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  • Q's about fiberglass and epoxy!

    Ok guys, I want to gather somem info before I venture my self into doing a custom panel for my car. I was wondering were does everyone buy the fiberglass cloth and the epoxy and bondo? Any local stores where you can find all of the stuff needed or should I go ebay?! Reason why I ask, is because 3 days ago, some @sses broke into my car and stole everything so I would like to make something better than stock to hide my stuff...

    Israel

  • #2
    i go to a local plastics supply shop (www.plasticareinc.com). Truly though, for 99% of in-car fiberglassing, you don't need anything exotic, so you could just go to your local hardware store and get chopped strand mat, polyester resin, bondo, brushes, masks, gloves... you name it. I could find everything i need to do a custom form project at Lowe's or Home Depot.
    Et ipsa scientia potestas est.

    Worklog for my 2007 Civic Si ...f*** it...
    Pictures of the Corolla (retired)here
    Need to make something? Here are a few ideas.

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    • #3
      Originally posted by GoHybrid View Post
      i go to a local plastics supply shop (www.plasticareinc.com). Truly though, for 99% of in-car fiberglassing, you don't need anything exotic, so you could just go to your local hardware store and get chopped strand mat, polyester resin, bondo, brushes, masks, gloves... you name it. I could find everything i need to do a custom form project at Lowe's or Home Depot.

      Thanks man.. So lowes or home depot should have the fiberglass/strand mat? Strand mat is the same as fiberglass right?!

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      • #4
        There's two main types of materials that are used in fiberglass fabrication: mat and weave. Mat looks like a bunch of strings pressed together with no real order because they take a string and chop it at intervals and then press it together once they have enough of 'em. Weave or cloth, looks like what you see in a nice carbon fiber piece, nicely arranged rows and columns of strings.

        Mat, if applied correctly is IMMENSELY stronger than cloth but it's hard to get a finish on without a ton of work. Cloth is still strong, but doesn't soak as much resin up as mat so it's a bit weaker. Cloth is easier to finish because you get a nice uniform surface to work with and it usually takes shapes and curves more readily than mat.

        Lowe's, Home Depot, Auto Zone, Advance Auto Parts all have cloth and mat. Some may not have resin, some may not have body filler it's really a crap shoot.

        They all also sell nitrile gloves. I'd recommend these because they're stronger than latex and they keep you from getting resin/body filler all over yourself.

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        • #5
          commonly refered to as CHOPmat.

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          • #6
            I just did (started) this messy job over the weekend.
            Lowes sale Elmo brand resin, mat, and cloth. Homedepot and everywhere else sale Bondo brand. If you use mat, buy a roller. Otherwise, it is a BIG STICKY MESS.
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            • #7
              i tend to disagree about the strength of chopped strand mat versus woven cloth. Perhaps chopped mat is more omnidirectionally strong, but it's ultimately the glass that takes the load. resin is brittle and merely serves to keep the glass strands aligned to whatever shape they've been given. a longer strand more closely oriented in opposition to a load is going to be stronger. I believe that'd be the reason you don't see things like "chopped carbon fiber". The whole point is to try and align the longest possible strands to the load. There are threads here and elsewhere that discuss how to take advantage of this and orient adjacent layers at 45 and 90 degrees to eachother.

              also... i think it is far easier to get chopped mat to follow compound curves than cloth. Cloth has a tendency to bunch up unless you cut reliefs and darts around tight compound curves. Mat is held together with a resin-soluble binder. Once that binder dissolves, you can move strands more or less completely independent of eachother to follow a curve. with no bunching up.

              as far as finishing goes, that depends partially on your methods. As an experiment, I made a form with chopped mat and polyester resin, and instead of just stippling it with a brush to get air bubbles out, i used a vacuum bag and a squeegee to work air bubbles out. Between the pressure and vacuum, the part i pulled was not only glass smooth (with very minor imperfections) but it was almost completely transparent.

              just food for thought. not trying to start any fights.
              Et ipsa scientia potestas est.

              Worklog for my 2007 Civic Si ...f*** it...
              Pictures of the Corolla (retired)here
              Need to make something? Here are a few ideas.

              Comment


              • #8
                Mat is stronger because there's a bunch of different overlapping strands. It's the same reason that OSB is stronger than sheet ply.

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                • #9
                  http://www.fibreglast.com/contentpag...inates-84.html

                  this link explains some of the differences between woven cloth and chopped strand mat.

                  i think mat can appear stronger because it is more rigid across all axes, whereas you could easily flex an equivalent thickness of woven cloth off it's two axes. I still have to maintain that given an uniaxial load, parallel to the fibers, a woven fabric will be stronger than chopped strand mat.

                  We should probably clarify at this point that it's all the same glass... so it really all boils down to it's orientation in opposition to a load.

                  Think about structural concrete. Concrete buildings are reinforced by creating matrices of steel rebar typically oriented parallel to anticipated loads. House construction uses 2x4s and beams oriented in direct opposition to the major loads. I have no doubt you could create something structurally sound by cutting tiny bits reinforcement and cramming it randomly into a matrix of binder...

                  but i think the real question here is strength-to-weight ratio and structural efficiency. In this case, woven fabric laminates are going to be superior to chopped strand laminates PROVIDED that the plies are oriented adequately in opposition to the load.

                  Composite engineers chime in anytime and correct me if i'm wrong!
                  Et ipsa scientia potestas est.

                  Worklog for my 2007 Civic Si ...f*** it...
                  Pictures of the Corolla (retired)here
                  Need to make something? Here are a few ideas.

                  Comment


                  • #10
                    BSME in composite materials engineering chiming in...

                    Clif's notes: either will be fine for our applications. Use what's easier to work with for you. I use cloth just because I don't have good luck with chopmat.

                    As is referenced in GoHybrid's link, the woven cloth is stronger in an on-axis tensile situation. In a subwoofer enclosure, I would say that either cloth or mat would be acceptable, given proper layup techniques. The key here is to minimize voids and inclusions in the resin. While it is there simply to hold the reinforcement in place, the resin ultimately contributes to the overall strength of the composite part. If a crack propogates in the resin, it will ultimately find it's way through the part around the fibers and cause the entire part to fail. The point: Get rid of all of the air and don't allow contaminants to get into your cloth or resin. I would also do whatever I could to do all of your structural layup in one step to maximize strength. Don't lay up new layers over hardened ones. The new resin will not chemically bond with the hardened stuff and there is the chance of failure along this surface.
                    Granted, this probably isn't going to be an issue with a reasonably designed enclosure, but it is an issue none the less.

                    You're experiment with vacuum bagging was exactly what we can do to maximize strength and uniformity of resin. My experiment years ago was to build an enclosure using flat sandwich panels of 1/2" closed cell foam with 3 layers of 90 degree carbon cloth on each side. Layed the panels up, bagged them and let them harden. Then we assembled the panels with a baffle of 2 layers of 3/4" MDF (Density for subwoofer mounting.) After initial assembly, we filament wound the entire enclosure with carbon fiber and bagged that. The result was quite strong because the entire enclosure was wrapped with continuous fiber (Look at a fiberglass nitrous bottle or soft water bottle...) The entire enclosure was probably less than 30 lbs (48 by 12 by 10 or so), and plenty strong for 4 10W3s sharing about 2kW.

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                    • #11
                      glad we got that cleared up thanks damon
                      Et ipsa scientia potestas est.

                      Worklog for my 2007 Civic Si ...f*** it...
                      Pictures of the Corolla (retired)here
                      Need to make something? Here are a few ideas.

                      Comment


                      • #12
                        Thanks for all the inputs guys.. I really appreciated it alot.. I think soon I will start doing a mess in my garage..

                        Comment


                        • #13
                          I found a place to go to buy fiberglass cloths are hobby stores. We use them on RC airplane bodies and such. Bigger hobby stores usually have decent prices. Only problem is they usually sell it in small quantities (a pint or two of resin versus gallons...)

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                          • #14
                            To answer your question, we buy resin at Walmart for our smaller projects.

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                            • #15
                              **STARTED WRITING THIS 4 HOURS AGO BUT GOT DISTRACTED SO THERE MAYBE NEW POSTS SINCE**

                              at what has been written so far!

                              my turn (if anyone asks masters degree in aero eng specialising in materials and now teaching structures and materials at Uni)

                              1. Chopped mat: supprisingly good - especially for the amature or quick job. Why? because the strands are so random you end up with a pretty much quasi-isotropic material (the quasi is there as no conventional 2D composite has good through thickness strength as this is a resin only dimension). This is the equivalent of carefully laying up woven material in equal amounts of 0, 90 and +/- 45 degree and realying on the relative angles to not change much over curves etc etc.

                              2. Chopped strand is also good from an in-life point of view as unlike woven and uni-driectional (more about these later) it will not suffer from different layers contracting in different directions during curing, heating (hot car) or from deformation - this causes delamination between layers.

                              3. The first big problem with chopped strand mat has to be with the drape. it is more difficult to drape over curves then woven material.

                              4. The second big problem is resin rich areas. Resin is poop. it is only there to hold the fibres in possition and the more resin you have the weaker it will be (providing you are not too dry). In a carbon/epoxy system we calcualte the strength of a resing dominated layer as 10% of the strength of a fibre dominated layer. On a uni-directional fibre this is basically any angle greater than 30 degress away from the axis of the fibres. Choped strand can leave you with large areas of resin.

                              5 however on the plus side chopped strand is easier to get the resin between the fibres than some tightly woven materials that really need vacuum bagging and pressure applying to consolidate the material. With chopped strand the average DIY'er can get away with a resin roller (ridged roller).

                              6. Wet layup is basically something that we avoid at all costs. it always results resin rich area and voidage purely because the application of resin is not very controlable. We use rpe-preg materials or resin transfusion systems but wet layup is by far the cheapest for a home user and requires less specialist materials even though it is much messier.

                              7. Chopped strand will never be as strong as you simply do not have the continuous fibres or the close packing ratios and you cannot optimise it for any particular direction so you are only ever going to be as strong as aluminium in the 2D plane at very best (UD carbon fibre will have the strength of steel in that one direction).

                              8. Finally...at the end of the day all you are producing is dash parts of sub enclosures so strength to weight is not critical. What is critical is toughness, cost, ease of manufacture and a good overall strength to prevent movement from pressure.

                              My choice would be chopped strand using proper rollers - afterall this is what many kit car body shells are made of (due to the reasons i have listed). If i was doing a large panel that had to have a good strength to weight and was easily draped then i would go with a woven cloth.

                              If you need a goof finish then use a chopped strand surface tissue over the coarse stuff.

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