Education please: Resin differences and uses

[Guest]

If you are working on an epoxy built hull, you don't want to use Vinyl ester on it.

Stick with epoxy, even if it is built with Vinyl ester ! No shipping hassles., and will probably work better.

Jim, I hope you don’t mind my taking this to a separate thread, but I do know what I don’t know, and one of those missing pieces is the difference in use and application between resins. I know I’ll never use polyester resin again, and I’ve never used Vinylester, only epoxy resin.

I have heard the consensus opinion that Vinylester (or, ugh, polyester) resin over epoxy is a bad idea.
I have heard, more consensus opinion, that poly resin sucks at adhering to wood. Is that also true of Vinylester resin over wood?
I have heard that epoxy resin over Vinylester is OK, and of course that either like-material over same should work (so it is important to know what resin was originally used on a canoe).
And that Vinylester resin is less expensive than epoxy resin, and that epoxy is “generally” superior.

“Heard”, but I don’t know what I don’t know and need some education from the builder folk.

Are there applications where, expense aside, Vinylester is a better choice than epoxy resin? Can Vinylester be used to adhere things together?

Can Vinylester be used to make thickened fillets? How well does Vinylester store over time once opened and partly used? I know the MEKP for evaporates once opened.

Is there a difference in wetting out cloth, cure time or top coating prep? Etc, etc.

I’m not really thinking of adding Vinylester to the shop supply, especially if it is as stinky odorous as polyester resin, but I’d like to know the builder skinny on resins.

 

[pblanc]

My knowledge is limited but I will share a few things I know, or think I know.

I would never take the chance of using a polyester resin, including polyester gel coats, over epoxy even if the epoxy is well-cured. Apparently the amine excess that occurs with epoxies can interfere or prevent completely the cure of a polyester resin. This is not the same as the amine blush that can be washed off of recently cured epoxy. The amines even within the cured epoxy can leech into the fresh polyester resin. I have known some people who applied polyester resins over cured epoxy and gotten away with it. But I have also heard of multiple cases in which polyester resin did not cure satisfactorily, leaving a real mess that had to be scraped and sanded off.

I have been told a couple of years ago by a well-known boat builder (I believe it was Dave Curtis) that vinylester resins have advanced in strength and quality to the point that they are as good or perhaps sometimes better, than epoxy resins so far as strength is concerned. It seems that the great majority of builders now use vinylester as it is cheaper and they are using resin in bulk.

I have done repairs on many canoes built with vinylester resins using epoxy. These came from a variety of builders and a variety of vintages so I presume the vinylester resins were varied. I have never had any failures to cure or bond to vinylester resins with epoxy so long as the surface prep was adequate. I have never used anything but epoxy resins for boat repair work and see no reason to change. I don't care to have to mess around with MEKP if I don't have to, and in the quantities of resin I am using, the cost differential between epoxy and vinylester is not significant. The ease with which batches of small to moderate size can be mixed up with epoxy trumps the difference in cost IMO.

I have used a variety of epoxy resins to bond fabric to wood and never had any issues. I have not tried vinylester resins. I have heard many stories about cloth delaminating from wood, sometimes a long time after bonding, when polyester resins were used.

 

[Alan Gage]

I've used vinylester resin a bit. The "standard" vinylester resin is MUCH thinner than the standard epoxy resin. As a result it wets out cloth much more readily and it's what I used when I was vacuum infusing seats. It would wet out the part much quicker. It's also nice being able to adjust the curing time by adding more or less MEKP rather than keeping separate hardeners on hand.

The standard vinylester resin will not completely cure on the surface when exposed to air. This means you can lay down multiple layers with no need to sand or otherwise prep the surface and still get a chemical bond. If you're infusing or vacuum bagging it should cure fine because it's not exposed to the air. Same should be true if you cover it with something like saran wrap. The alternative is to buy 'waxed' resin which, like the name implies, contains a wax that forms on the surface and allows the resin to completely cure. This wax would need to be cleaned off before any successive layers are put down or repairs done.

I had a disastrous vinylester over epoxy failure when I knowingly went against conventional wisdom thinking it would be fine over fully cured and prepped epoxy. And maybe it would be and maybe mine wasn't fully cured or cleaned. Either way it was a mess and I'm not going down that road again.

That debacle also had the cloth wrapped around cedar as well as in contact with the epoxied hull. The next day, after I realized the vinylester was a sticky un-curing mess where it came in contact with the epoxy, I was surprised that I could cleanly peel the cloth off the cedar gunwales with relatively little effort (it took some strong pulling but nothing herculean) despite the fact that to the touch it felt cured and hard. I don't know if that's because all the vinylester was compromised as it mixed with the stuff in contact with the epoxy or if it reflects on its ability to bond to wood. Again, either way I'm not going to do another experiment to find out.

I think there can be a place in the canoe tinkerer's shop for vinylester but there's not much you can do with vinylester that you can't do with epoxy. And there's more you can do with epoxy that you can't do with vinylester. Overall I find epoxy more pleasant to work with and only use the vinylester when I need something really thin.

As far as the strength of vinylester when it comes to composite canoe construction I don't see any reason to avoid canoes made with it. People can tout that epoxy is stronger (and maybe it is, I don't know) but the fact seems to remain that canoes made with vinylester (nearly all of them) aren't failing.

Alan

 

[BWCA66]

I've used vinyl ester more than anything else and it does have some advantages but also drawbacks. One is it is much more UV resistant than epoxy and since it uses a catalyst you can adjust the pot time to a pretty wide range. The vinyl ester I use does completely cure in the air without wax in it so multiple layers work just fine without doing anything between layers. I've never used it over or under epoxy or polyester resin so I can't comment on that. I know everyone says vinyl ester doesn't adhere to wood well and that is why it isn't use for strip canoes but the ribs in a Merrimack canoe are put in with vinyl ester and coated after the fact with it too and then no other coating is used and they last for years without the need for varnish.

On the other hand it is the most toxic of the resins and smells the worst.

All that said I am very tempted to try it on a cedar strip canoe.

 

[Guest]

It seems that the great majority of builders now use vinylester as it is cheaper and they are using resin in bulk.

People can tout that epoxy is stronger (and maybe it is, I don't know) but the fact seems to remain that canoes made with vinylester (nearly all of them) aren't failing.

That begs the question, which canoe manufacturers use epoxy resin?

Souris River does, and espouses the benefits with some braggadocio:

https://sourisriverdealer.wordpress...s-souris-river-vs-brand-x-epoxy-does-it-best/

I wonder what other manufacturers use epoxy in their composite lay ups. I recall there is (was) at least one other, if not more. Bluewater maybe?

 

[BWCA66]

There are some eco friendly plant based resins starting to be used. Name escapes me but there is a Canadian canoe maker who only uses ecopoxy.

 

[stripperguy]

I've built a few strippers in the late 70's and early 80's using both polyester and vinylester resins. None of those boats have survived to the present day. My epoxy boats of similar vintage are still around. The polyester was on white pine, redwood, western red cedar, none of them had an adequate resin to wood bond.
The resin to wood bond was tenuous at best, typically just anxious to delaminate. The styrene monomers that escape the resin as it cures will permeate everything...I had a left over burger in a sealed tupperware container, in the fridge, in the living space above my work space and it tasted like polyester resin the nest day. And without a respirator you'll catch quite a buzz, and not a good one either. The catalyst MEKP can cause severe, irreversible vision damage.
It does cost roughly half the cost of most epoxy resins, and generally has lower viscosity, making it attractive for production boat builders.

IIRC, per my Whitewater Boat Builders bible, polyester resin is stronger than most epoxy resins, but more brittle. Epoxy is more flexible, but not as strong. Layups with an abundance of glass and nylon benefited from epoxy resin by allowing more flexibility before laminate failure. Lay ups with more glass and Kevlar and/or carbon would be better off with polyester.

I can't see any reason to keep polyester or vinylester resins in my shop...There are low viscosity epoxy resins resins available if I need them for laminating a thick lay up.

 

[Guest]

There are some eco friendly plant based resins starting to be used. Name escapes me but there is a Canadian canoe maker who only uses ecopoxy.

Hellman Canoe has been using Ecopoxy since 2010, and prior to that I believe they used standard epoxy resins.

http://hellmancanoes.com/canoe-contructions/

Smaller wood boat manufacturers as well, Oyster Bay Boats. Interesting stuff:

https://smallboatsmonthly.com/article/ecopoxy/

 

[BWCA66]

Hellman Canoe has been using Ecopoxy since 2010, and prior to that I believe they used standard epoxy resins.

http://hellmancanoes.com/canoe-contructions/

Smaller wood boat manufacturers as well, Oyster Bay Boats. Interesting stuff:

https://smallboatsmonthly.com/article/ecopoxy/

Mike,

I've talked to Helman and they like the resin and are still working with the manufacturer on the gel coat. Might be worth trying, no vocs.

Greg

 

[Guest]

Add Savage River to the list of builders using (regular) epoxy resin.

 

[Foxyotter]

I am no professional and I have only used epoxy but I can google and read so I will share what I have found. To give a few numbers to help quantify some of the differences with polyester, vinylester and epoxy resins taken from Dave Gerr The Elements of Boat Strength.

Ployester- 2% elongation and 9400 psi/65mPa tensile
Isopolyester-2.5% elongation 9400 psi/65 mPa tensile
Vinylester- 5% elongation 11800 psi/82 mPa tensile
Epoxy- 5%+ elongation 12500 psi/86mPa tensile

Polyesters- don't have enough elongation to allow modern fabrics to be effective. The resin will crack before the fabric even begins to be stressed. It is cheap and can be used with mat to add thickness.

Vinylester- Is thinner and from my understanding much better to use for vacuum bagging. Vinylester can also be used with polyester shop equipment and will also bind with mat and polyester resin.

Epoxy- A little stronger and a little more flexible and great for gap filling. Not so good with poly resins.

In most of our shops epoxy is the way to go. If you are professional producing many crafts and vacuum bagging on molds etc go vinylester. If you are fixing the old school poly boats with some woven roving and chopped strand use either polyester or vinylester resin.

My understanding is that the glass to resin ratio would be more important for ultimate strength of a canoe more then vinyl ester or epoxy. For any practical purposes two boats with the same layup schedule and same resin to glass ration vinylester vs epoxy would make zero noticeable difference in performance and strength.

I have wondered if an innegra/ kevlar/ dynel layup is so flexible that only epoxy could be utilized. I have noticed a canoe manufacture that puts gel coat on top of some similarly flexible hulls and I assume that gel coat which is in the polyester class will not last. Hence why many manufactures are using resin and not gel coat.

Cheers