Resin choice

Discussion in 'Materials' started by mcdc, Jun 15, 2012.

  1. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Tunnels, the number on these products tell you what they are: 1708 is a 17 ounce biax, stitched to an 8 ounce mat. 1208 is a 12 ounce biax stitched to an 8 ounce mat. 1700 is straight 17 ounce biax, no mat, etc. They're commonly referred to as knitted or combo fabrics. The binders question isn't an issue, unless you've purchased NOS that's several years old and even if you did, it doesn't matter as this material remains in suspension in an epoxy laminate. I don't understand why folks have difficulty with this subject. It doesn't matter, regardless of resin choice.
     
  2. swade
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    swade Senior Member

    op,

    While the experts discuss the hard stuff =)

    If you want a newbie (very) perspecitive on the resin i'll give you mine as all of my projects have been simple stuff or mostly cosmetics, par recommended epoxy on my transom repair.

    I found it tons easier for a newbie. Mix parts done. With the stuff that uses mek i always find myself guessing everytime but florida is a bit difficult for me, high humidity, high temps, and for a newbie like myself i cut back mek for working time, but then of course i sit there hoping it kicks. 1st batches were always a guess. I found the epoxy *tons* easier and much more predicable so much i didn't even think about it, i could work on trying to figure out wth i was doing type stuff instead of worring about is this going to kick in 5 minutes or 30.

    I can't tell you about tensile strength, binders, any science and stuff like that, only for repairs, working on diy time constaints, if i was going to be mixing bunches of batches... unless specifically not recommended I'll use that. For me being completely unskilled and that i typically touch this sort of stuff only every few months I really trusted when I was mixing it that I knew when and that it was certainly going to gel....not putzing about guessing or hoping. That and i could do some stuff in the garage at night without stinking up the house. Also left over shelf time is much better which if you diy stuff here and there you're going to have a 1/2 used gallon sitting going bad in 6 months and even then at 4 months you'll say hrmmm is this stuff and the mek going to kick? For a diy'r i think that alone pays for the extra epoxy cost.

    In case you haven't ran across mixing it yet, this worked perfect for me

    http://www.youtube.com/watch?v=XnyPm9BMSyM

    Only downside i noticed is patience waiting for cure whereas before i could do some more stuff pretty quickly in florida.
     
  3. mcdc
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    mcdc Junior Member

    Hey, I do have one question. If epoxy is stronger than poly, then why would using epoxy with CSM become the weak link in the Lam due to the resin rich layer? By using epoxy in place of ploy would this not be considered just a much better resin as poly and CSM are resin rich? I created a few test panels using 4 layers of 1700/ epoxy to compare the the 2 layers of heavy CSM/ 2 Woven...........looks like the woven/csm is much stroger....will know more latter this weak when I can get it back to the shop...stiil debating on a layup that will get me back to aleat 2/3 of the MFG
     
  4. PAR
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    PAR Yacht Designer/Builder

    Mat is simply a sponge of randomly oriented fibers soaking wet with resin. The strength of the laminate is three fold, fiber type and orientation, resin modulus and how well these match each other.

    Simply put, using mat insures you will have a high resin to fiber ratio, which isn't good for strength and weight. Also since mat is a bunch of haphazard little fibers, load paths have to jump from one the the next, because of the lack of fiber continuity. This is an inherently weak arrangement, much like not organizing the steel skeleton, within a bridge and just relying of a random pile of I beams.

    In an ideal laminate, the resin elongation modulus matches that of the fibers and the fibers are oriented with the load paths expected. This means when a load is applied and the fibers start taking up the strain, the resin and fiber both fail approximately at the same time. Epoxy and directional fabrics have this symbiosis. Vinylester is much better than polyester, but lacks inter-laminate tensile strength, so needs some mat to insure a good bond (read heavier and weaker). Polyester is the worst comparatively, with the resin failing long before the fibers in the fabric, so it has to be bulked up with lots of fabric and inter-laminate bulking (mat) just to get reasonable stiffness and strength.
     
  5. mcdc
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    mcdc Junior Member

    Thanks Par....makes sense. If you had to suggest the layup, what would think it should be to create the same strength on this 30 foot boat .......since I am not using csm....bi only. Thanks!!
     
  6. PAR
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    PAR Yacht Designer/Builder

    This thread has meandered around a good bit, please refine the laminate request. Laminates should be matched to loads. You pretty much have a good pan for your stringers, so what other laminates are you asking about?
     
  7. mcdc
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    mcdc Junior Member

    Sorry Par, I am still looking at the stringer. The test panel with 5 layers of 1700 is no where as strong as the the VE, 2 thick CSM/2 Heavy woven from the MFG (12/18MM)....not sure 9 total layers of 1700 will be as strong in the tabbing area as before
    My plan was to run 5 layers of 1700 (out 8 on the hull and up 2, then out 7 ect) then cover with 4 layers of 1700, over the tape and up the stringer.....not sure how to stagger over the 5 layers of tape.

    Also, can I switch epoxy brands while laying up if I run out? Thanks!!
     
  8. ondarvr
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    ondarvr Senior Member

    Did you measure strength or stiffness, they are two different things, CSM will bulk up a laminate and make it stiffer, but will add less strength than something like 1700.

    CSM holds a great deal of resin, which has little flex, and the lower glass % results in less strength.
     
  9. mcdc
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    mcdc Junior Member

    I did a cheap deflection test for stiffness. I took a 8 by 8 inch square of 4 layers 1700, setup a small block on each side, setup a dial under it to measure flex using a 5 then 10 lb weight, did the same with the old lam from the side of the stringer (12mm). The 1700 flexed alot more.......thats why i started to question my schedule. Do I need the stiffness or strength or both for the engine stringers. These support a set of twin 6,2s on this 30 footer......really do not want to have a vib from the engines. Thanks
     
  10. PAR
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    PAR Yacht Designer/Builder

    Strength is what you want, stiffness will come with things tied together, such as the stringers to the hull shell, etc. Vibrations are also better managed with better elongations properties then stiff, less yielding characteristics. It's also important to compare apples to apples and a 1/2" CSM and rove laminate compared to a 34 ounce biax laminate (what, about 1/8" thick?) just isn't a fair comparison.
     
  11. mcdc
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    mcdc Junior Member

    Thanks!! With that being said, I still plan to run 5 layers of staggered tape (8 out on hull and 2 up the stringer, 7 out and 3 up ect.) then 4 complete layers of 1700 from the top of the stringer and over the tape. How should i start the full glass sets over the tape on the first one? Out on the hull 9 then 8 ect to cover the tape and to build 9 layers of 1700 in the joint?
     
  12. PAR
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    PAR Yacht Designer/Builder

    Rephrase the question, maybe take a breath and talk slowly, for us old men with hearing issues.
     
  13. mcdc
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    mcdc Junior Member

    Sorry Par. issue, plan was/is to tape 4 or 5 layers of 10 inch wide 1700 staggered, then come back with 4 layers of 1700 over the stringer and the tape to create 9 or 10 layers in the tab area..... since the the MFG was soooooo thick. I questioned the schedule after I laminated 4 layers of 1700 that seemed really weak....or not as stiff.

    Do you think this the best plan or should I add something else to the schedule.

    If this works, how should I run the 5 layers of tape and the 4 larger sheets?

    Lay the 5 staggered layers of 10 inch tape then the 4 larger ones staggered over the top of the tape? Or should it be tape then full sheet then tape then full ect. Seems like a lot of glass.
    Thanks!! Hang in there!! Owe you a case.....or two next time Im your way!!
     
  14. PAR
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    PAR Yacht Designer/Builder

    To be honest, it doesn't really matter what the schedule is, so long as the seams are staggered, you have good contact between the layers and you force out excess resin as you laminate. Arguments can be made for both approaches you've outlined, but I'm a big to little guy (which is what my other half tells me). I'd get a good bond with the biggest piece, then insure chemical bond with subsequent layers over it. Others would do it the other way around with the little pieces first, working up to the biggest piece last, which does look nice, but has the potential for bubbles and air pockets at the seams.

    I like my beer in bottles, preferably long necks and an under 25 year old bikini wearing waitress to hold the church key.
     

  15. mcdc
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    mcdc Junior Member

    LOL..... Long necks it will be !! Think I will run the biggest one first, then stagger a run of tape, then the next biggest one staggered, then a run of tape and so on.....that way I can ensure each one is staggered properly and build up the tab/seam area.......would seem hard to run all the tape first then try to run the larger ones and still keep them ending in a different place. So it sound like the 5 layers of tape and 4 ful layers will work then and still be strong enough.......just need it to stop raining now. Thanks
     
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