Vinylester vs Epoxy

Looking at my next project hull and considering my resin choices. I'm not 100% on what core I will use just yet, but I need to nail down the resin type so I can start repairing the hull. For reference the hull was built with polyester in the late 80's.

So I can get both VE and Epoxy at a similar price per gallon, so cost isn't the issue. I've used mostly Epoxy the last decade or so, and some polyester before that, but never done much with vinylester. So my pros and cons

Epoxy;
Pros:
- easy to mix
- waterproof
- very forgiving on time
- strongest resin (marginally?)
- no wax or coatings needed to cure
- very little fumes or smell
Cons:
- must sand between fully cured layers
- blush is possible
- allergic reactions experienced by some
- must be painted as gelcoat won't stick well

Vinylester;
Pros:
- Strong
- highly water resistant
- any paint or gelcoat will work
- no sanding in between layers of work (within reason)
Cons:
- fumes or smell
- must use a wax, coating, or modifier to cure
- must adjust MEKP for different temps

Am I missing anything? Thoughts? Preferences?

 

Vinylester is slightly is slightly lighter (less dense) and more sun resistant.

 

Good to know. Do you have a preference?

 

I've used untold gallons of epoxy over the years . I built one stripper canoe with vinylester as a demo project at a canoe rendezvous many years ago for the speed of setup and light weight. Epoxy is way more versatile for fillets, gluing etc.

 

There is normally a rather large difference in price.

First you need you ask yourself what the resin is going to be required to do, and what you expect it do, then see which one may work better for that purpose.

The epoxy won't be significantly stronger unless it's post cured, it may or may not matter though since both will be stronger than the existing laminate. So from that angle it really doesn't matter.

If it were me choosing between the two, I'd go with the VE, mainly because the polyester and VE are so similar you can treat everything on the boat the same. Fillers, primers, paints, gel coat, adhesives, etc, will all work the same on either one. No having to remember to possibly treat some areas differently than others, especially ten years later when you can't remember exactly what's where.

But I could make an argument to go with epoxy too.

It comes down to the fact that I've done so much of this type of work and rarely needed to use epoxy for a successful and very long lasting repair. But some people can't sleep at night knowing that epoxy wasn't used, even if it wasn't needed, so they should use epoxy.

 

I'm a little curious abut the American resin market,would you normally be sold laminating resin that needs added wax?Here in the UK the only time we might add wax is to a gelcoat if we don't have a prepared flowcoat on hand and we need to coat a bilge or locker with it as a finish.

 

VE resin has gotten more expensive the last few years, and I can still get decent deals on epoxy if I buy it in kit form. So the price difference per gallon is within a few dollars of each other.

My only reasons for maybe going with the VE is so gelcoat could be used, but I will most likely use a paint system of some kind. Especially on the hull bottom where it looks to have been painted before after a repair and is flaking off. So I'll have to sand it off and repaint.

 

Poly any vinylester resins are generally sold without wax. Gelcoats can be purchased with or without wax. I think what you call flow coat is just what we call gelcoat with wax.

 

This might be the best summation of about 90% of the in person conversations I have with guys fixing their boats.

 

99.999999999992% of all resin and gel coat sold in North America is without wax. There is only a very small, and almost insignificant amout that has wax in it. But it's available in any quantity if needed.

 

I recommend you try a small test batch first. My first experiment with VE produced a vomit inducing, stomach churning, nose assaulting chemical fog.
No way I could work in that.

 

I think I'll be sticking to epoxy. It gives me warm and fuzy feelings since I'll likely be using wood and plywood for the cabin of this build.

 

Now that you added the wood part of it, use epoxy.

 

In general, Epoxy is superior to Vynil Ester. VE will be as strong as EP if post cured. EP can achieve the same strength at room temp though it can be enhanced by post curing.

The problem lies in the formulation and the compatibility with the fiber that it will be matched with. Though EP belongs to the same group as VE in terms of elongation, there is too much range available. My datasheet shows it starts with high modulus epoxy, regular formulation to high elongation (toughened epoxy, such Silver tip epoxy) which have a claimed elongation of 8%. This is associated with the research done that high tenacity or toughened resin resist cracking much longer. Not true because you have to mix it with a fiber.

Fibers elongation range from 0.9% of Carbon fiber to 4.0% for Eglass. Resin ranges from 1% to 8% from Ortho, DCPD, ISO, VE, to Epoxy.

It is the matching of the maximum strength at failure (max elongation at X strain) that matters. Choose strain failure that matches each other.

And yes, Epoxy is a glue and works well (penetrate deeper) with wood. Poly resins are not though much cheaper.