# E glass equivalent to S glass weight?

Discussion in 'Materials' started by skaraborgcraft, Feb 28, 2024.

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### skaraborgcraftSenior Member

I went down a number hole and confused myself with variables. I have read that S glass is up to 40% higher in tensile strength compared to E glass.
If i have 4oz (135gm) S glass as a sheathing, what would the E glass weight be to have comparable strength? Thanks.

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### fallguySenior Member

You'd need to compare actual tds.

or

S(strength) = 1
E(strength) = x
1/x = 1.40
x = 1/1.4 = 0.71
4 oz S glass / 0.71 = 5.63 oz E glass

however, the math may reflect the 40% correctly, but I offer zero confidence ~ some googling will tell you S glass is 3x stronger than E glass

4 S glass / 0.33 = 12 oz E glass

The only way to really tell is the datasheet for each.

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### ondarvrSenior Member

Frequently when stronger fibers are used and the laminate becomes thinner you end up doing other things to regain stiffness and durability, or at least the perception of durability.

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### fallguySenior Member

A good point by John, because E glass may also only be 1/7th the stiffness of S glass per some reading I've done, so brings us back to TDS which is not a derangement syndrome but a pathway to truth.

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### skaraborgcraftSenior Member

True. This would be a a protective sheathing for a plywood hull, so no structural element in it, in this use.

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### skaraborgcraftSenior Member

I hear you. New Bing updated browser gives me stuff it thinks i want to buy, not the data i specifically enter into the search bar. I will try another browser this morning.
I have not read that S glass is 3X stronger.
Thanks.

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### TopsSenior Member

JPS Composite Materials
page 15 E-glass
page 16 S-2 Glass

I would believe S-2 glass fiber is 'mo bettah' 37% ultimate tensile strength and 18% breaking strain than E-glass fiber comparing mid-range values between the two.
It would seem 6oz E would be a substitute for 4oz S-2 with a weight penalty for more glass and resin.
For abrasion resistance...does this matter so much? Maybe better off having a second and third layer as smaller pieces in critical areas?

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### skaraborgcraftSenior Member

Thanks for the info. Variation between some sources. For abrasion purposes AND elongation, Dynel seemed like an ideal choice till i heard it soaks up about 3 times as much epoxy. A friend met a boat that had a collision with something that ruptured the plywood hull on the inside, but the sheathing actually kept the water out until they made landfall. I believe it was nylon "cascover" sheathing. I believe the plywood will rupture on point impact before E glass, but I was looking for ways just to reduce epoxy usage, not for weight or cost, just because im not a fan of standing around stirring pots of the stuff. S glass does appear to be a much pricer option, even with the extra epoxy for heavier E glass. The fabric is double E glass price from my usual supplier.

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### fallguySenior Member

If you want to pushdown epoxy; you go carbon on plywood.

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### skaraborgcraftSenior Member

As in "from the inside" on on the sole area? I hear kevlar is best laid up also on the inside rather than out. Have not used either, believe special cutting tools are required and a PITA to wet out. Anything applied will be done by hand, no vacumn bagging. I can deal with rolling out resin on a wood interior, I am not enamoured on the idea of glassing it inside. The hull was designed as ply on stringer on frame, to avoid excess goo work; but I am more than prepared to give the outside bottom a quality sheathing, again, mainly for abrasion wear purposes.

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### fallguySenior Member

This is sort of a wandering thread, if you don't mind.

For ply on frame; if you want a traffic glass; you'd probably want to lay some piece if 1208 underfoot or maybe just some csm. Or you could just put paint down, but it'll also wear quick underfoot. Maybe some Kiwigrip might be nice.

Or an eva foam pad under the chair stations is easier.

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### skaraborgcraftSenior Member

I dont, but it was you who bought up carbon into the mix. Im getting some test patches sent out, so will do my own hammer tests. The numbers are interesting but smashing something is more satisfying.
Appriciate the links provided. Thanks all.

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### KD8NPBSenior Member

For the cost, I'd just run basalt.

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### skaraborgcraftSenior Member

From what I have read, basalt is in the same park as S glass when compared to E glass, and unavailable at my usual supplier.

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### Dave G 9NJunior Member

Epoxy usage is a function mostly of fabric thickness, and the tables in the handbooks are the only way to find that information. In my opinion, 4 oz glass cloth provides some abrasion resistance, prevents fir plywood from checking and does next to nothing for strength, stiffness and impact resistance except when used to hold a stripper together because 6 mm of cedar has no strength perpendicular to the grain.

Looking at styles 4522 and 2165, the differences in warp and fill count and possibly the number of yarns twisted together result in the E glass cloth being stronger than the S glass cloth of the same weight. That is not at all what I had expected to find. Page 49 of the Hexforce handbook talks about the heat treatment to remove sizing and the effect on strength and the large difference between the HT grade and standard grade of the same style number.

JPS Composite Materials has copied their data from the Hexforce technical fabrics handbook which is easier to read and may be more complete. If you find Tables 1 and 2 in the hexforce handbook, they explain the codes in the tables. ECG is E glass, Continuous filament, G=9 micron diameter fiber. SCG is S glass, rest same. ECG 150 1/0 compared to SCG 150 1/2 is interesting. Best to read page 4 of the JPS handbook, which seems clearer to me than page 46 of the hexforce handbook. The 1/2 and 1/0 indicate piled and unpiled

Dynel fabric is an organic fiber so I expect a density of 1g/cc give or take. E and S glass are 2.5 g/cc. Kevlar is 1.44, and spectra 0.95. So yes, Kevlar is organic and the density is rather high for a organic. The problem with comparing the fabric weight to thickness here is that the Dynel is a low density yarn, so there is 2.5 times as much fiber volume for the same weight as glass, and If I remember correctly, the Dynel yarn is piled or twisted to increase bulk. I don't have a data sheet handy, but it is at least three times as thick as the same weight of glass fabric, so it takes a lot of epoxy to fill. Everything I read indicates that it is tough, but not as stiff or strong as glass. Toughness and strength are often going in different directions. The materials property triangle again. One corner is cost, the other two are the properties you want. You never both desired properties without maxing out on cost.

Cascover is Nylon cloth set in resorcinol. The link is to the old Borden technical information booklet that tells how to apply it. I see no particular reason why a polyurethane resin would not be at least as good. Nylon (PA) cloths are notoriously difficult to bond, so I would be hesitant to try substituting epoxy for Cascophen (\$1143.00/5 Gallon). Polyurethane (PU) is generally the best resin for PA, and much easier to use. The PU used for SOF boats would be good. Having gone down that rabbit hole, I have to say that polyester (PE) cloth should also work similarly. PA swells in water, so it should be stretched on wet and allowed to dry before bonding. Look to the SOF builders for information. PA and E are handled differently to avoid wrinkles.

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