Chop Gun or Hand Lay

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

  1. OFFSHORE GINGER
    Joined: Nov 2011
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    Location: Mich

    OFFSHORE GINGER Junior Member

    Hey guys ...............the bottom line is if you are going to use a Chopper gun for making Go Cart Bodies / parts , so be it because in the long run it most likely will be very cost effective ( CHEAPER ) in the long run opposed to a traditional style layup having to use more people and material to achive a very simple layup or part .....................which actually only amounts to common sense .
     
  2. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Midnitmike said it exactly right - if weight is not a significant issue.....

    That is the part tunnels just kept denying.

    Midnitmike, thanks for the realistic conclusion.
    of course, several others said it several times, so I don't know why tunnels wouldn't agree then.
     
  3. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    I know better than to jump in…but here goes.

    If the OP is asking whether replacing CSM with chop will yield the same strength in the laminate…then yes, if done correctly the results will be about the same. When laminates are designed they typically don’t include the strength of the CSM or chop because it adds so little strength. The majority of the strength is coming from whatever other fabric (woven or knitted) that is being used.

    I believe some are comparing a 100% chop layup to a laminate made with other fabrics included also, but 5mm of CSM has about the same strength as 5mm of chop. Of course a laminate that includes knitted or woven fabrics will be stronger, and it will be stronger yet if it was infused, but on this type of part the cost would skyrocket. It would be worth it for high end racing components, but for the average amusement park ride it wouldn’t make a difference (I’ve built and repaired both types).

    The difficult part is chopping small parts and keeping the thickness uniform and not wasting a great of deal material on the floor from overspray, both cost money and lead to inconsistencies in the parts (I didn’t look at the website to see the individual part size). These inconsistencies make little difference on an amusement park ride part, if it fits in place it’s good enough because cost is the driver, not quality or strength to weight ratio. Without knowing the volume of parts that need to be made it’s hard to say if the cost per unit will be lower than a part using CSM. The cost to buy and then maintain a chopper gun can be high, what you save in the cost of glass and man hours in building the parts can be eaten up in maintenance, down time, waste and mistakes.

    As for the increased chance of blisters with chop, CSM has a higher probability of blisters due to the binder used to hold it together.
     
  4. tunnels

    tunnels Previous Member

    Why should weight or strength or anything be differant between the two panels ????


    Ok i will discribe yet again !!
    HAND LAID like i discribed before ! , 1mtr sqr x 2 layers of 450 gram csm off the roll =.900 grams !!! right ? resin from the drum , resin measured out on a set of digital scales , in a container 1.25 kgs ,catalysed ratio at 1.5 % !!

    Ok gun laid glass -same size 1mtr sqr same weight of csm but done with the chopper =.900 grams !! ! right ? resin sprayed through the system catalysed 1.5 % , resin used by the gun 1.25 kgs (oh yes we always used scales for the glass , resin , and the catalyst !! ). quantities and weights were worked out before the job started and recorded after !

    PLEASE explain in very simply terms where is the differance ??.

    Ohh nearly forgot gel time is the same on each panel and when the resin went hard and the panels were trimmed they both weighed the same !! :(:confused::eek::mad:
     
  5. tunnels

    tunnels Previous Member

    The cost to buy and then maintain a chopper gun can be high, what you save in the cost of glass and man hours in building the parts can be eaten up in maintenance, down time, waste and mistakes,

    yes i agree but like any and all spray equipment its lack of use thats the biggest problem and why seals leak etc a drop of oil each morning and a diligent operator guns dont have problems .
    One company i worked as forman the gun went 6 hours of a 8 hour working day . Every 6 months we replaced just the seals only on the resin pump and the catalyst pump seals and balls . Day in and day out week after week it never missed a beat and we sprayed 8 cheese rolls of glass every day .

    The guns we have here in China came as secondhand units that i completely reconditioned after i got here , in two years we have only had one misshap when a adjustting nut came loose !!, thats all in 2 years !!.
    This particular gun is over 20 years old and came from a power boat company and has had a lot of use during its life .

    As i recall the man asked about csm only !! other fabrics we never mentioned but most all the poster here have been assuming without actuall knowing !! :(:eek::confused:
     
  6. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    That's why I said this before the sentence you quoted "Without knowing the volume of parts that need to be made it’s hard to say if the cost per unit will be lower than a part using CSM."
     
  7. tunnels

    tunnels Previous Member

    I cant believe this thread is still Rabbiting on when the question wasnt even one line long !!!:confused:
     
  8. midnitmike
    Joined: Apr 2012
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    Location: Haines and Juneau

    midnitmike Senior Member

    You're right, and over a third of the posts belong to you.

    MM
     
  9. tunnels

    tunnels Previous Member

    Only a third jezz my popularity is slipping !!:D:p
     
  10. waikikin
    Joined: Jan 2006
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    Location: Australia

    waikikin Senior Member

    C'mon, a third is "nearly" half.....................
     
  11. tunnels

    tunnels Previous Member

    Yeah ok !!:p
     
  12. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    All the facts are here to be found. If you don't have your head... in the sand.
    Gone.
     
  13. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    Well,you have a lot of experience and knowledge, but as you say
    . That would seem to imply that while chopper gun layups can be as good as the same thickness of a hand layup of csm, "very few" will be.

    You also say somewhere that chopper gun layups can be better than csm layups because there are no laps or seams. If it matters, seams can always be ripped and blended, and laps can be a good thing as they supply localized stiffening as ribs and frames do. I would think that localized strength areas would be very handy in something like a "racing" go cart body. In "real" racing bodies localized stiffening is used extensively and very specifically and incorporates a variety of materials such as cloths and fabrics of fiberglass, graphite, kevlar etc., resins, cores and metals and structural shapes. To put localized stiffening in with a chopper gun would be difficult, but it could easily be incorporated with a chopper gun layup.

    The OP is vague and even though I "assumed" he was asking about the relative strength between chopper gun and csm layups, if you actually read what he posted, nowhere is csm mentioned.

    In post 4 he says
    . That's pretty garbled, but what I think/guess he's saying is only parts of the small go cart body would be chopped and it sounds like he might think a chop layup could be stronger than a csm hand layup and in an offhand way is asking if that's so.

    The whole thread is kind of odd, comparing the strength and durability of the two crappiest ways to make a layup. Taking what you seem to be saying and what he seems to be asking, odds are a chopper gun layup won't be as strong as a hand layup of csm.

    If it's only used on parts of a small mold, it will not be economical at all as far as comparable costs.

    There are different types of strength, but assuming this is a chopped fiber layup, it's a brittle, un-flexible, inefficient, 'weak' strength he's dealing with. If he's interested in improving it's 'holding up' and 'hit taking' properties, there are much easier ways to do that than buying a chopper gun.
     
  14. tunnels

    tunnels Previous Member

    Why is there such a hang up over chopped strand matt ???

    Why do people have such hang up about chopped strand matt ??? . One company i worked we build all and every part of there boats all with a chopper gun all completely out of chopped matt . one particular model was a cruiser 36 foot usually had twin stern drives and big fuel tanks the boat number we 155 when i left .
    You can make anything from chopped stand matt !!! anything at all !!!its only in recent time that we now have better materials in the way of fabrics stitched to work with !!
    If you were bought up just 25 years ago you wouldnt thing twice about using chopped strand ! .
    I have done some exsperimenting of my own by removing 1 or even 2 blades out of a chopper gun so it would lay long strands . Laid ,rolled, and looked just normal but i would take it the strength could be a little better .
    Get over it! its been round much longer than some of you have been alive and will be still here long after you have passed away !!:p
     

  15. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    I seriously doubt the chopper gun will be around much longer due to the workplace environment issues unless they can spray an environmentally friendly resin.

    PS 30-40-50 years ago there was no chopper gun and no osmosis but I guess that was just an unlucky co-incidence
     
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