please advise on making a male mold?

Discussion in 'Fiberglass and Composite Boat Building' started by tugboat, Aug 10, 2013.

  1. groper
    Joined: Jun 2011
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    groper Senior Member

    Oh man, those imperial calculations are doing my head in - ... isnt canada supposed to be metric now anyways????

    im doing this in metric coz imperial system should be banished to the dark ages forever!

    So you have a 38.5sqm hull area. Your going to apply a ~750gsm triax reinforcement in in 6 layers.

    So you actually need about equal weight in gsm to fibre ive found from practical experience. So this means 38.5sqm*0.750kg/sqm*6layers = 173kg assuming no wastage.

    So your pretty close...

    The CPS is the resin viscosity, it wont change how much you use, only the wetout characteristics and flow characteristics etc... it wont matter which resin you use, you should use roughly the same amount regardless.

    VE and PE both give off styrene fumes, theyre the same in this regard. VE is a better resin, with high mechanical properties and slightly better resistance to osmosis. Epoxy is the only resin that is completely non porous, so osmosis should not be a problem, ever. Most people dont consider this, as it will happen long after your in your grave...

    Honestly, the difference would best be considered by your workshop environment considerations. I have no idea what temperature youll be working in and what the ventilation is like? This may dictate which is a better choice for you, but no doubt the PE and VE will always be a lower cost option compared to epoxy - but you wont be stinking the place out with styrene everytime you mix it - i cant stand this personally, and i doubt i would get away with building in suburbia if i used it - the neighbors would dob me in to local council for sure as theyd be sick of smelling it through their house. Epoxy is practically odourless so noone complains, not even my wife :)

    I wear a charcoal filter respirator when working with VE or PE as the fumes are a bit overwhelming... with epoxy i wear nothing at all - although i probably should.... All this makes building with epoxy my choice, despite the extra cost....
     
  2. rwatson
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    rwatson Senior Member

    for a little boat like this, PE would be adequate - its not like it will be sitting in water for most of its life.

    VE is the most awfull smell to work with - makes me sick to the stomach. Imagine melting a vynil chair seat with a blowtorch.

    Do get some small trial samples, and make sure you can live with whatever process you choose.
     
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  3. waikikin
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    waikikin Senior Member

    Tugboat,
    I think you really need to have a go with some of these materials, & put the clock on & rate the laminates on a $ per meter square basis for thickness that's adequate for the vessel, maybe even work in with a composites shop for some free on the job training. Polyester & chopstrand come at a big discount over the others, sure you need some stitched or woven in there too but thickness= stiffness, this is a slow displacement vessel not some wave jumping offshore powerboat doing 50 knots. Even if your boat does spend it's whole life in the water, a couple of pails of vinylester in the skincoat would look after the laminate, plenty of good boats still osmosis free decades later,. Sandwiching a WR or stitched in between layers of chop is really straight forward & easy cooking, been working for half a century or so. In open molding the chop really helps in laying down a neat & tidy void free layer & sucks up resin like a beauty so builds thickness more quickly. Chasing weight & getting great resin to fiber ratios is great, but your looking at a boat previously considered in steel....
    Epoxies are great particularly in cored construction where weight savings are being considered as you can drop the resin hungry choppy, but with styrenated resins you NEED to interleave layers of csm, you also NEED to calculate for overlaps & wastage.
    I haven't followed all your considerations but maybe your boat could be formed & laminated within a female batten mold lined with thin gelcoated panels flexible enough for your developed shape with segmented(for minimum fairing here) radius chine molded from pvc pipe, in this your mold lining becomes your finished gelcoated surface, less sanding all round, & using a rapid wetout laminating resin each layer only needs a quick scuff or scrape between sessions, looks possible with what you've posted here http://www.boatdesign.net/forums/at...97d1374732214-can-done-steel-doable-steel.jpg.
    Jeff.
     
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  4. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    Hand laminating with the higher CPS and harder wet-out might be an issue also.
     
  5. tugboat

    tugboat Previous Member

    RWatson- I like it when your sense of humour shows up--but its food for thought- your description brings back electrical fires as a kid when I burnt
    e-cords through experimentation. (thankfully I didn't fry myself). but that smell lasted for days and is gawd awful! Your correct I never forgot that smell to this day.
     
  6. tugboat

    tugboat Previous Member

    I have to be honest Groper- I absolutely want the epoxy- its low shrinkage rate will perform exactly as needed on the initial coat of c-flex. its tough and sticks to anything. but the costs are about 2-3 times the costs of v-ester.this adds about three months to my build in having to save.

    I am told v-ester is close to the properties of epoxy...do you know the shrink rate of VE? if its shrinks more than an epoxy? if so how much more?

    :) Canada is "metrimp"!. meaning we all have to convert back and forth..so we know both systems well...yep--it sucks too! but the U.S. is still, imperial and then the EU is not...we cant win ugh! so we have to know both systems ...:mad: its a real PITA


    btw - what do I do if using epoxy between coats? sand? or will it just bond well to further laminates coats if not done all in one shot?
     
  7. tugboat

    tugboat Previous Member

    Hi Jeff- I don't know if you saw my previous posts- I am using c-flex so a simple male mold is all that is needed. its really a amazing time saving product- www.seemancomposites.com

    Cheers - thanks for the post!
     
  8. tugboat

    tugboat Previous Member

    so epoxy would be harder to hand layup?
     
  9. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    Great, would be awesome to see photos when your doing it, haven't seen that c-flex in a long time.
    All the best from Jeff.
     
  10. groper
    Joined: Jun 2011
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    groper Senior Member

    TB,

    Firstly, its worth listening to waikikin carefully, he knows his **** when it comes to composites and a shipwright by trade.

    Your asking some pretty basic questions about laminating, it wouldnt hurt to use the search function through the forum, this kinda stuff has all been covered ad nauseum...

    But quickly, on some stuff thats harder to find...all resins can be found in a wide range of viscosity, you cant say that epoxy or VE or PE will have a higher or lower cps, they all vary. For hand laminating, you should be somewhere around 500-600cps as any thinner/lower cps and it starts to drain out of vertical laminates and pools at the bottom, and any thicker/higher cps and it just gets slower to wetout the fiber.

    You can alter the viscosity yourself, by adding thixotropic powders such as colloidal silica or cabosil etc to increase the viscosity and non sag characteristics... you will also do this later when you make up your fairing compound, using a little thixotrope to tailor your non sag, and microballons/q cells/ to build bulk for a lower density product which is easier to sand.

    The VE is versatile resin, you can do all sorts of things with it, such as adding a retardant to acheive very long gel times, its compatible with gelcoat so you can mold things with gelcoat finish rather than paint it afterwards etc - the lower cost is definately worth considering, but you havnt told us about your workshop and where you will be using it. Will you be doing this in a shed or outside or what? What about temperature control, can you control the environment your laminating in - this will effect what you can do, especially when temperatures are cold over there.

    Epoxy needs to be sanded, and also perhaps washed, between layers if you dont use peel ply over it - dont even consider this, you should use peel ply and save yourself hours of work and get a flatter finish to the laminate - its also worth doing with VE or PE aswell in certain circumstances.

    Epoxy generally doesnt shrink... VE shrinks a little, PE shrinks a bit more, but again they all vary depending on the exact formulation. I dont know why your considering the shrink anyway - this is generally only a consideration when your molding something in a surfaced gelcoated mold and associated cosmetic reasons like print through etc you dont need to consider it with your build method....
     
  11. tugboat

    tugboat Previous Member

    Groper- Ill check other forums -- IF I add the c. silica- wouldn't this stop it from penetrating the glass?

    I plan on building a shelter- not a full blown garage- just a cheap disposable shelter covered in clear plastic or a tarp of some kind.
    I plan on glassing in cool temps in the springtime- say around +10 c. or maybe higher.

    as for peel ply how does that work exactly- do I put it on before or after I have done a laminate? or when it is hardening up? where can I find info(other than searching the forum)

    there is a very good reason to consider the shrink.
    since I am using c-flex- the critical part of the whole procedure is during the first coat of resin to the outside of the c-flex in order to firm it up to allow for the main laminate.

    the Makers strongly suggest a marble casting resin ...but it is stated by the makers of it to use (they use bold lettering)

    a wax free, non thixotropic, clear laminating or casting resin of low shrinkage with a viscosity range of 600-1000 cps . this resin does not have fillers and is frequently used as a marble casting resin...

    so that's the big dilemma and why I need a certain type.

    its a real eff'n PITA!

    however epoxy meets this requirement -so the v-ester would need to adhere to the epoxy. or if v-ester meets these- then I could use that as my initial coat- see the picture for what happens when you do not coat the c-flex properly or with the wrong resin or both...
    note scallops...
    also note the good hull..
     

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  12. groper
    Joined: Jun 2011
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    groper Senior Member

    Well, check the manufacturers data sheets on the resin - the bold lettering suggests that almost any resin can be used - they are referring to standard PE or VE laminating resins as nearly all the ones available here fall within that range.... Be nice if they defined "low shrinkage" like how many percent???

    Google works for searching too mate, doesnt have to be just this forum.

    You put down peel ply (thin polyester taffeta) on the wet laminate and massage it in so its sitting flat, careful use of squeegee helps too, then let it cure. When your ready to work with that surface again, you pull off the peel ply by hand, and it leaves a slightly textured surface which can be secondary bonded directly - no need to sand it. Independant testing has shown that the bond is lightly better if abraided, but its perfectly adequate without sanding if using epoxy. If using PE or VE, a 10-20% reduction in bond strength compared to abraiding is evident - fine for non critical bonds, but highly stressed bonds are still best abraided with VE or PE as they have 3x lower bond strength than epoxy anyway.
     
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  13. tugboat

    tugboat Previous Member

    Groper- I started a new thread- strictly for c-flex. but Ill keep posting on this one- wanted to say thanks - you've been a huge help and given me a LOT of great info..

    as to your post-- I cant agree more the manufacturer should define the "exact shrinkage rate" Im going to email them today and ask...

    I have been looking through Google...trust me its my mission in life these days...
     
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