Look at my Fabrics

My E glass comes from fiberglasssite.com. It’s 5.6 oz with a very tight weave as shown below. It takes a long time for the epoxy to soak in. Meanwhile My S-2 Glass (bottom photo) has a large open weave and wets out very fast.

What I don’t understand, is why the tight weave and high quality looking fabric cost half the price of the S-2, which looks like cheap fabric with little substance.

Teach me about glass. Why is loose weave, less fabric, more expensive and considered stronger. Instincts would say the opposite.

From my limited understanding, it has to do with two factors.

  1. What is the glass made out of. ( E vs. S-2 vs. quartz vs. etc…) This gives each fiber it’s potential load carrying capacity.

  2. The weave. The more up and down / side to side each fiber has to do per inch of cloth reduces the final laminates strength in both compression and tension.

i.e take a stack of rectangular kids blocks and lay them down end to end. - - - - The resulting line of blocks is surprisingly strong in compression, especially if you block it from moving out of alignment (like what resin does). Now if you lay them down at an angle to each other ////\ they have much less compressive resistance. the tighter the weave, the more bends each fiber has in it.

From what I hear the best fabric is uni-directional because the laminate can be made with no kinks in the fibers. I know they make multi-axial uni fabrics 0/+45/-45/90 that have very good strength to weight ratios.

That’s how I understand it at least.

Howzit Dwight, The first thing that doesn’t sound right is you saying the s-glass wets out easier than e-glass. s-glass has always been harder to wet out because it is twisted and it is also not steamed cleaned as much as e-glass, yes,that is how they clean fiber glass they use steamcleaning. The twisting is one of the factors that makes s-glass stronger and if you ar pay twice as much for s-gass than e-glass tan you are either paying to much for your e-glass or you are getting a deal on your s-glass since s-glass normally runs around 3 times the price of e-glass Aloha,Kokua

I can see fraying in that cloth already. S glass burns out the liners of the ovens far more frequently due to much higher temperatures, hence the increase in price. Or that’s what I was told.

Sorry for being misleading on the cost. My E is 50" wide and my S is 30" wide, so my cost quotes were very rough.

I should have posted a photo with both fabrics in the same shot, because these don’t accentuate enough the differences in tightness of the weave. My E is so tight, you can’t see through it. While the S is so loose, I can see the blank through it. It really makes the S look cheap-o.

As marko said the more bends in the glass fibers the less stiffness. Take a power cord from whatever and place it on the floor with the cord all wavy. Now pull the two ends apart… takes no force whatsoever to straighten your fiber model. Now lay it on the floor dead straight and try to pull it. A lot harder aint it. (Got this example from boardlady.com).

When the weave is really tight, the fibers must bend a lot more to “weave” around each other (Think wavy power chord). When the weave is a little more open, the fiber bending is less, so you get a stiffer material.

You cannot equate the quality of your cloth to the tightness of the weave.

I’d like to see a direct ‘torture test’ comparison. Lay both up and stab them a screwdriver or knife. My hunch is that the tight weave stuff is more resistant to penetrating damage. The tight weave cloth I’ve used is more difficult to hand laminate compund curves. As a longboard nose outline was being lapped it became tougher to accomplish without creating folds. The looser weave cloths allow more fore/aft shifting of the fabric.

If I’m not mistaken the tight weave is designed more for flat panel projects.

With all due respect to the Boardlady, I’m not sure the power cord test is valid when testing fabric that has been saturated and cured. Kind of like pushing and pulling a piece of string… theoretically yes, but once it’s in a laminated matrix??

In surfboards I’m more concerned with gashes that occur when the board hits something sharp/solid.

John, you bring up a great point. Tensile properties are not the only thing important. I do like boardlady’s analogy (even with a cured matrix), im trying to think of how I can explain my logic but Im a bit braindead right now. Considering tensile properties Id be inclined to say that fiber waviness is not good, but for impact failure prevention it very well may be good. Now I have something to think about. Thanks!