I was perusing Keith’s glossary and noticed that S-glass is only 10% stronger than E-glass. No kidding? Is this really the case?
http://www.tapplastics.com/shop/product.php?pid=88&
S-2 glass was the first developed for military missle applications. It`s a different glass than standard E-glass and is about 30% stronger and 15% stiffer. Most commonly used to provide greater strength with less weight than with E-glass. S-2 glass is compatible with polyester and epoxy resins.
30% stronger sounds better, especially at twice the price. Thanks.
They say 30% but ive heard its really only 10%. Wonder which one it really is?
Hey
That stuff came out about 35 years ago, maybe more.
MIGHT… 30 % stronger if layed up perfectly by itself.
.... 10 % if layed up on a blank
But… your actual glass job makes more than 20% difference in strength, so YOU control the overall equation.
And when you dilute with colors, sand thru in spots, cut too deep, leave some dry spots and some too wet, lay your reinforcement layers wrong, don’t tie everything together, your glass job has little to do with your materials used.
http://www.swaylocks.com/cgi-bin/discussion/archive.cgi/read/28482
http://johnrsweet.com/Fabric.html
S-glass, which stands for high-Strength, is stronger and stiffer and more expensive. What is commonly called S-glass nowadays is actually S2-glass. The original S-glass, sometimes called military S-glass because it was developed for military applications, is somewhat stronger than S2 glass but it is extremely expensive, due to stringent testing and certification requirements of the military. There is no chemical difference between S and S2…
S2 glass was developed in the 1960s by Owens-Corning to bridge the gap between E-glass and mil-spec S-glass… Compared to E-glass, S-glass provides about 40% higher tensile and flexural strengths, about 10 to 20% higher compressive strength and flexural modulus, and greater abrasion resistance.
http://www.fiberglasssupply.com/Product_Catalog/Reinforcements/reinforcements.html
To the best of my knowledge S2 glass is one manufacturer’s nomenclature. I put the 10% in as a rough indicator, certainly that’s not a hard and fast number but was intended as an indicator only – quality of the laminate is the key thing. Didn’t mean to start any huge debates, but it’s fun to watch!
I once had a first hand comparison test when travelling. Two boards, bottom up on a trailer, one ‘s’ one ‘e’. Went through a hailstorm. The ‘e’ was left with hundreds of small dent shatters, the ‘s’ was left unmarked. Percentages of strength gain are hugely dependant on personal workmanship, among other things.
both the 10% and 30% figures are correct ,just depends on which test is being performed ,a while back i said i had more data than you could poke a stick at,well here comes a little recorded data,
im gonna give some figures for carbon e glass and s glass all which had the same tests done on them, most were done with strips of different fabrics of the same weight(4oz e glass,4oz s glass,4oz carbon) ,laminated up to look like rulers of between 2 and 10 layers thick depending on the test …as a point of interest the tests were done with epoxy resin which can elongate further before the fail ,whereas polyester resin can only elongate 2% before it fails ,so combining it with a fabric that elongates 30% before failure is a waste of time,coz the resin is the weakest link youd just be wasting money …
tensile strength ; the test peices were stretched till breaking point,clamped securely at each end then continueously loaded with weight till breaking,a large bucket was loaded with bricks till the laminate strap broke…
e glass; 13 bricks
s glass; 17 bricks
carbon; 18 bricks
flex resistance; the test peices were laid across a gap with a set of electronic scales about 1 mm underneath weight was placed on the samples till they bent enough to make the scales register,a plastic cup with 25 grams lead weights placed in …
e glass; 225 grams
s glass; 250 grams
carbon; 525 grams
flexural strength; the same test as above with out the scales underneath the samples were loaded till they snapped ,one interesting thing about carbon is it gives little warning before it breaks…
e glass 675 grams
s glass 875 grams
carbon 675 grams
in flexural strength s glass was the surprise package ,with both glass samples they bent a little more each time weight was added till they finally broke,the s glass kept bending and bending along way before it broke ,the carbon was predicted to be the strongest but blew me away how easily it broke ,at first it took heaps of weight before it even bent slightly ,it then bent in tiny incriments as weight was added when it finally broke i reckon maybe a few degrees of flex before it broke without warning ,where as the e glass was almost 45 degrees before it went .
i have more tests but these are the most relevant to this discussion.
so from the above tests you can see s glass is 30 % stronger till breaking point …
and 10% stronger till bending point.so in reality its 10% stiffer 30% stronger…
hope that clarifies it
regards
BERT
Interesting stuff. Tensile strength is not real important in surfboards. Actually not in most composites and yet this is the standard most fabric companies use in gauging strength. Compression strength is what matters and this is difficult because of two things. One. In glass composites, compression is usually only half of the tensile strength. This leads to difficult imbalance in the strength between the side of the board that is in compression and the side that is in tension. If compression and tension in fiberglass composites were equal, we would see far fewer boards breaking. Carbon fiber raises compression significantly and carbon composites are more equal. This is reason carbon composites can be made significantly lighter.
Second, most fabric companies won’t give compression stats because the cloth has to be laminated before you can compression test. This tests the resin as much as the fabric. We had a fabric company in MD use our 2000 resin for their carbon tests because they got better physicals with that resin than with any other. It has to do with the stiffness of that particular resin and how well it matches the stiffness of the fabric. Stiff resins should be used with stiff fabrics. Flexible resins should be used with flexible fabrics. 2020 was actually originally designed to be used with synthetic fabrics with very good elongation. In impact and tension tests 2020 actually does significantly better but I certainly wouldn’t say that resin makes a stronger board.
As for s vs. e here’s an old post I wrote some time ago. Sorry if it’s a little redundant.
As Havard said S glass is the top dog amongst fiberglass. But good tensile strength doesn’t really mean much in surfboards. Compression strength does and they (the fabric manufacturers) really can’t accurately test compression without a resin to hold it in a compression test. This tests the resin as much as the fabric and different resins obviously will give different results. In practice S glass does give you between 5-10% advantage over e-glass. Remember, this all has to do with strength to weight. So, what this means is that an s-glass laminate of 4 oz. is equal to an e-glass laminate of about 4.4 oz… maybe. In a typical shortboard this will save you about 2-3 ounces of weight in the finished board and add about $15 – $20 in costs. Whether this is worth it is up to the builder and the customer.
I have to agree with Greg.He really explained that well.We were using S glass for a while in various different glass schedules and I couldn’t see any difference.Resin is one of the main factors(and the foam).Unfortunately the surfboard industry uses super cheap resin (I call it the bottom of the barrel).If the polyester glassers would do what Greg did with epoxy we may have a better product.Go figure eh??
This discussion sent me back to George Orbelian’s book, “Essential Surfing.” On page 197, item #5, George writes,
“The ultimate breaking strength is (normally) a function of the resistance to buckling on the compression side of the board’s bending. This strength is extremely dependent on the foam-fiberglass bond. A board’s breaking strength is also influenced by a stiff fiberglass ‘skin’ which helps distribute the forces trying to break the foam-fiberglass bond over a larger area.”
In the same chapter, Orbelian talks about experimenting with an “L” shaped piece of fiberglass cloth set in next to the stringer and bent over on the deck prior to glassing. The point was to increase the strength of the fiberglass-foam bond on the compression side of the board–and he says it worked. It was heavy, but it was much stronger. Anybody else tried this?
Okay, thanks for the comments, I think the cheaper glass with epoxy and better technique might be at least as good as the “S” glass.
Peter
i dont understand. if you stomp with your heel you leave a dent where the fabric stretched … doesn’t that dent create tension and is more affected by tensile strength than compressive strength? A breaking board is in compression on top of the crack and tension underneath… so in this case the compression is the most important factor?
H’mmm have you ever gone to Harbour’s website? By far the best manuacture website I’ve found. He gives a ton of info on design. Here’s what he says about S-glass.
S-Glass has great memory, but this may be its undoing. It won’t stay bonded to the foam as well when severe denting occurs.
The glass is now being stretched and is still trying to bond to the foam.
http://harboursurfboards.com/design.html#top
I have personaly found that S-glass is great when aplied to 8pound PVC foam like divinnicell. Generaly found in very high end wave riding skimboards
id hate to say it and remind you guys again of the benifits of sandwich contruction…
mentioned earlier was the fact most boards fail in compression when snapping …sometimes they fail in tension when this type of snap ocurs it looks like its been blown up (because of massive tension build up before the snap)
but most of the time a board will fail in compression ,it has creases leading into the snap ,showing the compression failure…
now in a sandwich formula where you have a layer of glass either side of a sandwich material ,which you then have on both sides of the board…
lets look at the compression side of the board ,the sandwich will need to bend one way or the other as this happens ,one of those layers of glass on the compression side of the board will be now under tension again ,thus taking advantage of the tensile strength of fibreglass …
ive got some intersting data on snap ratios ,also im currently building 9’ longboards at 4 kilo which are ten times less likely to break over a conventional polyester board at twice the weight ,the sandwich puts tension back on the compression side of the board…so it helps to distribute the load more evenly across the whole board rather than focus the energy on to a small area …
regards
BERT
Sandwich construction as in what they do with divinicell and sailboards? And what kind of resin are you using? Seems as though it would be much heavier. Any diagrams?
Nice post Bert. All boards are sandwich construction but what Bert is talking about is a sandwich using a core material like divinycell. This increases compression strength dramatically. They do come out exceptionally light and do have high compression strength. I once built a 9 foot longboard that weighed 7 lbs. They are also expensive and difficult to build.
Wow three different spellings for Divinnicell, Divinicell, or Divinycell!!!
Either way, You guys have my fullest atention here. Please Greg or Bert go into more detail on your longboards made out of PVC foam. Did or are you guys changing “H” ratings of the foam starting with a H-100 or H-80 on the outter surfaces and using a H-20 on the inner? Any carbon tape or rods for inner stringers?
With no shaping experience yet, comming very soon, building racks, templating, setting up lighting, and what not but reading as much as I can. I have been very interested in making a finless board with channels as a crossover that would allow me to paddle into the wave but instead of turning out I could take on the beach break barrel like a skimboarder and slide up the beach. This would require making it out of divinnicell.
So please preach on.
Soup that’s the coolest Icon I’ve seen yet… right down to the single fin.
Is it really the compressive strength of the material, or the bond between the foam and the glass that dictates the point of failure? Does the sandwich have to be thin in order to get that tensile layer of glass close to the deck?
Data? Bert, I always like to see data. The more the better.