Resin Types In Catamaran Construction

[s/v Jedi]

Originally Posted by clockwork orange

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.

I am not familiar with the resins you use, but in general epoxy resins have a higher tensile strength and a better bond with cured laminates. It surprises me that you would use an epoxy resin that is weaker than vinylester.

[Matt Johnson]

Using ATM D-638 tensile strength testing, West System 105 is 7900psi and AOC vipel - a readily available generic laminating Vinyl Ester is 12,800 psi. The TDS are all online to compare

Epoxy varies a lot more than VE in all properties; there are some incredible epoxies and then there are basic ones like West System that are less than VE in a lot of categories.

[Matt Johnson]

Here are the TDS

[Tupaia]

Originally Posted by catsketcher

I like this thread.

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.

Phil

In response to Catsketcher.

Phil, I think you are confusing strength with the ability to resist fatigue. Yes, fatigue is a major cause of failure that is often ignored. It is a long term process of cyclic stress. I wrote FE analysis software as part of my degree thesis that was subsequently used in the North Sea oil industry to design steel welds on platform legs. It is relatively easy to over build and avoid fatigue completely, with enough material there reaches a point where the cyclic resistance becomes infinite but this results in an unnecessarily heavy structure.

The alternative is to accurately analyse the stresses in particular to identify the hotspots, stress concentrations and reinforce the structure in specific areas accordingly. In the case of composite structures this means understanding and accurately orientating the fibres to spread the loads and dissipate them throughout the structure.

A PE laminate with a fully integrated fibre layout and orientation will have a superior strength to weight ratio and be better able to resist fatigue than an epoxy laminate where the fibre orientation is less than optimal. If fibre layout and orientation does not exactly match the stress modelling for the whole structure the use of a superior resin is just compensating for poor laminate engineering. Again I use 'superior' resin loosely as not all epoxies are equal. This is the essence of true composite engineering.

So I am not saying that an fully integrated PE composite structure will superior to an integrated oven cured pre-preg composite structure. What I am saying is that there is more to a composite structure than just the resin.

[s/v Jedi]

Originally Posted by Matt Johnson

Using ATM D-638 tensile strength testing, West System 105 is 7900psi and AOC vipel - a readily available generic laminating Vinyl Ester is 12,800 psi. The TDS are all online to compare

Epoxy varies a lot more than VE in all properties; there are some incredible epoxies and then there are basic ones like West System that are less than VE in a lot of categories.

Yes, vinylesters I googled are in the 8000psi range just like epoxy, a little stronger maybe.

It’s basically to get away from polyester. In stretch I understand polyester breaks at 1% stretch, while fiberglass is 6%, so the resin breaks before fiberglass was fully loaded. Epoxy and many vinylesters are in the 6% range so a good match.

Also, epoxy is easier to work with than vinylester. Easier with temperature and is shelf stable for years while vinylester only for months.

[clockwork orange]

Originally Posted by Matt Johnson

Using ATM D-638 tensile strength testing, West System 105 is 7900psi and AOC vipel - a readily available generic laminating Vinyl Ester is 12,800 psi. The TDS are all online to compare

Epoxy varies a lot more than VE in all properties; there are some incredible epoxies and then there are basic ones like West System that are less than VE in a lot of categories.

Thank you Matt,
its nice to see someone understands where i'm coming from. There are so many formulations out there of all the different chemistries that you can't just generalize. There are even substantial differences within one formulation if you look closely. For example, while you show the tensile strength of West 105 as 7900psi that is with the 205 fast hardener. If you use the 206 slow hardener it drops to 7300psi but the elongation improves.

[clockwork orange]

[QUOTE=s/v Jedi;3745316]Yes, vinylesters I googled are in the 8000psi range just like epoxy, a little stronger maybe.

It’s basically to get away from polyester. In stretch I understand polyester breaks at 1% stretch, while fiberglass is 6%, so the resin breaks before fiberglass was fully loaded. Epoxy and many vinylesters are in the 6% range so a good match.

Also, epoxy is easier to work with than vinylester. Easier with temperature and is shelf stable for years while vinylester only for months.[

General purpose epoxies may be easier to work with in a repair type environment, but VE and PE resins are easier to process in a production environment which is one of the many reasons they are preferred.

[clockwork orange]

Originally Posted by s/v Jedi

I am not familiar with the resins you use, but in general epoxy resins have a higher tensile strength and a better bond with cured laminates. It surprises me that you would use an epoxy resin that is weaker than vinylester.

I suspect that you are familiar with the West epoxy resins we use at work which are in fact substantially weaker in tensile strength than the VE we infuse with as are all of the readily available and commonly used GP epoxies used in boat shops, at least in the US. We do typically use the West for general bonding of cured laminates but that's not what this thread is about.

[Chotu]

[QUOTE=clockwork orange;3745372]

Originally Posted by s/v Jedi

Yes, vinylesters I googled are in the 8000psi range just like epoxy, a little stronger maybe.

It’s basically to get away from polyester. In stretch I understand polyester breaks at 1% stretch, while fiberglass is 6%, so the resin breaks before fiberglass was fully loaded. Epoxy and many vinylesters are in the 6% range so a good match.

Also, epoxy is easier to work with than vinylester. Easier with temperature and is shelf stable for years while vinylester only for months.[

General purpose epoxies may be easier to work with in a repair type environment, but VE and PE resins are easier to process in a production environment which is one of the many reasons they are preferred.

I was about to mention this myself.

Epoxy is significantly more difficult to work with than vinylester and polyester.

It takes a lot longer to use epoxy. Everything is so quick and easy with the esters.

It’s remarkable how much more quickly the work gets done. My hull would have taken probably 1/3 as long to build if I had used the esters and a polished female mold.

I am scared to admit this but it took 2 guys an entire YEAR to fair my boat. Full time.


As a sidenote, it is interesting how all of the properties are so different on various products. I used a pretty hard epoxy to infuse the crossbeams, hull shells and dagger boards and rudders.

Then I purposefully used a softer epoxy to put them together with each other. So my fillet/cove joints are done by hand using a softer epoxy with more give to withstand forces in these areas where large panels intersect. Yet, the large areas are ridiculously stiff.

[I14]

Originally Posted by slowNlow

nothing bonds well to epoxy but more epoxy or engineered paint systems. Regardless of how you prep it.

more stuff to confuse;

There are versions of VE that have an epoxy component https://polymerdatabase.com/polymer%...er%20type.html

more stuff to think about... brominated epoxy vinyl ester resins as they yield a class 1 flame spread rating (resist burning). required by certain building code. Dont know if they make a version of that product (Dow 510) that can be infused etc but.. having a boat that didnt burn or would not burn well seems like it woiuld be a hell of a selling point.

Apologies I have not read to the end of the thread, so this may be a repeat of someone else's post. In my polymer manufacturing days I have made both 'base' epoxy (epichlorhydrin/bisphenol A) and vinyl ester. The vinyl ester was made using a lowish molecular weight epoxy (Epikote 834) with methacrylic acid tacked on to give a double bond for the styrene to react with. Tricky to make as the methacrylic acid wanted to react with itself, not the epoxy, resulting in a solid mass in the reactor! So you can see a VE is primarily an epoxy with polyester type handling and cure. There are fish hooks everywhere with repair of differing resin types of laminates so often a professional job. There are in-mould gelcoats available now that will adhere to an epoxy I believe but I've been retired for 10 yrs so out of touch

[Redreuben]

Originally Posted by noelex 77

I

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.

No mystery at all, the modern buyer wants European quality at a Chinese price.
You get what you pay for.
I agree with the poster who suggested getting a quote on 100% vinylester.

[catsketcher]

Thanks everyone for the contributions, I have learnt a lot.

I was told of a great thread on sailing anarchy where Julian Bethwaite (the designer of the 49er and 29er amongst other boats) talks in a very detailed manner about the design and build process of his new 89er. It looks amazing.
In it he says.

the late great Dave Ovington always thickened his initial coat of epoxy with 10% of Aerocell, because it stuck to the Polyester gelcoat better. If you go to the experts they will tell you that you can never get Epoxy to stick to cured Polyester, I think 3,000 49ers later, those experts look a little stupid (and about 100 18teens)

He and I, and later Chris Turner, who brought Ovigy’s, have done a lot of tweaks, and played around a lot with different formulations, so absolutely, don’t trust your supplier because he is only reading the crap he is given and probably never got his hands dirty.

So all of the 49 ers out there are gelcoat with epoxy laminates.

I live and learn

Cheers

Phil

[clockwork orange]

Originally Posted by catsketcher

Thanks everyone for the contributions, I have learnt a lot.

I was told of a great thread on sailing anarchy where Julian Bethwaite (the designer of the 49er and 29er amongst other boats) talks in a very detailed manner about the design and build process of his new 89er. It looks amazing.
In it he says.

the late great Dave Ovington always thickened his initial coat of epoxy with 10% of Aerocell, because it stuck to the Polyester gelcoat better. If you go to the experts they will tell you that you can never get Epoxy to stick to cured Polyester, I think 3,000 49ers later, those experts look a little stupid (and about 100 18teens)

He and I, and later Chris Turner, who brought Ovigy’s, have done a lot of tweaks, and played around a lot with different formulations, so absolutely, don’t trust your supplier because he is only reading the crap he is given and probably never got his hands dirty.

So all of the 49 ers out there are gelcoat with epoxy laminates.

I live and learn

Cheers

Phil

Very interesting Phil,
I have never tried laminating over polyester gelcoat with epoxy or had any desire to do so. As you know gelcoat is insanely heavy due to the required mil thickness so has no place in serious lightweight construction, but compromises need to be made when it comes to production building in production female tooling and i don't think there is a viable option so far. The Gougeon Brothers of West Epoxy fame used polyester gelcoat when they attempted to build their wonderful little G32 catamaran with their then new Proset epoxy and they had a huge failure rate and only built about a dozen boats. They were trying to build a high quality product to a reasonable price so probably felt the need to use gelcoat rather than an in mold primer and then paint after removing from the mold although the Stilletto cats had been done that way i think and had a good production run.

[OneBoatman]

Construction should be absolutely high on the list. Regardless, if you are careful mariner, either boat should easily survive for 30 yrs. What matters most? Is it weight? Is it cost? Is it resale value? Sure Epoxy is better and perhaps stronger depending on how it is built. Are these pre-preg laminates or hand lay up? Ask the builders questions. What about thickness'. You can always put 3-4 coats of epoxy barrier coat on the one with some unstated mix of vinyl and polyester resins. If you are spending most of your time on the boat the lay out of the rest of the boat might outweigh near equivalent construction.

[neilpride]

Originally Posted by catsketcher

Thanks everyone for the contributions, I have learnt a lot.

I was told of a great thread on sailing anarchy where Julian Bethwaite (the designer of the 49er and 29er amongst other boats) talks in a very detailed manner about the design and build process of his new 89er. It looks amazing.
In it he says.

the late great Dave Ovington always thickened his initial coat of epoxy with 10% of Aerocell, because it stuck to the Polyester gelcoat better. If you go to the experts they will tell you that you can never get Epoxy to stick to cured Polyester, I think 3,000 49ers later, those experts look a little stupid (and about 100 18teens)

He and I, and later Chris Turner, who brought Ovigy’s, have done a lot of tweaks, and played around a lot with different formulations, so absolutely, don’t trust your supplier because he is only reading the crap he is given and probably never got his hands dirty.

So all of the 49 ers out there are gelcoat with epoxy laminates.

I live and learn

Cheers

Phil

Julian is a clever guy, for sure, but if you keep reading the thread, this pops up.

Prior to glassing the plug (with polyester to get a vacuum seal) I took the opportunity to pre-fit the foam, by screwing into the plug, yes brutal, but the polyester/CSM/cloth/gelcoat will cover all ills.

I'm not sure what this means when the whole thread talks about epoxy and carbon.
Or this layup schedule its just to make the mold?
Maybe i'm wrong.