Chop Gun or Hand Lay

Discussion in 'Fiberglass and Composite Boat Building' started by mrbcurry1, Dec 3, 2012.

  1. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The question isn't if it'll hold up, Tunnels, but if it will be a viable alternative to what he's been doing. Sure you can make it your way, but he'll lose on race day to everyone else's hand, vacuum or infused layup. Your insistence that chopper can be done just as effectively, just can't stand to known parameters, which has been the whole bias of my debate on it. The proper answer to the OP's question is no, because he wants the same thickness. A switch to chopper will require a thicker, heavier laminate for the same stiffness and strength. You know this is true, in spite of your bluster, other wise everyone would still be using chopper, instead of the other, more costly methods. There's no business model in the world, where switching to more costly materials and labor, is the reasonable way to go, if you have something that's as good as you suggest it is.
     
  2. powerabout
    Joined: Nov 2007
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    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    chopper gun addicts continual use becomes a self fulfilling prophecy...
    the longer they do it the more the styrene fries the brain the better the system gets
    so they never change
     
  3. tunnels

    tunnels Previous Member

    Its why i changed long long ago . there are no old laminators my age they passed away long time ago . I do remember quite a few i worked with over the years . I done the hard yards and smelled my share if styrene . i also see the same questions getting asked over and over and professional know it alls giving the same answers i heard a hundred times before now they back it with computer predictions that are as relyable as a weather forecast . Most are only part way to the reall truth as they wave there big sticks and stamp there feet to get there point across .
    Sorry not carrying on with this pointless going round and round till the one that yells the longest and loudest shuts every one else out and they smile and chalk up another victory on there score board . :(.
     
  4. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    in all seriousness Tunnels they are destined for history due to the EU/EPA regulations in the west
    I guess they will be around in the 3rd world for some time to come
    ( did anyone mention polyester resin+chopper gun = osmosis magnet)
     
  5. tunnels

    tunnels Previous Member

    osmosis has little to do with the use of a chopper gun !!,
    like i keep repeat regularly its poor workmanship and poor rolling coupled with not doing a resin rich first 2 skins behind the gel coat AND not letting those layers cure properly before carrying on with the rest of the build . most all boats done these days get vinylseter for the first two skins ,sorry has nothing to do with using a gun !!
    During one of the many jobs i had we made spa pools with hot water and all the chemicals they would get signs of osmosis in a matter of a few hours
    so would have to drain the pool and take out and replace with another pool . out of a hundred pools only ever did that twice , back to the factory and completely sanded the gel coat and roll a special spa pool epoxy resin over that was the same colour as the gel coat and sold as a second .
    No guns have nothing to do with getting or not getting osmosis , its just plain bad workmanship !! :(
    ID be more worried about the polyestermite than osmosis !!
     
  6. powerabout
    Joined: Nov 2007
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    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    I will agree there..
    its just that its easy to do a bad job with a gun
     
  7. tunnels

    tunnels Previous Member

    Thats plain lazyness pure and simple . its also a mind set . a gun is easy to use, its easer to make a really nice job as well ,but your mind has to be on the job !!! you need to be thinking a few seconds ahead of what your body is doing and totally focused . To gun a hull is child play take a 18 foot boat mould right up on its side ,the bottom is almost vertical ! your scales are set and you know how much glass has to go on so you start sprayng resin from the back working forward to the bow making sure the totall surface has resin specially in corners and the keel and 10mm on the other side , as you approach the chine at the bow you start spraying glass ,keel to chine and back to just over the chine and in the smaller passes they get done quickliy gradually slowing as the passed get longer . the pass speed remains the same so you get a consistsnt thickness just takes a fraction longer because if the distance you have to cover , me i can spray 450 crams consistantly all over from end to end . as you aproach the last couple of passes you sight the scales and they should be Just about back to zero then its done but when you have got 1/3 of the way down the hull the laminaters come and start rolling so you angle the gun away from them so the spray goes towards the stern as you gradually move along the hull bottom . all done correctly there is usuall no need to add more resin to the glass because you did that before you started and pressing the glass down into the resin then the bubbles come up as is rolled !! simple ??
    Alway remember Its easyer to bring resin up from under the glass than to try and push the resin down ,agree???
    Do you know why you start at the front and work to the back ?? AS the glass is being sprayed it is actually going on in layers ! these layers are like fish scales and in the event of a boat hitting and punchering the scale effect has a tendancy to deflect what ever you have hit . same when you laying cloth of fabrics always lay from the front to the back so if theres any joins they are lapped the right way , Its what i was shown 30 years ago and what i have always done to this very day . its logical and in practice when you building boat to a survey standard its one of the first things they look for and have a grin when they see thats what you done and they dont say anything usually because you have proved to them you have what is needed for there approval of building methods . :D
     
  8. midnitmike
    Joined: Apr 2012
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    Location: Haines and Juneau

    midnitmike Senior Member

    I think one has to keep in mind what the OP intends to do with the final product. There is after all a single word in his post that can make all the difference in the world as to weither or not chopped bodies are suitable for his application. When he said he built "racing" go cart bodies were these racing carts meant for little kids to blast around a track as a rental unit, or are we talking about more elaborate machines meant for serious enthusiasts? Because the term wasn't clearly defined, and the OP failed to answer the question when it was asked, we are left haggling over technicalities that may have little to do with his situation.

    Although the performance parameters are as yet undefined I have a sneaky feeling that the OP's intent is to build these cart bodies using a chopper gun to speed up his production, and not to create the ultimate in light weight race machines. "IF" this is the case then I think a middle ground can be found where the chopped material is used as his skin coat (replacing the hand laid CSM) and cloth, roving, or bias ply material added to the stress points in the structure as needed.

    We all know that this lay-up schedule will impose certain weight and strength restrictions, but it maybe that the increased speed in production (if there is any) is worth considering no matter what our personal opinions might be. While I can't wholeheartedly support Tunnels assertions, in this particular case we may find that the OP's intent is more inline with his general philosophy of "Spray 'em Up, Lay 'em Up, and Pop 'em Out". For all we know these "racing carts" may just be fodder for Mini-me sized fun seekers no higher then our belt line. So lets try to keep things in perspective.

    MM
     
  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I was working with the same assumption Mike, though did assume "racing" was indeed racing, not bumper cars or other domestic restriction. Some OP clarification would be in order, but I know of not a single racing series, using 'glass bodies that incorporate chopper or CSM, unless, as I noted the weight restrictions are assumed by all and production is the only concern.
     
  10. wet feet
    Joined: Nov 2004
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    Location: East Anglia,England

    wet feet Senior Member

    If the OP is serious about racing use of his products he would be much better off using oven cured glass/epoxy prepreg.Not hugely expensive and total control of the fabric/resin ratio.
     
  11. midnitmike
    Joined: Apr 2012
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    Location: Haines and Juneau

    midnitmike Senior Member

    Agreed,
    When I Googled Greensburg and Carts I came away with the impression that the majority of businesses in the area catered more toward the recreational end of things and so modified my initial impression that these were indeed meant for high end serious racers. Also the OP's stated mission to use a chopper gun in the production of his bodies shows me that he couldn't possibly be intent on building to those much higher standards. I am of course making several assumptions along the way that may be in error, but until the OP clarifies his goals that's about all I have to go on.

    MM
     
  12. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    Maybe he needs the high production of a chopper gun because the CSM bodies break so easily.
     
  13. tunnels

    tunnels Previous Member

    Look at the oringinal post !! :(
     
  14. midnitmike
    Joined: Apr 2012
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    Location: Haines and Juneau

    midnitmike Senior Member

    Yes, Tunnels I looked at the oringinal post.

    Originally Posted by mrbcurry1

    I build fiberglass racing bodys for go karts. I am just wondering if I switch using a chop gun system, does it hold up in same layer thickness?

    ***********

    If you notice he uses the term "go kart" which is often used to describe the recreational version, so I can postulate (until the OP says otherwise) that we're probably not talking about competitive machines. Further research into the subject also leads me to believe that Kart racing in general is class oriented, and any weight differences are taken into account to insure that all competitors have a level playing field.

    Taking into consideration what I've learned in the last few hours I see no reason why this particular poster can't use a chopper gun to increase his production numbers, and or lower his labor costs. If weight is not a significant issue but production costs are then he may find some economic advantage in doing so.

    The one thing that struck me when looking at these parts is how small they are. Because of that diminutive size he might find it hard to keep the resin and material in the mold rather then on the floor. If thats the case he may find that his expensive system provides no real benefit at all.

    MM
     

  15. tunnels

    tunnels Previous Member

    Very good now at long last we getting some where . Its like mating elephants , lots of noise and shuffling about and very little happens but eventually it gets there !!
    :p:);)
     
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