Resin Types In Catamaran Construction

[mattinacan]

Hi All. I was hoping some resin experts could chime in here on my question. I am looking at purchasing a new catamaran, and it has come down to two choices for me. An Outremer and an ITA. They are both light and performative and similarly priced. The Outremer is constructed with vinylester and polyester resins, and the ITA is 100% epoxy. They both have carbon bulkheads and reinforcements, foam core and eglass. I know that epoxy is the stronger resin, but Outremer has been around for many years building great boats and has a solid reputation. I also like the Outremer styling/layout more but should I go with the epoxy boat? Is this a big difference? Am I overthinking this? My intent is world cruising/liveaboard. Thanks so much in advance!

[noelex 77]

Welcome to the forum.

The fundamental hull construction method is vital. Unfortunately, many new buyers ignore these critical details.

I think you doing the right thing placing importance on the materials used in the build.

I would to be careful with manufacturers that claim both vinyl-ester and polyester are used. Sometimes the boat is fundamentally constructed with polyester with just thin barrier layer of vinyl-ester to help retard water absorption. At other times the boat is constructed primarily from vinyl-ester with only a small amount of polyester used on non critical mouldings. The difference is significant.

Of course all epoxy is much better again.

[neilpride]

Epoxy hands down,if the resin used in the construction is important to you

[Chotu]

I don’t think there is a difference. Especially if vinylester is used below the water line. (avoid polyester below the waterline)

and this is coming from someone who built his entire boat out of epoxy.

The thing is, the boat is going to be engineered for whatever resin was used. So I wouldn’t get too hung up on it.

yes, epoxy is a stronger resin. It’s better at bonding things. It has better properties overall when it comes to stretching and breaking. however, the designer took the resin into account when they designed the boat and what the laminate schedules were.

Typically you might be able to make a lighter weight boat out of epoxy because you don’t need as much stuff to hold the boat together. However, maybe not. It’s down to the individual design of the boat.

so, it doesn’t make any difference at all.

down the road, if you have repairs to make, you will use epoxy no matter what resin the boat was made from.

So find out exactly where the Polyester and vinylester are on that Outremer. also find out how well-built the ITA is. It doesn’t have the brand recognition Outremer does. I don’t know what it is. Check if any of the previously sold boats are having issues.

[neilpride]

Originally Posted by Chotu

I don’t think there is a difference. Especially if vinylester is used below the water line. (avoid polyester below the waterline)

and this is coming from someone who built his entire boat out of epoxy.

The thing is, the boat is going to be engineered for whatever resin was used. So I wouldn’t get too hung up on it.

yes, epoxy is a stronger resin. It’s better at bonding things. It has better properties overall when it comes to stretching and breaking. however, the designer took the resin into account when they designed the boat and what the laminate schedules were.

Typically you might be able to make a lighter weight boat out of epoxy because you don’t need as much stuff to hold the boat together. However, maybe not. It’s down to the individual design of the boat.

so, it doesn’t make any difference at all.

down the road, if you have repairs to make, you will use epoxy no matter what resin the boat was made from.

There is a difference.
And repairing a polyester boat can and sometimes should be repaired in the same type of material used. Eg, Polyester.

I'll give you a vague example, many insurance companies require that the same material be used in the repair if possible. It has happened to me personally in some cases.

You can use Epoxy, but you have to make sure that the repaired area meets the same characteristics as the surrounding areas.

Repairing or reinforcing something specific in epoxy is not the same as patching a hole in the hull.

[Flobble]

It's true that Outremer build with an outer vinylester barrier layer, then I believe they use polyester resins for the foam sandwich that makes up most of the hull. Other than the underwater sections which are solid GRP, and some of the key structural bulkheads which (I think) are carbon/epoxy.

This is a design choice that they make. It's not that they can't build epoxy/carbon boats: Gunboat (part of the same company) build in the adjacent shed. And I doubt it's material cost either - the resin is a tiny part of the overall build costs.

I've also read somewhere that part of the reason is ease of repair in far flung places where getting reliable epoxy work done is challenging. Can't find the reference now though.

[Chotu]

Originally Posted by neilpride

There is a difference.
And repairing a polyester boat can and sometimes should be repaired in the same type of material used. Eg, Polyester.

I'll give you a vague example, many insurance companies require that the same material be used in the repair if possible. It has happened to me personally in some cases.

You can use Epoxy, but you have to make sure that the repaired area meets the same characteristics as the surrounding areas.

Repairing or reinforcing something specific in epoxy is not the same as patching a hole in the hull.

I disagree that there is a big difference. Unless you are talking about Polyester. But I thought we were talking about a vinylester boat with some l3ss than critical parts done with polyester.

I don’t really think we know exactly how the boat is constructed yet. The OP doesn’t know that.

but either way it doesn’t matter. Epoxy or vinylester. No worries. The designer had a resin in mind and called out the laminate schedules based on that.

[noelex 77]

I think the bottom line is polyester resin is around 1/3 the cost of epoxy.

Why boat manufacturers make these fundamental compromises and use polyester in weight sensitive cats is a mystery. Especially considering that hull construction is a small fraction of the total cost.

Epoxy has less water absorption (no osmosis) , is stronger, has less micro cracking, has more flexural strength, strong bonding strength (less delamination) etc.

A further concern is manufacturers are very coy about detailing the fundamental structure. If it is good they would be proud.

[mattinacan]

Originally Posted by Chotu

I disagree that there is a big difference. Unless you are talking about Polyester. But I thought we were talking about a vinylester boat with some l3ss than critical parts done with polyester.

I don’t really think we know exactly how the boat is constructed yet. The OP doesn’t know that.

but either way it doesn’t matter. Epoxy or vinylester. No worries. The designer had a resin in mind and called out the laminate schedules based on that.

I know a little bit more. NPG gelcoat, vinylester and polyester resins, carbon and E Glass fibers, Dyvinicell foam cores.

All structural bulkheads are carbon/vinylester. All polyester is above the waterline.

[noelex 77]

Originally Posted by mattinacan

All polyester is above the waterline.

Does this mean that polyester resin is used for the hull construction above the waterline (which is poor in my view) or that polyester is used only for non structural components above the waterline?

When a company does not spell this out, make it clear, or even boast about using more advanced resins and hull layup you can generally assume the worst.

Outremer produce some great boats, but I wish manufacturers were more transparent about the fundamental structure of their products.

Many new boat owners know in detail the accessories they have chosen, the colour scheme and cushion colours etc but have no idea what resins and hull layup is used.

[Tupaia]

https://www.bfginternational.com/wha...l-ester-resins


God discussion of the various properties is given here. Includes the advantages and disadvantages when compared to polyester and epoxy.

[Kinkircating]

So I'm currently building a 100% epoxy/carbon fiber catamaran and went through this decision making process recently, so just throwing out there that I'm admittedly biased. But yes there is a difference, it costs a whole hell of a lot more in materials, but the bigger aspect is there is a lot more labor involved to hand fairing. You get what you pay for.

Manufacturers choose polyester gel coat because it is cheap and makes the boat go together fast which equates to higher profit. Nothing wrong with that. Is it worth the extra cost, that is for you to decide.

Interesting final (2) choices you are deciding between and honestly I would not let hull material be the deciding factor. When I was deciding Outremer told me I could request a boat made fully of vinyl ester for an additional cost, but not sure if that is still the case. I think the Outremers are a fantastic boat but it boggles my mind that they are still cutting corners and using the cheapest polyester resin they can get their hands on to build their boats but charging the prices of using higher quality materials. But other than that, there is not much to not like and their aftermarket customer service is the benchmark in the industry in my opinion.

Negotiating the maze of subtle differences in what you are buying is extremely difficult, and although I briefly looked at the ITA it did not make our short list, the Outremer 55 did although we ultimately went a different direction. So many factors to consider, and yes hull material is exteremely important, but not a show stopper. If you've looked at every available option availbable to you and your heart is between these two, I'd tell you to go with Outremer as they have the track record and resale down the road will be very strong. ITA has for some reason just not resonated with buyers the same as other brands, but maybe someone could correct me if there are a lot of hulls out there or under contract.

Good luck in your decision making process!

[slowNlow]

Originally Posted by neilpride

There is a difference.
And repairing a polyester boat can and sometimes should be repaired in the same type of material used. Eg, Polyester.

I'll give you a vague example, many insurance companies require that the same material be used in the repair if possible. It has happened to me personally in some cases.

You can use Epoxy, but you have to make sure that the repaired area meets the same characteristics as the surrounding areas.

Repairing or reinforcing something specific in epoxy is not the same as patching a hole in the hull.

This is false and a fundamental, reason why I might chose ve/poly over epoxy

You get an epoxy boat, you can’t repair it with poly or ve…. You gotta go epoxy. Get a poly or ve boat (they are essentially the same from a process perspective) you can fix it with any of the three.

Ask outremere what the upcharge would be to go with a full VE build. Cost is maybe a few bucks a pound, these boats are only 40 percent resin at best…. It’s not much. Breaks my mind that they even mess about with the different resins.

[slowNlow]

Originally Posted by noelex 77

I think the bottom line is polyester resin is around 1/3 the cost of epoxy.

Why boat manufacturers make these fundamental compromises and use polyester in weight sensitive cats is a mystery. Especially considering that hull construction is a small fraction of the total cost.

Epoxy has less water absorption (no osmosis) , is stronger, has less micro cracking, has more flexural strength, strong bonding strength (less delamination) etc.

A further concern is manufacturers are very coy about detailing the fundamental structure. If it is good they would be proud.

Second paragraph … nailed it. Why lord why?

[noelex 77]

Originally Posted by slowNlow

You get an epoxy boat, you can’t repair it with poly or ve…. You gotta go epoxy. Get a poly or ve boat (they are essentially the same from a process perspective) you can fix it with any of the three.

Polyester resin does not stick well to cured polyester resin. Therefore epoxy resin is often used for the repair of polyester boats, but this creates a discontinuity in the hull structure where there is a transition between the different properties and flexibility of polyester and epoxy resins. Therefore polyester resin is sometimes used despite the drawbacks of poor adhesion.

An epoxy repair on an epoxy structure does not suffer these problems. Epoxy resin sticks well to both cured polyester and cured epoxy resin.

Epoxy resin is not hard to source.