What is difference between Epoxy & Polyester Resins [Archive]

alan white

11-14-2009, 10:04 AM

There are quite a few epoxy hardeners to choose from, each working best at a particular temperature range. West System must have four or five temp ranges at least.
Actually, slow hardening can be ideal because recoating requires sanding unless the previous coat is still green. In that case, a chemical bond can still be achieved.
In cold weather, it's possible to do a good sized area and to know that you can continue with another coat within 24 hours, for example. This slows the work enough for a one-man shop to keep up.
Sometimes, of course, it can seem to take forever, particularly on a small repair. Luckily, epoxy can sit for ages before hardening, and as long as the ratio was correctly mixed, when warmth eventually arrives, the epoxy kicks.
If you miuxed too much, in other words, stick it in the freezer.

Homefront

11-14-2009, 10:28 AM

My personal opinion.

Polyester is far less pleasant to work with than epoxy. It tends to set up much faster, and stinks so bad it will burn your nose hairs out. :eek:
It doesn't have the water resistance of epoxy, but has it's uses. I replaced the cockpit sole in a friend's sport fisherman, and used 2 coats of polyester on the underside of the plywood panels before cutting and installing - this saved some $ on epoxy costs. On the walking surface I used MAS epoxy and glass, and painted with a good enamel with non-skid additive. Ten years later it has held up well. After much use the boat itself is about shot, so the surgery was well worth it.
I just looked over your other thread.
From what I can see in the picture, the break has significant overlap. Your choice is to try to push it out, or to leave it and fair it as-is. That will be up to you, based on how difficult it is to push out.
After sanding all the paint away underneath (go well beyond the area of repair so you don't apply epoxy over paint), I would apply epoxy with Cabosil and chopped glass strands as a thickened paste, in the depressed area to bond the broken section. Be sure to work it into the crack. Apply this like a first coat of spackle with a 6' plastic spreader, nice and smooth, but not beyond the depressed area. I'd then apply a heavy glass cloth or glass mat, and 2 coats of plain epoxy, followed by a last coat of epoxy with microballons or other fairing compound so you can shape and sand it all to your liking.
If you can access the bilge above the repair, I would reinforce the fix from the inside as well. Rough up the surface well with a sander so the epoxy will bond, and apply glass cloth or mat as below. You probably don't have to be as fussy appearance wise, but a bit of paint here wouldn't hurt.

Read all you can about the use of epoxy - mixing, cure times, how to wet out cloth, chemical and exothermic hazards, etc. - it's not that complicated or difficult, but there are some rules to follow strictly. Avoided skin contact, especially with the hardener, and be sure to wear a dust mask and goggles.
Good luck.

Fanie

11-14-2009, 11:06 AM

Hi Jim,

There is nothing wrong with polyeaster resin or epoxy. The main difference is epoxy is 5 to 6 times more expensive and epoxy takes about 24 hours to gell properly.

Polyester cures much faster which is temperature dependant more than epoxy. If you can keep polyester below 15 deg C you have a longer work time than we have here. In hot conditions I have about 15 mins max before the polyester gells and you cannot shape it any more.

Polyester is more smelly, but you have to work in a ventilated area in any case. Epoxy irritates the skin and a lot of people develop an allergic for it. I have been working for 25 years plus with polyester and it burns your skin but no allergic reaction I know of. I actually like the smell, it is not unpleasant in a ventelated area.

Keep a solution of washing powder and cool water handy to wash your hands in often and a rag to dry with and you will be ok.

Performance wise there is little difference between epoxy and polyester, I personally prefer polyester. Stick to the required hardner to resin spec, mix small volumes at a time and you will be ok. Polyester resin cures much faster if you can put it in direct sunlight, I suspect it is the UV that cures it faster.

TollyWally

11-14-2009, 11:29 AM

An interesting thread. As a fiberglass dilletante, I have found polyester easier to use in many of the little repairs I have done. Epoxy seems better on paper but polyester done with modest care has worked out quite well in the field.

I find it easier to wet out poly and for me, for the little things I do, that is a critical component of a successful application. Cost is of little matter as I have sufficient quantities of either on hand in "ships stores" to tackle my modest projects.

I am interested in the tips and techniques mentioned regarding epoxy. I'm all for using superior products and respect the views and the experience of several who have posted here. I find the quicker curing times of polyester to be helpful, yet cheerfully acknowledge my relative inexperience with epoxy.
I'm not sure if this post is worth the customary two cents but there you go. Perhaps I may glean a few new arrows for my boat tending quiver.

Fanie

11-14-2009, 11:44 AM

You can talk to Manie if you want tips on epoxy, he has done a lot of experiments to get layups on one another right. Resin does not have the same 'isolation' trend, but you have to make layups in one go and before the resin or epoxy cured. I never trust any job especially big parts that gets done in multiple sessions. Any part should be one integral glassed part, no joins after it has cured if you can help it.

There is no superiority between epoxy and polyester. I checked some spec sheets recently and I was quite happy to see that polyester can actually outperform resin. That said, remember both epoxy and polyester come in different grades. So I won't put my head on a block as to which is the superior.

The deciding factor what you want to use is probably the method you are going to use and what it is you are about to do.

alan white

11-14-2009, 01:33 PM

It makes little sense to lay up a hull using epoxy. Polyester sticks very well to itself. The cost is substantially less and the physical properties of polyester allow for light and strong structures to be built.
Epoxy is an amazing water barrier, and also an amazing adhesive. Because of this, there are places aboard a polyester hull for epoxy, especially as a barrier coat to prevent blistering of the underwater hull, something that can pretty much destroy susceptible layups if not caught in time.
Stringers and webbing/tabbing and bulkheads (particularly down in the often wet bilge area) do a lot better over time if they are sealed in epoxy prior to being installed.
It's not necessarily a choice between the two resins, but a selective use of both that makes the most sense. Rather than competitors, they are really different products for different jobs. Sometimes the two can be interchangable, depending on many factors such as level of familiarity, budget, expectation of longevity, and whether or not it is already on the workshop shelf.
Only experience and the study of available information over time can hone one's ability to choose right each time. Otherwise, asking here on the forum is great for doing projects on a case by case basis.

apex1

11-14-2009, 01:53 PM

Homefront

11-14-2009, 03:18 PM

Polyester is water permeable, Epoxy not. Poly sticks to nearly nothing, Epoxy to almost everything. Poly has to be mixed in extremely narrow proportion, Epoxy is a bit more forgiving. Poly has a short shelve life, Epoxy not. Means your dealer can sell you old poly cr.p that does´nt cure properly.
Both resins Poly and EP should (no MUST) be applied in one go, to form a mono - molecular structure. And only that has the max. technical properties. Letting one layer cure before laying the next, produces a onion, not a boat hull! No matter how much and good you sand it.

Jim - the above has been my experience as well.

This can all be rather confusing, especially in light of the fact that all of the statements presented here concerning both products are true in certain circumstances.
This is why I recommend reading up on it.
Glen-L published a book many years ago, which instructed on the use of epoxy in boat construction. It was my first guide, and a good one. Apparently it is now available on a free online page, containing at least the salient points. They are naturally promoting their own products, Poxy Shield and Poxy Grip, which are fine products, but if you substitute that name for whatever brand you choose the directions are the same: http://www.glen-l.com/supplies/pxman-content.html

gonzo

11-14-2009, 06:06 PM

Come on polyester not a boatbuilding material. What are the millions of floating objects with a high percentage of them decades old?

apex1

11-14-2009, 06:13 PM

Crap........

ok, ok, maybe I´m a bit biased........

not much though. Have you ever seen a demand for this?....http://www.gelplane.co.uk/
on a Epoxy surface?

gonzo

11-14-2009, 06:24 PM

I have seen them used a couple of times. I use an industrial sandblaster to take care of blisters. With the planer you still have to go back with a grinder to clean the holes. There is some myth going around for years that the sand will cut the glass fibers when the hull "works'. Glass fibers are silica like the sand. And whatever little dust is left behind gets mixed with the resin.

apex1

11-14-2009, 06:32 PM

Hähähh.................
I do´nt care of blisters..............

Fanie

11-14-2009, 06:45 PM

There is for sure no doubt, Epoxy is by far the superior choice in ANY case!

Polyester is water permeable, Epoxy not. Poly sticks to nearly nothing, Epoxy to almost everything. Poly has to be mixed in extremely narrow proportion, Epoxy is a bit more forgiving. Poly has a short shelve life, Epoxy not. Means your dealer can sell you old poly cr.p that does´nt cure properly.

BS Richard :D The samples Manie gave me delaminated as easy as the polyester did which was new on old. Polyester resin has the advantage that you can chemically 'melt' the surface to make a good bond. Imo not desirable, as a matter of principle I like my stuff in one piece, even if I was using epoxy I won't do it any differently.

As for boats out there Richard, for every old epoxy boat I can show you a polyester one. If I'm not mistaken then most boats are polyester, even old ones.

The ONLY reason epoxy is used is because of it's viscosity and prolonged gell time - hence you can vacuum inject easier with epoxy. As I said earlier the spec sheets I compared does not tell stories or thumb suck. I have never seen epoxy used in a mould. The method determine the choice of material.

Just because the price is more expensive does not mean it is a better product. Epoxy is used for it's properties as I mentioned above, not because it makes a better boat or because it will last longer, or because it holds water out better. The epoxy or resin is only the binder for the glass and neither epoxy or resin contributes much to the strength of the glass. Of the same ratio to glass resin and epoxy is applied the results will come out very much the same.

If you seal wood then epoxy should come out better, again because of it's viscosity, it should penetrate the wood deeper. Glass only I can tell you that the results will come out very much alike in all aspects.

Shelf life on polyester, if the conditions are not radical then months. As for the calculation of the resin hardner ration I haven't had a problem with that either.

Just becaus you guys are snobs doesn't mean your expensive epoxy boat is better :D

Fanie

11-14-2009, 06:48 PM

Oh yeah, I forgot to mention another drawback with epoxy. If the lightning hits your boat directly, you will have a good chance of the epoxy being evaporated. They have this propblem in epoxy built earoplanes, hence the shield that gets glassed in between the layers ;)

apex1

11-14-2009, 06:59 PM

Fanie

sure you know I build in both materials. Yes you did.

And EP does´nt penetrate deeper than Poly. It just sticks twenty times better.

Regards
Richard

wardd

11-14-2009, 07:02 PM

http://www.redrockstore.com/resin.htm

Fanie

11-14-2009, 07:14 PM

You can use polyester resin only with glass, it does not work with carbon fiber. Epoxy work with other than glass materials.

Hi Wardd, I saw that article before. I am talking about my own experiences. There are things some critics mention that I do not always buy like 'resin is used where weight is not a concern'. If the glass vs resin and glass vs epoxy is the same the weight will be very little different. It is again, the method of application that makes the difference.

The other thing mentioned is the scrinkage. Tbh, if resin scrinks, I haven't noticed before, but then I haven't built things the size of a soccer field.

I have seen some pretty old resin boats, like in really before my time - and that said I may not be as old :D as some of you guys. They weren't disintigrating and they were probably what, 70 / 80 years old. May not be the best hull design I've seen, but nothing wrong with the material. If there was problems with the lifespan of the materials then we would know it and authorities would require hulls beyond a certain age be scrapped. This does not exist.

If I build a boat that will last only 50 years I won't have a worry in the world :D Btw, how old is your car :D

I wonder how old a boat can get.

If you ask me then the sales people all say epoxy is the better because it is more expensive. When do you make the most money - if you sell at $20/kg with a 40% markup or when you sell at $120/kg with a 40% markup ? I have yet to see a salesman unhappy when you pay more.

gonzo

11-14-2009, 07:15 PM

Fanie: I was saying about polyester being a good material. Go fight with
apex1

Fanie

11-14-2009, 07:41 PM

I have some samples Manie made up for me a while ago in epoxy. Looking at it and feeling it's stiffness and flexing it I can see very little difference. If I didn't know it was epoxy it could just as well have been resin.

Polyester attacks some materials like polistirene and certain plastics which epoxy doesn't.

apex1

11-14-2009, 07:49 PM

Fanie could we be so nice and use a correct terminology?

Polyester is a resin and Epoxy is a resin too.

Thanks

Fanie

11-14-2009, 07:55 PM

Fanie: I was saying about polyester being a good material. Go fight with apex1

Corrected. El typo there. And I'm not fighting with anyone, but lets get our facts streight :D

The pic is a layup Manie made with epoxy. The epoxy delaminates the same as polyester does. If I didn't know it was epoxy it could just as well have been polyester.

See, I even got my finger stuck in there :D

Fanie

11-14-2009, 08:17 PM

Ok, one last thing. The guy who does my boat parts strength calculations does the calculations purely on the basis of the amount of glass I use. He has never asked if I used polyester or epoxy. If this was a factor in any way he would have mentioned it to me for sure. They are professional fiberglass builders and work with various materials, and since they do the calculations for me for free (cost me the phone calls though) they have no reason not to give the correct information.

What does make a big difference in stiffness and weight is the type of material you use, carbon is lighter than glass (I felt that :D, and it makes your pocket a lot lighter too) and the orientation of the glass (or other materials) does determine the stiffness in a direction.

So, if I am to patch a piece of glass in somewhere, like Par said in the first post, I would firstly consider polyester. If I want to make something in a mould hand layup, I would use polyester. If I was to use a vacuum injection process, I would use epoxy.

Some people want to use epoxy, fine. Others prefer polyester - like me and I'm stingy so I want to pay less for the same thing - also fine. The thing is going to be the same in any case and like cars, the best one is the one you have and use.

apex1

11-14-2009, 08:20 PM

Fanie
that was most probably glass with a silan treatment in Manies example! Thats good for Poly (`cos poly sticks to nothing, not to glass either if not prepared), but it makes a bad surface for Epoxy!
A perfect designed and executed Epoxy layup cannot delaminate, no matter on glass, Kevlar, carbon or wood.
Before the next contradiction pops up: PERFECT I said! Nothing less you shoul expect from your builder. (so, do´nt buy mass produced Poly boats, that is not even near to good, let alone perfect)

And I do´nt argue with your building method! I do´nt say that Poly is weaker then Epoxy, but it IS water permeable, there is absolutely no doubt possible! And when your gelcoat gets cracked, you have issues, there is no doubt also.
The fact that there are 50 years old boats still afloat does´nt make it a better material. (older than 50 are just 5 or 15, the method is´nt much older)
There are wooden boats out there which are over 100 years old! But thats a completely different topic. Until the late 70ies Polyester boats were so extremely heavy overbuilt (most of them), with a "fear factor" of 3 to 5 that it was hard to destroy tem.
And of course you CAN build a boat from EP in a mould, and it is done when other materials as Kevlar or Carbon are involved. Because then the price difference in EP to Poly is not much a factor anymore.
We will never see EP in mass production, its just the price what makes poly a material of choice.
But for sure it is the inferior in every case.

Regards
Richard

Fanie

11-14-2009, 08:31 PM

I can accept that. Each one have their 'rules' to work by, ignoring them would be stupid. My wife doesn't like the almond smell of polyester, I do.

Just the mention of fiberglass makes some of my 'friends' itch, no wonder none of them want to help me build the friggen boat. The pictures of guys catching fish from boats does excite them though :rolleyes: I bet they won't be late or have urgent stuff to attend to when the time comes.

A bit like you have lots of friends when you have booze in the house and few when you don't.

Reminds me I think it's time for the old witch to bake an almond cake for a change ;)

PAR

11-14-2009, 11:45 PM

Doesn't arsenic smell like you've cooked up some almonds? No wonder your wife doesn't want anything to do with it. She's afraid of you Fanie!

Just to get into the mix, all the polyester resins including vinyl are weaker then epoxy. When you look at elongation, compression, tensile, peel strength, hardness, etc., epoxy is far better. There's no debate over this, it's well documented. From a mechanical point of view it's fairly simple to understand once seen at a molecular level.

Think of the polyesters as a plate of spaghetti, some intertwining, but most of it just laying on top of other long polymer chains, it's this very thing, a two dimensional cross link, that limits it's peel strength. Epoxy on the other hand looks like the same plate of spaghetti, except the strands of pasta are all intertwined and better still, they have more then just two ends. They have many ends, all intertwined or bonded to other spider like molecules. This 3 dimensional linkage makes it much stronger, resist separation and penetration to a greater degree, etc.

Polyester is used in situations where strength to weight ratios aren't that critical. You can just bulk it up until it's strong enough for the tasks. When strength becomes more important and/or more chemical resistance and bond elongation are required, vinylester is a economic option that will fairly closely match some of the high tech fabrics available today. When interested in more strength to weight ability and matching resin to fabric physical properties, then you don't have a much of a choice, epoxy is the answer.

From a novice user's view, I think epoxy is a much easier product to get a handle on. You can screw up over a wider range of conditions and situations, with some level of success, which pretty much describes the usual novice's repair attempts.

apex1

11-15-2009, 05:51 AM

Thanks Paul,

as always, you brought it to the point.
But you have it easier to express it clear. I´m not so familiar with the typical Spaghetti pattern.;)

cheers
Richard

Fanie

11-15-2009, 06:26 AM

gonzo

11-15-2009, 06:34 AM

The strength depends on the conditions.
Epoxy is more flexible and streches more before fracturing. That means it will be better for shock loads. Compression is mainly a factor of the fiberglass and won't have a significant difference. In high temperature conditions, epoxy will get soft and polyester will be superior. If there are free solvents, epoxy is more resistant. Etc,

apex1

11-15-2009, 07:20 AM

Can someone give me an indication of the difference in strengths between say 10 layers of glass, one with polyester and one with epoxy, applied same ratio and same glass. Also indicate the grade of polyester and that of epoxy.
Thank you.
I wonder why a layup's trength is determined by the glass and not wether you use polyester or epoxy.

Because mainly the glass (or better fiber) content provides strength, to a lesser extend the resin.

But there is no general layup comparison (as far as I know). Too many different Poly and many more different Epoxy mixtures are available. Even high temp EP is on the market, to prevent failures as Gonzo described.

If there was´nt the substantial price difference, I would never produce our larger designs in Vinylester, but in EP!
But at 100 tonnes per boat you feel the difference, really. And the market does´nt pay for the better resin.

Regards
Richard

Fanie

11-15-2009, 07:37 AM

In all the time buggering around with boats I still have to see a boat getting bent through 90 degrees, never mind 180 :D

Are we talking anything practical here or is it minute's again. How much further than a same polyester resin will an epoxy layup bend ? How is this practical :D

If two boats are built identical, same everything, the one polyester and the other epoxy, if at exactly the same conditions they hit at the same speed a rock, how much bigger will the polyester's hole be ? 1mm ?

While there are many differences between the two under various conditions, if one say the one is superior then surely there must be a practical reason. If one dissolved in sea water for instance then it would be fair to say use the other one because this one has that drawback.

In the high temperature conditions Gonzo, I suspect one will be well cooked long before the difference in the two materials become aparent :D Again, is this a practical indication of the one is better than the other ?

gonzo

11-15-2009, 07:45 AM

Military boats specify high temperature fire resistant resin. As far as I know, that is only acomplished with palyester.
90 degree bends, or close, happen when sharp objects hit a laminate, like in puncture damage.

apex1

11-15-2009, 08:33 AM

Fanie
Are we talking anything practical here or is it minute's again. How much further than a same polyester resin will an epoxy layup bend ? How is this practical

Depends on layup design of course, so no one line answer.

If one dissolved in sea water for instance then it would be fair to say use the other one because this one has that drawback.

Poly resin cannot withstand water ingress. That IS a drawback. And it is the main problem behind the so called osmosis. In fact there is no osmosis in the first moment when water ingress happens.
Osmotic and micro molecular chemical processes start within the glass poly matrix and make the blister and delam problems.
The main issue is the gelcoat that has to protect the poly glass matrix. It is hard (good) and brittle (bad), and tends to get haircracks. Through these cracks you get water ingress and sometimes severe issues inside the laminate. You might not notice for a long time, that the boat you are sailing is already shot!
Epoxy does´nt know such issues.

To the temp. question: yes Poly can stand a bit higher temp.s than EP, but 125°C should be sufficient for non military use.

If you´re interested in a deeper insight have a look here:http://www.yachtsurvey.com/BlisterBlues.htm
and here:http://www.yachtsurvey.com/HiTech.htm
and go to the other related articles on his website too.
Though I do´nt see Pascoes elaborations as the last and only true word spoken, it tells the truth in all cases. His opinions sometimes seem to be a bit biased. But we all have more or less biased opinions.

Hope that could help a bit.
And when we come back to the original question:

the answer is clear, and doubts are not possible, in the hands of a novice, only Epoxy will make a good repair job!

Regards
Richard

Fanie

11-15-2009, 11:12 AM

Now you're talking about gell coat :D That is something totally different from polyester resin.

But we all have more or less biased opinions.
No kiddin :D I still stick with my opinion that one uses what is suitable for your application method. It just makes sense.

The polyester resin I'm using for my boat is specifically for prolonged exposure to sea water, I won't use gellcoat (yuk !). But I will probably paint it.

Eh Par, I actually got my almond cake. If I stay alive then the arsenic levels was a bit low :D The wife like baking and cooking so at 03h00 when I went to bed and whispered 'almond cake' I got the 'ihmm' reply (as to the usual 'uhh uhhhh' :D)

gonzo

11-15-2009, 11:23 AM

Gelcoat is resin with a load, pigment and usually UV protection.

apex1

11-15-2009, 01:13 PM

Now you're talking about gell coat :D That is something totally different from polyester resin.

No no Fanie! I was still talking poly..

The polyester resin I'm using for my boat is specifically for prolonged exposure to sea water, I won't use gellcoat (yuk !). But I will probably paint it.

A wise decision to paint it. With Epoxy of course!

Eh Par, I actually got my almond cake. If I stay alive then the arsenic levels was a bit low :D The wife like baking and cooking so at 03h00 when I went to bed and whispered 'almond cake' I got the 'ihmm' reply (as to the usual 'uhh uhhhh' :D)

Have fun..............:D

PAR

11-15-2009, 04:32 PM

This stuff is all well covered in several references, but some high lights.

Ortho polyester tends to be brittle, because it's elongation is quite low, before fracture. This makes it unsuitable for modern fabric weaves or high modulus materials. The resin system will fail, long before the reinforcement. Ortho's have a less then stellar chemical attack properties as well. In spite of these short comings, it's the plane Jane of the industry and heavily used for it's cost and because shops are geared for it's use.

Next up the polyester ladder is isophthalic. Is has a little better elongation and a little better chemical resistance. It's about 20% less brittle then ortho. As a result you can vacuum bag a mat/roving laminate with fairly strong results and only a modest change in resin system cost.

Moving further up the polyester scale is vinylester. This stuff is about as good as you can get with a two dimensional molecule. It's elongation is twice that of iso's and can have a tensile strength near 11,500 psi when used with modern fabrics in a well controlled laminate. It's interlaminate bonds are much better then the other polyesters and it's peel strength is also much higher. Vinylester is also even more resistant to chemical attack.

This stuff was developed partly to address production shops around the world in a polyester environment, as this resin is compatible with all the polyester products. Used with biax, stitch mat, E-'glass or other high modulus material, a strong laminate and still cheaper then epoxy, though not by much, plus a production shop doesn't have to retool and retrain for the different resin system.

By every way you measure epoxy (at least the stuff we use) it's better then vinylester, except cost. Because of it's 3 dimensional cross linking, it doesn't need to be "bulked" up with mat products. Using mat with epoxy is just wasting resin (lots of it). Epoxy's peel strength and interlaminate bonds are so strong, mat will actually weaken the final product. How strong? Let's take a 1/4" thick, biax S-'glass, bagged laminate. It's flexural strength will be in the 80,000+ psi range. This is stronger then stainless steel of the same weight and makes all the polyesters quiver and hide by comparison.

ondarvr

11-16-2009, 04:45 PM

Well engineered items that need to hold up to extreme stress, need to be light, use fibers other than, or in combination with glass, are less effected by cost, or are being used over a wooden structure are good candidates for epoxy.

Mass produced items that need to hold up well, but can tolerate slightly more weight, are using only glass fiber (with some exceptions) and are affected a great deal by cost are good candidates for the “correct” polyester.

There are many horror stories out there about how a polyester failed and how it was the resin’s fault. Little research is actually done to find the real cause though.

Blisters can be caused by many things, but even if all the best methods are used, a low cost polyester that was never designed to be used in a hull can, or will, blister. If the “correct” recommended products are used then the chance of blisters are drastically reduced, even to the point of them not being much of a concern, especially when barrier coats are used.

There was a time during the boom in polyester boat building that almost any resin that got hard was used in production, cost was the deciding factor. This along with poor methods of production and shoddy workmanship created a huge fleet of boats that didn’t fair well a few years after they were put into use. This is where most of the bad rep for polyesters was born, that, and that if you had a 1 gallon bucket and 4” brush, you were in the boat building business.

While there are still some (very few) boats built this way, many have upgraded the products and methods used to avoid most of these issues, price still becomes an issue at times, so the “best” products may not always be used.

Skill of the worker and the equipment used (spray type for the most part) can still be a factor though, so while the polyester resin used may be fine for this application, there can still be issues with other parts of production that may cause problems. This is where many of the differences in the survival of final products made from either epoxy or polyester come from.

Almost everything made from epoxy is less price concuss than items made with polyester, this means good experienced engineers are involved, these items tend to be custom built and in lower volumes, more actual craftsman are employed and shop conditions tend to be better. This results in fewer items on the market and more care taken to produce the products. As price comes into play, each of these factors is compromised.

The other issue has to due with cost of production, while the cost of using epoxy compared to polyester seems clear at first by just looking at the price of each product, that’s only the beginning of the difference. Epoxy isn’t as user friendly in production and the same type of equipment can’t be used and when equipment is available, the cost will be much higher. There are also the health problems associated with epoxy, while I don’t recommend being exposed to polyester for good health, exposure hasn’t been a big problem in the industry, where epoxy can have some real issues when the correct handling procedures aren’t used. These all add up to a much higher final cost of an epoxy product when compared to the same type of item made from polyester.

If non engineered epoxy products were made with the same poorly trained employees, in shops with shabby working conditions there would be horror stories about them also. Then factor in the epoxy being sold on price alone, not physical properties or suitability for the application and you would have resins that were junk being used to build to a price point. How do you think these hulls would hold up?

Fanie

11-16-2009, 05:39 PM

The mentioning of methods is going to keep on surfacing.

Anything poorly designed an build is going to be problematic. If a boat or parts are properly designed you won't have problems. It does not matter if you use polyester or epoxy.

The differences between polyester and epoxy have been mentioned numerous times by now, still, the strength of a layup is determined by the glass and not whether epoxy or polyester is used.

If it was so that epoxy makes such a big difference in strength then surely one can get away using less glass and hence possibly make up some of the difference in price to make epoxy more attractive. Doesn't work that way.

Even if the molecule structure of epoxy leans itself to glue more dense to the glass strands, the end product doesn't make such a big difference. It is the glass that produces the strength, the binding epoxy or polyester adds very little to the strength of the structure.

That is why only the glass is considered in design strength.

The method used to create the structure is the factor that determine which will be used, epoxy or polyester. And off late it seems personal preference as well :D

If anyone wants to buy a boat he chooses between fiberglass, wood, iron, aluminum as the basis for the construction. I have never heard of someone looking at a boat to buy, asking if it is an epoxy or a polyester boat. It does not matter.

Sure, if a shape is casted, one in polyester and one in epoxy, both without glass, then the epoxy may bend more than polyester or prove the epoxy is stronger.

But you have to remember when the glass is used then the epoxy or polyester required is limited only to wetting out the glass properly. More just adds weight. Less compromises the strength. Now only the strength of the glass matters.

apex1

11-16-2009, 06:03 PM

Even if the molecule structure of epoxy leans itself to glue more dense to the glass strands, the end product doesn't make such a big difference. It is the glass that produces the strength, the binding epoxy or polyester adds very little to the strength of the structure.

There you have hit the nail without noticing! Epoxy bonds far better to everything than Poly, that in general makes a superior laminate! Second point is, that Epoxy curing is much better (predictable) to handle, than Poly. This makes a far superior layup in the average manufacturing process. In clear words: a much, much better layup.

That is why only the glass is considered in design strength.

That is right and valid in scientific analysis, where always a perfect executed layup is part of the game (even then it is not true to the last extend).
In average boatbuilding there is´nt a perfect world. And a partly shot poly layup is a complete loss.

And off late it seems personal preference as well :D

Sorry thats BS

I have never heard of someone looking at a boat to buy, asking if it is an epoxy or a polyester boat. It does not matter.

Nonsense, it does matter! But of course you are right, NOBODY asks Poly or EP! So, why should we shovel our money through the door to provide a better product, when the market is´nt willing to pay for?

ondarvr mentioned a "barrier coat" in his post above. Do you know what that is? EPOXY
So, when poly has to be coated by Epoxy, which one is the better product? (and if it was only in this case, what it is´nt)

Quite obvious you did not take the time to read some of Pascoes articles I linked to!
And you do´nt believe us people using the goo daily?

By every way you measure epoxy (at least the stuff we use) it's better then vinylester, except cost. Because of it's 3 dimensional cross linking, it doesn't need to be "bulked" up with mat products. Using mat with epoxy is just wasting resin (lots of it). Epoxy's peel strength and interlaminate bonds are so strong, mat will actually weaken the final product. How strong? Let's take a 1/4" thick, biax S-'glass, bagged laminate. It's flexural strength will be in the 80,000+ psi range. This is stronger then stainless steel of the same weight and makes all the polyesters quiver and hide by comparison.
You should!

Regards
Richard

PAR

11-16-2009, 06:28 PM

the strength of a layup is determined by the glass and not whether epoxy or polyester is used.

This isn't correct, 'glass is used with most of the polyesters because the resin needs the mechanical help of the reinforcement. With a better resin system you can work to the limits of each material, which is the ideal engineered structure, when everything fails all at once.

I have never heard of someone looking at a boat to buy, asking if it is an epoxy or a polyester boat. It does not matter.

Actually, several production shops are advertising all epoxy laminates, specifically because they know what their clients want. Or, in the case of a polyester boat, asking if it's been barrier coated with epoxy.

You are under the false impression that it's the 'glass that makes the product. The matrix (resin/reinforcement combination) makes the product. The 'glass alone is useless, polyester resin alone is brittle and epoxy alone is as well, though less so.

Epoxy and carbon, epoxy and Spectra, epoxy and Kevlar, epoxy and polyester, epoxy and modified acrylic, combinations of each - these are all fairly common laminates now and they have none, zero, no 'glass in them. Apparently 'glass isn't as useful as believed. In fact, there will soon come a day when we will look fondly back at the days when there was only 'glass to use as a reinforcement fabric. I'm personally looking forward to the day they can build a machine to weave Spectra and treat it with a sizing.

And yes, you can use thinner laminates and less materials for the same strength with epoxy, compared to polyester, which is the whole point (and done all the time). Lighter is faster, given the same strength, which just leads to more capacity, higher ballast ratios, stiffer boats and bigger sail plans, etc.

ondarvr

11-16-2009, 06:36 PM

PAR

You left out a whole class of polyester resin, DCPD's, these are the lowest cost and most used resins with many of the poorest physical properties. The main reasons DCPD's are used is because of their low cost and low shrink characteristics, the other reason is they require less styrene to thin them to a usable viscosity.

The down side is they tend to be brittle, weak, have poor water and UV resistance and secondary bonding over them needs to be done with more care.
The secondary bonding problem was where a great deal of the bad rep came from with polyesters, not all of it though. DCPD’s will cure on the surface much more like a waxed resin, so the window of bonding over it is very short. If they cure for very long, the surface needs to be sanded very well before the next layup.

DCPD’s took the industry by storm when they were first released because of their low price, it wasn’t until later that these limitations were understood and how they were used changed. Now DCPD’s are blended with other resins (Ortho, ISO, VE) to lower the cost and make them conform to MACT compliant regulations (FRP industry limits on hazardous air pollutants). Ortho is considered a big upgrade from a DCPD.

apex1

11-16-2009, 06:53 PM

Ondarvr
you think DCPD´s are still the most used resins? I thought even my dumbest competitor would have given up on that crap!?

ondarvr

11-16-2009, 07:14 PM

PAR

[quote]Second point is, that Epoxy curing is much better (predictable) to handle, than Poly. This makes a far superior layup in the average manufacturing process.

Not exactly, one of the big reasons polyester is chosen to be used so often is because of how easy it to use in production, the gel time, cure profile, visc and thix can be adjusted easily to conform to most any need. Gel times can be from 2 minutes to more than a day if needed depending on the formula and catalyst. The laminate can be very thin, at less than 20 mils, or many inches thick and be done all at one time. In a laminate polyesters tend to stay in place and not drain out, so they are much easier to work with in a vertical application.

There is other research and testing going on right now that may convert much of the epoxy infusion production over to VE. The reason is that as the viscosity of epoxy is reduced to the point where it can easily be infused, the physical properties are reduced to that of VE or very close (sometimes better, sometimes worse). So with the price difference (almost double for epoxy) and the ease of use, VE may more often become the resin of choice for high end applications.

ondarvr

11-16-2009, 07:46 PM

apex1

The barrier coats I'm talking about are VE products being used behind the gel coat, not the epoxy products used in post coat applications, although these epoxy products do work very well.

I have read most of Pascoe's stuff, in detail, it was more than a year ago though, so if he's released new information that says he has witnessed a composite boat being built, or knows the names of the products used in the process, this will be new information. He had stated these things in an article he released titled something about not recognizing the products used in building production boats.

As far as getting sticky and working with the goo, I've been working on and/or building composite boats since I was around 12 years old, the last 15 years I've been involved in tech service to the marine industry, plus many others industries in the composite tent, so my experience is not limited. Just this week I was involved in gel coating an 85’ yacht and infusing a 40’ offshore racing hull with carbon, Kevlar and in places a foam core. I almost forgot, there was also the infused wind blades. I have 40+ years of hands on work in the composite industry.

pamarine

11-16-2009, 08:26 PM

Can someone give me an indication of the difference in strengths between say 10 layers of glass, one with polyester and one with epoxy, applied same ratio and same glass. Also indicate the grade of polyester and that of epoxy.

Thank you.

I wonder why a layup's trength is determined by the glass and not wether you use polyester or epoxy.

A layup's strength is determined by the following:

Matrix used and density (Wood, E-Glass, S-Glass, Kevlar, Carbon, Aluminum honeycomb, etc)

Fiber Weave (Plain, Crowfoot, Twill, Uni-directional, bi-directional, mat, etc)

Resin Used (Epoxy, Polyester, Vinylester, etc)

Binding agent used on the Fiber (if applicable)

Resin to Matrix Ratio

With most boats only three of these variables come in to play (although all could in more engineered constructions), Resin used, Matrix Used, and Resin to Matrix Ratio.

Anyone computing the strength of the layup should want to know all of the factors, however, not just how thick the glass is.

apex1

11-16-2009, 08:26 PM

apex1
I have read most of Pascoe's stuff, in detail, it was more than a year ago though, so if he's released new information that says he has witnessed a composite boat being built, or knows the names of the products used in the process, this will be new information. He had stated these things in an article he released titled something about not recognizing the products used in building production boats.

Do´nt know if there are updates, except for the never ending core nonsense.

I think you misunderstood me quite a bit. I did not question your knowledge. I had a question in my last post thats all. And we are processing around 800 to 1000 tonnes of resin per annum (actually we make boats with it), both VE and EP, each where it belongs.:idea:

PAR
[quote]Second point is, that Epoxy curing is much better (predictable) to handle, than Poly. This makes a far superior layup in the average manufacturing process.

Not exactly, one of the big reasons polyester is chosen to be used so often is because of how easy it to use in production, the gel time, cure profile, visc and thix can be adjusted easily to conform to most any need. Gel times can be from 2 minutes to more than a day if needed depending on the formula and catalyst. The laminate can be very thin, at less than 20 mils, or many inches thick and be done all at one time. In a laminate polyesters tend to stay in place and not drain out, so they are much easier to work with in a vertical application.

You adressed this wrong, it was´nt PAR, I made that statement.:cool:

And it is completely valid, though I was not talking about infusion and did not talk about special applications. What I had in mind was a amateur build.

We are not in the "Industry has a question" sector here. A novice asked for help!
And it is 200 times easier for a novice to completely fu.k up his job with poly then with EP.
Just the fact that your layup schedule in EP is easier to fix and handle makes the difference between producing a onion or a boatskin. Right?

Regards
Richard

pamarine

11-16-2009, 08:27 PM

Oh, and you asked for a comparison:

Comparison of Boat Building Resins (http://www.c-cyachts.com/images/company_assets/512F1C7F-0D64-4A5E-9D91-785DC064755F/16cf4_Adv_of_Epoxy_v_Poly.pdf)

apex1

11-16-2009, 08:45 PM

Oh, and you asked for a comparison:

Comparison of Boat Building Resins (http://www.c-cyachts.com/images/company_assets/512F1C7F-0D64-4A5E-9D91-785DC064755F/16cf4_Adv_of_Epoxy_v_Poly.pdf)

Thanks!
though I did´nt ask......I know.

ondarvr

11-16-2009, 08:51 PM

Ondarvr
you think DCPD´s are still the most used resins? I thought even my dumbest competitor would have given up on that crap!?

Yes they are, and by a large margin.

Part of the problem was created by the industry itself. There were agreements made with the regulatory agencies to reduce HAP (hazardous air pollutants) content to lower than 35%. Most resins aren't very user friendly with this level of styrene (or other products), they're thick, poor curing, difficult to roll and spray, don't saturate the fabric well and have other issues. If you blend Ortho, ISO or VE with a DCPD you gain back some the good handling aspects and can get below the 35% mark, but you also end up with a lesser product. Right now the 35% level is sort of limiting which products can used in production, although some companies can get around it, it can be costly to do so.

pamarine

11-16-2009, 08:57 PM

Thanks!
though I did´nt ask......I know.

that was for Fanie, you snuck a post in between:D

ondarvr

11-16-2009, 08:58 PM

apex1

This is getting so busy its hard to keep track of who you're responding to, but is fun.

apex1

11-16-2009, 09:12 PM

apex1
This is getting so busy its hard to keep track of who you're responding to, but is fun.
Oh,
I´m on track, do´nt worry...:D
And producing in Turkey we do´nt know about regulations. That means WE set the standards, and they are worlds ahead of the average US sweat shop, like See Räi and other horse bucket manufacturers.

Coming from plain wood Epoxy building (which remains to be the biggest part by numbers), we just recently went to VE for the larger formats above 32meter. So we had to build completely new, and had the opprtunity to build the shops to proper standards.

ondarvr

11-16-2009, 10:23 PM

Just so its clear, I have no argument that epoxy is a superior product to polyesters and VE in most ways. The problem is that many think epoxy is "the" only resin that can be used to build many products and they use the standard "see it failed in this application one time" argument and discount its use in most any application.

Most people here use epoxy and it is the product they should be using for what they build and their clientele, but epoxy isn't the only resin that can be used successfully in the marine industry. Most of the failures are from a poorly chosen resin based on a few cent per pound difference that isn't even recommended for marine use. Then using untrained and under paid workers with little supervision to build a poorly thought out design with incorrect methods. When it fails in some way they blame it on the junk poly-stuff that smells so bad.

As PAR has mentioned before, there was building boom that took place where everyone though polyester would work very well over a wooden hull. As many of these hulls began to fail for one reason or another, many just from poor workmanship, the line of thought swung the other way and epoxy was the only product to use in every application. As time goes on its now beginning to swing back a little in the other direction and people are re-examining the data to find that other resins will fit in and when used correctly the result can be very good.

Fanie

11-18-2009, 05:03 PM

pamarine

11-18-2009, 05:08 PM

You guys can believe what you want, but here is another reason for using polyester resin.

MCRS uses polyester resin to build their aeroplanes with. This includes the Express, Tango, Kiss cruiser and the MCRS series. The reason - polyester resin is more fuel resistant than epoxy and leave less micro holes.

For any aircraft manufactured with polyester resin I can show you 10 manufacturers using Epoxy Resins. In Fact, the FAA doesn't even mention using Polyester resins on certified aircraft repairs. And I should know, I'm a certificated Airframe & Powerplant Mechanic with an Inspector Authorization.

Not only that, but it is recommended that polyester resins not be used on wood due to the risk of fire from the extremely unpredictable exothermic curing reaction. (unpredictable in the field due to the less-than precise resin to catalyst ratios used by most repair technicians.)

Also do yourself a favour. Get some spec sheets of polyester resins (you get different grades) and compare them with that of the epoxy range.

You guys seem to forget another very important factor. The glass you use is either prepared for polyester resin or for epoxy. This glass coating is what allows the binder you use to work optimal with that glass. If you use the wrong type of glass or use uncoated glass you will have a less strong layup.

There is very little, if any difference between a polyester resin layup or an epoxy layup. The important factor is the method of application.

See my post above for the variables that affect the strengths of a composite layup.

if you want to use Polyester Resin, then that is your choice and for most boat-building applications it will be adequate. But generally speaking, even though Polyester Resin may be good enough for a given lamination, epoxies will outperform them in the same use.

apex1

11-18-2009, 05:23 PM

You guys can believe what you want, but here is another reason for using polyester resin.

Fanie

just say you love the smell................:D ok?

The other "arguments" are in favour of Epoxy.
And be sure, we know the many many different treatments of glass and other fibres, on the market.
We make our business based on such knowledge.

Regards
Richard

PAR

11-18-2009, 05:24 PM

I have no idea where you're getting you information, but it is direct conflict will known testing and facts Fanie. It could be that we are all wrong (even though I've been beta for these tests on occasion) or that you are grossly misinformed about the abilities of 2 dimensional resin systems (polyesters). You may be a fan of polyesters and they have a place, but your statements can't be supported with facts or testing.

Fanie

11-18-2009, 05:27 PM

Hi Pamarine,

I wouldn't use polyester on wood either. If I used wood I would use epoxy. And it is not due to the fire hazard, epoxy loans itself better and does bond better to wood. If you choose to use the wood method then you would use epoxy.

The only time I would have wood on the boat is when there is a BBQ.

Fanie

11-18-2009, 06:48 PM

Sorry I got disconnected due to the weather here.

If you all agree with that there is such a big difference in performance between polyester and epoxy, then I would like to see some evidence.

Surely someone must have built two boats somewhere and the polyester boat btoke while the epoxy lasted, or the polyester whatever but the epoxy didn't.

You keep on hammering on the structures of the polyester vs epoxy, show me in real life that there is such a big difference.

All I see is people saying things but no hard evidence.

gonzo

11-18-2009, 08:25 PM

pamarine

11-18-2009, 09:11 PM

There are many polyester resin formulations as there are many epoxy resin formulations. Seems like the discussion is missing that. Early polyester boats which were built resin rich didn't blister. During the oil crunch, new resins started to have blistering problems. Also, companies like Uniflite, were building boats with milspec polyester resin. It is fire resistant, a good thing for the Vietnam era patrol boats. However, four or five years after launching they were getting blisters the size of watermelons.

Several posts have stated that selecting the proper resin for the intended use is key to good performance. IT really matters not if the resin is polyester, vinylester, or epoxy in this case.

What we are saying is pick any application and choose the best suited polyester resin and the best suited epoxy resin for that application, and with equal quality in the layup and curing processes, the epoxy resin will out-perform the polyester resin.

ondarvr

11-18-2009, 09:49 PM

Several posts have stated that selecting the proper resin for the intended use is key to good performance. IT really matters not if the resin is polyester, vinylester, or epoxy in this case.

What we are saying is pick any application and choose the best suited polyester resin and the best suited epoxy resin for that application, and with equal quality in the layup and curing processes, the epoxy resin will out-perform the polyester resin.

How many people here buy only "the best" product(s) for anything in life? Does anyone here live in the best house made with only the best materials and only drive the best car..... and on and on, its a compromise, we buy what fits the need, but you can always spend more and get better stuff.

Would it make a difference if my boats were made from epoxy instead of polyester, not really, except that I wouldn't be able to afford them. As far as how they get used and how they perform, it would have little affect.

I drive an F150 4X4, I could upgrade to a heavy duty diesel, because in almost every way its better, but would it make a difference in how I use it....not at all....it would only cost me more to buy it.

pamarine

11-18-2009, 11:02 PM

How many people here buy only "the best" product(s) for anything in life? Does anyone here live in the best house made with only the best materials and only drive the best car..... and on and on, its a compromise, we buy what fits the need, but you can always spend more and get better stuff.

Would it make a difference if my boats were made from epoxy instead of polyester, not really, except that I wouldn't be able to afford them. As far as how they get used and how they perform, it would have little affect.

I drive an F150 4X4, I could upgrade to a heavy duty diesel, because in almost every way its better, but would it make a difference in how I use it....not at all....it would only cost me more to buy it.

Your analogy would be better if you were comparing your 150 to a tundra or some other 1/2 ton. but anyway,

I always recommend someone buys the best they can afford, because in the long run it will save them money.

The OP was asking about making a repair to an existing FRP structure. Any epoxy that is available at a reputable Marine Supply Store will provide better mechanical adhesion of the repair to the existing hull.

ondarvr

11-18-2009, 11:38 PM

The question was what should he use to do the repair, epoxy or polyester, in reality it will make no difference which one gets used, they are both up the job. You can under or over build with each one and as far as the bond, the prep work is the same for each product and while the bond with epoxy is better, the bond with Polyester isn't bad, its actually quite strong and durable.

apex1

11-19-2009, 05:22 AM

in reality it will make no difference which one gets used, they are both up the job. ...the bond with Polyester isn't bad, its actually quite strong and durable.

Sorry to contradict you here,
that is just NOT TRUE! Not even the manufacturers of poly resins claim that it sticks well.

I really cannot understand why this idiotic statement pops up here ever and ever again.

Poly sticks good to nothing, absolutely nothing, not one single boatbuilding material, not even to cured poly, not to untreated glassfibre, just to nothing!

It does not stick!

And it is water permeable, no matter which one u use. Gelcoat is even worse than straight poly, it just looks nice (for a while).

Does anyone here assume we do our wood epoxy boats because we love epoxy? Anyone familiar with barrier coats? That´s epoxy. Why?

Please stop telling people which come here for serious advice, they could use poly for repairs. They could use plaster as well. (in fact that is done on wooden boats)

Regards
Richard

gonzo

11-19-2009, 05:29 AM

I have made many repairs with polyester resin. For example transom and stringer replacement in runabouts. It is the same way they were built. At one time we were doing maybe six or seven a week with no failures ever. They are not high performance, minimum weight hulls, so the repair is adequate.

apex1

11-19-2009, 06:55 AM

Gonzo

would you say you are a novice?:rolleyes:

pamarine

11-19-2009, 11:17 AM

I'm not sure how a Polyester Resin resin will adhere as well as an Epoxy resin.

For one, Polyester has a high shrinkage ratio during curing and will pull away from the repair, weakening the mechanical bond. (This is why Epoxy is used on aircraft)

The adhesion of epoxies (Maas. West, and System3 that you will find in marine supply stores) approaches 2,000psi or higher. Vinylesters are only around 500psi and polyesters are even less.

gonzo

11-19-2009, 11:24 AM

Polyester resin will not adhere as well as epoxy. The shrinkage, if any, is not significant in a resin rich repair. The styrene disolves some of the old resin and helps in the bond. The adhesion is adequate for some repairs. Epoxy has as much failures with amateurs as polyester. The wrong ratio or bad mix makes a gooey mess. I find polyester easier to work because the amount of hardener controls the work time. However, I would have to be really broke to do fiberglass work any more.

pamarine

11-19-2009, 02:50 PM

However, I would have to be really broke to do fiberglass work any more.

I agree with this completely:D

Fanie

11-19-2009, 02:53 PM

pamarine

11-19-2009, 03:08 PM

Richard, you seem to forget that time is marching on, and with it comes new technologies that makes things possible that were not possible before.

If I want to stick polyester resin to old polyester fiberglass then I can. Our local supplier sells a solution you wet the to be glassed fiberglass with. This makes the surface soft and it allows the new polyester to make a decent bond. I have not used it myself before but I was told by the supplier that it works so well it can be considered a permanent bond and will not delaminate. I don't know how many PSI's per whatever it will be.

Also, the boat I'm building will simply be painted. I don't see how water will seep into it. Even without paint a simple four layer glass only layup which is quite thin does not leak - from personal experience, one layer probably would, maybe even two layers, but I bet it's the same with epoxy.

A polyester repair does not have to be resin rich. For small layups I don't plaster the glass in place, I wet the glass then place it in place. There is no extra resin that is associated with the usual, well, I call it plaster where there is 100g glass and 400g resin. The resin does not add to the strength, only the glass does and the glass requires only so much resin to be at optimal strength.

The backyard mechanic that wants to fix his boat up buys a liter of polyester (any type that is the cheapest), some chop strand and sets off to replace the bulkhead in his boat or replace the rotten floor. He glasses over the old dry and when he hits the first wave the glass begins to delaminate. There's your problem. Polyester is crap and sticks to nothing.

I'm sorry you guys are so broke :D

Fanie,

You do need to realise that there is a minimum acceptable standard for a repair and that a properly chosen polyester resin will normally meet that standard. But we are talking about what is the best, not what is passable.

As far as the snide remarks, some of us have made careers out of composites, and the benefit of that accumulates knowledge should never be outweighed by anecdotal evidence.

When you start talking about "softening up" an existing laminate, you are then going beyond mechanical adhesion to a chemical bond. Chemical bonds will always out-perform mechnical ones with the same resin. But then again, you can only safely "soften" so much of the resin before the overall integrity of the structure is compromised.

And yes, I know that was addressed to Richard, but you attitude and post in general seems to be address many of us.

apex1

11-19-2009, 03:10 PM

Fanie
>>>>Richard, you seem to forget that time is marching on, and with it comes new technologies that makes things possible that were not possible before.<<<<

do you believe I am a complete idiot?

We built a complete new yard to produce the larger boats series in VE, 2 years ago. Another newbuilt for the wood epoxy production this year (just the latter was 33 mio€). Do you assume we use grandfathers rules of thumb?

Richard

ondarvr

11-19-2009, 06:21 PM

Sorry to contradict you here,
that is just NOT TRUE! Not even the manufacturers of poly resins claim that it sticks well.

I really cannot understand why this idiotic statement pops up here ever and ever again.

Poly sticks good to nothing, absolutely nothing, not one single boatbuilding material, not even to cured poly, not to untreated glassfibre, just to nothing!

It does not stick!

And it is water permeable, no matter which one u use. Gelcoat is even worse than straight poly, it just looks nice (for a while).

Does anyone here assume we do our wood epoxy boats because we love epoxy? Anyone familiar with barrier coats? That´s epoxy. Why?

Please stop telling people which come here for serious advice, they could use poly for repairs. They could use plaster as well. (in fact that is done on wooden boats)

Regards
Richard

I'm not sure which Polyester manufactures say it doesn't stick to anything.

I work for a very large world wide manufacturer of polyester and VE and I do tech service, we do not recommend repairs should be done with epoxy, it is possible that some should be, but most can be done very well with standard products. I've also repaired more things than most here can imagine are being made from these resins and the failure rate is so low its not much of a concern. So if a polyester to polyester bond is so poor that it can't possibly last in use, I would have seen this to be true first hand.

We test bonds frequently in the lab and I've done real world destructive testing in the field and the statements like “it won't bond to anything" and "it should never be used" just aren't supported by the facts.

It makes no difference if epoxy bonds 100 (just a number) times better than polyester if the bond strength of the polyester is never exceeded in the part or repair, which is normal.

gonzo

11-19-2009, 06:36 PM

This resin type discussion is more heated than a religious war.

Fanie

11-19-2009, 06:55 PM

This resin type discussion is more heated than a religious war.
No it isn't, not really, no I don't think so :rolleyes:

I know the thread started out with what to use for a repair, but the argument got started by some that polyester resin is a substandard product.

Polyester is a brilliant product. It produces boats all over the world and some even stay afloat for more than a day and a few years after that and a few decades after that. Some weigh the same as epoxy boats and will last just as long, will never break, looks just as good, and will fetch the same market price if sold.

do you believe I am a complete idiot?
I don't think you are an idiot Richard. Ok well, not a COMPLETE one :D
Nobody can be that good anyway ;)

If you build using wood and epoxy, then that is the right combination for your building method. If it was me, I would not have used polyester and wood either.

I did not know your Grandfather.

Thank you Ondarvr. 4 5 c, what took you so long :D

ondarvr

11-19-2009, 07:54 PM

This resin type discussion is more heated than a religious war.

I enjoy it, I don't love one product more than the other because they both have their place in the industry. The information passed along needs to be accurate though.

apex1

11-19-2009, 09:03 PM

ondarvr

that:
I'm not sure which Polyester manufactures say it doesn't stick to anything.

was not my statement!
Reading thoroughly and quoting correct makes a discussion fair. You did bend the meaning in a unfair way.
Not a nice way to discuss.

And I do´nt know why I have to say this another 20 times, but here it goes again: WE USE BOTH RESINS! VINYLESTER AND EPOXY, each where it makes sense. And Epoxy is by far the superior resin in ALL applications. period

Ah, not to forget: Polyester sticks good to nothing

Regards
Richard

ondarvr

11-19-2009, 09:50 PM

Sorry if I misquoted you, I just got back in from a 4 hour drive, I was at an account of mine that makes Yachts up to around 200' from VE and I was tired.
We were spraying a new style of gel coat and looking at a new plug for a tool, I think it was in the 140' range.

I agree that epoxy has better properties in most ways, but what needs to be understood is that better means nothing if the properties aren't required for the application.

elhix

12-21-2009, 10:06 AM

I'm finishing building a 32 foot Shuttleworth cat. The hulls, bridgedeck and bulkheads used polyester. The chainplates, daggerboard and case, rudders and forward beam used epoxy. Whilst epoxy has superior properties, as many have pointed out, in many areas of a boat these aren't taken advantage of so the considerable extra expenditure is unnecessary. In my case the structures most subjected to dynamic loads have utilised epoxy.

My cat has been painted with multiple coats of epoxy-based hi build so the water penetration issue is covered, not that it is a significant concern for me anyway. A surveyor I spoke to told me it was far rarer to find genuinely serious cases of osmosis than the widespread fretting about it warrants.

Last of all John Shuttleworth himself - one of the most highly regarded multihull designers in the world, particularly known for his structural savvy - recommended polyester for my build. I'm very grateful to him for this as otherwise I'd have thrown an extra £6000 ($10,000) into the boatbuilding chasm and begun suffering from epoxy allergy much sooner.

apex1

12-21-2009, 12:47 PM

Fully concur.
Horses for races..........what else.

But your surveyor should do some survey from time to time! And he should know that nearly NOBODY talks about osmosis!!!! (well, yes yachties do, pro´s do´nt)..
Does´nt the local MC Don... provide a adequate job for him?

elhix

12-21-2009, 04:35 PM

eh???

Scrumble

12-27-2009, 01:58 PM

2Sheets2Wind,

You asked "What is difference between Epoxy & Polyester Resins"

Strength

AndrewK

12-28-2009, 07:39 PM

From my local observation very few boat builders ( professional & amateur ) post cure their boats.
There are many epoxy resin formulations and many curing agents being used, and unless you post cure epoxy resin systems you can not assume that ALL epoxy mechanical properties are superior to PE & VE resin.
For ambient temperature cure the only two properties that you can safely say that epoxy resin is superior in are water proofing and low shrinkage. This is based on information from the data sheets for the locally available marine epoxy systems.

My recommendation to anyone building a boat from scratch is to ask for full resin properties for the cure conditions you are going to achieve and make your selection based on facts. This includes getting the properties for the individual hardeners in a epoxy system.

If only doing a repair to a polyester boat then, if the intention is to gelcoat the repair I would use either iso-PE or VE resin. If the repair is going to be painted then use epoxy if you wish. Either way they all are fit for purpose.

Like Fanie I too would like to see comparative laminate test date showing the difference that the resin properties make to a laminate.

Cheers
Andrew

Jimbo1490

12-28-2009, 11:40 PM

Although quite smelly, polyester resin is potentially less toxic than the typical epoxy resin, at least with the exposures that an occasional user will ever see. The usual epoxy formulations, like West, system 3 and others, use very toxic amine curing agents like DETA and TETA which are dangerously toxic, even though they smell rather sweet. These agents are easily absorbed through the skin as well as by inhalation. You can take sensible precautions and practice good industrial hygiene for these and avoid these issues with epoxy completely.

But it seems that people are more likely to practice these precautions with polyester resin than they are for epoxy resin, because polyester has certain 'warning' properties (it smells bad and it burns your skin upon prolonged contact) while epoxy does not (it smells OK and does not irritate skin much until that fateful day you discover you have become sensitized:( ) , even while the epoxy curing agent is doing real damage to your liver and kidneys and the polyester is just burning your throat and eyes and making your skin red, and not much else. I'm telling you this not to scare you away from using epoxy resin, but motivate you to use it right.

Jimbo

Jimbo1490

12-28-2009, 11:48 PM

From my local observation very few boat builders ( professional & amateur ) post cure their boats.
There are many epoxy resin formulations and many curing agents being used, and unless you post cure epoxy resin systems you can not assume that ALL epoxy mechanical properties are superior to PE & VE resin.

Cheers
Andrew

Elongation and fracture toughness are always better, even before post-cure. And both of these improve dramatically after post-cure. These are important parameters for achieving good toughness and damage tolerance. If the hull NEVER sees hot summer type weather, then it will never be 'post-cured' unless the builder does it. But if it does see such weather(especially while dry), then it will be post cured during the weeks of its first exposure to that weather, when hull temps will probably be over 38C for hours on end.

Jimbo

mark775

12-29-2009, 01:44 AM

"What is difference between Epoxy & Polyester Resins" - To me, owning a poly boat and not wanting to have future adhering problems, I do mods and repairs with poly unless the strength of the repair is critical. All around it boils down to incompatabilty issues - want to fill a small gap or make a nice radius? Break out the Cab-O-Sil (fumed silica) and whip it thixotropic. Everything else is gelcoated - why change now? I've always wondered just how strong epoxy is, once you mix enough wood flour to make it thixotropic - can you fill a screw hole with it, then paint or gelcoat and have it last?
I have an acquaintance (Ren Tolman) who swam in epoxy for years and is paying the price in more ways than one. I swear, looking at his hands, I itch. I get near epoxy and I itch (psychosomatically) but I also know that the days of mixing up more than you will need and throwing away sheet after sheet of cardboard palettes with a big glob of half-hard thixo are gone. It is time to work smarter, neater.
One thing I wonder about, if I were to ever build another boat, is making it lighter by using carbon, maybe not that much more expensive because of less need for carbon and resin but I also wonder, with this stiffer material, "does that deadhead penitrate the hull?" Do I need the dumb brute heavy layup afforded by poly or will some combination of wunderproduct (Kevlar?) make up for those missing layers of glass?
I'm not much of a fan of infusion (for my purposes), so that leaves, what appears to me, carbon prepreg. I just can't get visions of Goetz neatly laying the pieces, everything engineered and oriented just so, in an upside down sailboat he was building. No dust, no walking on the work. Everything exactly like you want, then turn up the heat and walk away. To me, this is the future (even tho that proboat was maybe fifteen years old) - at least my future and it requires epoxy.
Richard, how do you repair Vinylester? I thought nothing would stick to it once cured?
Par, I have been watching the Spectra developement since there was Spectra. I'm with you on that stuff. Just too slippery still?

apex1

12-29-2009, 07:46 AM

Richard, how do you repair Vinylester? I thought nothing would stick to it once cured?

Whith Epoxy.

And the Spectra, Dyneema stuff is a good choice in some cases. (but not easy to work)

Regards
Richard

AndrewK

12-29-2009, 06:05 PM

apex1

12-29-2009, 07:21 PM

Jimbo, the data sheets for the locally available resins shows that a good number of the epoxy resins have a lower elongation, tensile strength, flexural strength and much lower HDT than VE even at 40'C cure. And these are premium and not cheap epoxies, 2 to 3 times dearer than premium grade VE. There are also toughened VE resins available that have elongations of 8 - 10%, dont know how these compare on price.

This is why I recommend that you get full data sheets when selecting a resin. For epoxy this includes data for each individual hardener, do not assume that the fast and slow will give you the same properties.

That is all well known and does´nt change the general statement!
And of course it is NOT the resin which makes the properties of Epoxy, it always is the hardener mainly! And comparing apples and apples you will not change the fact, that Epoxy IS the far superior material. And what means a 40°C curing temperature? Go over 70°C to talk about post curing.

Regards
Richard

Jimbo1490

12-30-2009, 12:09 AM

Jimbo, the data sheets for the locally available resins shows that a good number of the epoxy resins have a lower elongation, tensile strength, flexural strength and much lower HDT than VE even at 40'C cure. And these are premium and not cheap epoxies, 2 to 3 times dearer than premium grade VE. There are also toughened VE resins available that have elongations of 8 - 10%, dont know how these compare on price.

This is why I recommend that you get full data sheets when selecting a resin. For epoxy this includes data for each individual hardener, do not assume that the fast and slow will give you the same properties.

My previous post on the subject of http://www.boatdesign.net/forums/wooden-boat-building-restoration/epoxy-comparisons-21105-2.html#post182681.

Jimbo

AndrewK

12-30-2009, 08:13 AM

Hi Richard,
Like you I also think epoxy resin systems are superior and that is why I am using it for my current boat.
And yes it is mostly the hardener and cure temperature that governs the final mechanical properties.
Various posters have made general statements like epoxy is tougher, stronger etc without specifying the system or cure conditions.
I was trying to compare apples with apples, and stated that my observations are that locally most boats are not post cured. In this case the fair comparison is for resin properties at long term ambient cure. And the data sheets for local epoxy systems used for boat building show that they are not always stronger or tougher at these cure conditions.
"And what means a 40'C curing temperature?" this was a response to Jimbos statement that even if boat builders do not post cure their boats, that they will see temperatures of over 38'C for hours on end. Once again my data shows that the referred epoxies at a 40'C cure will not necessarily have a higher strength or elongation than a VE resin at long term ambient cure.

So my message is once one has decided on the cure conditions that are going to be achieved is to go and get data for these conditions. Then make a choice comparing apples with apples.

Cheers
Andrew

apex1

12-30-2009, 09:33 AM

Right............

Fanie

12-30-2009, 12:56 PM

Good grief Richard, are you blokes still on this thread :D

It is true that epoxy resin offers a little better characteristics ie flex etc than polyester resin.

I would again like to point out that wether you work with either the calculated strength is done on the glass allone - and not on the binder resin.

No one could so far offer a comparasson between the same layups regarding strengths and pro's or cons on either.

apex1

12-30-2009, 01:34 PM

It´s all known Fanie, no need to make a comparison.

The glass is the same, no matter which one of the thousands of formulations of resin we use. The resin makes the difference.

Commuter Boats

12-31-2009, 02:23 PM

This thread has run its course and thanks to a few mechanics with some respectable hands-on time, polyester came out of it with better representation than it normally gets in these discussions.
Having read seven pages of this discussion, I suspect that many readers are going to come away more confused than they were when they started.
For the benefit of the layman, I'm going to try to elaborate ( while trying not to get too technical) on some of the differences and hopefully, install some confidence in polyester repairs.
Epoxy obviously has some structural benefits but to suggest that all repairs should be done with it isn't very realistic. Not only has polyester proven itself in millions of successful boats but also in millions of well executed repairs.
For little understanding of the relationship between the fiberglass reinforcing and the resin, fiberglass will elongated approximately 4.8% before rupture with 100% elastic return up to rupture. An iso-resin (a good polyester) will elongate just over 2% before failure at 9400 pounds per square inch (which is better than an ortho or a DCPD resin), a vinyl ester resin will elongate over 4% and provide a tensile strength of 11,800 pounds, and most laminating epoxies had elongation's in the 5 to 6% range and a tensile strength near 12,500 pounds per square inch. With those values in mind you can understand how a resin can become overloaded before the fiber was fully loaded and how that might affected ultimate strength and damage tolerance a laminate. Admittedly, all of that is not very complimentary to the polyesters but keep in mind the outstanding success rates and the fact that recreational boats are not designed with a very sharp pencil ( the safety factors are supposed to be huge).
Most repairs are pretty straightforward and with good bonding techniques, an understanding of structure, and a good iso-resin, satisfactory results are very predictable. Occasionally it's difficult to determine which resin system was used ( Polyester will not stick to epoxy) or for some other reason, the reliability of secondary bonding is a concern and in those situations a peel test should be conducted.
The purpose of a peel test is to prove repair-ability of an existing panel ( damaged or in need of modification, boat, airplane, pipe, whatever). The test is conducted by preparing the panel being tested in the manner recommended by the resin manufacturer and then laminate 3 x 6" test panels half on the panel and half on mylar tape. After curing the test laminates are levered off the panel with a wonder-bar and the delamination is evaluated. It is generally accepted that less than 10% failure on the bond line is acceptable but much better results are typical with good procedure.
I recently did a presentation and in interest of showing the repair ability of fiberglass products with several resins, I prepared two test panels. The first a scrap piece of fiberglass that previously served as a baffle in a diesel fuel tank for over 25 years. I chose that piece of scrap in the interest of illustrating the reliability of repairs to integral fuel tanks and expected less-than-perfect performance. The second panel was a nice, clean iso laminate cut off. The test laminates were of iso-resin, vinyl ester resin, and West system epoxy.
Of the first three that I delaminated, the iso-coupon failed within the coupon ( test laminate), the vinyl ester and epoxy coupons both tore fibers from the test panel. On the second panel, all three failed within the test laminates. These would be referred to as “ peel failures” ( a repair laminates weakest loading) and the epoxy was handicapped by being the thinnest of the laminates but in all cases the bond was 100%.

Fanie

12-31-2009, 03:10 PM

The idea of any repair job is to restore the original part as close to what it was previously or better.

Delamination is a reality but depends where the repair was done and how much endurance the patch have to withstand. I have delaminated both epoxy as well as polyester.

In all cases it is always better to add mechanical strenth to prevent delamination. One such method I have used that was very successfull is the use of rivits. These cannot always be used but it depends where the repairs are to be done. Another layer or two hide the presence of these rivits, but they defenately contribute huge strength to the repair. I have once stripped such a part from the boat I had, and it was a nighmare. I couldn;t believe how well it kept the glassed parts together and how strong it was.

Another method is to add new material from both sides, say inside and outside but so the new (and still wet) repair at least makes a good bond with each other.

And yet another would be to extend the repair to where other parts of the structure whould force the new material to stay in place.

One should keep in mind that a repair, and even a bad repair will work in calm weather. If you end up in a storm and waves, you don't want to lose the patch and make water, or have structures getting torn loose, or have decks become soggy under your feet. Most guys just want the thing fixed up, but it makes a difference in the long run if you do it well.

Preperation is probably the most important factor that will improve the repair. So will experience and a knowledge of the material you use.

Personally I don't like the use of wood, but if you do then epoxy is the binder material to use.

I have made structures on a few occasions using a pre-made former that I have used polyester for. The former removed left a pure glass structure which I then glassed into place. Worked awesome and never had problems with these. No wood that will rot over time and saved a bit on weight.