I’ve been wondering why fiberglass cloth isn’t used for backpacks? If you compare the specific strengths (tensile strength in comparison to the material’s density) of nylon 6 vs E grade fiberglass fibers, fiberglass has two and half times higher specific strength (if you use S grade fiberglass cloth, it will be 3.4x higher specific strength). If you are curious, E glass fiber glass’s ultimate tensile strength is 5.6x higher that of nylon 6’s, but again, when you factor in density and that fiberlgass is about 2.24x more dense than nylon, it does lower the overall strength to weigh ratio in comparison.
Besides its significantly higher specific strength as compared to nylon 6, it has other attractive properties. It doesn’t absorb moisture, it is not affected by UV at all, very high microbe resistance, it is inexpensive (especially when you buy in bulk–typically at least 16 yards), it can handle very high heat with no issues (unlike nylon), and it’s more stiff than nylon (which in a pack I think is a good trait because it will carry weight better).
The downsides are that the fibers are potentially irritating to the skin* with less flex durability than nylon. * To me, the former is a non issue because if you use fiberglass cloth, you have to encapsulate it within a bonding matrix of some kind, which for my purposes, I would use thinned silicone caulk (because of accessibility, expense, relative ease, and you can bond to other silicone coated fabrics). If there is a thick enough coating of silicone over the fibers, there won’t be any chance for the fibers to come out of their yarn and weave.
As to the second part of this, I think it is less important for a piece of gear like a backpack than it is for say clothes, tarps, tents, and the like, where the latter often get folded over, twisted, etc. repeatedly. In all reality, a pack only has to flex and fold a little here and there. Comparatively, it is a more static and homogeneous shape/structure/function.
I guess the other downside is that you would have to make the fabric yourself (treat the fiberglass cloth with silicone and/or silicone bond it to other silicone coated fabrics), but this is not a barrier to me or most DIY/MYOG type folks.
More specifically, why couldn’t you say, take a 2.1 or 3.7 oz/yd2 fiberglass cloth and silicone bond it to silpoly (for greater waterproofness and better sewing), and have the light weight silpoly fabric on the inside and the siliconized fiberglass on the outside? Silicone is considered to have significantly better UV resistance than nylon and even more than polyester, and as mentioned the fiberglass cloth is unaffected by UV and so, the material would last as long as the silicone does.
Honestly curious why something like hasn’t been done by people before? Am I missing something major?
Another cool thing you could do with fiberglass cloth, is if you wanted a very stiff framed, high load backpack, you take a piece of thin’ish plywood and bond fiberglass to it with high strength epoxy and for the rest of the bag that is meant to be flexible, you do the above of siliconzing it and bonding it to a silpoly. If constructed well, theoretically such a pack could carry very heavy loads well (good for hunters or the like).
Seems like a decent and more low cost alternative to UHMWPE fabrics. Besides the expense of these fabrics, bonding to them is very difficult unless they are specially altered by cold plasma treatments or the like. Not easy to do for the average DIY’er. Meanwhile, they need to have some kind of film or bonding agent otherwise the fibers can come apart within the weave (and for waterproofness). If inexpensive and bondable/already treated UHWMPE fabrics ever become a thing, then yeah, this would be the ultimate pack material, but meanwhile, if I’m not missing anything, it seems like fiberglass cloth/silicone/silpoly composite fabric would be an improvement over other inexpensive options as to strength per weight and especially long term durability (particularly due to very high UV and microbe resistance).
Fiberglass cloth, also known as fiberglass fabric, is an excellent choice when you are looking for a strong, light weight part.
All of our fabrics must be used with a resin system (polyester, vinyl ester or epoxy) to create a composite part. The fiberglass is what gives any part it’s strength. It is used in a great variety of applications. Boats, bathtubs, wind turbines, RC, surfboards, kayaks, canoes, aerospace . The list could go on and on.
The fabrics we have can be separated into 4 popular categories-
RC
Boat/marine
Aerospace
Surfboard
Keep in mind that these different fabrics are not limited in their category. They can be used in a variety of projects.
The RC cloth is style #106 and #108,
Style #106 is a .75 oz. cloth. It is very lightweight and most often used on model airplanes. Because it is so lightweight, it can be tricky to use. You will want to use protective latex gloves or some other kind of smooth gloves. Any kind of skin tag will catch on the fabric. Style #106 is stronger than mylar. You don’t want to use it on anything requiring strength though.
Style #108 is another RC cloth. It is 1.5 oz. You will still need to be careful when working with this fabric but it is stronger than the .75 oz.
Style #1522 and #3733 are our most common surfboard cloths. They can also be used on canoes, kayaks and boats
Style #1522 is a nice, smooth 4oz. cloth. Surfboard hobbyists use it to coat foam core. It can also be used as a surfacing layer. It creates a clear, transparent laminate when saturated with resin. This cloth wets out easily.
Style #3733 is a 5.6oz., aka sailboat cloth. This cloth is typically used on surfboards and general purpose projects.
Style #120 and #7781 are mainly used in the aerospace industry.
Style #120 is 3.2 oz. It is a 1:6 scale cloth for RC airplanes. You want to use this fabric when strength is needed. It is used on RC racing planes that go up to 140mph. This style is aerospace grade.
Style #7781 is an 8.9oz., four harness satin weave. Four harness means there is a three by one interfacing where a filling yarn floats over three warp yarns and under one. This weave conforms to curved surfaces. It is aerospace grade and is the second most popular aerospace cloth behind style #120.
Styles 7532 and 7500 fall in the boat/marine category.
Style #7532 is a 7.5oz. cloth. It is more commonly known as an 8oz. cloth. It is a popular boat cloth. It is a plain weave and is stronger and sturdier than the 6oz. It is often used for waterproofing boat decks.
Style #7500 is the most popular general purpose fabric and also a great boat making cloth. It is widely used in the fiberglass industry. It is good for making molds. It is typically used after the mat layer in a mold. It gives it strength. It is also used in boat construction and repair.
We also carry fiberglass tape in widths from 1” to 12”. They are 50 yard rolls. They have selvage edges that keep it from un-raveling. They do not have an adhesive backing. Just like our regular fabrics, they are meant to be used with resin. Our tapes work great on smaller applications and if you will be winding. They are also often used on glass seams and in repair work.
All of our fabrics are pretty easy to handle. Remember you will want to pick the best weight of fabric for your project but you will also want it to be strong enough.
To see all of the products we have available, go to www.fiberglasswarehouse.com .
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