder, Jul 21, 2010.

  1. CatBuilder

    CatBuilder Previous Member

    Can anyone define all of these terms?

    Working time:

    Pot Life:

    Open Time:

    Gel Time:

    All I want to know is how long I can expect an epoxy to last before it cannot be bagged while I laminate large sheets of plywood together on a mold.

    Not sure which of the above fits. :confused:

    Boat building is difficult, not because any concepts are difficult, but because the language used difficult. Little help? :D
     
  2. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    Pot Life: The time you have to work the mix quantity before it begins to gell. Always better to work small volumes at a time than to try the whole boat in one go. Trust me on this one :D Most volumes can be calculated to cover the next area.

    Gell time is probably the time it takes before the applied begins to gell. If applied in a thin layer less heat develops and should take longer to gell than the mix bucket would where a larger volume develops more heat and gell faster.

    I don't know what open time refers to. Maybe the time since you open the beer to when it has gone flat.
     
  3. kyle@raka.com
    Joined: May 2010
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    kyle@raka.com Junior Member

    As far as I can tell all them are the same. I may be wrong on the working time because that could be inturrepted as time on the wood and working it into the cloth. I know for a fact though that potlife/geltime are the same because pot life defines the amount of time before the epoxy (in a pot or tray) goes off (gets clump or reaches i believe if memory serves right 6000centipoise)
    Kyle
    Raka Epoxy
     
  4. CatBuilder

    CatBuilder Previous Member

    Ok, thanks, Fanie.

    I did find out that Gel Time is the time it takes for a standardized sample in a standardized cup to produce some torque on a special machine that mixes it until it gels. So, that's kind of like having it in a cup and kind of like pot life.

    Working time and Open time are, I think, the same thing. That is how long you have to work with the stuff before you need to clamp or bag it.

    Follow on question: What is the epoxy with the highest working time or open time?

    I need a very *very* slow epoxy to be able to lay up my hull panels. They go up in one shot (3 layers of ply), the panels are 48 feet (14.63 meters) long, 8 feet (2.43 meters) wide and are epoxy laminated and vacuum bagged. This process is a financial disaster if the epoxy is unworkable before you can get the panels wet out, put in place and bagged.

    My temps are 97F (36C) during the day and 84F (29C) at night.

    You can see Charly did the same thing here:

    [​IMG]
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  5. kyle@raka.com
    Joined: May 2010
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    Location: FL

    kyle@raka.com Junior Member

    Sean, I just received your email and even have the owner typing up a reply right now. In vacume bagging is there a limit to the thickness of the epoxy? for example we have a guy out in tx thats using our tropical for a cat too and hes been using our tropical and 900 which gives about 1hr - 1.5hrs but with our thicker resin the 1500 our test have shown between 1.5hrs-2hrs of time till it reaches gel state. I should have an email done for you before the day is out.
    Kyle
     
  6. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    You should ask Manie about that, he made a whole friggin study of how what will do when.

    Your day temp is quite high - wanna swap weather :D It's winter here and I don't function too good in these sub artic wether. I work with polyester, which gives me about 30 mins max - which is why I am going to use another method to apply my glass - but I cool the resin down to prolong work time.

    With epoxy you can have many hours cure time - again, ask Manie - but too long times are not desirable either, it will mean your vac pump has to run all the time and you have to supervise in case you develop an air leak (somewhere). Ideally you need to know how long you have to apply everything, bag it and vacuum say 30 mins to an hour before the resin kicks, another half hour to an hour you can cut the vacuum and let sleeping dogs I mean boats be.
     
  7. CatBuilder

    CatBuilder Previous Member


    Thanks, Kyle!

    The epoxy will need to bond with the wood and from what I understand, you need nice, thin, liquid epoxy to bond to wood so it gets into the pores.

    Looking forward to the email. Thanks!
     
  8. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    Q - Why are you using vacuum baging, and why not vac injection ?

    Vac bagging you have to wet out everything and then vacuum, with vac injection you suck the resin in and it distributes itself. It takes more prep and carefull planning but the process wets itself out no matter how large the areas are if done right and you can take as long as you want to prepare before starting to mix...
     
  9. CatBuilder

    CatBuilder Previous Member


    Because I'm poor. :D

    This is the best boat I can afford to build. It's a damn good boat, but I can't pay for all those fancy toys the pros use, especially to build a single boat. I'm more of a boat user - an on the water professional - who is building one because I can't afford to buy one.
     
  10. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    I guess we are all poor. Sucks but wtf, it doesn't keep us off the water :D

    I would suggest you get a couple of guys to help you. A one man show is going to keep you extremely busy. You may have to bag the hulls as an exersize a few times to find the time consuming actions and pitfalls. It's just going to streamline the actual doing it.

    I assume you're going to wet the glass using rollers - some hold more resin than others and may work faster. You could have a play and see what size layup you can wade through say in 10 mins. It will be cheap but worth the while to see what the outcome is. Last thing you want is some unforseen development. I would also consider some spare bagging and loan a spare vac pump, have a power generator handy. Make sure it works :D You never know. If you're prepared, it won't happen.
     
  11. AndrewK
    Joined: Mar 2007
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    AndrewK Senior Member

    CatBuilder, unfortunately the industry still has not standardised on all the terms used.
    You have to read the data sheets carefully, gel time and pot life usually are taken as the same thing. The standard should be 100g at 22'C but its not always so.

    A good supplier will be able to give you the standard test gel time (100g at 22'C) as well as 100g at other various temperatures. Plus for larger quantities eg 1000g as well as thin laminate gel time (time for a ~600 - 1000gsm laminate to gel).

    Working time and open time are also taken as the same thing by some, I take the open time as the latest time you can apply vacuum to a bagged laminate and working time a bit shorter than this.

    I think you will want a hardener with ~120 minute gel time as a minimum, this will give you about 4 hrs to get your vacuum on ( ie thin film open time) assuming you will spread the glue mix with ~2mm notched trowel ? But as you are sandwiching two glue lines between 3 sheets of ply this time may be shortened.
    Find out from Charlie what gel time hardener he used at what temperature, time for getting the vacuum on and extrapolate that for your temp and larger hull.

    Also consider getting a glue mix rather than adding filler to the resin your self as it all adds time to the ticking clock.

    Also make sure you are considering all of the resin properties all at once not just one or two at a time. eg a 120 minute hardener is about the limit for room temperature cure even at your favorable temperature conditions anything slower you will need to post cure.
    Can you share the properties you require for the job and any data you have collected so far so that we can make further comments.

    Cheers
    Andrew
     
  12. CatBuilder

    CatBuilder Previous Member

    Agreed absolutely on all points! :D

    I have planned to and will do everything you mention above.
     
  13. hoytedow
    Joined: Sep 2009
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    hoytedow Bananas

    This is excellent advice. Do a dry run with a timer. Make sure the task is do-able within the time limitations you have vis a vis the epoxy. Points! Somebody give Fanie points!
     
  14. CatBuilder

    CatBuilder Previous Member

    Absolutely, Andrew - and thank you for the response.

    I have found that West System Tropical Hardener has a 1 hour "working time" at 84 degrees F.

    I have also found that System Three Hardener Number 3 has a 2.5 hour "open time" at 84 degrees F.

    84 degrees (or 29C) is about my 3am or 03:00 temperature here. The minute that sun comes up, it heats up fast.

    Both data points were found from calling technical support lines and asking. I was surprised West Tropical was not able to deal with my tropical temperatures here in the context of this large job.

    One thing is for sure, I have not seen any hardener that can give 120min gel time in my temperature conditions. Kyle from Raka is on the case and I am expecting some information from him shortly on Raka's performance for this job.

    Luckily, I need no fillers at this step. This is neat epoxy to bond the sheets of ply together. The technique for applying the epoxy is to literally dump it on your 8' x 8' pre-scarfed panel, splash it all around with a roller and then take the excess off. This is done in the interest of speed, I think. You also have to roll the scarf joints that join the larger panels together.
     

  15. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    Sorry to go back right to the start - the pot life and gell time is defenately different. Just made a small layup, the resident resin has gelled and hardened already in the cup while the 4 layer glass has just gelled but not hardened yet.
     
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