well looks like some conflicting opinions on s-glass…
my experiece has been positive with it…the laminate feels stiffer with the thumb press test…good call for heel patches as mentioned…
as far as clark green foam density at 2.4pcf there must be something im missing cuz my std go to shape weights break down as follows:
clark blue = 3.75lb
#2 eps = 2.5 lb
#1 eps = 0.9lb
wild guess the green is closer to 3.5+pcf
strange…the clark catalog doesnt publish actual density numbers…only the green as a base reference and all other products are shown as a percent up or down from that…didnt notice that before…i have noticed their foam varies quite a bit in density within the same color class…might be tough to control density distribution in production…too much human variation…???
Yeah, we need someone to weigh a clark blank of blue and green and let us know. Rich Harbour has found quite a variation in weight of blanks supplied to him that are supposed to be the same. His design info page has the following:
Quote:
The weight of two identically ordered surfboards can vary as a result of several variables.
Foam is mixed by weight for each particular blank. Since it is about the consistency of waffle batter, getting the same amount into the mold from the mixing bucket each time is difficult at best.
Blanks are left in the mold a given time to expand. When removed, a slight bit of swelling still occurs. On larger blanks, the overall thickness of the blank can vary an eighth of an inch due to weather and time left in the mold.
Foam has a density gradient, the most dense at the surface, and the deck being the most dense of all. If the blank has an over-growth and is shaped to the same specifications as one that has been left in the mold longer, it will be lighter.
The stringer, being a natural wood product, can vary in weight due to what part of the tree it comes from. The amount of moisture it has will also affect the weight. Stringers glued in the summer will always have less moisture content.
He posted today that he weighed a 9’0" high performance blank before glassing with 6 bottom 6+4 top and it came back (from watermans i assume) 5.7lbs. more than when it left. If so, I’m inclined to believe you that the clark numbers for weight of their foam are way off. If superblue was really 2.3lbs. per cubic foot, then a 9’0 blank for a thinish high performance longboard of about 3 cubic feet would weigh less than 7 lbs. and a total board be less than 13 lbs. and I know that’s just not right… I bet the blank weighs more like 10 lbs!
This is important to me to figure out because I was almost about to just use Clark if the difference between it and 2# eps was really that close. But if Clark’s numbers are fudged…then there is a significant savings by using 2# eps.
S-2 Glass Surfboard Fabrics, are industry standard for high performance surfboards and sailboard fabrication. When compared to E-glass, S-2 laminates show significant improvements in tensile strength, flexural strength, flexural modulus and compressive strength. S-2 Glass Laminates also exhibit improved impact resistance and toughness.
{End Quote}
that’s a nice sales pitch off the website…but get the guy on the phone and he tells a different story…and as for his personal glass jobs, he uses E-glass. granted, he told me all this several months ago…things may have changed since.
Use s-glass for a better strength to weight ratio, 30% stronger at the same weight, skip the volan.
Aloha Brant
I don’t mean to put you on the spot but… Tell us something about your experiences with S-Glass and why you feel it is 30% stronger. I have heard it mentioned here and there and was just wondering. Others feel free to weigh in on their experiences also.
Bill,
I must admit, even though i smelled a trap i was willing to take the bait
truth is, (as you know) brant is correct:
s-glass has 30% better strength and modulus, as well as better elongation.
I’m sure you’re not blaming the glass if the total package doesn’t benefit due to limitations of configuration and other materials.
I think this ties in with your comments regarding the evolution of epoxy for surfboards in a recent thread.
Changing one material for what is considered desirable properties is usually the beginning of a ‘slippery slope’ to actually take advantage of those properties.
Does anyone know the strength diferences between s-glass and Carbon Fiber? Im thinking of doin a board in carbon, but if its not all that stronger, i wont waste the money.
Soulstice: Yep you’re right. I shouldn’t have quoted a sales pitch, trusted source or not. Especially after all things considered, I choose to use E-glass. lol@myself.
Does anyone know the strength diferences between s-glass and Carbon Fiber? Im thinking of doin a board in carbon, but if its not all that stronger, i wont waste the money.
It’s probably stronger, but…
I’m guessing you’re talking about the glass with carbon strands every 1/8" or 1/4" in the warp direction (parallel to the stringer).
A friend of mine tried that in the late eighties and he said it was a nightmare to keep the carbon strands straight during glassing. I think he tacked the cloth down by using his finger to squeegee a small bead of lam resin down the stringer to help keep it straight, but he said it was too much of a pain in the arse to mess with.
That was a long time ago, and materials and techniques might have changed considerably since then.
“But if Clark’s numbers are fudged…then there is a significant savings by using 2# eps.”
MaraboutSlim -
I’m not sure that the density of the Clark Foam posted by Gr8day is an absolute. Also, not sure that the density numbers are from Clark. He appears to be quoting from Harbour website?
"After doing some research on the Harbour web site, I found this.
Dents are a natural Bi-product of surfboards. The old balsa boards, when whacked really hard, will dent. I have been in this business since 1959 and have seen no production foam boards with more than a total of 20oz of glass per side. When using contemporary resins, the real problem in denting is the substrate or foam. Even with the early 60’s when foam weighed about 3.9 lbs. per cubic foot, surfboards still dented. Think of this: put one layer of 4oz glass on concrete and you will not dent it. To make a surfboard of reasonable weight, we cannot apply enough layers of glass to make it ridged enough to be dent resistant. Today’s longboard typically is made of CLARK “supergreen” foam. This name has nothing to do with anything but a name for foam that is approximately 2.44 lbs. per cubic foot. Supergreen is the standard of the longboard industry.
I guess we should just ask, huh? I couldn’t find a phone number for Clark so I just emailed Foamez sales. I’ll post when they get back to me. Or if you guys have a scale and some unshaped blanks sitting around, you can weigh them and then we can look up the displacement volume of the blank in the catalog and figure it out on our own. 6’2"C is 2 cubic feet so that one would make the math easy…
Please check my math on this. I shaped a chunk of “superblue” to a chunk measuring 4.9" X 6.9" X 1.25". (cu.in. = 42.3) It conveniently weighed 1 ounce(!) on a crappy spring postal scale I have. Any error at this level will be multiplied as we extrapolate up so take it with a grain of salt please.
I multiplied this by 16 to get cu.in./lb… 677.
12" X 12" X 12" = cu. in. in a cu. ft… 1728.
1728/677 = 2.55 lb/cu. ft.
Sounds like Rich Harbour was right. The piece of foam I measured was core material with all crust, glue and stringer absent. I suspect that an unshaped blank even without a stringer or glue would be more dense because of crust.
"Supergreen is approximately 2.5 lbs. per cubic foot so just figure the other
percentages off that."
I guess the only question is how “approximate” it really is. It’s gotta be heavier than that. If it’s really 2.5 and superblue would then be like 2.3 then it’s possible to be nearly identical in weight to the “2#” sfoam eps (“nominal 1.9 to 2.4”).
johns math is correct so greens got to be heavier than 2.5…i guess the bass stringers add about 1/3 of a pound to a short blank…that would explain the heavier results but then again the #2 eps i’ve made also have stringers…my experience is that relative to a shaped #2 eps with a stringer, a shaped clark blue is roughly 50% heavier
On August 1 the following was posted by MaraboutSlim:
“He posted today that he weighed a 9’0” high performance blank before glassing with 6 bottom 6+4 top and it came back (from watermans i assume) 5.7lbs. more than when it left. If so, I’m inclined to believe you that the clark numbers for weight of their foam are way off. If superblue was really 2.3lbs. per cubic foot, then a 9’0 blank for a thinish high performance longboard of about 3 cubic feet would weigh less than 7 lbs. and a total board be less than 13 lbs. and I know that’s just not right… I bet the blank weighs more like 10 lbs!"
The weight information on the Harbour web site that includes Clark Super Green foam at approximately 2.44 lbs. per cubic foot is probably more than 20 years old. It was never written by Clark, only told to me by one of their employees. Clark has never written foam weights per cubic foot because it varies so much throughout their wide range of sizes. They only list density comparisons using Super Green as the base.
Earlier this month I posted a comparison of a glassed board against a shaped blank. I believe the finished board was a sand only finish. Today I weighed several shaped blanks and gloss finish boards and have the following weights of boards that are the same shape and all nine foot in length.
Shaped blanks between 7.5 and 7.6 lbs.
Completed glossed and polished boards:
15.4 lbs with a foam spray
15.8 with a resin tint bottom
16.4 with a resin tint top and bottom
The reason that resin tints are heavier is that they must have extra pasting on the overlap during the hot coat process to protect against any abrasions from sanding.
I’v never worked with carbon fiber with surfboards, but have with sailboats (see thread about Dennis Choate). We made test panels of carbon/foam sandwich, and of regular glass roving/ foam. We set them up like bridges and started loading lead weights on the panels . The regular glass at certain point started failing, crackling and bending under the weight and eventually lost all rigidity and hung like a hammock. It was limp but still hanging together. The carbon fiber on the other hand took the weight without any appreciable flex. We kept loading it and loading it and were blown away by the strength. Then it exploded into a million pieces. When carbon fiber fails it does so catastrophically! Does anyone remember the America’s Cup class boat that snapped in two and sank in less than a minute?
Carbon fiber’s great quality is stiffness. It is also light weight. It is obligatory in racing sailboats nowadays. But do you want a surfboard to be totally stiff?? Maybe not.
Did weight testing of Clark in a lab. The results I got were:
Green 3.1
Blue 2.75
Superlight 2.5
Ultra 2.35
These were done at Polymer Chemistry Innovations about five years ago and I’m pretty sure they are about as accurate as you can get. Since there are issues like density gradient and differences in densities from one plug to another there is no prefectly accurate measurement.
Since there is no such thing as a cubic foot of Clark Super Green foam, I assume that one would take a (for example) 2 cubic inch sample, weigh it, then do the math to get a cubic foot. The problem is, where was this sample taken and from what blank? There would be a significant difference in the weight of a 2 cubic inch chunk of foam removed from the front third of the deck of a Super Green 6-3R, and the middle of the bottom of a Super Green 11-3. The foam from the 6-3R would have tighter cell structure on both the top and bottom surface, due to the fact that the deck is at the mold’s surface, and the bottom of the sample would be very close to the surface of the bottom of the mold. Whereas the sample taken from the 11-3 would have a dense deck surface, but the cell structure would be very large on the bottom of the sample. The point I’m making is that I’m certain that multiplying these two samples to get a cubic foot will surely provide significantly different results. I’m not sure anyone has the exact answer, and many years ago the folks at Clark Foam explained to me that this is the reason that there is no foam weight numbers in their catalogue.
