Visit our Popular Forums

OldYachtie · 23-11-2007, 20:45

Here's a quote from - type_Document_Title_here - Vinylester strength, 78 N/mm2, elongation to breaking 4.9% Epoxy strength, 76 N/mm2, elongation to breaking 5.7% Iso-Polyester 5% (Which I just don't believe-TD) E-glass elongation to breaking, 4.8% - So the question arises, can epoxy's 16% greater strength than vinylester be useful in an e-glass laminate? Based on these figures, it seems to me that epoxy's extra strength only becomes useful if you use carbon fiber, kevlar, etc. - These claimed properties are probably better than usually attained in boat building, however. The figures I find from resin manufacturers show much lower properties than Baltic Yacht's. I am using a vinlyester resin, Reichhold 9300, ( http://www.reichhold.com/docs/bullet...0FR%209300.pdf ), that isn't that strong, having a maximum elongation of 4.%. It does not require heat treatment after lamination. You can get stronger vinylester resins, if you are willing to heat your parts 150 or more degrees farenheit for 2 hours post lamination. - West claims an elongation of between 3.4% and 4.5%, depending on the hardener used. The resin I am using is not meant to be heat treated. Proset epoxy isn't even as strong as Dion 9300 vinylester, unless you heat treat it with 180 degrees for 8 hours post lamination. ( Proset Laminating Epoxies ) - Reichhold claims a maximum elongation of 1.7% to 3.3% depending on the product, for their polyester boat-building resins. - My reinforcement is from Vectorply, which unfortunately does not give is any figures for percent of elongation before breaking. I do notice, however, that they believe that their E-QX 3600 quadra-axial fabric will be 31% stronger if infused with vinylester versus hand laid up with polyester resin. This may be in part because they expect a higher glass content with the vinylester infusion, 68% glass versus 55%. However, when I consulted with an engineer, he felt that this resin used with this fabric hand laid up would be about the same strength as when infused, because the laminate would be a bit thicker (and of course, also a bit heavier.) - It seems, then, that a good epoxy resin is at most 12.5% stronger than a good vinylester resin, even though it costs almost twice as much, and that whether this makes a practical difference in boat building may be questionable, if the reinforcement used is no "stretchier" than vinylester resin. Both resins are very corrosion resistant, and both are supposed to be impervious to blistering, though I have not found any quantification of this. - ( http://www.marinecomposites.com/PDF_..._materials.pdf also gives an elongation to breaking of 4.8% for e-glass, which give properties of other reinforcements and resins, as well.) - Tim Dunn, near Seattle

Evan · 23-11-2007, 22:21

Vinylester is a good "compromise" resin if you are seeking better material properties than standard iso or ortho resins. But saying "at most 12.5% stronger" is misleading. There are lots of different epoxies and vinylesters. 4% elongation is a lot more typical of most vinylesters. I've never seen a 5% one in the wild.

I'm a naval architect and mechanical engineer. When we added a big bridgedeck cabin to our catamaran, I only used epoxy. It's more than 12% stronger in most cases.

Epoxy is lots more costly, though the gap is narrowing these days. Vinylester as I said is a good compromise with added strength and not that much additional cost as epoxy.

Whimsical · 24-11-2007, 05:26

I read a piece, can't remember where though, discussing the characteristics of epoxy/poly resins. This suggested that the fibres are what carry the loads rather than the resin. The problem with poly is that its elongation is less than the fibre and hence fails. Epoxy on the other hand has an elongation slightly higher than the fibre allowing the fibre to load up before failure of the resin.

Mike

fastcat435 · 24-11-2007, 09:24

You are right , it is the challenge to match the elongation of the resin and the fibers used.
Epoxy has many different quality,s just like polyester and vinylester
If you match the fibers elongation with the resins elongation you are able to built the strongest and lightest structure, Epoxy has an elongation depending on quality up to 9 % while polyester stops with 3 % and Vinylester around 4 %.
There are however other advantages by using epoxy over the other resins
No water intake
No styrene smell
Slightly lower weight
With infusing epoxy a vacuum of 98 % can be used while the other resins start to boil with 50 to 60 % vacuum and therefore the resin glass ratio can be made more favorable with epoxy.
We care able to get a resin to fiber ratio of 40 to 60 % and that makes a stronger structure. Fiber is what makes the structure strong so if the fiber to resin ratio is high on the fiber side you get a strong boat.
This is the reason why all racers are resin infused or made with prepreg fiber
to create a high fiber content and low weight

OldYachtie · 24-11-2007, 10:59

12.5% is misleading? I don't think so. I am giving you figures from the actual manufacturers of well respected resin manufacturers and posting the sources so you can double check them. If you are a naval architect and engineer, why don't you bring a little rigor to the discussion? - Also, I think anyone posting about this should mention whether or not they are using heat post-treatment. The majority of epoxy and vinylester resins strengths posted online assume heat treatment. I am using one of the few vinylester resins whose figures don't assume heat treatment.

Quote:

Originally Posted by Evan

Vinylester is a good "compromise" resin if you are seeking better material properties than standard iso or ortho resins. But saying "at most 12.5% stronger" is misleading. There are lots of different epoxies and vinylesters. 4% elongation is a lot more typical of most vinylesters. I've never seen a 5% one in the wild.

I'm a naval architect and mechanical engineer. When we added a big bridgedeck cabin to our catamaran, I only used epoxy. It's more than 12% stronger in most cases.

Epoxy is lots more costly, though the gap is narrowing these days. Vinylester as I said is a good compromise with added strength and not that much additional cost as epoxy.

OldYachtie · 24-11-2007, 11:42

Hi, Fastcat Neither Gougeon nor West claim an elongation of anywhere near 9%. Please cite a reference for this, as I have never heard it claimed that there are better epoxies than theirs. Your figures are way too low for glass content. Even in the days of hand lay-ups, we got 50% with careful workmanship and a high woven roving content. You imply that you can't get high glass contents with resin infusion of polyester or vinylester, but that isn't true. You can get a 67% glass content with vinylester, see vectorply.com. Vinylester doesn't soak up much water, either-I have seen 2.5% claimed, which is about 1/2 of what polyester laminates will soak up. I have read claims of one to two percent water take up by epoxy laminates. It is true that vinylester is a bit heavier than epoxy, resulting in a laminate maybe 5% heavier. And it is true that some people don't like the smell of styrene. In my experience, the styrene smell doesn't last long, however. Maybe six months or a year, if the boat is kept closed up. - Also, I think people extolling epoxy should mention whether or not they are post curing the epoxy with heat. Epoxy is nothing special without heat treatment post lamination. Epoxy has an elongation depending on quality up to 9 % while polyester stops with 3 % and Vinylester around 4 %.
There are however other advantages by using epoxy over the other resins
No water intake
No styrene smell
Slightly lower weight
With infusing epoxy a vacuum of 98 % can be used while the other resins start to boil with 50 to 60 % vacuum and therefore the resin glass ratio can be made more favorable with epoxy.
We care able to get a resin to fiber ratio of 40 to 60 % and that makes a stronger structure. Fiber is what makes the structure strong so if the fiber to resin ratio is high on the fiber side you get a strong boat.
This is the reason why all racers are resin infused or made with prepreg fiber
to create a high fiber content and low weight[/quote]

fastcat435 · 24-11-2007, 11:44

If you mean by heat treatment post curing , yes epoxy needs post curing but so does vinylester and polyester, all harden without post curing but to get to the maximum strenght post curing is neccesary.
If you read the manufacturers manuals and tech data sheets you will find that post curing or heat treatment helps getting the strenght up and it also prevents at some later stage softening of the resin

fastcat435 · 24-11-2007, 11:56

It all depends up on the type of epoxy used and there are many types the marine industry does not use the top level epoxy as for instance the aircraft industry does but If I look at the manufacturer we work with Hexion and Uppc , they have over 100 diffrent types of epoxy with different pro,s and con,s 9 % is possible but not neccesary in the boating industry but 5 to 6 % is good for us since this coincides with carbon Fibre , I know that 50 % glass or fiber content is possible but as you mention with very carefull and good workmanship however there is not much of that around,I visited a yachting factory 2 weeks ago where gellcoat spraying was done in a mould , 600 grams of gellcoat per squire meter is how it should be and in this factory they where able to get 1.6 kilo per squire meter into the hull.
We get better than 64 % fiber content in a controlled environment all the time, we could go to 70 % but have found out that that creates pinholes in the laminate and this is a lot of extra work for the spray painters. So when the infusion is almost finished but the flow is still going we cut the vacuum back to 55 % in order not to get a dry laminate.

OldYachtie · 24-11-2007, 12:26

Actually, Fastcat, Reichhold is aware that the average boat builder doesn't want to heat treat hulls, and makes, as I have mentioned several times, a vinylester resin that isn't meant to be heat-treated. It looks like you are conceding my point that you can get equally high glass content with any resin. Do you heat treat your hulls? I notice that you are still not citing any sources for your claimed figures. If you want for me to take your figures seriously, you are going to have to cite sources. Let's remember, however, that my thesis isn't that epoxy is never superior to vinylester, it is that epoxy is only superior to vinylester if you use exotic fibers and heat treat it. I really question whether epoxy is superior to vinylester in a room-temperature, e-glass application, because vinylester resin's properties are so well matched to e-glass's properties. Check out the tables in this link: ResinNavigator.org - The marine resin authority. Permeation Barrier Vinylester looks pretty darned good, if you accept their figures. - TD

fastcat435 · 24-11-2007, 21:18

You are right there a couple of resin manufacturers that make resin that does not need to be post cured but the qualitys of all resins improve after post curing and yes we post cure our yachts for 8 hours at 80 degrees C. I am presently in South Africa but my office is in the Netherlands and i keep all my documentation there, and as you say vinylester is very good , epoxy is just better if treated right but the same goes for vinylester.

viking69 · 24-11-2007, 22:12

ok so if post curing is the go then what is the home builder to do??? I guess living here in oz we could sit the hulls out in the sun in the middle of summer when the temp hits high thirties. Being in the direct sunlight i would suspect it would heat the hulls to some degree but I am not sure if it would help at all????

Joli · 24-11-2007, 22:19

Interesting read. Certainly there are applications where the exotics make sense but for the average cruiser I can't imagine these construction techniques will be practical.

OldYachtie · 24-11-2007, 22:26

FastCat, you are obviously a well above-average boat builder, and I am sure you get the all of the benefits of using epoxy. I just doubt if anyone who doesn't go the extra mile with post-curing at 180 F (80C) and using exotic fibers will-such as me! Do you use much in the way of exotics, such as Kevlar or Carbon Fiber? What is your boat company called? I'd like to check out your website! -Tim Dunn

Celestialsailor · 25-11-2007, 01:05

I was told once (and believe it), that a bare hull is only 10% of the boat cost. So looking at it that way. the total cost of a Cat might only be 15% higher in the end. I think the other part of the problem might be the lay up and clean up hassle of the mould.