Polyester versus Vinylester or Vinylester skin ?

Discussion in 'Materials' started by leaky, Oct 19, 2015.

  1. leaky
    Joined: Sep 2008
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    leaky Senior Member

    Hi,

    I'm having a new downeast boat built, taking it as a kit with the bottom, top, shaft, and rudder, then doing the rest.. I'm in the northeast. The purpose of the boat is going to be commercial rod & reel fishing.

    The standard boat from this builder is polyester resin all around, spruce stringers, airex core on the gunnels & top. Going to have coosa used on the stringers to eliminate the rot potential.. Probably also a more dense material used in the gunnels since I need them resistant to crushing under the pressure of bolting on a zillion heavy duty rod holders..

    I've got some experience with polyester and a fair amount working with 2 part epoxy (like quite a bit for someone who is just a fishing boat owner, burning 25 gallons a year or so on my boats and friends, not like a boat builder burning thousands). I've never even seen a can of Vinylester though.

    On some boats, as an option that adds cost, this builder uses a Vinylester skin. I haven't spoken to him about it, but since I don't understand exactly why it's used or how it changes the process, I'm hoping someone can help explain that so I understand what I should end up requesting (and ultimately paying for!).. Also have noticed other builders offering options of doing 100% vinylester layup..

    Can anyone take a stab at what the purpose is of using vinylester in a solid glass layup and/or if it's good as a skin, or for the whole layup?... Also interested in understanding how it changes the layup process, like does it end up being a mechanical bond for that first layer, or can you lay polyester over wet vinlyester etc.. etc..

    Thanks in advance!

    Jon
     
  2. ondarvr
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    ondarvr Senior Member

    VE is an upgrade from polyester and used in the same way with the same fabrics. VE is more water resistant and tougher than polyester, so there is far less of a chance of any blisters forming, although using the correct ISO polyester does very well against blistering too.

    Using VE as a skin gets you the blister resistance, but only part of the toughness. If engineered correctly a VE hull would be slightly lighter than a polyester hull, but most of the time they use the same laminate schedule.

    Polyester is generally easier to work with than VE, VE isn't hard to work with though.

    VE resin could be double the cost of polyester, depending on how the hull is made it would be in the 60/40 resin to glass ratio (this can change a great deal with some build methods). So 60% of the total hull weight could be twice the cost of polyester. You can do the math.

    VE and polyester play well together, so there are no bond or compatibility issues.

    The exact polyester resin would need to be spec'd prior to the build, there are hundreds (thousands actually) of different formulas. Some are targeted to a price point, others meet a performance goal, the cheap products are where a builder can get run into problems with blisters. There are also many blends of different resin bases to try and get the best of both worlds, many VE/poly blends, or DCPD/poly blends are used to build boats. Picking a resin can be like going to Starbucks for the first time to order coffee, there are so many possible choices that you don't even know where to start.

    Almost any VE resin will do the job well.
     
  3. SukiSolo
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    SukiSolo Senior Member

    I've not had any problem bonding to Vinylester with either epoxy or polyester resins, or importantly repairing the gelcoat with polyester gelcoat. My understanding (and hands on feel) from data tables on stiffness etc is the VE is stiffer than polyester but more expensive. My own take would probably be a poly gelcoat and VE layup for ease of repair and long durable life. On small craft the use of VE is definitely to get a weight saving for the same (or more) stiffness, without incurring the extra cost of epoxy.

    Only you can make the call, but ondarvr's wise words should help you come to a decision.
     
  4. rwatson
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    rwatson Senior Member

    Do a small VE test project. I found the stink overpowering and sick making. Imagine inhaling fumes from a burning plastic office chair. And it hangs around the shed for days.
     
  5. leaky
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    leaky Senior Member

    Thank you very much guys!

    That brings up one point - no idea what the builder uses by default as far as the actual blend of polyester. I know he said the resins they use have changed a lot, but when asked he just said "polyester" - that may be the simpler way to explain it. Will seek more information there - I may find he's using a blend already.

    I do know with his boats there are more or less 0 problems with quality or blisters anyone talks about.

    Hull bottom is 2500 lbs, so might be talking 1500 lbs of resin, or 160 gallons I think, $3200 assuming an extra $20/gallon, as a ballpark, provided there isn't a labor surcharge - does that sound right?

    As far as the toughness of the resin - with VE versus PE is it a stability/longevity thing, or crack resistance? Like is VE capable of greater flex without damage or is it just less likely to crack? Over time will VE "wear" better or retain more of it's original properties? How much of a difference is it?

    Comparing PE to 2-Part epoxy for instance, I've noticed the difference in stiffness - the 2-Part epoxy is a lot more resistant to damage, however isn't as stiff as polyester in a similar layup. So, for instance, if I was building a deck out of solid glass, and wanted to use 2-part epoxy (no idea why one would do this but just for instance), I'd probably need to support the epoxy deck more or build it thicker for a similar solid "feel", than polyester, although even if it flexed the epoxy would be stronger I'm sure.. Is there a similar comparison with VE and PE?

    Thanks!

    Jon
     
  6. ondarvr
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    ondarvr Senior Member

    The difference between resins is very specific to the exact resin used, there are high flex and rigid resins made in each type.

    In general a VE will perform better in every category when compared to a polyester.

    It's hard to compare an epoxy laminate to a polyester laminate when it comes to stiffness, the polyester laminate is normally made with different types of glass and is thicker, making it stiffer. If the two laminates are the same thickness one of them is not designed correctly.
     
  7. leaky
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    leaky Senior Member

    Thanks again!

    My comment on the flexibility is based on something I noticed when doing bonding experiments. I had a bunch of small pieces of 6 ounce along with the same of stitched mat + roving - I was attempting to bond to an unknown piece of fiberglass with polyester and 2-part epoxy, ripping them off once cured to check results. Obviously the 2-part epoxy worked better..

    Those little thin pieces of epoxy fiberglass were incredibly flexible. Like to the point where it was hard to induce a crack, where the polyester was not so flexible at all (most people would call it "stronger") but when subjected to the same force it would easily crack, however it took a lot more to flex it.

    Jon
     
  8. ondarvr
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    ondarvr Senior Member

    You are correct, there's a big difference between stiffness and strength, but you can get polyester or VE resins that are modified for flex, so comparing just one formula of a polyester to one formula of epoxy doesn't mean much.

    DCPD resins are very stiff, so they frequently are blended with other bases to gain some impact resilience. This is about what 80% of the resin made is now, or at least has DCPD in it. It's low in cost, doesn't shrink much, has good water resistant, not high in strength, and rigid almost to the point of being brittle.
     
  9. BKay
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    BKay Junior Member

    Leaky, you don't mention whose hull you are getting, but vinylester used throughout is great protection against blistering. Skin coat only is very good protection. As mentioned elsewhere, if it weren't for the cost, everyone would probably use vinylester only. I believe the only better product would be epoxy, which would probably be cost prohibitive.

    As a couple data points, the Wesmac 36 added $4,415 for complete vinylester resin (this was a few years ago on a $42,180 hull). The Young Brothers 38 charged around $1,400 extra for a skin coat of vinylester (this was on a hull costing $30,000). These were the advertised numbers and may be a couple years old.

    Epoxy sticks equally well to polyester and vinylester I'm told. I can't independently confirm that statement but I generally trust the source.
     
  10. leaky
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    leaky Senior Member

    Thanks for that - I didn't mention it because sometimes on forums people like to criticize and attack things, so left the good builders name out of it. Will drop you a PM.

    Sounds like the ballpark probably really is $3000. In the northeast I don't think we get so many blistering problems, at least from what I read on blistering, and these hulls I've seen no such reports of blistering, so honestly I don't think that's even a consideration for me..

    But what I do like is the idea of having a stronger hull without adding any weight, and without any core (really do not like cored hulls, even when it's a synthetic material).. Plus I bet on resale down the road, being able to say it's a solid VE hull, will gain me at least that cost in value.

    I will see what the builder says when we meet in the winter to put the final options down on paper. One thing I do not want to do though is add a quirk into his process that will lower quality - so if he has never done one solid VE, I probably will opt for a skin and not be the first. I've seen a similar solid glass boat the same builder laid up > 35 years ago and it was doing real well.

    Oh and as far as epoxy goes - you could, it wouldn't even be that outrageous in solid form, when you consider what a finished boat really costs - probably 3X polyester when they buy in bulk, but the trouble with epoxy is you can't gel coat it, and it's probably just not needed in solid glass.

    Jon
     
  11. SukiSolo
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    SukiSolo Senior Member

    You can have both polyester gelcoat and an epoxy gelcoat option with epoxy as the main adhesive for the layup. However and very importantly if using a polyester gelcoat a tie coat must be used. For repairs this is not an issue and polyester gelcoat can be applied quite happily to epoxy/cloth layups. Easier to use a polyester gelcoat for initial build as this is so widely available but the builder MUST know how to use the combination with epoxy or the hull will be scrap, or require stripping and painting...;)
     
  12. PAR
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    PAR Yacht Designer/Builder

    Agreed, epoxy can be gel coated and it doesn't cost 3 times as much as polyester either.
     
  13. leaky
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    leaky Senior Member

    Thanks for that guys, this isn't meant to be a criticism rather a question.. Is there really a whole lot of benefit to a 2-part epoxy, versus VE, in a solid glass layup?

    Granted I get the impression us folks up north, especially the guys in maine, do not exactly operate on the cutting edge of boat building technology.. But with that said, after quite awhile of being around boats, folks that do all aspects of boat service/repair, and even boat builders - I'm the only one I know personally that's done any amount of solid glass layup with 2-part epoxy, actually and anyone else I know that's even used it did so because I was involved and recommended it ;)..

    Actually one exception - I know an old harpooner who built a plywood cored boat, and he did use 2-part epoxy.

    Is anyone anywhere really building many solid glass boats with 2-part epoxy? I think it's great if they are, just I've never heard of it.. I know it's real popular with folks in the know for repairs, and in home building plywood boats and stuff.

    Jon
     
  14. leaky
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    leaky Senior Member

    Oh and on the cost - I think I was told $1300 for a drum of VE about a year ago. That's from a friend who builds boats, before I decided to build new I almost took on an older project instead..

    I think the cheapest I can get 2-part epoxy for, at least with stuff I know I like, is Marinepoxy and that's about what I'd pay for 25 gallons that way (kit of 15 is like $800/shipped)..

    So was figuring 2X VE for 2-part, with VE being about 2X PE.. (ie $15/gallon for PE, $25 for VE, and $50 for 2-part epoxy, in bulk, as a ballpark, but could be off)..

    Jon
     

  15. BKay
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    BKay Junior Member

    Since you are getting a hull from a reputable and experienced builder, they will have very well formed opinions on materials and methods. I think you are wise to work within the range of materials and methods they are using at the yard. If it was some custom, one off boat it would be a different story. But for guys that have built hundreds of DE hulls over decades, I'd give their opinions a fair amount of respect.

    BTW - my understanding of blistering is the same as yours. The warmer the water and the longer the season, the greater the concern. If you haul every year and the water is cold, it's much less of an issue. Nevertheless, your comment on resale by having full up VE seems logical.
     
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