Resin choice

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

  1. mcdc
    Joined: May 2012
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    mcdc Junior Member

    Working on a stringer repair and need some advice. The boat has stringer issues on the inboard engine up thru the gas tank area. The engine stringer is wet and has dark samples from the very bottom. The end of the gas area that meets the engine stringer is shot. The plan was to replace the gas area with wood and VE and then cut the cap on the engine side stringer, remove the wood and pour Sea Cast. The transom checks fine.The ER has gel coat so the plan was the recoat with gel since I already have it. I was told to drop the VE plan and go with epoxy since the VE will only have a mech. bond and epoxy will have a chem and a mech bond. I am not against going with epoxy but I need to know what cloth to use since I have not worked with epoxy, then what would I top coat it with to match the rest of the ER? This is a newer Sea Ray made with VE.
    Thanks!!
     
  2. ondarvr
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    ondarvr Senior Member

    While some feel epoxy is the only choice for any repair, it really won't make a difference which resin you use, both will hold up fine long term.

    This type of repair is normally done with either polyester or VE and it's not typical for a repair to fail unless it's done poorly.
     
  3. ondarvr
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    ondarvr Senior Member

    The main reason for the rotten wood is poor workmanship or design, unsealed screw holes, areas with no glass over the wood, etc. It's common for even a rookie to do a much better job of rebuilding stringers and transoms than what was done in the original build because the owner actually cares about the outcome

    While epoxy does bond better, the bond only needs to hold up to the stresses it will actually experience and even the cheapest polyester has proven to be up to the job.
     
  4. mcdc
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    mcdc Junior Member

    Thank you!! I will stick to my plan and use the VE.
     
  5. mcdc
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    mcdc Junior Member

    Any VE mfg i should use
     
  6. ondarvr
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    ondarvr Senior Member

    Many times you won't know the actual brand of resin. The retail suppliers buy it in drums from the few large manufacturers and then pour it down into smaller containers and put their own labels on it. They may also change suppliers depending price, so it is what it is sometimes. You may be able to find a supplier that can tell you who made, but it won't make much of a difference, they will all work well.
     
  7. mcdc
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    mcdc Junior Member

    If I do decide to use epoxy, what glass will i need to use. Thanks
     
  8. Steve W
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    Steve W Senior Member

    I assume you would be using a stitched fabric such as DB1708 which has a 3/4oz mat on one side with the VE, if you were to use epoxy you would use similar but without the mat, such as DB1700.You dont need/want the mat with epoxy as it is wasted weight and mat is held together with a styrene soluble binder and the epoxy wont disolve the binder.

    Steve.
     
  9. mcdc
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    mcdc Junior Member

    Have to switch plans I guess. Since the middle stringer being replaced is backed with foam, a thin glass sheet between it and the stringer………… VE needing air to cure.
    Option 1. Epoxy the inside section of ply to the foam section and bulk heads, stop and then use VE with 1708 with mat to finish?
    Option 2. Start with Epoxy and use epoxy for all repairs. 1708 stitched mat with the last layer being powder mat or veil to match the other panels topped with two part poly paint to match?
    Do you guys have an epoxy brand you like that is better than the other. I have heard some do not like west because of it becoming brittle after cure.
     
  10. PAR
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    PAR Yacht Designer/Builder

    There's no advantage in switching between vinylester and epoxy. If you vinylester first, then come back over it with epoxy, you'll be okay, but not the other way around, as vinylester don't have nearly the mechanical bond strength to epoxy as epoxy has to it.

    I wouldn't worry about matching the texture of your stringer repairs, with mat and epoxy. It's just wasting epoxy and under the sole, who'd to know anyway.

    West System doesn't go brittle with a cure, so stop listening to those that have suggested it does. There's a good reason they're the industry leader and a brittle end product isn't one of them.

    Talk to Paul over at Progressive Epoxy Polymers (epoxyproducts.com) or Joel over at Bateau.com. Both have epoxies at much lower costs than West.
     
  11. mcdc
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    mcdc Junior Member

    Thanks par. Did not really plan to apply one over the other. Using epoxy to set the ply into the already formed glass panel....as a glue and only on the back then using VE and glass to finish the exposed side of the stringer......the one by the fuel tank. Thanks
     
  12. mcdc
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    mcdc Junior Member

    Does anyone have a VE resin they like better than others or is it mostly the same? Looked at Hi Bond but it is as much as epoxy. US Composites is dirt cheap for some reason.???
     
  13. Sheetbender
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    Sheetbender Junior Member

    Re-laminated the entire bottom of my 40' sailboat with five layers of 1708 and the mat wetted out just fine. 1708 uses stitch-mat, no binders, or at least if there are any binders, they are epoxy compatible nowadays. Over the past three years, have used three different brands of 1708 and never had a problem with wet-out. I do use a low viscosity resin and hardener though. When I use a thicker hardener, I heat the resin first to above 100F.

    US Composites is the cheapest epoxy and is as good as any other. I use the 635 thin resin with the slow hardener. To use the slow you should have to have temps above 70 degrees for the entire cure. The medium hardener is thicker and needs to be heated in my opinion for the best wet-out.

    US Composites uses Reichold Epotuf epoxy.
     
  14. Steve W
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    Steve W Senior Member

    Sure the 1708 will wet out ok with epoxy,(ive used it in a pinch myself when its all i had on hand) even if the binders dont dissolve, because the mat is very light but why would you want to on a big job where you are ordering speciffically for the project? its not needed with epoxy and is as i said wasted weight, not just the weight of the mat but also the resin used to wet it out, its not insignificant. (its a mindset,take care of the ounces and the pounds will take care of themselves) I dont know for sure but i suspect that the mat on 1708 still has the styrene soluble binder.

    Steve
     

  15. PAR
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    PAR Yacht Designer/Builder

    The binder on 1708 remains in suspension in epoxy, unlike the polyester, where it's soluble. You'll use a significantly higher amount of epoxy to wet out 1708 than just straight 17 ounce biax. The resulting laminate will be weaker, because of the higher resin to fiber content and considerably heavier too.
     
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