Resin Types In Catamaran Construction

[catsketcher]

One nice thing about polyester is that you can get a big, thick, (weak and heavy) gelcoat layer over the whole boat.

Polishing gelcoat is a lot easier than painting and a nice gelcoat can last longer than 20 years before painting is required. I think that this a large incentive for production builders to use polyester.

That said, my boats are all epoxy, because I built them myself. I have to fair and paint them. I never wish they were heavier.

cheers

Phil

[mattinacan]

Originally Posted by catsketcher

One nice thing about polyester is that you can get a big, thick, (weak and heavy) gelcoat layer over the whole boat.

Polishing gelcoat is a lot easier than painting and a nice gelcoat can last longer than 20 years before painting is required. I think that this a large incentive for production builders to use polyester.

That said, my boats are all epoxy, because I built them myself. I have to fair and paint them. I never wish they were heavier.

cheers

Phil

Can you do the gelcoat layer if it was 100% vinylester?

[s/v Jedi]

A gelcoat layer thicker than specified by the gelcoat manufacturer will quickly lead to cracks, especially when done over vinylester. I know… I have all of that.

[clockwork orange]

Rather than asking a bunch of strangers online about the merits different materials i would suggest the OP should ask the builders exactly what resins are used and where and then download the technical data sheets of each and actually compare. It is really quite ridiculous when people make the blanket statement that " epoxy is strongest" as this is not necessarily so. There are hundreds of formulations of Epoxy, VE and PE. I would be particularly interested in what the actual resin used by the 100% epoxy cat is. It would not surprise me at all if it were Epoxy vinylester and there would be nothing wrong with that. A lot of folk think of epoxy as 100% solids resins such as West systems , Systems Three, etc but most vinylesters are also epoxy based and can exhibit even better physical properties than the epoxies that have been heavily advertised for the last 50 years. You need to actually look at the data sheets.

[catsketcher]

I don't think many boatbuilders would call epoxy modified vinylesters - epoxies. Any resin that can be catalysed by MEK or a tiny amount of hardener is not a two part epoxy (the usual amine type).
Two part epoxies are good for a whole range of things that sometimes are hard to spot in a data sheet. For one, when mixed properly you can post cure to get full cure. With catalysed resins you usually still have flashing off of styrene components (which is why poly boats smell for years).
Micro cracking is an issue with resins other than epoxy. Strangely enough, being flexible is a really good thing for a resin to be. It allows the resin to impart loads to the re-inforcement rather than take the load itself for large distances. Again polys are usually pretty stiff and so can take load before the re-inforcement, causing tiny microcracks on light laminates (that is why Lasers go soft in the deck and hull).
Another hard to gauge property is secondary bonding. Again, two part epoxies are tops here. So you can install composite chainplates, bulkheads, floors, and basically anything onto the hull with more guaranteee that it will not delaminate, or you have to have lower stresss on a less reliable resin system.
As a builder of four epoxy multis, I really like amine based two part epoxies ease of use for higher tech boatbuilding. It is really easy to produce innovative and intergral components, such as beams, prodders, jib tracks, pulley systems, engine mounts, outboard nacelle systems, special fittings, even my steering wheel is epoxy based. Your poly boat will probably have fewer integral fittings, and fewer stainless fittings is great news in a modern boat. No leaks, far lower stresses and much lower loads with much lower stress concentrations. And you save huge dollars by making them yourself instead of going to some stainless guy. I have no bolts or leaks in my cabin even with the jib sheets and jib tracks being placed on the top - all intergral uni and epoxy work - cheaper for the custom builder but maybe not the production guys.

As for differences in epoxies - mostly it is a viscosity thing. You will want a lower viscosity resin for thicker fabrics - the thickest I have ever laminated was 1134gm triax. We did that with ATL 246 all okay. It was less viscous than 105. Yet 105 and its clones are still a great resin. Unless you are building a race boat, a generic based two part amine epoxy will be plenty flexible, strong enough, reliable and cured for a cruising laminate schedule.

cheers

Phil

[SailingHarmonie]

This is such a strange thread.

There are good, well built, long lasting boats made of epoxy, ve, and PE. There are far more of them made of PE than epoxy. The idea you can not build a good boat unless you use epoxy or 100% ve is silly on the face of it.

A boat is a holistic machine. Its design should take into account the materials it is being built of, and build it strong enough, and light enough to do what it is supposed to do. Boats from two different designers and build shops are never so close that the hull material should be the ONLY selection criteria left on the table.

There are designs that can really only be built out of epoxy and carbon. Replacing those with glass and PE would make a bad boat. Taking a bad design out of PE an glass and building it of carbon and epoxy does not turn it into a good boat.

[clockwork orange]

All good points Phil. However my point is that most people when they think of epoxy, they are thinking, as you are, of the 2 part epoxies such as West systems 105/205/206. Why, because they have been heavily advertised for 50 years in all the retail boating magazines. Most do not realize there are epoxy vinylesters which have better physical properties, sometimes substantially so, than the epoxies they are familiar with so should not be considered to be second tier. As i said, read the data sheets. If i were looking to buy a $ million boat i would have no problems asking for the actual resin part numbers so i could download the data sheets rather than ask a bunch of strangers for opinions. I have recently compared the technical data sheets of a VE infusion resin i was using with West 105/205 as a control since we use that on a daily basis. Both resins were tested using the same ASTM tests and the VE was superior in every way that was of interest to me. 7900psi tensile for the 105, 11300psi for the VE stands out. Better elongation too. I have not used polyester for many years so i have not looked at them. I did partake in a large infusion at a Derek Kelsall workshop about a decade ago using polyester infusion resin though. Derek had been designing and building custom foam cored large racing multihulls and monohulls longer than anyone on here (or the planet for that matter) and remained committed to polyester throughout his career. I prefer VE for infusion and epoxy for secondary bonding. I have infused with Proset infusion epoxy also but the VE has better physicals but more importantly much lower viscosity which is important for infusion.

[chris95040]

I can't even order socks from amazon without a human in the loop screwing the order up, so it makes me wonder: The sequence of events for doing lamination and structural bonding with epoxy must pay attention to cure time, blushing, etc. With laminating polyester resin you have a lot more leeway with a crosslinkable surface remaining long after initial cure.

While under the watchful eye of competent folks epoxy is the winner, it seems it also provides more opportunity to get it seriously wrong.

No actually experience working with any boatbuilders, mind you, just basing this on my own countless hours working with these materials as an amateur. And the socks thing.

[s/v Jedi]

A more important question is on which layup method has been used. From spoolgun to a vacuum infused resin layup? These differences are drastic, much more so than changing from vinylester to epoxy.

The problem with polyester is osmosis, but I think it can be avoided by doing a better layup method that eliminates voids. Did a vacuum bagged polyester layup ever got osmosis? I don’t know.

Jedi is built using the SCRIMP method.

Here is a good overview of materials and methods: https://wavetrain.net/2010/12/15/fib...ng-techniques/

[Tupaia]

I agree with sailingharmonie this is such a strange thread.

What we should be discussing is appropriate technology. There is no resin that is appropriate for every occasion. Be that, strength, finish, ease of use or cost.

For example the notion that only epoxy can be used with carbon. Carbon in conjunction with PE has been around since the early nineties. Many of them are still around today. Early Kelsall boats using PE and foam are still out there sailing 40 years on.

Take a carbon reinforced VE monocoque hull built in a mould with gelcoat finish and it will be as strong, be more durable having a lasting finish and will be quicker to build when compared to the same using epoxy. Given the long term osmosis concerns using PE less so, but not if done well.

Once you have you super strong monocoque there is little if any technical reason to use VE or epoxy for internals like furniture, in fact with clever moulds gelcoat finishes in heads and shower pods is simple and easy and cheap to achieve with PE. Attaching them to the hull and any secondary bonding is most certainly better with epoxy.

So insisting that a boat be built exclusively from epoxy, VE or PE is just nonsense. Nor is one better than the other under all circumstances.

I had to replace my boom and considered using carbon for the replacement, lighter, stronger, sexier. WRONG, aluminium was lighter and provided more than the required strength, it was less sexy and quarter of the price, it was the most appropriate material for the job.

[mattinacan]

Originally Posted by SailingHarmonie

This is such a strange thread.

There are good, well built, long lasting boats made of epoxy, ve, and PE. There are far more of them made of PE than epoxy. The idea you can not build a good boat unless you use epoxy or 100% ve is silly on the face of it.

A boat is a holistic machine. Its design should take into account the materials it is being built of, and build it strong enough, and light enough to do what it is supposed to do. Boats from two different designers and build shops are never so close that the hull material should be the ONLY selection criteria left on the table.

There are designs that can really only be built out of epoxy and carbon. Replacing those with glass and PE would make a bad boat. Taking a bad design out of PE an glass and building it of carbon and epoxy does not turn it into a good boat.

I don't think it's strange at all, i've learned quite a bit and appreciated all the feedback. Literally no one on this thread has said the only good boats are 100% epoxy so not sure why you are saying that.

[mattinacan]

Originally Posted by clockwork orange

All good points Phil. However my point is that most people when they think of epoxy, they are thinking, as you are, of the 2 part epoxies such as West systems 105/205/206. Why, because they have been heavily advertised for 50 years in all the retail boating magazines. Most do not realize there are epoxy vinylesters which have better physical properties, sometimes substantially so, than the epoxies they are familiar with so should not be considered to be second tier. As i said, read the data sheets. If i were looking to buy a $ million boat i would have no problems asking for the actual resin part numbers so i could download the data sheets rather than ask a bunch of strangers for opinions. I have recently compared the technical data sheets of a VE infusion resin i was using with West 105/205 as a control since we use that on a daily basis. Both resins were tested using the same ASTM tests and the VE was superior in every way that was of interest to me. 7900psi tensile for the 105, 11300psi for the VE stands out. Better elongation too. I have not used polyester for many years so i have not looked at them. I did partake in a large infusion at a Derek Kelsall workshop about a decade ago using polyester infusion resin though. Derek had been designing and building custom foam cored large racing multihulls and monohulls longer than anyone on here (or the planet for that matter) and remained committed to polyester throughout his career. I prefer VE for infusion and epoxy for secondary bonding. I have infused with Proset infusion epoxy also but the VE has better physicals but more importantly much lower viscosity which is important for infusion.

Why can't I both have discussions with the engineers (which is currently ongoing) and also ask the opinion of experienced strangers? Is there some kind of problem with that?

[Kinkircating]

Originally Posted by mattinacan

Why can't I both have discussions with the engineers (which is currently ongoing) and also ask the opinion of experienced strangers? Is there some kind of problem with that?

Because this is the internet and keyboard warriors like to pontificate! Myself included

[catsketcher]

I like this thread.

If a buyer is happier with a heavier boat, that will stay shiny with its gelcoat finish and has been designed for the weight of the structure, then PE is a great choice. You will get more boat for a certain cost.

If you want to have a higher spec boat - like the Catana the OP states - then vinylester is a great choice. It can have gelcoat as well.

If you want to go lighter with higher spec materials then you will seriously consider epoxy. You will have to forgo gelcoat but modern paints can last up to 15 years and still look nice. You will be able to install many modern looking features like integrated secondary bonding forebeams and composite chainplates for lots of items.

There is no better resin, just appropriate resin choices for each boat setup.

Respectfully, I would disagree with Tupai - but I am not a composite engineer. I have designed two cats and had to read a fair bit of stuff to engineer composite beams, folding beams, chainplates and composite hinges, but I don't have a degree - or any higher learning.

BUT - I don't recommend using a low spec resin with a high end re-inforcement. The whole idea of a composite is to make a matrix. A carbon matrix is highly loaded and as such it makes good sense to use a flexible resin like epoxy, rather than Poly. Poly is subject to micro cracking at rather low loads and it is not flexible. This means the resin in a high stress carbon laminate could start cracking and not distributing stress around the matrix.

Kelsall did some interesting stuff with carbon. He used pultruded carbon rods on the top of beams. This is pretty dodgy in many ways as it is hard to see how the loads get into and out of the beams in a distributed manner. He was a great designer, but even the best do things we don't do anymore.

cheers

Phil

[clockwork orange]

Originally Posted by mattinacan

Why can't I both have discussions with the engineers (which is currently ongoing) and also ask the opinion of experienced strangers? Is there some kind of problem with that?

Sorry if i offended you, that was not the intent. I was just trying to point out that most people assume that somehow epoxy is an upgrade but in fact it depends on the actual formulations that are being compared. That so many people just assume that epoxies are automatically the best choice for everything is imho a product of the fact that they have been marketed to in the retail boating magazines for the last half a century while the manufacturers of PE and VE resins only advertise in trade publications. It is for this reason that i suggested that, since you seem to believe that the choice of the all epoxy cat may be a better choice, that you obtain the actual the technical data sheets for the actual resins used so you can make an informed decision. Nobody on this forum can do this for you. The usual recommendations that are found on forums, such as the blanket "epoxies are stronger, or have better elongation" nonsense is not very helpful and not necessarily so, it depends on the formulation. I recently did a good sized infusion with Corezyn Corve 8101 resin and when comparing it to a Pro set epoxy that i have also infused with ( inf 114/212) found that it showed better physicals in every way that mattered to me such as tensile strength, elongation and particularly viscosity and cure time. I have never done any comparisons with polyesters because i don't use them but they would be quite appropriate for for many applications to save money.