Do you have a project in mind but have no idea where to start?  Let us help you.  One of the first things you will want to do is decide what kind of fiberglass you want to use.  Do you need to build up thickness fast?  Are you concerned about strength? Do you have tight corners you are working with?  Let us break things down a bit to help you decide if fiberglass cloth is right for your project or if you are needing chopped strand mat. Keep in mind that you can actually use both together to achieve your desired outcome. Here is an overview - 

(Plain weave fiberglass cloth)

Fiberglass Cloth is a woven fabric. Plain, 4 harness satin and 8 harness satin are the weave styles we carry. The 46 and 10 ounce plain weave fabrics are the most commonly used. In this simple plain weave pattern, warp and fill yarns are interlaced over and under each other in alternating fashion. The plain weave is the easiest to handle since it does not unravel as much as the other weaves when cut.

In the four-harness satin weave pattern there is a three by one interfacing where a filling yarn floats over three warp yarns and under one.

The eight harness satin is similar to the four harness satin except that one filling yarn floats over seven warp yarns and under one. The satin weaves are slightly stronger and more pliable than the plain weave and are easier to conform to curved surfaces. They are more difficult to handle than the plain weave, though. Use fiberglass cloth when you are looking to create a strong, light weight product.

Chopped Strand Mat (also known as fiberglass mat) has short strands of fibers held together with a resin binder. The fibers are randomly oriented. Mat is only compatible with polyester and vinyl ester resin. When resin is added to the mat, the binder dissolves and the fibers can be moved around. It is easier to conform mat to tight curves and corners than it is with weaved fabric. The reason chopped strand mat is not compatible with epoxy resin is because the binder holding the fibers together needs styrene to properly dissolve.  Polyester and vinyl ester resins have styrene in them. (There are some places that sell chopped strand mat that is compatible with epoxy but it is hard to come by and much more expensive). Chopped strand mat is the least expensive fiberglass and is often used in mold construction or projects where thickness is needed. Mat is often used as the first layer (before the gelcoat) in a laminate to prevent print through. Print through is when the fabric weave texture shows through the resin. Chopped Strand mat does not have much strength. If you need strength you should choose a woven cloth or you could mix the two. Mat can be used between layers of woven fabric to help build thickness quickly and aid in all layers bonding well together. If you have any questions feel free to comment.  We will do our best to reply with an answer. Or, you can visit our product website Fiberglass Warehouse for more information. Save

By Dallin Leach 34 comment


comments (34)

  • Bob Schmidt

    I want to cover an old car floor that has some pitting and minor holes. The floor has been protected with PPG DP 90. I think using fiberglass cloth would be my best option, as it should be stronger and thinner than mat. Do you know of any issues I may encounter? Thanks.

    REPLY from fgwarehouse: Fiberglass Cloth would be the best option. A couple layers of the 10 oz cloth with epoxy resin will last a long time. The DP 90 is an epoxy primer, so epoxy resin should be used. Depending on how long ago you applied the primer, you may need to rough it up a little.

    REPLY from Bob Schmidt: Thank you for the reply. I applied the DP 90 over 20 years ago, but will lightly sand/roughen up before applying the cloth and resin.
    Would the 1200 resin and hardener, along with the 10 oz. cloth, be a good choice for my use?

    REPLY from fgwarehouse: That would be perfect. I would used to 80 or 120 grit to roughen it up. Be sure to clean it with acetone afterwards.

    REPLY from Bob Schmidt: I just have to choose a hardener, then I’ll place an order.

  • chhana

    Can i do vaccum infusion process with fiberglass cloth

    REPLY from fgwarehouse: Yes you can.

  • Mark


    I need to reinforce an area on an old jet ski that is SMC. What would be the preferred fiberglass and I’m assuming epoxy resin only? Also what type of prep would need to be done before applying the fiberglass. Thanks for your help.

    REPLY from fgwarehouse: I would go with epoxy. Our 1200 2:1 epoxy will do great. If the fiberglass is cracked, you should try and grind out the broken part, the layer in fiberglass afterwards. I would probably use 6 oz fiberglass cloth, style 3733. It is a smooth fiberglass.

  • Nick B

    I want to make a standing platform on top of my canoe. The surface area will be approx 40”wX 60” l. What is my best option for strength. Thickness won’t be an issue so I can do layers. I haven’t decided if I’m going to use a polyurethane/ styrofoam mold (for insulating properties, or just use a plywood frame. Also what resin would be best for strength with both and water proof for plywood?

    REPLY from fgwarehouse: For strength and waterproofing, epoxy is always the best. If you don’t want to spend the money on epoxy, go with vinyl ester resin. It is much better than polyester resin and almost as good as epoxy. And also much cheaper. Also, you can cover it will gel coat afterwards to help protect the fiberglass.

    As far as plywood or styrofoam, the plywood will be stronger, but also heavier. If you use styrofoam, you will need to go with epoxy. All the ‘ester’ resins will eat the styrofoam.

    Let me know if you have any more questions.

  • Scott

    I am replacing the floor of my run about boat. I have 3/4″ marine grade plywood for the replacement.
    Not necessarily needing strength just water proofing that I can add carpet to. What would be the best fiberglass type and thickness as well as the appropriate resin/epoxy system?

    REPLY from fgwarehouse: Scott, since you don’t need to worry about strength, I would either go with the chopped strand mat and vinyl ester resin or 6 oz fiberglass cloth with the 4:1 epoxy resin. Vinyl ester and chopped strand mat will be cheaper than the cloth and epoxy. Epoxy will be the better waterproofer, but vinyl ester is almost as good.

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