.053 thick glass. How much oz??

Discussion in 'Fiberglass and Composite Boat Building' started by jrork, Nov 26, 2011.

  1. jrork
    Joined: Oct 2011
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    Location: Silverdale

    jrork Junior Member

    Hi guys. I measured the glass that I took off my stringers and it's .053" thick.

    Is there a way to determine the amout of fabric was originally used?


    Thanks very much.........john
     
  2. CatBuilder

    CatBuilder Previous Member

    I'd like to take a stab at this and see what others come up with as well.

    I come up with 1300gsm or about 36 oz of glass.

    As to the type... you probably need something that will bend easily to wrap those small curves, so you will have to use something much less than 36 oz, and install it in multiple layers.

    Let's see if that was right. jrork: Don't take this post too seriously yet. I'm trying out some new knowledge! :)
     
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  3. michael pierzga
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    michael pierzga Senior Member

    I dont often work with glass. A simple examination would be to take a sample of layup , then cook it....burn the resin off...then you are left with fabric only. Resin melts at a low temperature. With the remaining fibers you should be able to infer the layup orientation and weight
     
  4. jim lee
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    jim lee Senior Member

    That's less than a 1/16" When we infuse 1700 (17 oz/yd) we get about 1/16"

    -jim lee
     
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  5. jim lee
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    jim lee Senior Member

    Oh, and for supplies at reasonable coast and quantities less than a truck load..

    http://www.fiberglasssupply.com/

    These guys are just a couple miles from my shop. They do a pretty good job supplying projects of your size. We use them on occasion when were doing experiments.

    -jim lee
     
  6. CatBuilder

    CatBuilder Previous Member

    +1 on Fiberglass Supply. They have been supplying my infusion materials, microballoons, silica and chopped fibers.

    I also cleared them out of those plastic T's a week or so ago! :p:p
     
  7. PAR
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    PAR Yacht Designer/Builder

    It depends on what it is, .053" of laminate could be 3 layers of 10 ounce cloth, then again if mat it could be several layers of a light mat or a couple of a heavy. Then there's the resin/fabric ratio to consider and also construction, such as knitted fabrics. A picture would help tremendously. It's likely it's just CSM, but it could have a mix of roving, cloth, who knows, all of which will affect the "schedule".
     
  8. waikikin
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    waikikin Senior Member

  9. rxcomposite
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    rxcomposite Senior Member

    Michael is right. Weigh it, then burn it. Whatever is left is the glass. That is how they do it in the lab. But then again PAR is correct in saying it could be a mixture of several different type of glass which make it complicated because different type of glass have different resin content.

    After burning, you should be able to separate the different layers of glass. Take it to the glass supplier and compare it with the samples they have to identify the type and weight of glass samples. That is the only practical way. No need for math.

    If you don't like burning, use a heat gun and steel spatula to carefully separate the layers. The glass supplier should be able to identify the type of glass and weave irregardless of glass content. Glass weights are standard so they should come close.
     
  10. rberrey
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    rberrey Senior Member

    Best as I can tell these are average numbers on FG laminate wet , 17.3 oz dd bias =.029 , 1610 fabmat =.050, 34.5 oz triax =.050 1oz mat = .030. 10 oz finish cloth =.016, 16 oz woven roving = .024. 34.5 Triax or a combo of say a 16oz woven roving with 1oz mat, or 1708 should be a close match. Rick
     
  11. jrork
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    jrork Junior Member

    This is really great information guys. Thanks so much. I just may learn something. I'll try burning it off and will let you guys know what I find out.

    Jim, thanks for the tip on the place in Burlington. Much appreciated
     
  12. CatBuilder

    CatBuilder Previous Member

    This is all over the place. Nobody has the same answer. Not a good sign.

    The way I calculated mine was with a "rule of thumb" I'd heard on a pretty reputable place. It went like this:

    .053" is 1.346mm then, using a rule of thumb...

    1.346mm thickness is *approximately* equal to a 1346g/sm cloth, wet out.

    Converting quickly (in my head without doing any math) from 1346g/sm to oz/yd, I know that 1150g/sm is 34oz, so I'd say this laminate is about 35-36oz of laminate, wet out.

    Has anyone else used this conversion before?

    I saw it in a group where Derek Kelsall, Kurt Hughes and several others regularly read and respond and nobody corrected it.

    Would you guess it's accurate?

    I ask because many of the laminations in my plans are say stuff like, "biax to 3mm"

    I am using this rule of thumb in many places in my build.
     
  13. rxcomposite
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    rxcomposite Senior Member

    Proportion required is by weight because it is harder to calculate by volume. Trouble is glass density is by weight per area and resin is sold in liters or gallons. Resin specific gravity varies from 1.2 to 1.38 so that complicates things.

    To make life easier, Glass content by weight is the benchmark and the typical ratio is more or less followed in hand layup.

    CSM- 0.30 to 0.33 glass content or gc
    WR- 0.47 to 0.5 glass content
    Uni or stitched- 0.5 to 0.53

    So take your glass, any size you want weigh it and multiply it by the following ratio and WEIGH the equivalent amount of resin. That is the resin you will need. Thus:

    CSM- 2.1 to 2.3 (a little more than twice the weight of glass)
    WR- 50/50 or 1:1 the resin is the equivalent weight of glass or just a tad MORE


    Uni- A little LESS than the weight of glass. Say 0.97 or 0.98.

    Veil Cloth is a little harder because it is very thin and light and the Gc is 5%. Without doing any math I think it is around 20 or 23 times the weight of the veil. Another way is to estimate is as if you are applying gelcoat, say 450-600 grams of resin per square meter and just throw in the veil (30 gr/m2 or 50 gr/m2).

    Nominal thickness of a hand layup laminate is 0.70 mm for every 300 gr/m2 of CSM glass. About half, 0.37 mm for cloth.

    Maybe it is forgotten because it is in metric system but I have posted the glass/resin calculator in Cats thread before and the method of Professional Boatbuilder and Lloyds Rule validates each other.
     
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  14. SamSam
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    SamSam Senior Member


  15. jrork
    Joined: Oct 2011
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    jrork Junior Member

    This is great stuff guys, thanks!

    To help, I did as some suggested and burned the resin off.

    Here's what I found

    One layer of cloth on the outside = 0.015" thick

    One layer of chop matt on the inside = 0.021" thick

    Not much for sure!
     
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