E glass vs S glass?

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Morecowbell
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E glass vs S glass?

Post by Morecowbell » Mon May 21, 2018 3:43 pm

Just wanted to ask this question in case anyone has a strong opinion. I'm attempting (note the choice of words) to build a canoe using foam as the core. Of course its much more flexible than wood, but I've done some test panels and once the fiberglass and epoxy is on its very strong. I've used both S glass and E glass in the samples and can't really tell any difference. S glass is more expensive but technically tougher and stronger than E glass, so my question is will this additional toughness and strength will be noticeable in a 17 foot canoe used in lake conditions (boundary waters)? S glass is about 3 times the cost and some of what I've read says the benefits are more geared towards highly technical layups, so if there's no appreciable benefit in a hand layup I'll stick with the E glass.

As usual, thanks for any thoughts!

Clay

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Cruiser
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Re: E glass vs S glass?

Post by Cruiser » Mon May 21, 2018 8:42 pm

Hi Clay, at the end of the day you are making a composite ... whether it is FG/wood/FG or FG/Foam/FG wouldn't make much difference, as long as you choose the sandwich filling for it's lack of compressability. The foam doesn't need to be as stiff or strong as wood, it needs to not be very compressible, as I understand it, that is what contributes to the composite panels strength.

As far as E vs S cloth goes that is just a matter of where you draw the line of what is strong enough. That line is drawn all over a build, from strip thickness, gunnel/thwart/yoke size, layers of FG .... at some point you say "that's strong enough" .... we don't all draw that line in the same place.

While S glass is stronger, it is a lot more costly and from what I have read, it can also be a pita to wet out ... maybe consider just what you expect to gain by using it. Using the standard 6 oz, means you will have a stronger boat than using S glass over E glass, if you reduce to 4 oz, you may save weight and get the same strength ... but how much stronger or lighter and does that difference actually matter to you?

The weight of the FG/epoxy skin is roughly 1/3 the weight of the finished canoe, so any weight savings are weighted to that .... so if you save 20% of the FG/Epoxy weight, that amounts to 20% of 1/3 ... which will eventually translate to 5-6% of the final weight ... if you you use the same weight cloth obviously weight saving would be negligible ....

At the end of the day, I think weight would be the only reason I would go to the tougher glass, slipping down from 6 oz to 4 oz will result in using less epoxy and less glass and provide the weight savings, which comes at $$ cost .... you have to decide what is important to you and how you intend to use the boat. It is however useful to try and estimate what benefit you are paying for (i.e how much weight am I saving, or how much strength am I getting).


Brian

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Patricks Dad
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Re: E glass vs S glass?

Post by Patricks Dad » Mon May 21, 2018 9:03 pm

I'd like to have Jim Dodd comment on this. He's built canoes with both E and S glass.... My understand is that S-glass is not only stronger it is also more resistant to abrasion. I'm close to starting a build with kevlar, carbon and (S?) glass and would be interested in your progress. What foam are you planning to use?
Randy Pfeifer
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Morecowbell
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Re: E glass vs S glass?

Post by Morecowbell » Tue May 22, 2018 5:58 am

Brian,

Thanks for the thoughts. At this point I'm going to stay with the 6 oz cloth - I've read a lot of guys looking for weight savings saying its overkill for these boats, but the foam core will drive the primary weight savings so I'm okay with the 6 oz. cloth. I had read about the S-glass being tough to wet out but didn't have any issues on the sample panels I did. It was maybe not as clear as the E glass but pretty darn close, which surprised me - and since the boat is foam clarity is not an issue.

Randy,

There are two primary marine foams that I've run into: Corecell and Divinycell. I did my samples with Corecell and was about to order it when I learned that Divinycell is cheaper and "basically the same"...but its not, its much less stiff - so the challenge is that it will "give" between the forms when sanding. I'm creating additional forms for support between the forms - long story but will know if it works in a week or two, will report either way! But next time it will be Corecell.

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Jim Dodd
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Re: E glass vs S glass?

Post by Jim Dodd » Tue May 22, 2018 5:43 pm

Morecowbell
My experience is more limited, than some believe !
Choice of components is critical !
First, S-glass. The last I used was a very tight weave. That was the problem getting entrapped air out. Yes, the cost is high. That is the price of a stiffer more abrasive skin. There are charts that compare the qualitys between S and E-glass.
Every builder has to weigh that cost for himself!

Foam ! I believe you are on a better track, than the foam (Owens Corning Pink 1/4") I used . It's JUNK !

I've resorted to thinly cut WRC for my cores (1/8").I stripped this on my forms to simulate the stripper shape.

I'm not sure, what you are using for a mold. I used a stripper as a Male mold. So my lay up started with Kevlar/ Carbon fiber/ S-glass. Once that was laid up, and cured, I pulled the hull off the Mold.
Then I laid in my prestripped thin wood core. That covered the bottom up to about 1 1/2- 2" waterline, and epoxied it to the inside of the hull. This was glassed with 6 oz E-glass.

At that point the hull is stiff enough for me.

The thing is, you can always add another layer, to the inside if you need !

I'll be interested in following your build ! Please post !!!

Good luck !

Some pics.
In the second pic, I laid down, and wetted out, a layer of 6 oz E-glass prior to wetting the Kevlar.
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Jim
Keep your paddle wet and your seat dry!

Morecowbell
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Re: E glass vs S glass?

Post by Morecowbell » Tue May 22, 2018 8:23 pm

Wow Jim, that's fascinating, thanks for posting!! Please keep us updated, I really enjoy seeing new approaches.

I had a long conversation with someone at Sweet Composites today and his advice was basically to bite the bullet and use the S-glass, which I think I will do on the outside. Frankly at this point, if I can get to the point where I'm ready to fiberglass it, I don't think I'll care about the additional expense :laughing

Thanks everyone!

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