plug stuck in the mold

Discussion in 'Boatbuilding' started by Trick Powerboats, Feb 2, 2013.

  1. Trick Powerboats
    Joined: Apr 2008
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    Trick Powerboats Junior Member

    We've got a console locked up.

    The plug was built from mdf wrapped around plywood jig frames. Once the MDF was faired (a little q-cell/resin mix in areas)we rolled on a very thin coat of GP resin in hope of preventing the MDF from "moving" and for waterproofing. Then we did the final fairing. The we shot it duratec 707-002 surfacing primer. We sanded and wet sanded through 1000, polished it and waxed continuously with 20 coats of mirror glaze #8 mold wax. No pva was used. I understand the advantage of pva but we didn't want to have to wet sand the finished mold to get the mirror finish.

    We are in the process of cutting everything out from the inside. More than 50% of the surface has stuck and various areas.


    We're getting ready to start the hull mold but I'm about to without understand what happened on the console.

    Any ideas?

  2. gwboats
    Joined: Sep 2005
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    Location: UK

    gwboats Naval Architect

    Plug Stuck

    Maybe a good idea in the future to finish your plugs with a good coat of 2-pack gloss, primer only is too unstable on its own. Will need to be well cured and maybe de-nibbed before use, then apply wax.

    Good Luck
    Graham Westrook
  3. tunnels

    tunnels Previous Member

    I think you have a wax incompatability problem plus a few other things aswell !!

    The plug was built from mdf wrapped around plywood jig frames. Once the MDF was faired (a little q-cell/resin mix in areas)we rolled on a very thin coat of GP resin in hope of preventing the MDF from "moving" and for waterproofing. Then we did the final fairing. The we shot it duratec 707-002 surfacing primer. We sanded and wet sanded through 1000, polished it and waxed continuously with 20 coats of mirror glaze #8 mold wax. No pva was used. I understand the advantage of pva but we didn't want to have to wet sand the finished mold to get the mirror finish.

    We are in the process of cutting everything out from the inside. More than 50% of the surface has stuck and various areas.


    We're getting ready to start the hull mold but I'm about to without understand what happened on the console.

    Any ideas?

    Get you mirror glaze wax and take it for a long walk in any dirrection and dont bring it back !!
    20 COATS ,40 coats or even 100 wouldnt make any differance !!!! .
    After the first 3 times you apply your wax all you really are doing is wasting time and materials !!
    You never really build coats of wax as you build thickness like coats of paint !!
    WAXING is best done with a damp sponge and a light well ribbed coat applied each time and left for 10 minutes to 20 minutes then lightly polished !! an hour between each time you wax is normally sufficcent and gel coat within that hour so your wax is still fresh !! all the things you aere told never to do !!
    heavy applications of wax is just wasting product ( wipe it on and wipe it off again ) Plus heavy thick coats soften and remove the layer of wax below what you just put on !! :eek:

    Ok next
    what gelcoat did you use and how did you apply it ??
    sprayed or brushed ??
    If you sprayed how did you spray ?? pressure pot or just a spray gun ???
    You didnt thin you gel coat did you ??
    if you did what did you use and how much ?????????
    one coat or two ??
    and if two what ratio was the second coat catalysed at ??
    what was the temprature when you applied each coat ??
    and what was the gel time for each coat ??
    what percentage of catalyst did you use ??

    What is your problem using pva ??
    how do you use pva ??
    how would you apply it ??
    spray or wipe and with what ?? .
    sponge rag or brush ??

    Answer all those questions in order and i will tell you what i think was your problem's ! and what i have done and never once ever had a stick up using this method and you will only have to wash your mould and should have a really good shine .

    On a big project we were doing we almost got caught the same as what you just discribed and the answer was really simple !! but need you answers first !!

    I await your reply !! .:confused:
  4. tunnels

    tunnels Previous Member

    Have used duratech on plugs since i dont remember when and its much better than any 2 pack paints i have seen any where in any country .
    Thats not the problem its something much simpler than that but just need some answers first before i say any more !!. :p
  5. Trick Powerboats
    Joined: Apr 2008
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    Location: Al Raha Beach

    Trick Powerboats Junior Member

    Norpol tooling gel 1.75% at 26*c rolled on 1.5 hrs between coats. Not sure of the catalyst percentage. Gelcoat was tacked up at 40 minutes. We did not thin the gel

    Don't like pva cause it diminishes the finish.

    I ordered pva a few minutes ago. I'd spray appy it
  6. midnitmike
    Joined: Apr 2012
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    midnitmike Senior Member

    Sticking a part on fresh plug or mold isn't uncommon. I know you've done everything by the book and it still stuck. Now when you're peeling the thing apart piece by piece you ask yourself WTF did I do wrong? How is it possible when I followed the instructions and then some..I mean 20 coats of wax...surely that's enough.

    The simple fact is that there were enough free radicals left exposed on the surface of your plug to react with your tooling gel and bond the two together. For the time being I'm going to assume you have enough draft and that your surface prep was adequate. So the culprit was very probably the wax layer failing to prevent your tooling gel from binding to your mold surface...this is on a molecular level so it's not something you can see or feel.

    If I can make some suggestions:

    1) Make up some small 12"x12" MDF test panels and treat them exactly as you would your mold / plug surface.
    2) Use these sample boards to help determine the correct application techniques before moving on to your plugs.

    You'll find that even the experts are going to disagree on why this happened and how to resolve the I'm going to advocate that you determine for yourself what works and what doesn't without risking a valuable plug. You've spent a lot of time, money, material and man hours in creating the plugs for your console and hull and now one of them lays in ruins. Use this experience to make sure it doesn't happen on the replacement console or on your hull.

    I know I'm repeating myself when I say that waxing a mold should be done with application per more. I don't care what the book says or what the instructions on the can reads...if you apply more then one or two coats a day you're simply replacing one coat of wax with another. So after ten or even twenty coats applied continiously you really haven't done much to protect the surface. I learned this the hard way 30 years ago from a mold maker that worked in your shop, and by golly that old cigar chewing conch was right.

    That console plug should take about a week...that's right seven wax. Even after that I'd hesitate laying it up until I had a coat of PVA on it just because of all the features involved in it's surface. That's another reason to make up those test're going to want to practice your PVA spraying. The stuff doesn't shoot like anything else you've put through your gun so lots of practice is in order before you commit yourself to a part. For the last 2 years I've been using my 1.4 to shoot PVA but last fall I had a small job that i wanted to do and grabbed my little 1.0 gun. I was amazed at how nice the PVA looked on my mold surface...I'll be using it a lot more this year that's for sure. Whatever you do...please don't thin your PVA...shoot just like it comes out of the jug.

  7. tunnels

    tunnels Previous Member

    Every question i asked you should have know the answer to straight off the top if you head
    catalyst percentage
    Those 3 alone can make or break a project
    Gel time is critical and again those 3 all together or just one can and will change you gel time .
    Slow gel time and more time for the gel coat chemicals to bite into and dissolve your waxed surface

    Ok lets get to wax .
    Mirror glaze is used a lot but the formulation of gel coats over the years has changed and like i thought they are not completely compatable any more .
    if you spray your gel coat with a 25 to 30 minute start to gel time you could get away with in BUT ONLY MAYBE !! If you brushing or rolling you will get what you got !! massive stick ups because the gel coat chemicals soften and mix with the gelcoat and are not doing there job any more !!. So the more you roll and brush the more it happens like all over as in total on one such job i was involved with .

    So mirror glaze is a no no . TR wax is reasonable! , Honey wax reasonable !! My personal favorite but have not seen for long long time use to be Ceara wax . Worked like it was magic and did things non of the other waxes can do . If mirror glaze was used then one coat of ceara over the top and could gel coat straight away no waiting !!, never failed in the 10 years we used it .
    But the good old stand alone never fails Johnstons floor wax or traffic wax as its call in some countries, works every time . Easy to apply !,easy to shine ,blow a steady stream of air over the plug from a fan and by the time you done one side can just round the corner and carry on down the other side round and round without stopping .
    Wax a 36 foot hull and deck plugs 4 times in just one day and remember use a damp (Not wet ,soft sponge ) and the secret is rubbing the wax into the pores of the surface , the more you rub the better it will be so if you have a lazy person tell him to take a hike . only have to leave 5 to 10 minutes and then polish lightly ,then on with the next section .

    PVA the solution every one hates to use !!,but saves there bacon usually everytime !
    Dont read the lable on the bottle of the instructions , follow what i am about to tell you to the letter .
    Take a 1 litre bottle and 1/3 fill with pva from the container ,now add another 1/3 or a little more of just plain straight from the tap water and give it a good shack !! let it stand !!
    Your spray gun i hope you are completely familiar with !!
    The flow control needle wind fully in so nothing will come out !!
    about half fill the clip on container on the gun with your PVA and WATER MIX .
    plug your gun to the airline and turn the air pressure to max (hope you have inline water traps !!) the fan control wind in fully as well !! now hold you gun up so you can see when the pva mix starts to come out of the nozzle slowly wind the flow needle out maybe only half to three quartes of a turn at max now adjust the fan so its wide but completely misted top to bottom . if theres to much air the middle has almost no spray its just top and bottom of the fan !! need to be consistant !!
    You with me still ??
    Now the theory is when you spray the plugs surface with pva if you can see it you have to much on !! Now thats completely beyond your thinking at this point and i can see the look on you face as you shaking your head in disbelief !!. No im not mad and im not pulling your leg !!, The thinner the spray the better it works !!.
    The high air pressure and lots of air carries the spray and the water helps to thin and disperse the pva evenly all over the surface and if you blow just air over the surface you just sprayed the water evaporates quickly and its dry before you realise it .Now blow dry your hand and with the air still blowing you can wipe you hand very gently over the surface but dont stop your hand anywhere ! you will see the pva and water mix has made the surface even more shiney that it was before !


    One company i worked in in Australia never had any fornof wax in the factory ,this is all they used!!! PVA !!.
    Plugs ,moulds what ever ,just pva . the company bought pva in a 20 litre container and then mixed water with it so ended up 40 litres that was more than we needed for a whole year . once you see the advantages of using pva you will wonder why the hell you even bother with the hassles of wax and the time and effort involved specially with big parts and if you have non slip surface to mould over it comes out completely clean everytime .

    I will do some searching and see if i can fine the PVA post here on boat design and you can read the comments some people posted !! one guy even posted almost a year later and he was doing something that he could get to work any other way !!:eek:

    Happy reading !! :D
  8. Trick Powerboats
    Joined: Apr 2008
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    Trick Powerboats Junior Member

    Morning update,

    The seat (leaning post) mold and console mold both stuck. Both are in the process of being removed piece by piece. Strangely enough in many of the "stuck" areas the duratec flakes off with little pressure once the mdf is removed. I can't say yet as a whole. After we get all the loose material out we'll fill the molds with water and soak the mdf to ease the removal of the balance.

    Mirror glaze wax. I hear you loud and clear. Until this, I've never had any problems using it on production parts following the same application process but obviously fewer coats.

    PVA. Midnitmike / Tunnels. Both of you seem to have alot of successful experience with PVA. Mike says don't thin in and Tunnels says thin it 50%. So we have a delima. Tunnels, why do you thin your PVA. Mike have you thinned your PVA in the past with bad results? I like the 1.0 tip size recommendation.

    Guys, Thanks so much for taking your valuable time and knowledge and sharing it with me.

  9. tunnels

    tunnels Previous Member

    Two people ,two methods ! make test panels !! your choice .

    Differant products !differant countries !so its up to you what you choose !!
    Make test samples and divide it up and do some exsperimanting of your own its the only way for you to be satisfied what you got is going to work for you .

    Like i keep pushing over and over the fact is !! pva does not have to be on the surface thick !! If you can see it, its to thick !! water thins it really thin.
    The thinner it is the better , Its like a skin of plastic between the wax beneath and the gel coat above ,spraying your gel coat theres almost no chance of disturbing or breaking that skin !! ,but brushing or using a roller you asking for trouble .

    I have used this method i dicribed since 1985 and never had the slighest hint of a problem and deffinity never a failure with either making moulds off plugs or making articals out of brand new moulds!!
    Its worked a zillion times even on old molds that have has lots of repairs and even big patchs of resurfacing where theres been dammage from heavy handed no hoppers with a rubber hammer pounding because it wasnt waxed properly . One coat pva and its out not a problem!!
    I would stake my life on what i have said .

    Do test samples right to the point of a skin of glass .
    Write down temprature , humidity , catalyst ratio , and make sure you get the gel time right !! 1.5% to 1.75 is usual for the first coats and if you second coat add a little resin to the gell and makes it easyer to apply and rolles out much smoother and so easyer to glass over . plus the resin helps to lower the risk of getting alligators if there thin gel any where . Your second coat catalyst ratio should never come below 2.0%and should be just about rock hard in an hour of being applied !!. :p:D
  10. midnitmike
    Joined: Apr 2012
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    midnitmike Senior Member

    Proper PVA application is just one of those things that Tunnels and I are destined to disagree over. I think people should use the product as it was formulated from the factory...this insures a positive release first time every time. Applying an invisible layer as Tunnels describes can lead to problems UNLESS the applicant is an experienced operator. I can not in good conscience advise anyone to adulterate a product that works just fine the way it is. Learn to shoot PVA in it's original form...when you're confident in your application techniques and your satisfied that you can do the job...then by all means do as you see fit. I'm not saying it won't work but I would feel awful if I told you do something that had even the slightest chance of failure.

    I know this is a long thread but I feel it's relevant and well worth your time to read.

  11. tunnels

    tunnels Previous Member

    Right from the moment i first started work in glass PVA was a no no and the places i worked in the next 13 years all shyed clear of using it . not one place could make a decent job and left marks and dust etc on the surface and spent hours sanding the pva marks out of brand new moulds , 1985 i had been living and working in Tahiti and gone Queensland Australia for a while . i worked for industrial company and we made everything you could think of except boats . There was a english guy there and i used to watch what he was doing !!, release a product, hose it out ,and a quick blast of air to dry the mould ,and then a even quicker blast of what looked like nothing coming out of a spraygun andanother quick blass of air !!, hang up the gun and he'd catalyse his gelcoat and straight into it . after lunch glassing and at the end of the day samething again release and regelcoat . I was intreaged and wanted to know more so asked and he showed me how to use PVA like i never seen before !!
    After a week of repairing a mould i was working on i went looking for wax and was told they dont have any wax at all just use pva !!! wow after 13 plus years and no wax required ?? you must be joking !! so fred took me to his department for a day and we worked together . I saw PVA use in a way i had never dreamed of .
    Since then i been using it all the time where ever i worked and have shown countless number of guys in every country i worked how simple and fool proof it really is . I have seem molds that were really difficult to release and after a pva they just about fell out of there moulds . Done properly and with a little care there is a better shine on the product and the mould .
    Never get wax build up any where on the mould and have to spend time cleaning it off . no more countless hours of waxing and polishing and waiting for wax to gas off so you can gel coat . Waxing a plug can take a week one wax in the morning one in the afternoon each day !! well all thats gone !!
    Sure i am all for waxing a brand new mould or a plug but theres ways of speeding the process to just one day not a whole week ! Johnsons floor wax ( forget about all the others )and apply sparingly ,well rubbed round and round and let it dry then polish off 4 waxes is all thats required (not 20 times !!) and then pva and gel coat all in one day for a 36 foot hull and the deck .Next morning we split the crew into two teams of 5 people and started glassing . Glassing was all done with time between layers and was finished and fitting framing etc etc to the outside and was released and sitting on its wheels in just 10 working days later .In a month after the moulds were finished we had 4 hulls and 4 decks sitting ready to be glue joined together once the special rubber fortified epoxy glue had been air freighted from New Zealand .
    When you have a very tight shedual to stick to you make things work the way you know how they can be used and never have failures !! Pva made all these things happen !! without it the project i was manager of would have never made it !! we managed to gain a week to spare for the sailing crews to test sail there boats, sorted and be able to go racing before the boat show started

    Pva done as i discribed works and works well most manufactures know little about what there product can do and will do . thin pva mixed with just plain tap water and sprayed so you cant see it is all thats required . i have proved this hundreds of times without a shadow of a doubt and i dont even have to think about it any more its what i do and will keep doing till i cant do any more !!
    Takes practice to get a consistant coat as thin as possible all over specially when you cant see it .
    Bit like the emperors trouses story !! Its there just you cant see it !!

    Just as a matter of interest you can also use silicone car wax as a release wax if you live on a desert island in the middle of the pacific . You only need one coat and it works all the time ,everytime never a problem !! so much for all those long lists of special over priced waxes and the countless ways everyone has of applying them .

    All these things i have posted a few times before on boat design !!,just takes to long to go looking to find them now .

    Your choice !! what ever you do make test panels and the one process that works best for what you doing remember how you did it !!!

    Even at 68 years old its never to late to learn new tricks !!!,just takes longer to fall through the hoops these days !!.
  12. midnitmike
    Joined: Apr 2012
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    midnitmike Senior Member

    There is one thing that Tunnels and I agree on and that's using Johnson's floor wax for a mold release. It is by far the best canned wax product on the none...and you can pick it up at a grocery or hardware store. With a decent surface it will provide a smooth release with just a single coat (but you never heard me say that). Unlike most mold waxes it's fairly thin which is perfect for getting just the right amount down for each layer...and it hazes over nicely even in cool weather (which I like). You don't have to be a pro to use it and you won't wear yourself out getting it to shine...heck I don't even buff it out most of the time....with a power tool that is.

    As good as the stuff is new molds should still be waxed the old fashion coat per day...two if you do one in the morning and one at the end of the day. That will give you a solid 12 hours between coats which is just enough drying time to allow the product to harden up before applying the next coat. On bigger projects, like the ones you're working on, schedule a week for the waxing stage...yeah I know it seems like forever, but the consequences of short cutting can be catastrophic.

    I suppose this is why I can't advise someone (hell anyone) to thin down their PVA and then procede to shoot an invisible coat trusting that they'll get it right the first time. And I would never proclaim that you can do this sans wax...because I've done it a million times. The truth of the matter is if someone comes onto this forum looking for advice because they stuck a part or they're about to make their first mold they are not in a position where I can advise them to take on even more risk. The last thing I want to do is put someone in a position to fail...potentially costing them enormous amounts of time and money.

    It's one thing if it's my part and I screw it up...that's my tough luck...but I'm not going to advise you or anyone else to take a shortcut. I know the odds going in and I've weighed the risk vs reward based on years of experience. Even then things can go wrong and I'll stick a part and have to start over, but that's the risk I took.

    I think the best advice either of us can give you is to make up some test panels and decide for yourself what works. You're already looking at two failed parts..lets not make it three.

  13. afteryou
    Joined: May 2012
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    afteryou Junior Member

    what he said ..:D..
  14. rxcomposite
    Joined: Jan 2005
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    rxcomposite Senior Member

    Mold will stick to an uncured plug, Guaranteed! There is no hurrying up on the process. You either let your plug cure in a warm room for several days or bake it until it is fully cured.

    The rest of the posts, I fully agree. PVA, thinned or unthinned, it works, but in both cases you should be a good sprayman. You need to apply as thin as you can so as not to dull the finish. It takes a lot of experience to do that. I use lukewarm water to thin down PVA if it gets too thick, or just thin it down whenever I dont have a good spraygun. Warm water will dissolve whatever PVA is left in the mold.

    And yes, I have used Johnson wax. It works, but I use it only in "broken in" molds. PVA is still the best insurance against sticking.

  15. tunnels

    tunnels Previous Member

    Make test panels and have a clip board and record everthing you do and use including weather conditions ,specially humidity and temprature also catalyst ratio and type and of course the all important GEL TIME !!

    As time has gone by since the 1970s products have changed and without use even knowing it manufactures are still adding a little of this and a little of that and never saying anything , so one tin you get works perfectly ok and no problems come the next project a few months later you order the same product and it has differant BATCH numbers and could behave differantly and you are left wondering why should this happen !! its no good asking the sales people most dont even know which way is up !.

    The big boat company i worked the head chemist and the guy batching and formulating mixes used to come and spend a day every so often and work with us ,watching and taking samples and recording times etc and getting small test samples that we would spray during the process of gelcoating hulls and decks , that way they knew first hand the guys doing our spraying and what epuipment we were using and the conditions we worke under . So gel coats were formulated exactly to best suit our condidtions . Call it personal service ! everyone was on first name terms and thats how i like to work!!, we helped them ,they helped us plus the guys in the shop enjoyed t there work more because they know and understand the products better . Problems simply disappeared because the operaters saw first hand what was involved in the making , testing and batching of each and every product that they got to use . Same with colour matching and the process involved . Nz has one of the highest uv sunlights in the world and the testing of overseas products aginst the local was a eye opener for many.

    As a factory manager i always want the best for everyone in my workshop and the learning never stops ,information never sat on my desk it was copied and each member of the staff was given a copy ,they all had folders and the foreman used to out of the blue sit and ask questions and they needed to know the answers . This is done not only for the benefit of the company in having a better and higher skill level but also for the guys themselves as well as they could get better jobs if they at some time chose to move on .

    I made it a rule one day a week i spent the whole day working along side and with the guys on the floor doing what they did .
    One ,the guys knew when i said something needed to be changed its was with good reason and
    second i saw first hand what each member of the staffs skill level was like and i could do something about Pairing that person with someone that would teach and show a better way .

    Was a while later i got serious and built everything to survey standards and have worked to those standards ever since no exception !!.
    Its not hard it just a mind set and a much better way of working !! one day the industry will wake up to that fact and as a worker you will have your name and number on a register to say what you skill level is !
    Its been tried a few times in differant places but needs to be stricter and adhered to and made to work . so if you not on the register you start at the bottom !
    When i employed staff first i asked everyone in the shop have you worked with this person?? if no then they were on a 3 day trial ,anyone can show there worth in just a matter of hours .:confused:

    Learning never stops !:p
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