Epoxy vs. Vinylester

I have wondered about this for years... why not use an epoxy vinylester that has superior physicals to the typical epoxy? Here's an example:

  West 105/207 Vinylester



Tensile 6748psi 12500psi

Tensile elongation 3.8% 3-4%

Tensile modulus 4.4EX05 5.5EX05

Flexural 11324psi 19000psi

Flexural modulus 4.12EX05 5.5EX05

HDT   F 117 300


These are some of the corresponding numbers that I could find. Help. 


16 replies:

« Previous Post       List of Posts       Next Post »

RE: Epoxy vs. Vinylester

I don't know where you got those numbers---if that's all there is to it, I think we'd be reading about vinylester F-22 fighter jets.  As long as I've been building boats as a professional---since 1991 or so---it's never been in dispute that epoxy is stronger than vinylester.  I can't find a citation in an engineering manual to refute that.

Here's an excellent start to read up on the differences:  http://www.netcomposites.com/Education.asp?sequence=7

Vinylester is designed to be used in tightly controlled manufacturing settings.  It's thinned with liquid styrene, so it's horribly toxic to be around. (It's usually "infused"---an enormously esoteric factory process---rather than rolled on by hand, to contain the VOC's.)  The cure is usually designed to be air-inhibited, making it REALLY hard to use outside of a closed mold.  (If you're not sure what THAT is, you don't want to try to use the stuff in a small shop setting.)  The main advantage of vinylester is that it's stronger than polyester resin, but cheaper than epoxy. Perfect for middling-to-higher quality production fiberglass boats being popped out of molds on an assembly line.

RE: Epoxy vs. Vinylester

I know this is a hot button topic for some. Thanks for the quick reply. First off I want all to know that I work in the composites industry and have used all types of resins, epoxy, polyester, vinylester, and urethane. You are right F22s are made with "aerospace epoxy" not vinylester or west. The physicals of which are far better then the ones for the west 105/207 or the Derakane 470 that I quoted. Aerospace epoxies are costly too, I once priced some for a project and one drum  of Huntsman cost fifty thousand dollars. But lets compare the west and the VE. The reason this came up is because I recently saw a FRP mold made with VE in our bone yard that was built three years ago. As usual the exterior plywood reinforcing was flood coated with VE and it still looks like the day is was made. No white chalking or milky cruddy looking mess like old polyesters. That would seem to be a good indication of weather ability, no? Apart from weather ability the published physicals for the VE seem to be better. Have you heard of anyone else using VE for composite wood building? As far a styrene is concerned, yes it's nasty stuff but so are the solvents in varnish or paint and don't get me started on the "trade secret" ingredients that we don't get to see on the MSDS of epoxies. Properly used all these chemicals are OK. Not arguing just curious about the feasibility of using VE. Oh, and I think given a side by side chance to use each resin most people would find the VE easier to handle.

RE: Epoxy vs. Vinylester

VE, as I understand it, is significantly more "toxic" than the marine epoxies we use, though I don't have anything but hearsay to support that claim.  I have a bunch of friends who ask me about using polyester resins, but I can't handle the fumes of those, personally, even with a respirator mask.  That's the big issue for me, especially since you can often get the polyester resins cheaper than the marine epoxies we use.

As for ease of use, I haven't noticed much difference, personally.  I have much more limited experience with the polyester resins though.  For what it's worth, surfboards have been made with polyester resins for a very long time and they are quite successful being used year round in all the same conditions our boats get used in, except possibly ice.


RE: Epoxy vs. Vinylester

I never thought about the surfboard analogy, but your right they have been using Poly, VE and even epoxy. That makes me feel much better about the outcome of using VE in my boat experiment. Thanks.  

RE: Epoxy vs. Vinylester

One important thing to keep in mind is that one can't just pick the mix that has the biggest numbers. The numbers have to also make sense for the application. The numbers listed above are valid only for chunks of cured resin. They don't say anything about what happens when the resins are used as part of a glass lamination. Nor do they say anything about what happens when the layups are put on a wooden core. Also unmentioned is the peel resistance and the porosity (which would let water pass through to the wood), as well as the tendency of ester-based resins to shrink as they cure.

Then there's the question of flexibility. The flexural modulus is saying that the epoxy is actually more flexible than the vinylester. Flexibility is good for kayaks made of thin wood. Resin that is too brittle could let the seams pop open. Is vinylester too brittle? Can't say, depends on the rest of the boat design.

Another good number to have, which isn't there, is the coefficient of thermal expansion. It needs to be compatible with both wood and glass. Otherwise there will be telegraphing of the weave and possibly microcracks.

Be careful using the surfboard analogy. Surf boards use foam cores which are designed to be chemically and mechanically compatible with polyesters and vinylesters. That does not guarantee that  those resins are compatible with wood. In fact, there are known problems with wood and polyester resins.

So while vinylesters are great for applications that have been specifically designed to work with them, don't assume that they'll work for a boat designed for epoxies , especially in the long term

Have fun,





RE: Epoxy vs. Vinylester

I hear you. There are a lot of questions, sometimes you have to just dive in and see what the water's like. It's that three year old mold that has me convince that VE is a contender. I was sent out to tag the reject mold for disposal and I kept walking by this "new" looking mold while I was looking for the "old" mold. I'm not kidding when I say it looked new, the ply was as fresh as the day it was flood coated. So I'll build one kayak in epoxy and one in VE and see what happens. 

RE: Epoxy vs. Vinylester

I was wondering do you have to use a mold

I was wondering because it is cheaper



RE: Epoxy vs. Vinylester

Thanks for the comments, Laszlo.  I will say I've seen plenty of wood boards that also used polyesther resins, so I was basing my comments on those as well as the foam core boards.  Your points are important considerations, though, and I think it would be an "experiment" to try this out on a kayak with wood and glass core the thickness we use to see how it would turn out.  I suspect it will be fine, but I wouldn't bet my boat on it.


RE: Epoxy vs. Vinylester

@salamander, no mold, just building a stitch and glue as per usual procedures and substituting epoxy vinylester for the epoxy. 

RE: Epoxy vs. Vinylester

thanks i think i will try the vinylester on my yatch tender then on bigger better boats


RE: Epoxy vs. Vinylester

Hi, just thought I'd add a few comments.  Vinylester resin is not good resin for impregnating wood.  It is best used in a mold with vacuum bagging to reduce exposure to the toxic VOC's. This is the primary way the boating industry uses it & particularly with infusion into the a lay-up already with a bag over it.  A high volume exhaust fan is a must, plus respirator during use in an open environment, then it will still smell for several days and I can tell you this is not something you want to breath.  I am a cancer survivor from these kind of fumes/VOC's - hydrocarbons - and this is not something you want to try just for some experience.

Vinlyester has nowhere near the properties of epoxy when it comes to using plywood as a core.  It is not a glue, so not adequate to put on decks or use for fillets, etc. 

A great epoxy for kayaks is MAS.  Easy to mix, forgiving a 2:1 ratio and has a variety of elongation properties.  The MAS Flag resin has higher elongagtion as is suited for fillets and gluing.  This allows the glass or carbon to carry the stress loads and not crack the resin when stressed. I have seen forum comments about exact ratios.  The best thing is don't get too much hardner in a mix; if it goes beyond the 2:1 as in 1+, this will not allow the epoxy to fully cure; a little less will not hurt.  This applies to all epoxies.  Get small, medium and large mix cups at specialty paint stores with oz and number levels on the side - makes mixing easy w/ a 2:1 resin.

For small mixes use small circles on a piece of plastic (like milk carton) and draw a circle around a penny and a 50 cent piece.  That is a 2:1 ratio.

MAS hardeners can be mixed in ratios up to 25% to change room temperature hardening rates, e.g. 25% fast/75% slow, or 25% medium will speed things up some in a cooler shop.  Nice to speed things up occasionaly.  Flag resin and their medium hardener can be sanded next day if warmed a bit after application & initial set, e.g. turn up the heat to 80 or use a shop lamp near the hull.  Works great.

Anytime you mix in wood flour, colloidal silica, graphite or a hard filler, you need a slower mix as the heat is retained and builds up in the mix very fast.  Cool the resin &/or hardner in separate cups prior to mixing and this will help from wasting resin and give you lots of working time.

If your shop has been cold and your resin turns white opaque and nearly solid, just warm it up in some water about 110 F and let it come back to room temperature.  It will come back to clear and be fine to use.  You can put it outside in a black garbage bag in warmer weather and it will do the same.


RE: Epoxy vs. Vinylester

 Sorry, I did the last message, but don't know how to get me name up in the submitted line & accidently hit some key to send. 

I have extensive training in laminating, composite cores, resins and design use of each from the top professionals in the yachting industry, mainly thru International Boatbuilders, aka IBEX, and the group from Abaris  Composite Training in Reno, NV.  I have designed & built a 30' racing yacht out of epoxy composites and several kayaks, & consult on yacht repair; I have two years of yacht design training.


RE: Epoxy vs. Vinylester

What Dirk is saying is true.  As a former builder of experimental aircraft, we tried vinylester resin on foam core wet layups.  It was a miserable failure and made a lot of people sick.  It should never be used outside of a controlled enviornment.  Quit trying to re-invent the wheel.  CLC has done all of the testing and determined that MAS is the way to go.  Use it.

RE: Epoxy vs. Vinylester

I'm always surprised by people who pooh pooh a material because they tried it once and had trouble making it do what the can said it should. I'm just saying that maybe there is a second or third or whatever option available in addition to epoxy. I've made tons, and that's no exaggeration, of epoxy, polyester and VE parts, all performed as designed and the customers were all happy. Right now I'm making some coupons of VE, Vectorply and Corecell to verify the FEA models of a new product. This is great timing because I'll have some resin to use in my kayak experiment. I've always said that no one material is superior to another when used by a skilled craftsman. I've heard that some guys even build boats out of reeds, can you imagine that. If it's OK here's the blog. Be kind it's my first one.


RE: Epoxy vs. Vinylester

   Hi Rossco,  I just came across your posts on here,   I was wondering how you went with the vinylester kayak , stitch and tape ?.. if you can remember back that far....2011 . I am 90% done with a 32 foot yacht and have become sensitized to epoxy so am trying to fing an alternative for the last few pieces.

« Previous Post     List of Posts     Next Post »

Please login or register to post a reply.